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Thermophysical properties of glycine and glycylglycine in aqueous tartaric acid at different temperatures: Volumetric, acoustic and viscometric studies
Journal Pre-proof Thermophysical properties of glycine and glycylglycine in aqueous tartaric acid at different temperatures: Volumetric, acoustic and viscometric studies Shashi Kant Sharma, Abhishek Thakur, Dinesh Kumar, Vikas Nathan PII:
S0167-7322(19)33218-0
DOI:
https://doi.org/10.1016/j.molliq.2019.111941
Reference:
MOLLIQ 111941
To appear in:
Journal of Molecular Liquids
Received Date: 7 June 2019 Revised Date:
18 September 2019
Accepted Date: 14 October 2019
Please cite this article as: S.K. Sharma, A. Thakur, D. Kumar, V. Nathan, Thermophysical properties of glycine and glycylglycine in aqueous tartaric acid at different temperatures: Volumetric, acoustic and viscometric studies, Journal of Molecular Liquids (2019), doi: https://doi.org/10.1016/ j.molliq.2019.111941. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.
1
Thermophysical properties of glycine and glycylglycine in aqueous tartaric acid at
2
different temperatures: volumetric, acoustic and viscometric studies
3
Shashi Kant Sharma*, Abhishek Thakur, Dinesh Kumar, Vikas Nathan
4
Department of Chemistry, Himachal Pradesh University, Shimla 171005, India
5
Email id: [email protected]
6
Abstract
7
Thermophysical properties like density, ultrasonic velocity and viscosity of glycine,
8
glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 aqueous tartaric
9
acid solutions as a function of concentration at different temperatures ranging between
10
(298.15 and 318.15) K have been determined. These data have been utilized to calculate
11
apparent molar volume ( ), apparent molar isentropic compressibility ( ), and viscosity
12
B-coefficient values of the studied solutions. The partial molar volumes ( 0), partial molar
13
isentropic compressibility ( 0) and experimental slopes (Sv* and Sk*) derived from the
14
Mason equations have been interpreted in terms of solute-solute and solute -solvent
15
interactions. The viscosity coefficients A and B have been determined from the Jones-Dole
16
equation. From the volumetric and viscometric data, hydration number (nH) has been
17
calculated and further, the structural effects of glycine, glycylglycine in tartaric acid solution
18
has been discussed. The results were explained in terms of structure making and structure
19
breaking properties.
20
Keywords: apparent molar volume; apparent molar isentropic compressibility; partial molar
21
volumes; partial molar isentropic compressibility; structural effects.
22
1. Introduction
23
Life began with advanced and continuous series of chemically synthesized reactions
24
which raised the organization of inanimate matter to successively higher levels. Atoms
25
first accumulated to simple compounds, then these metamorphosed into more complex
26
ones and finally, the most complex of them ultimately became organized as living cells.
27
Water is present in these living cells, and is responsible in maintaining electrolytic
28
balance of the body and further small portions in between living cells are also deposited
29
in conjunction with protein and carbohydrate. So, protein having large molecular size
30
plays an important role in the exchange of fluids between the circulating blood and the 1
31
interstitial fluid [1]. So, having knowledge, how these proteins interact with water and
32
their properties vary with temperature and different composition of solvent and solute;
33
became a topic of interest for many researchers. Because of the complex nature of
34
protein, it becomes tedious and quite challenging to get viable information for proteins
35
with water and to study their thermophysical properties [2] so, it’s been worth to use
36
amino acids and peptides, as these are model compounds for understanding the solvation
37
of proteins and by this, we can easily render our discussion on proteins by studying
38
aqueous amino acid/peptide system. In fact, extensive work have been done related to
39
volumetric, acoustic behaviour of aminoacids/peptides in aqueous solutions and in
40
different solvents [3-7], but their study in organic acids are scant. Amino acids, the
41
biologically important compounds is of immense importance as their behaviour in
42
aqueous and mixed aqueous solutions in different temperature range determines how the
43
proteins tends to behave in living cells and this leads to open field of curious research [8-
44
11]. The solution structure of amino acids/peptides is because of the intermolecular
45
interactions and the understanding of these intermolecular interactions have a decisive
46
role for determining the outcome in biological systems and even these are in close contact
47
with the thermodynamic properties of liquids, solids and gases. A change in temperature
48
or concentration significantly affects the charge distribution in molecules, which also
49
influence the different types of molecular interactions (H-bonding, ion-dipole, dipole-
50
dipole etc.) [12].
51
The amino acid used is glycine, a natural osmolyte that can act as osmoprotectants
52
and are of immensely important in the renal medulla. Glycine is used for treating
53
schizophrenia, strokes and other uses in cancer therapy, memory enhancement. Studies
54
shows that glycine may help people with type 2 diabetes by controlling their blood sugar,
55
and got the ability to protect the liver and kidney from damage caused by chemicals such
56
as alcohols. Research are going on the subject that glycine acts in a way to promote the
57
healing of overworked or damaged muscles, soothe an upset stomach, stress reliever,
58
boost the immune system and increase human growth hormone. Glycylglycine, is
59
dipeptide of glycine and because of its low toxicity, act as a buffer for biological systems
60
at different pH [13]. The solvent chosen was tartaric acid, a white crystalline dicarboxylic
61
organic acid found in plants, particularly in tamarinds and grapes. Tartaric acid is used to
62
generate carbon dioxide through interaction with sodium bicarbonate following oral
63
administration. Carbon dioxide, thus produced extends the stomach and provides a 2
64
negative medium during double contrast radiography.
It is also used for protein
65
precipitation and curiously hardly ever studied and a better knowledge of its interactions
66
with different amino acid/peptide is certainly an interesting point for further studies on
67
protein purification and precipitation. [14]. In present study, we will report the densities
68
(ρ), speeds of sound (u) and viscosities (η) of glycine and its peptide (glycylglycine)
69
(0.05 to 0.40) mol kg-1 in pure water to (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 of
70
tartaric acid at (298.15 and 318.15) K. These data have been utilized to calculate apparent
71
molar volume ( ), apparent molar isentropic compression ( ), limiting apparent molar
72
volumes ( 0), limiting apparent molar isentropic compression ( 0) and experimental
73
slopes (Sv* and Sk*) derived from the Mason equations, A and Jone-Dole coefficient B,
74
hydration number (nH). All these parameters give a deep insight into the solute-solvent
75
interactions and structure making/breaking behaviour of glycine and glycylglycine in
76
aqueous solutions of tartaric acid at temperatures (298.15 and 318.15) K.
77
Experimental
78
2.1 Materials
79
The amino acids (glycine and glycylglycine) and solvent (tartaric acid) were used after
80
drying over anhydrous calcium chloride for more than 24 hours and then, weighed using
81
electronic balance SHIMADZU A X 200 (model no D432613208, Japan) a digital balance
82
having a precision of ±0.1 mg. Triply distilled and deionised water with specific conductance
83
< 10-6 ohm-1 cm-1 was used.
84
Table 1 Specification of chemical samples. Chemical name
Molar mass
Provenance
(g mol-1)
Initial Mass fraction
Purification
Final
purity
method
fraction purity
Tartaric Acid
150.087
Merck Specialities Pvt. Ltd. India
>0.99
None
>0.99
Glycine
75.07
Merck Specialities Pvt. Ltd., India
>0.99
None
>0.99
Glycylglycine
132.12
Merck Specialities Pvt. Ltd., India
>0.99
None
>0.99
Mass
85 86
2.2 Density measurements
87
The density (ρ) and speeds of sound (u) were measured with the help of apparatus
88
DSA (i.e. Density and Sound Analyzer) 5000 supplied by Anton Paar GmbH, Garz, Austria. 3
89
DSA 5000 is the first oscillating U-tube density and velocity of sound meter, which measures
90
to the highest accuracy in wide viscosity and temperature ranges. The studies were carried
91
out at atmospheric pressure P = 0.1 MPa at five different temperatures T = (298.15, 303.15,
92
308.15, 313.15 and 318.15) K with an accuracy of ± 0.01 K. The calibration of DSA (i.e.
93
Density and Sound Analyzer) 5000 was internal realized before in hand, by measuring the
94
density and speed of sound through dried air and triple distilled and deionized water. For
95
water, the measured values of density and speeds of sound are given in table 2 along with
96
corresponding literature values. The average reproducibility in density and speed of sound
97
data from experimental data was ± 0.01 kg m-3and ± 0.1 m s-1 respectively.
98 99
2.3 Viscosity measurements
100
The viscosity measurements were carried out with a modified capillary type
101
viscometer, which is thoroughly cleaned with chromic acid and the subsequently wash
102
with water and acetone followed with drying by vacuum pump. While performing the
103
measurements, the solution in the viscometer is allowed to attain the temperature of the
104
water thermostat for about 20-25 minutes. Stop watch was used for noting the time of
105
flow. The viscosity measurements at different temperatures was determined by using the
106
following equation [15]
107
ƞ⁄ƞ = ⁄
108
where ƞ, , and ƞ , , are the viscosity, density and time of flow of the solutions and
109
water respectively. The viscometer is calibrated with triply distilled and deionized water, the
110
values of relative viscosity (ƞ⁄ƞ ) so obtained is compared with literature values as shown in
111
table 2.
112 113
(1)
3. Results and discussion 3.1 Partial Molar Volumes & Partial Molar Compressibility’s
114
Values of the experimental density (ρ), viscosity (ƞ) and speed of sound (u) of
115
glycine, glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 aqueous
116
solutions of tartaric acid at T = (298.15, 303.15, 308.15, 313.15 and 318.15) K are reported in
117
table 2.The apparent molar volume ( ), apparent molar isentropic compression ( ) were
4
118
calculated from the experimental densities, and speeds of sound by the following standard
119
equations [16, 17]:
120
= ⁄ − 1000( − )⁄
(2)
121
= ( ⁄ ) − (1000( − )⁄ )
(3)
122
With the assumption that the absorption of the acoustic wave is negligible, the
123
isentropic compressibility, () can be calculated using the Newton-Laplace’s equation [18]
124
= 1⁄(u2 )
(4)
125
where m is the molality (mol kg-1) of amino acid/peptide in water and in different
126
molal concentration of aqueous tartaric acid solution, M is the molar mass of the solute
127
(kg mol-1) and , , , and are the densities (kg m-3) and isentropic compressibility’s
128
(Pa-1) of solvent and solution, respectively. The resulting values of , and the different
129
molal concentrations (m) of amino acids in water and in different concentrations of tartaric
130
acid at various temperatures are given in table 2.
5
Table 2 Values of density ( ), speed of sound (u), apparent molar volume ( ), apparent molar isentropic compression ( ), relative viscosity (η/η0) at different molal concentration (m) of glycine, glycylglycine in aqueous solutions of tartaric acid at different temperatures (T = 298.15-318.15) K and at pressure fP = 0.1 MPa with corresponding literature values. ma /
b * 10-3 / kg٠m-3
uc
d * 106 / -1
/ m٠s
m
3
-1
mol
e * 10 3
6
m mol-1
mol٠kg1
ma
Relative /
Viscosity
/
η/η0
mol٠kg-
b * 10-3 / kg٠m-3
uc
d * 106 / -1
/ m٠s
m
3
-1
mol
Relative
m3 mol-1
Viscosity
* 10
6
GPa-1
1
-
e
η/η0
GPa 1
g
Glycine + water 1497.5 (1497.6)[33] (1495.85)[17] (1496.98)[50]
T = 298.15 K Glycylglycine + water
0.0000
0.99708 (0.99702)[33] (0.997047)[17] (0.997045)[71] (0.997080)[50]
0.0496
0.99871 (0.99832)[33] (0.99874)[17] (0.998625)[46]
1500.0 (1500.28)[33] (1500.06)[17] (1500.32)[46]
42.41 (42.65)[17] (43.09)[46]
-26.44
1.0054 (1.0055)[33]
0.0493
0.99987 (0.99926)[33] (0.99982)[37] (0.99984)[6] (0.999656)[29]
1501.5 (1499.28)[33] (1500.53)[29]
76.09 (76.11)[33] (76.37)[37] (76.41)[6] (76.56)[29]
-38.92 (40.02)[29]
1.0114 (1.0065)[33] (1.017)[37]
0.0985
1.00031 (1.00025)[33] (1.000392)[17] (1.000403)[71] (1.000206)[46]
1502.6 (1503.01)[33] (1502.3)[17] (1502.73)[46]
42.59 42.75[33] (42.71)[17] (43.83)[71] (43.15)[46]
-26.25
1.0096 (1.0139)[33]
0.0974
1.00262 (1.00256)[33] (1.002044)[50] (1.002592)[37] (1.002740)[29]
1505.4 (1503.98)[33] (1504.20)[50] (1505.15)[29]
76.29 (76.43)[33] (76.40)[50] (76.48)[37] (76.68)[29]
-38.06 (38.86)[50] (39.3)[29]
1.0188 (1.0162)33] (1.031)[37]
0.1467
1.00189 (1.001899)[71] (1.001777)[46]
1505.2 (1505.14)[46]
42.81 (43.59)[71]
-26.04
1.0136
0.1443
1.00533 (1.00520)[6] (1.005168)[29]
1509.3 (1508.78)[29]
76.50 (76.55)[6] (76.78)[29]
-37.51 (38.6)[29]
1.0254
0.1942
1.00345 (1.003567)[17] (1.003401)[71] (1.003341)[46]
1507.8 (1507.23)[17] (1507.55)[46]
42.97 (42.82)[17] (43.65)[71] (43.28)[46]
-25.89
1.0174
0.1900
1.00497 1510.4 43.18 -25.66 1.00647 1513.0 43.37 -25.49 1.00795 1515.6 43.56 -25.24 1.00941 1518.3 43.73 -25.05 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.01020 1503.8 1.01177 1506.5 43.42 -25.22 1.01334 1509.2 43.47 -24.99 1.01488 1512.0 43.52 -24.84 1.01642 1514.7 43.57 -24.57 1.01795 1517.5 43.61 -24.32 1.01947 1520.3 43.65 -24.12 1.02097 1523.1 43.70 -23.94 1.02246 1526.0 43.76 -23.82 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02266 1511.6 1.02417 1514.4 44.48 -24.61 1.02567 1517.3 44.53 -24.28 1.02716 1520.1 44.57 -23.96 1.02863 1523.0 44.61 -23.62 1.03010 1525.8 44.65 -23.35 1.03155 1528.7 44.69 -23.02 1.03299 1531.6 44.73 -22.80
1.0211 1.0248 1.0286 1.0323
0.2345 0.2780 0.3204 0.3618
0.9322 1.0064 1.0119 1.0172 1.0223 1.0276 1.0327 1.0379 1.0428
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.9765 1.0073 1.0137 1.0197 1.0256 1.0316 1.0374 1.0428
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204
1.00801 1513.3 76.65 -37.22 (1.007894)[37] (1513.58)[50] (76.80)[37] ((1.00838)[50] (1512.95)[29] (76.67)[50] 37.93)[50] (1.00784)[6] (76.65)[6] ((1.007933)[29] (76.96)[29] 37.8)[29] 1.01065 1517.2 76.84 -36.86 1.01325 1521.1 77.03 -36.42 1.01581 1525.1 77.21 -36.08 1.01833 1529.0 77.40 -35.72 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.01020 1503.8 1.01295 1507.8 76.80 -35.69 1.01564 1511.7 77.07 -34.81 1.01829 1515.6 77.32 -34.11 1.02089 1519.4 77.59 -33.47 1.02345 1523.2 77.85 -32.92 1.02595 1527.0 78.14 -32.41 1.02842 1530.8 78.36 -31.91 1.03083 1534.5 78.65 -31.37 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02266 1511.6 1.02536 1515.6 77.37 -33.15 1.02799 1519.6 77.84 -32.22 1.03056 1523.5 78.27 -31.35 1.03305 1527.4 78.71 -30.67 1.03551 1531.4 79.08 -30.01 1.03787 1535.3 79.54 -29.33 1.04018 1539.2 79.95 -28.67
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325
0.8903 (0.8926)[33]
6
1.0317 (1.061)[37]
1.0377 1.0437 1.0494 1.0551 0.9322 1.0120 1.0230 1.0341 1.0449 1.0556 1.0659 1.0765 1.0865 0.9765 1.0133 1.0257 1.0378 1.0500 1.0614 1.0732 1.0849
0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.03443 1534.4 44.77 -22.43 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03526 1518.9 1.03668 1521.9 45.99 -23.84 1.03809 1524.9 46.03 -23.53 1.03949 1527.9 46.06 -23.22 1.04087 1530.9 46.10 -22.74 1.04225 1533.9 46.13 -22.34 1.04361 1536.8 46.17 -21.97 1.04497 1539.8 46.20 -21.60 1.04631 1542.7 46.24 -21.29 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04606 1526.2 1.04746 1529.3 46.15 -22.87 1.04885 1532.3 46.18 -22.32 1.05022 1535.3 46.23 -21.80 1.05158 1538.2 46.27 -21.20 1.05294 1541.0 46.32 -20.61 1.05428 1543.8 46.35 -20.09 1.05561 1546.6 46.40 -19.51 1.05693 1549.3 46.44 -19.06
1.0485
0.3618
1.0379 1.0082 1.0154 1.0224 1.0295 1.0364 1.0430 1.0499 1.0566
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
1.0878 0.0000 1.0095 0.0493 1.0180 0.0974 1.0265 0.1443 1.0344 0.1900 1.0424 0.2345 1.0506 0.2780 1.0586 0.3204 1.0663 0.3618 T = 303.15 K
1.04244 1543.2 80.36 -28.12 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03526 1518.9 1.03791 1522.8 78.08 -30.07 1.04048 1526.7 78.57 -29.21 1.04297 1530.5 79.08 -28.29 1.04539 1534.3 79.61 -27.42 1.04776 1538.2 80.03 -26.87 1.05004 1541.9 80.51 -26.20 1.05225 1545.7 81.00 -25.59 1.05441 1549.3 81.47 -24.86 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04606 1526.2 1.04863 1530.1 79.12 -27.17 1.05113 1534.0 79.62 -26.22 1.05354 1537.8 80.15 -25.30 1.05589 1541.5 80.64 -24.48 1.05816 1545.3 81.12 -23.96 1.06037 1549.0 81.58 -23.27 1.06250 1552.7 82.09 -22.66 1.06457 1556.4 82.54 -22.11
1.0966 1.0379 1.0140 1.0271 1.0408 1.0542 1.0672 1.0808 1.0940 1.1064 1.0878 1.0150 1.0293 1.0439 1.0583 1.0730 1.0872 1.1013 1.1154
0.0000
0.99568 (0.99566)[33]
Glycine + water 1509.4 (1509.87)[33]
0.0496
0.99730 (0.99696)[33] (0.997207)[46]
1512.0 (1515.36)[33] (1512.56)[46]
42.68 (42.68)[33] (43.41)[46]
-25.20
1.0057 (1.0060)[33]
0.0493
0.99846 (0.99789)[33] (0.998240)[29]
1513.3 (1512.6)[33] (1512.80)[29]
76.46 (76.26)[33] (76.98)[29]
-36.41 (37.1)[29]
1.0120 (1.0069)[33]
0.0985
0.99889 (0.99888)[33] (0.998773)[46]
1514.5 (1515.3)[33] (1514.92)[46]
42.87 (42.78)[33] (43.47)[46]
-24.90
1.0103 (1.0149)[33]
0.0974
1.00119 (1.00118)[33] (1.001301)[29]
1517.1 (1517.69)[33] (1517.23)[29]
76.64 (76.58)[33] (77.11)[29]
-35.71 (36.3)[29]
1.0201 (1.0172)[33]
0.1467
1.00045 (1.000329)[46]
1517.0 (1517.26)[46]
43.08 (43.54)[46]
-24.58
1.0147
0.1443
1.00388 (1.003709)[29]
1521.0 (1520.73)[29]
76.88 (77.23)[29]
1.0274
0.1942
1.00199 (1.001878)[46]
1519.5 (1519.61)[46]
43.27 (43.60)[46]
-24.31
1.0188
0.1900
1.00655 (1.006453)[29]
1524.8 (1524.82)[29]
77.04 (77.41)[29]
-35.19 (35.6)[29] -34.76 (-35)[29]
1.00351 1522.0 43.45 -24.10 1.00499 1524.6 43.66 -23.86 1.00646 1527.1 43.84 -23.62 1.00791 1529.6 44.02 -23.42 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00866 1515.4 1.01023 1518.0 43.63 -23.98 1.01178 1520.6 43.68 -23.75 1.01331 1523.2 43.74 -23.51 1.01484 1525.7 43.80 -23.22 1.01635 1528.2 43.85 -22.91 1.01786 1530.7 43.88 -22.64 1.01935 1533.2 43.93 -22.43 1.02084 1535.6 43.98 -22.14 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02100 1522.3 1.02250 1525.1 44.64 -23.28 1.02400 1527.8 44.67 -22.91 1.02548 1530.4 44.72 -22.46 1.02694 1533.1 44.76 -22.14 1.02840 1535.6 44.79 -21.65 1.02985 1538.0 44.84 -21.25 1.03129 1540.4 44.87 -20.77 1.03272 1542.9 44.91 -20.52 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03358 1529.1 1.03499 1532.0 46.11 -22.71
1.0231 1.0271 1.0311 1.0353
0.2345 0.2780 0.3204 0.3618
1.0416 1.0483 1.0549 1.0614
0.8367 1.0070 1.0131 1.0188 1.0244 1.0303 1.0357 1.0413 1.0465
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.8735 1.0078 1.0146 1.0209 1.0273 1.0339 1.0400 1.0464 1.0524
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.9206 1.0089
0.0000 0.0493
1.00916 1528.6 77.26 -34.35 1.01174 1532.3 77.43 -33.92 1.01429 1536.2 77.61 -33.65 1.01680 1539.9 77.77 -33.23 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00866 1515.4 1.01139 1519.3 77.13 -33.72 1.01407 1523.1 77.44 -32.66 1.01670 1526.8 77.70 -31.97 1.01929 1530.5 77.95 -31.33 1.02182 1534.2 78.24 -30.66 1.02431 1537.8 78.51 -30.01 1.02675 1541.4 78.78 -29.50 1.02916 1545.0 79.01 -28.93 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02100 1522.3 1.02369 1526.2 77.70 -31.23 1.02630 1530.1 78.17 -30.22 1.02884 1533.9 78.64 -29.33 1.03133 1537.7 79.08 -28.54 1.03374 1541.5 79.52 -27.80 1.03610 1545.3 79.94 -27.14 1.03840 1549.1 80.35 -26.48 1.04063 1552.8 80.79 -25.80 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03358 1529.1 1.03621 1532.9 78.41 -28.08
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496
Glycylglycine + water 0.7975 (0.8007)[33]
7
1.0346
0.8367 1.0126 1.0248 1.0370 1.0484 1.0606 1.0722 1.0835 1.0947 0.8735 1.0143 1.0277 1.0407 1.0537 1.0666 1.0795 1.0923 1.1049 0.9206 1.0147
0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.03639 1534.9 46.15 -22.10 1.03779 1537.7 46.18 -21.62 1.03917 1540.4 46.21 -21.14 1.04054 1543.0 46.24 -20.54 1.04190 1545.5 46.28 -20.12 1.04325 1548.0 46.31 -19.60 1.04460 1550.4 46.35 -19.18 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04416 1535.7 1.04555 1538.7 46.30 -21.61 1.04694 1541.5 46.34 -20.76 1.04831 1544.2 46.38 -19.91 1.04967 1546.8 46.41 -19.18 1.05101 1549.2 46.47 -18.37 1.05234 1551.4 46.52 -17.62 1.05367 1553.7 46.56 -17.04 1.05499 1555.7 46.59 -16.28 Glycine + water 1520.1 (1520.6)[33] (1519.14)[17]
1.0168 1.0245 1.0318 1.0398 1.0469 1.0544 1.0619
0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.9696 0.0000 1.0099 0.0493 1.0197 0.0974 1.0289 0.1443 1.0381 0.1900 1.0475 0.2345 1.0564 0.2780 1.0654 0.3204 1.0743 0.3618 T = 308.15 K
1.03875 1536.7 78.97 -26.91 1.04123 1540.4 79.50 -26.06 1.04363 1544.0 80.02 -25.27 1.04596 1547.7 80.50 -24.57 1.04822 1551.2 81.00 -23.85 1.05041 1554.8 81.49 -23.15 1.05255 1558.4 81.92 -22.63 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04416 1535.7 1.04672 1539.5 79.43 -25.14 1.04919 1543.2 80.01 -24.00 1.05159 1546.9 80.54 -23.22 1.05391 1550.4 81.05 -22.36 1.05617 1554.0 81.55 -21.64 1.05835 1557.5 82.04 -20.91 1.06046 1561.0 82.55 -20.25 1.06252 1564.4 82.98 -19.62
1.0297 1.0444 1.0590 1.0735 1.0877 1.1020 1.1167 0.9696 1.0161 1.0323 1.0483 1.0643 1.0797 1.0957 1.1110 1.1264
Glycylglycine + water
0.0000
0.99407 (0.99405)[33] (0.994031)[17] (0.994030)[71]
0.0496
0.99567 (0.995676)[17] (0.99534)[33] (0.995577)[46]
1522.6 (1522.89)[17] (1523.32)[33] (1523.08)[46]
43.03 (43.61)[17] (42.65)[33] (43.65)[41]
-23.57
1.0061 (1.0065)[33]
0.0493
0.99683 (0.99627)[33] (0.996748)[37]
1523.9 (1523.51)[33]
76.83 (76.42)[33] (77.30)[37]
-33.99
1.0125 (1.0075)[33] (1.016)[37]
0.0985
0.99725 (0.99727)[33] (0.997281)[17] (0.997108)[71] (0.997132)[46]
1525.0 (1525.9)[33] (1524.73)[17] (1525.37)[46]
43.20 (42.79)[33] (43.67)[17] (44.31)[71] (43.72)[46]
-23.23
1.0110 (1.0164)[33]
0.0974
0.99954 (0.99955)[33] (0.999518)[37] (0.998949)[50]
1527.6 (1528.14)[33] (1526.64)[50]
77.09 (76.76)[33] (77.48)[37] (77.21)[50]
-33.20
1.0214 (1.0187)[33] (1.030)[37]
0.1467
0.99880 (0.998680)[71] (0.998677)[46]
1527.4 (1527.65)[46]
43.39 (44.17)[71] (43.78)[46]
-22.95
1.0156
0.1443
1.00222
1531.2
77.28
-32.69
1.0296
0.1942
1.00032 (1.000371)[17] (1.000296)[71] (1.000216)[46]
1529.9 (1529.67)[17] (1529.95)[46]
43.59 (43.74)[17] (44.20)[71] (43.84)[46]
-22.66
1.0202
0.1900
1.00485 (1.004768)[37] (1.005201)[50]
1534.9 (1535.58)[50]
77.49 (77.80)[37] (77.49)[50]
-32.17
1.0375 (1.057)[37]
1.00183 1532.3 43.76 -22.40 1.00331 1534.7 43.93 -22.15 1.00476 1537.1 44.12 -21.90 1.00619 1539.6 44.29 -21.75 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00691 1525.6 1.00847 1528.1 43.83 -22.45 1.01001 1530.6 43.89 -22.11 1.01154 1533.0 43.94 -21.85 1.01306 1535.5 44.00 -21.50 1.01456 1537.8 44.04 -21.16 1.01605 1540.2 44.10 -20.88 1.01754 1542.5 44.14 -20.63 1.01901 1544.8 44.19 -20.31 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01914 1531.7 1.02063 1534.4 44.81 -21.77 1.02212 1537.0 44.84 -21.30 1.02359 1539.5 44.88 -20.83 1.02506 1541.9 44.92 -20.34 1.02651 1544.3 44.95 -19.87 1.02795 1546.6 44.99 -19.38 1.02939 1548.9 45.02 -19.02 1.03081 1551.1 45.06 -18.65
1.0247 1.0292 1.0336 1.0381
0.2345 0.2780 0.3204 0.3618
0.7533 1.0074 1.0139 1.0200 1.0263 1.0323 1.0383 1.0445 1.0502
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7864 1.0083 1.0154 1.0225 1.0294 1.0361 1.0429 1.0495 1.0561
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
0.7195 (0.7234)[28]
8
1.00745 1538.5 77.68 -31.73 1.01000 1542.1 77.90 -31.21 1.01253 1545.7 78.08 -30.88 1.01500 1549.4 78.29 -30.57 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00691 1525.6 1.00963 1529.3 77.43 -31.42 1.01230 1532.9 77.71 -30.41 1.01491 1536.5 78.04 -29.52 1.01748 1540.1 78.30 -29.02 1.02000 1543.6 78.56 -28.31 1.02247 1547.1 78.86 -27.73 1.02490 1550.5 79.12 -27.17 1.02730 1554.0 79.35 -26.74 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01914 1531.7 1.02181 1535.5 78.10 -29.11 1.02440 1539.2 78.57 -28.12 1.02693 1542.9 79.03 -27.23 1.02939 1546.6 79.47 -26.41 1.03178 1550.2 79.95 -25.61 1.03412 1553.8 80.39 -24.92 1.03641 1557.4 80.77 -24.27 1.03862 1561.1 81.19 -23.69
1.0452 1.0525 1.0600 1.0672 0.7533 1.0133 1.0267 1.0400 1.0533 1.0664 1.0792 1.0920 1.1047 0.7864 1.0153 1.0295 1.0437 1.0580 1.0721 1.0858 1.0993 1.1135
0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03091 1537.8 1.03232 1540.6 46.24 -21.06 1.03372 1543.3 46.27 -20.40 1.03511 1545.9 46.30 -19.89 1.03648 1548.5 46.33 -19.39 1.03785 1551.0 46.37 -18.91 1.03921 1553.3 46.41 -18.32 1.04056 1555.6 46.44 -17.78 1.04190 1557.7 46.47 -17.13 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04209 1543.8 1.04348 1546.6 46.45 -20.07 1.04485 1549.3 46.49 -18.98 1.04622 1551.8 46.53 -18.07 1.04757 1554.1 46.57 -17.21 1.04891 1556.3 46.62 -16.36 1.05024 1558.4 46.66 -15.60 1.05156 1560.4 46.70 -14.84 1.05287 1562.2 46.74 -14.15
0.8235 1.0093 1.0183 1.0262 1.0345 1.0427 1.0510 1.0588 1.0668
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.8645 0.0000 1.0104 0.0493 1.0208 0.0974 1.0319 0.1443 1.0422 0.1900 1.0529 0.2345 1.0632 0.2780 1.0738 0.3204 1.0842 0.3618 T = 313.15 K
Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03091 1537.8 1.03352 1541.5 78.77 -26.11 1.03606 1545.1 79.26 -25.03 1.03851 1548.6 79.86 -24.13 1.04089 1552.1 80.40 -23.14 1.04321 1555.5 80.89 -22.37 1.04545 1558.9 81.39 -21.63 1.04763 1562.3 81.86 -20.92 1.04975 1565.6 82.32 -20.26 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04209 1543.8 1.04463 1547.4 79.79 -23.22 1.04709 1551.0 80.36 -22.07 1.04947 1554.4 80.89 -21.15 1.05179 1557.9 81.39 -20.34 1.05402 1561.2 81.91 -19.57 1.05616 1564.5 82.48 -18.69 1.05827 1567.7 82.93 -17.89 1.06030 1571.1 83.41 -17.42
0.8235 1.0154 1.0319 1.0476 1.0635 1.0795 1.0958 1.1118 1.1277 0.8645 1.0177 1.0354 1.0530 1.0700 1.0882 1.1054 1.1220 1.1392
0.0000
0.99225 (0.99223)[33]
Glycine + water 1529.2 (1529.86)[33]
0.0496
0.99384 (0.99353)[33] (0.993753)[46]
1531.5 (1532.15)[33] (1532.06)[46]
43.31 (42.72)[33] (43.90)[46]
-21.91
1.0064 (1.0070)[33]
0.0493
0.99499 (0.99445)[33]
1532.8 (1532.56)[33]
77.30 (76.53)[33]
-31.15
1.0133 (1.0070)[33]
0.0985
0.99540 (0.99545)[33] (0.995297)[46]
1533.9 (1535.17)[33] (1534.30)[46]
43.49 (42.82)[33] (43.96)[46]
-21.62
1.0117 (1.0174)[33]
0.0974
0.99769 (0.99773)[33]
1536.2 (1537.08)[33]
77.50 (76.86)[33]
-30.37
1.0227 (1.0197)[33]
0.1467
0.99695 (0.996832)[46]
1536.2 (1536.51)[46]
43.67 (44.02)[46]
-21.32
1.0167
0.1443
1.00035
1539.7
77.70
-29.78
1.0316
0.1942
0.99846 (0.998361)[46]
1538.5 (1538.73)[46]
43.87 (44.08)[46]
-20.98
1.0217
0.1900
1.00296
1543.2
77.94
-29.30
1.0401
0.99995 1540.8 44.04 -20.77 1.00142 1543.1 44.21 -20.53 1.00287 1545.5 44.36 -20.37 1.00429 1547.8 44.54 -20.18 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00498 1534.2 1.00653 1536.6 44.06 -20.92 1.00806 1539.0 44.12 -20.58 1.00958 1541.4 44.16 -20.23 1.01109 1543.6 44.22 -19.86 1.01258 1545.9 44.28 -19.57 1.01406 1548.1 44.34 -19.16 1.01553 1550.4 44.39 -18.98 1.01699 1552.5 44.44 -18.61 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01708 1539.6 1.01857 1542.1 44.94 -20.19 1.02005 1544.6 44.97 -19.58 1.02151 1546.9 45.02 -19.02 1.02297 1549.3 45.06 -18.60 1.02442 1551.4 45.09 -17.97 1.02585 1553.6 45.14 -17.57 1.02728 1555.7 45.17 -17.16 1.02870 1557.7 45.20 -16.70 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.02947 1545.0 1.03087 1547.7 46.36 -19.51 1.03227 1550.3 46.39 -18.72
1.0266 1.0314 1.0361 1.0409
0.2345 0.2780 0.3204 0.3618
0.6829 1.0083 1.0152 1.0219 1.0285 1.0352 1.0418 1.0481 1.0544
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7098 1.0087 1.0165 1.0239 1.0315 1.0387 1.0462 1.0530 1.0604
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7408 1.0100 1.0193
0.0000 0.0493 0.0974
1.00553 1546.6 78.16 -28.89 1.00806 1550.0 78.37 -28.42 1.01058 1553.5 78.52 -28.15 1.01303 1556.9 78.74 -27.77 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00498 1534.2 1.00768 1537.8 77.79 -29.25 1.01033 1541.3 78.09 -28.36 1.01293 1544.8 78.40 -27.51 1.01548 1548.1 78.69 -26.75 1.01798 1551.5 78.96 -26.17 1.02044 1554.8 79.24 -25.55 1.02286 1558.2 79.49 -25.03 1.02524 1561.4 79.72 -24.50 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01708 1539.6 1.01973 1543.2 78.44 -27.10 1.02230 1546.8 78.97 -25.82 1.02482 1550.3 79.42 -24.90 1.02726 1553.7 79.89 -23.96 1.02964 1557.1 80.34 -23.16 1.03197 1560.5 80.73 -22.46 1.03423 1563.9 81.17 -21.76 1.03642 1567.2 81.61 -21.00 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.02947 1545.0 1.03207 1548.6 79.15 -24.12 1.03458 1552.0 79.70 -23.00
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985
Glycylglycine + water 0.6535 (0.6579)[33]
9
1.0482 1.0565 1.0645 1.0720 0.6829 1.0139 1.0286 1.0432 1.0579 1.0721 1.0865 1.1008 1.1154 0.7098 1.0163 1.0322 1.0474 1.0631 1.0781 1.0930 1.1081 1.1227 0.7408 1.0162 1.0337
0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.03365 1552.8 46.42 -18.31 1.03503 1555.2 46.45 -17.55 1.03639 1557.4 46.49 -16.89 1.03774 1559.5 46.53 -16.20 1.03909 1561.6 46.56 -15.64 1.04042 1563.4 46.59 -14.95 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03986 1550.5 1.04124 1553.2 46.59 -18.25 1.04261 1555.7 46.63 -17.23 1.04397 1558.0 46.67 -16.25 1.04532 1560.1 46.70 -15.31 1.04665 1562.2 46.76 -14.46 1.04798 1564.0 46.80 -13.52 1.04930 1565.6 46.84 -12.65 1.05060 1567.2 46.87 -11.87
1.0284 1.0373 1.0462 1.0548 1.0640 1.0728
0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7756 0.0000 1.0111 0.0493 1.0228 0.0974 1.0338 0.1443 1.0451 0.1900 1.0569 0.2345 1.0679 0.2780 1.0796 0.3204 1.0909 0.3618 T = 318.15 K
1.03702 1555.4 80.28 -21.95 1.03938 1558.7 80.80 -20.99 1.04167 1561.9 81.33 -20.13 1.04390 1565.1 81.81 -19.40 1.04606 1568.3 82.29 -18.63 1.04815 1571.4 82.78 -17.94 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03986 1550.5 1.04239 1554.0 80.16 -21.13 1.04483 1557.3 80.71 -19.96 1.04719 1560.6 81.28 -18.98 1.04949 1563.8 81.79 -18.08 1.05169 1567.0 82.38 -17.28 1.05384 1570.1 82.85 -16.57 1.05591 1573.2 83.36 -15.83 1.05792 1576.2 83.84 -15.17
1.0514 1.0683 1.0854 1.1029 1.1202 1.1372 0.7756 1.0189 1.0379 1.0576 1.0767 1.0955 1.1146 1.1333 1.1526
0.0000
0.99024 (0.990141)[17]
Glycine + water 1536.7 (1536.14)[17]
0.0496
0.99182 (0.991747)[17]
1539.0 (1538.94)[17]
43.64 (44.42)[17]
-20.21
1.0067
0.0493
0.99297
1540.1
77.71
-28.33
1.0138
0.0985
0.99337 (0.993309)[17]
1541.2 (1541.13)[17]
43.82 (44.52)[17]
-19.88
1.0122
0.0974
0.99564
1543.4
77.94
-27.54
1.0238
0.1467 0.1942
0.99490 0.99640 (0.996317)[17]
1543.4 1545.6 (1545.80)[17]
43.98 44.13 (44.62)[17]
-19.62 -19.45
1.0176 1.0228
0.1443 0.1900
0.99828 1.00087
1546.6 1549.9
78.14 78.38
-26.97 -26.51
1.0334 1.0425
0.2410 0.2871 0.3325 0.3773
0.99788 1547.8 44.31 -19.21 0.99934 1550.0 44.47 -18.99 1.00078 1552.2 44.64 -18.75 1.00221 1554.5 44.77 -18.61 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid
1.0280 1.0332 1.0383 1.0432
0.2345 0.2780 0.3204 0.3618
1.00344 1553.1 78.55 -25.98 1.00596 1556.3 78.75 -25.67 1.00843 1559.6 78.97 -25.30 1.01089 1562.9 79.15 -25.07 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid
1.0513 1.0602 1.0690 1.0775
0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.00288 1541.3 1.00441 1543.6 44.26 -19.51 1.00593 1545.9 44.32 -19.08 1.00745 1548.1 44.37 -18.69 1.00894 1550.3 44.44 -18.38 1.01043 1552.4 44.48 -17.94 1.01190 1554.5 44.55 -17.64 1.01336 1556.6 44.60 -17.31 1.01481 1558.6 44.66 -16.98 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01453 1546.0 1.01602 1548.5 45.09 -18.61 1.01749 1550.7 45.13 -17.79 1.01895 1552.9 45.16 -17.16 1.02041 1555.0 45.19 -16.61 1.02185 1557.1 45.23 -16.15 1.02328 1559.0 45.26 -15.68 1.02471 1561.0 45.29 -15.31 1.02613 1562.8 45.32 -14.82 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.02720 1551.0 1.02860 1553.5 46.48 -17.81 1.02999 1555.9 46.50 -16.89 1.03137 1558.2 46.53 -16.26 1.03274 1560.3 46.56 -15.34 1.03410 1562.3 46.60 -14.74 1.03545 1564.2 46.64 -14.00 1.03679 1566.0 46.67 -13.32 1.03812 1567.6 46.71 -12.66 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03826 1555.9
0.6209 1.0090 1.0166 1.0239 1.0312 1.0382 1.0452 1.0521 1.0589
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.6209 1.0147 1.0307 1.0464 1.0624 1.0780 1.0932 1.1089 1.1238
0.6435 1.0090 1.0172 1.0253 1.0333 1.0412 1.0486 1.0563 1.0641
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.6707 1.0106 1.0208 1.0308 1.0406 1.0504 1.0600 1.0692 1.0787
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.6996
0.0000
1.00288 1541.3 1.00556 1544.8 78.18 -27.00 1.00819 1548.1 78.49 -25.96 1.01077 1551.4 78.80 -25.15 1.01330 1554.6 79.09 -24.41 1.01580 1557.8 79.34 -23.85 1.01824 1560.9 79.59 -23.28 1.02064 1564.0 79.86 -22.68 1.02300 1567.1 80.11 -22.13 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01453 1546.0 1.01717 1549.5 78.86 -24.99 1.01973 1552.9 79.36 -23.66 1.02222 1556.2 79.82 -22.64 1.02465 1559.4 80.30 -21.73 1.02701 1562.7 80.74 -20.89 1.02931 1565.8 81.19 -20.08 1.03155 1569.1 81.62 -19.30 1.03374 1572.1 82.03 -18.67 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.027120 1551.0 1.02978 1554.4 79.52 -22.03 1.03228 1557.6 80.09 -20.81 1.03469 1560.8 80.70 -19.75 1.03704 1563.9 81.22 -18.90 1.03931 1567.0 81.75 -18.07 1.04151 1570.0 82.26 -17.15 1.04365 1572.9 82.76 -16.37 1.04573 1575.7 83.21 -15.51 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03826 1555.9
0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000
Glycylglycine + water 0.5963
10
0.6435 1.0172 1.0341 1.0511 1.0679 1.0846 1.1013 1.1178 1.1336 0.6707 1.0169 1.0359 1.0553 1.0742 1.0937 1.1129 1.1319 1.1504 0.6996
0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
131 132 133 134 135 136 137 138 139 140 141
1.03964 1558.4 46.71 -16.57 1.0117 0.0493 1.04077 1559.2 80.58 -19.52 1.04101 1560.7 46.75 -15.32 1.0241 0.0974 1.04319 1562.5 81.17 -18.23 1.04236 1562.9 46.79 -14.40 1.0361 0.1443 1.04554 1565.6 81.71 -17.13 1.04370 1564.8 46.84 -13.37 1.0483 0.1900 1.04781 1568.6 82.24 -16.17 1.04503 1566.6 46.88 -12.40 1.0610 0.2345 1.05001 1571.6 82.74 -15.37 1.04635 1568.1 46.93 -11.36 1.0726 0.2780 1.05213 1574.5 83.26 -14.50 1.04766 1569.6 46.96 -10.50 1.0848 0.3204 1.05418 1577.4 83.78 -13.76 1.04896 1570.8 47.00 -9.59 1.0969 0.3618 1.05617 1580.1 84.27 -12.97 a Standard uncertainties in molality are with in u (m) = ± 2 * 10-3 / mol٠ kg-1 b Standard uncertainties in density are with in u ( ) = ± 1*10-2 / kg٠m-3 c Standard uncertainties in ultrasonic velocity are with in u (u) = ±0.1 m٠s-1 d Standard uncertainties in apparent molar volume are with in u ( ) = ± (0.1 and 0.02) * 10-5 / m3 ٠ mol-1 for low & high concentration of amino acids e Standard uncertainties in apparent molar isentropic compression are with in u ( ) = ± (0.3–0.04) * 10-6 / m3 ٠ mol-1 ٠ GPa-1 for low and high concentration of amino acids. f Standard uncertainties in pressure are with in u (P) = ± 0.01 MPa. g Standard uncertainties in temperature are with in u (T) = ± 0.01 K.
From table 2, it is observed that the values of are positive which increase with
142
increase in temperature for all tartaric acid concentrations. The positive values indicate the
143
presence of solute-solvent interactions, which increase with increase of peptide bond from
144
glycine to glycylglycine. This effect is because of dissociation of amino acids into amino
145
(NH3+) and carboxyl group (COO-) in solutions [19].
146
The values of as obtained from equation (3) and reported in table 3 are negative.
147
The negative values of decreases with increase in concentration and with temperature.
148
The negative values shows that water molecules around solute are less compressible than
149
water molecules in the bulk because it is assumed that amino acid and ions are not pressure
150
dependent and electrostricted water molecules are already compressed to its maximum extent
151
by the charge on the ions and the amino acids. Therefore, the compressibility of a solution is
152
mainly due to the effect of pressure on the bulk water molecules [20]. Further, these
153
negative values as mentioned above predicts that water molecules around solute are less
154
compressible than water molecules in the bulk which is attributed to strong solute-solvent
155
interactions between ions of amino acid/peptide and ions of tartaric acid.
156
The apparent molar volumes ( ) have been found to vary linearly with molal
157
concentration (m) for glycine and glycylglycine in (0.1942, 0.3773, 0.5504 and 0.7142)
158
mol kg-1 aqueous tartaric acid solutions in accordance with Masson’s equation [21-22] given
159
below:
160
= 0 + Sv* m
161 162
(5)
Here, 0is the apparent molar volume at infinite dilution of the respective amino acid and ∗ is the experimental slope and m is the molal concentration of solution.
11
1.0202 1.0407 1.0621 1.0830 1.1030 1.1246 1.1450 1.1652
163
Further, the apparent molar isentropic compression ( ) for glycine and
164
glycylglycine in (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 aqueous tartaric acid solutions
165
vary linearly with respective molal concentration according to following equation [23-25]:
166
= 0 + Sk* m
(6)
Here, 0is the apparent molar volume at infinite dilution of the respective amino acid
167 168
and ∗ is the experimental slope and m is the molal concentration of solution.
169 170 171 172 173
Table 3 Limiting apparent molar volumes ( 0), limiting apparent molar isentropic compression ( 0) and experimental slopes (Sv*), (Sk*) for glycine and glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol٠kg-1 aqueous tartaric acid solutions with corresponding standard deviations at different temperatures (aT = 298.15–318.15) K and at pressure bP = 0.1 MPa along with standard deviation and corresponding literature values. Tempera t-ure T /K
Limiting Apparent Molar volume 0 6 3 * 10 / m ٠ mol-1
Limiting Experimenta Apparent l Slopes Molar Sv* 6 3 Isentropic * 10 / m ٠ L1/2٠ mol-3/2 compression 0 6 10 / m3 ٠ * -1 mol GPa-1 Glycine + Water
Experimenta l Slopes Sk* 6 3 * 10 / m ٠ L1/2٠ mol-3/2٠ GPa-1
Limiting Apparent Molar volume 0 6 3 * 10 / m ٠ mol-1
298.15
42.20 (±0.01) (42.58)[33] (42.68)[17] (43.5)[71] (42.81)[46] (42.14)[38] (43.24)[72] (43.19)[3] (42.54)[4] (43.14)[5] (43.19)[2] (43.01)[6] (42.9)[7]
-26.67 (±0.02) (-26.12)[38] (-26.33)[72] (-27.00)[5] (-25.97)[2] (-26.6)[7]
303.15
42.47 (±0.01) (42.61)[33] (44.2)[71] (43.14)[46]
308.15
4.07 (±0.04)
4.24 (±0.09)
75.88 (±0.01) (75.89)[33] (76.22)[72] (76.22)[50] (76.26)[37] (76.23)[3] (76.23)[5] (76.36)[6] (76.27)[52] (76.40)[29]
-39.11 (±0.13) (-39.64)[72] (-39.64)[50] (-40.20)[5] (-40.9)[29]
4.17 (±0.05)
9.61 (±0.55)
-25.42 (±0.03)
4.10 (±0.03)
5.41 (±0.14)
76.25 (±0.01) (76.04)[33] (76.84)[29]
-36.71 (±0.09) (-37.7)[29]
4.26 (±0.06)
9.83 (±0.38)
42.83 (±0.01) (42.62)[33] (43.56)[17] (43.38)[46] (42.21)[38]
-23.79 (±0.04) (-23.98)[38]
3.89 (±0.03)
5.62 (±0.16)
76.62 (±0.01) (76.18)[33] (77.04)[50] (77.19)[37] (77.32)[29]
-34.32 (±0.11) (-35.57)[50] (-35.4)[29]
4.57 (±0.05)
10.81 (±0.45)
313.15
43.13 (±0.01) (42.64)[33] (44.38)[17] (43.66)[46]
-22.11 (±0.05)
3.76 (±0.04)
5.33 (±0.22)
77.06 (±0.01) (76.30)[33]
-31.43 (±0.12)
4.63 (±0.06)
10.51 (±0.52)
318.15
43.47 (±0.01) (42.44)[38]
-20.39 (±0.03) (-21.19)[38]
3.48 (±0.03)
4.84 (±0.14)
77.49 (±0.01)
-28.58 (±0.14)
4.60 (±0.05)
10.29 (±0.59)
12
Limiting Experimenta Apparent l Slopes Molar Sv* 6 3 Isentropic * 10 / m ٠ L1/2٠ mol-3/2 compression 0 6 10 / m3 ٠ mol* 1 ٠ GPa-1 Glycylglycine + Water
Experimenta l Slopes Sk* 6 3 * 10 / m ٠ L1/2٠ mol-3/2٠ GPa-1
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
174 175 176 177
Standard
Glycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid
Glycylglycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid
43.37 -25.44 1.01 4.46 (±0.01) (±0.03) (±0.02) (±0.14) 43.58 -24.30 1.06 5.71 (±0.01) (±0.02) (±0.03) (±0.10) 43.78 -22.77 1.10 6.51 (±0.01) (±0.02) (±0.01) (±0.09) 43.99 -21.26 1.18 7.04 (±0.01) (±0.03) (±0.02) (±0.14) 44.20 -19.85 1.21 7.67 (±0.01) (±0.03) (±0.02) (±0.12) Glycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid
-36.16 13.49 76.49 5.89 (±0.10) (±0.41) (±0.02) (±0.07) -34.22 14.93 76.83 6.02 (±0.11) (±0.46) (±0.01) (±0.06) -31.87 14.71 77.13 6.19 (±0.14) (±0.60) (±0.01) (±0.06) -29.79 15.06 77.49 6.22 (±0.12) (±0.50) (±0.01) (±0.05) -27.48 15.15 77.90 6.14 (±0.13) (±0.56) (±0.01) (±0.06) Glycylglycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid
44.44 -24.92 0.87 6.54 (±0.01) (±0.02) (±0.01) (±0.10) 44.60 -23.75 0.83 8.69 (±0.01) (±0.04) (±0.02) (±0.18) 44.77 -22.23 0.77 9.68 (±0.01) (±0.04) (±0.01) (±0.15) 44.90 -20.63 0.82 10.55 (±0.01) (±0.06) (±0.02) (±0.24) 45.06 -18.93 0.70 11.17 (±0.01) (±0.12) (±0.01) (±0.48) Glycine + 0.5504 mol٠kg-1 Aqueous Tartaric Acid
-33.78 15.96 76.90 9.52 (±0.08) (±0.35) (±0.02) (±0.08) -31.90 17.10 77.22 9.82 (±0.09) (±0.38) (±0.01) (±0.03) -29.81 17.36 77.60 9.94 (±0.10) (±0.41) (±0.01) (±0.06) -27.75 19.02 77.97 10.02 (±0.14) (±0.59) (±0.02) (±0.07) -25.67 19.94 78.36 10.14 (±0.15) (±0.64) (±0.01) (±0.02) Glycylglycine + 0.5504 mol٠kg-1 Aqueous Tartaric Acid
45.95 -24.30 0.77 8.05 (±0.01) (±0.04) (±0.01) (±0.18) 46.07 -23.20 0.72 10.77 (±0.01) (±0.03) (±0.01) (±0.14) 46.20 -21.63 0.71 11.66 (±0.01) (±0.05) (±0.02) (±0.23) 46.32 -20.20 0.71 13.82 (±0.01) (±0.06) (±0.02) (±0.26) 46.44 -18.49 0.70 15.59 (±0.01) (±0.06) (±0.03) (±0.25) Glycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid
-30.75 16.40 77.53 10.82 (±0.10) (±0.42) (±0.02) (±0.09) -28.66 17.17 77.87 11.25 (±0.13) (±0.54) (±0.01) (±0.05) -26.86 18.65 78.19 11.48 (±0.10) (±0.45) (±0.02) (±0.09) -24.89 19.68 78.58 11.61 (±0.12) (±0.53) (±0.01) (±0.05) -22.85 20.41 78.96 11.85 (±0.08) (±0.39) (±0.02) (±0.08) Glycylglycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid
46.10 (±0.01) 46.25 (±0.01) 46.40 (±0.01) 46.54 (±0.01) 46.66 (±0.01)
-23.48 (±0.03) -22.34 (±0.06) -20.78 (±0.09) -19.15 (±0.04) -17.50 (±0.06)
0.90 (±0.02) 0.91 (±0.02) 0.89 (±0.02) 0.89 (±0.01) 0.90 (±0.01)
11.82 (±0.12) 16.18 (±0.23) 17.93 (±0.37) 19.48 (±0.17) 21.14 (±0.25)
-27.75 16.00 78.56 10.97 (±0.13) (±0.54) (±0.01) (±0.06) -25.78 17.38 78.89 11.35 (±0.10) (±0.44) (±0.01) (±0.05) -23.94 18.59 79.21 11.61 (±0.11) (±0.49) (±0.02) (±0.08) -21.81 18.81 79.57 11.83 (±0.13) (±0.54) (±0.01) (±0.06) -20.26 20.54 80.01 11.75 (±0.14) (±0.59) (±0.01) (±0.05) errors for Limiting apparent molar volumes ( 0), Limitng apparent molar isentropic compression ( 0) and experimental slopes
(Sv*), (Sk*) are given in parenthesis. a
Standard uncertainties in temperatures are u(T) = ± 0.01 K.
b
Standard uncertainties in pressures are u(P) = ± 0.01 MPa.
178
From table 3, it is observed that 0 values of glycine and glycylglycine in water and
179
in aqueous tartaric acid solutions are positive and increases with increase in concentration of
180
tartaric acid and temperature. The 0 values are indicative of solute-solvent interactions and
181
it is clear here that positive values of 0, suggesting strong solute-solvent interactions [26].
182
We have studied, when an overlap of co-spheres of two ionic species there is increase in
183
volume and if two hydrophobic-hydrophobic groups and ion-hydrophobic groups overlap,
13
184
there is decrease in volume [27,28]. And here, the observed positive values of 0 are
185
because of ion-hydrophilic interactions which dominate over hydrophobic-hydrophobic and
186
ion-hydrophobic interactions. We have also seen, in table 3 that mostly with the increase in
187
molar mass and hydrophobicity of alkyl side chain, i.e. from glycine to glycylglycine, the
188
0 values increase [29]. And with the increase in concentration, the increases in 0 values
189
are because of increase in solvation of glycine and glycylglycine with ions of tartaric acid.
190
From table 3, the negative values of
0
(loss of compressibility of medium) indicate
191
that the water molecules surrounding the amino acid/peptide would present greater resistance
192
to compression than water molecules present in bulk. With increase in temperature the
193
values become less negative which means that electrostriction reduces and some water
194
molecules are released to bulk. The strong interactions due to hydration of ions produced
195
from the dissociation of tartaric acid induce the dehydration of amino acid/peptide and
196
increase the water molecule in the bulk. Because of formation of ion pairs between the
197
zwitter ions of amino acid/peptide and tartaric acid ions, the electrostriction interaction
198
between amino acid/peptide and water molecules are suppressed. In addition to this, the
199
attractive interaction between the ions of tartaric acid and water molecules induces the
200
dehydration of amino acid/peptide and therefore, at high tartaric acid concentrations, the
201
water molecules around the amino acid/peptide are more compressible than those at lower
202
tartaric acid concentrations [30]. The positive values of Sv* and Sk* respectively are indicative
203
of solute-solute interactions in the system and here, less but positive values of Sv* accounts
204
for weaker solute-solute interactions. Moreover, an irregular trend of Sv* and Sk* values
205
suggest that solute-solute interactions are influenced by number of effects [31].
0
206 207
3.2 Temperature effects
208
The temperature dependence of 0 can be expressed by the following relations [32,33]:
209
0 = a + bT + cT2
(7)
210
Where T is the temperature expressed in Kelvin and a, b and c are constants. On
211
solving this equation for different values of 0 at different temperature, we get values of a,
212
b and c constants. The limiting apparent molar expansion i.e. ! 0 were obtained by
213
differentiating above equation with respect to temperature:
214
! 0 = (δ 0/δΤ)P = b + 2cT
14
(8)
215
And the double derivative of partial molar volumes is shown as
216
(δ2ϕv0/δΤ2)P = 2c
(9)
217
From table 5, (! 0) decreases with increase in temperature, which implies caging
218
effect is absent. The sign of (! 0) values is found to provide important information regarding
219
the size of solute and its hydrophobicity. Here, in present both systems, (! 0) values are
220
positive but having lower values, there by showing weak solute-solute interactions and also
221
indicate that the solute is hydrophilic.
222 223 224 225 226 227 228
The criteria proposed by Hepler (1969) [34], called hydrophobicity criteria, make use of the double derivative of partial molar volume with respect to temperature to explain the hydrophobicity of the solute. From table, in present both systems i.e. glycine and glycylglycine system, (δ2ϕv0/δΤ2)P< 0 as constant c is negative (table 4), indicating thereby the solute is hydrophilic. Qualitative information on hydration of solutes [35-38] could be obtained from the thermal expansion of aqueous solution by using the general thermodynamic expression:
229 230
(δCP0/δP)T = - T (δ2ϕv0/δΤ2)P
(10)
Here, in present studied system, we have
231
(δCP0/δP)T> 0 i.e. (δ2φvο/δΤ2)P< 0, for both glycine and glycylglycine systems which
232
indicates that glycine and glycylglycine behaves as structure-breaker in water as well as in
233
different compositions of tartaric acid at different temperatures.
234 235 236
Table 4 Values of constant c for glycine and glycylglycine in water and in aqueous tartaric acid solutions at different temperatures (aT = 298.15– 318.15) K and at pressure bP = 0.1 MPa. molality (tartaric acid) / mol٠kg-1
237 238 239 240 241
a
Value of c Glycine
Glycylglycine
0.0000
-0.000199
-0.000200
0.1942
-0.000067
-0.000133
0.3773
-0.000133
-0.000199
0.5504
-0.000200
-0.000200
0.7142
-0.000199
-0.000200
Standard uncertainties in temperatures are u(T) = ± 0.01 K.
b
Standard uncertainties in pressures are u(P) = ± 0.01 MPa.
Table 5 Values of limiting apparent molar expansiona(! 0),Falkenhagen’s Coefficient (A), Jones-Dole Coefficient (B) for glycine and glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol٠kg-1 aqueous tartaric acid solutions at different temperatures (bT = 298.15–318.15)
15
242
K and at pressure cP = 0.1 MPa along with standard deviation and corresponding literature values. Temperature T /K
Limiting apparent molar expansion, # 0∗ 106 / m3 ٠ mol-1٠ K-1
298.15
0.0650 (0.00790)[33]
303.15
0.0630 (0.00390)[33]
0.0074 (±0.0003)
0.0810 (±0.0006)
0.0910 (0.094)[29] (0.0289)[33]
0.0246 (±0.0010)
0.1274 (±0.0021)
308.15
0.0610 (-0.00002)[33]
0.0073 (±0.0006)
0.0883 (±0.0012)
0.0890 (0.079)[29] (0.0269)[33]
0.0233 (±0.0009)
0.1456 (±0.0019)
313.15
0.0590 (-0.0041)[33]
0.0071 (±0.0003)
0.0962 (±0.0008)
0.0870 (0.0249)[33]
0.0236 (±0.0011)
0.1586 (±0.0023)
318.15
0.0570
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15
Falkenhagen’s Coefficient, A * 103/2 / m3/2 ٠ mol-1/2 Glycine + Water 0.0079 (±0.0003)
Jones-Dole Coefficient, B * 103 / m3 ٠ mol-1
0.0722 (±0.0006)
0.0065 0.1036 (±0.0003) (±0.0008) Glycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid 0.0423 0.0050 0.1046 (±0.0005) (±0.0011) 0.0417 0.0061 0.1131 (±0.0004) (±0.0009) 0.0410 0.0053 0.1239 (±0.0005) (±0.0012) 0.0403 0.0072 0.1318 (±0.0006) (±0.0013) 0.0397 0.0086 0.1416 (±0.0004) (±0.0009) Glycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid 0.0327 0.0066 0.1174 (±0.0002) (±0.0005) 0.0313 0.0061 0.1284 (±0.0006) (±0.0014) 0.0300 0.0059 0.1384 (±0.0004) (±0.0008) 0.0287 0.0049 0.1514 (±0.0004) (±0.0009) 0.0273 0.0038 0.1630 (±0.0003) (±0.0007) Glycine + 0.5504 mol٠kg-1 Aqueous Tartaric Acid 0.0290 0.0059 0.1345 (±0.0004) (±0.0009) 0.0270 0.0059 0.1480 (±0.0006) (±0.0012) 0.0250 0.0053 0.1620 (±0.0006) (±0.0013) 0.0230 0.0038 0.1793 (±0.0004) (±0.0010) 0.0210 0.0031 0.1971 (±0.0003) (±0.0007) Glycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid 0.0330 0.0049 0.1672 (±0.0006) (±0.0013) 0.0310 0.0013 0.1944 (±0.0004) (±0.0009) 0.0290 -0.0057 0.2315 (±0.0007) (±0.0015) 0.0270 -0.0065 0.2498 (±0.0012) (±0.0025)
16
Limiting Falkenhagen’s apparent molar Coefficient, expansion, A * 103/2 / m3/2 ٠ # 0∗ 106 / m3٠ mol-1/2 mol-1 ٠ K-1 Glycylglycine + Water 0.0930 0.0270 (0.099)[29] (±0.0008) (0.0309)[33]
0.0850
Jones-Dole Coefficient, B * 103 / m3 ٠ mol-1
0.1061 (±0.0018)
0.0217 0.1761 (±0.0013) (±0.0027) Glycylglycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid 0.0687 0.0001 0.2377 (±0.0011) (±0.0024) 0.0673 -0.0033 0.2657 (±0.0012) (±0.0025) 0.0660 -0.0081 0.3008 (±0.0012) (±0.0026) 0.0647 -0.0143 0.3394 (±0.0017) (±0.0037) 0.0633 -0.0165 0.3677 (±0.0012) (±0.0027) Glycylglycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid 0.0790 -0.0002 0.2648 (±0.0015) (±0.0032) 0.0770 -0.0019 0.2903 (±0.0018) (±0.0040) 0.0750 -0.0032 0.3156 (±0.0021) (±0.0045) 0.0730 -0.0045 0.3442 (±0.0016) (±0.0034) 0.0710 -0.0097 0.3830 (±0.0019) (±0.0042) Glycylglycine in 0.5504 mol٠kg-1 Aqueous Tartaric Acid 0.0830 -0.0068 0.3035 (±0.0021) (±0.0045) 0.0810 -0.0095 0.3349 (±0.0016) (±0.0036) 0.0790 -0.0160 0.3758 (±0.0025) (±0.0054) 0.0770 -0.0193 0.4078 (±0.0021) (±0.0046) 0.0750 -0.0279 0.4594 (±0.0020) (±0.0044) Glycylglycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid 0.0670 -0.0082 0.3297 (±0.0021) (±0.0046) 0.0650 -0.0097 0.3628 (±0.0016) (±0.0036) 0.0630 -0.0114 0.4006 (±0.0022) (±0.0048) 0.0610 -0.0163 0.4443 (±0.0024) (±0.0053)
318.15
0.0250
-0.0077 0.2681 0.0590 -0.0200 (±0.0008) (±0.0018) (±0.0029) Standard errors for Falkenhagen’s Coefficient (A), Jones-Dole Coefficient (B) are given in parenthesis. a Standard uncertainties in limiting apparent molar volumes expansion, u(! ) = ± (0.0001-0.0004) ∗ 106 / m3٠ mol-1٠ K-1. b Standard uncertainties in temperatures are u(T) = ± 0.01 K. c Standard uncertainties in pressures are u(P) = ± 0.01 MPa.
0.4861 (±0.0063)
243 Water
(a)
0.5504 Tartaric Acid 0.7142 Tartaric Acid
0.090
φE0 * 106/ m3. mol-1. K-1
φ E0 * 106/ m3. mol-1. K-1
0.07
0.06
0.05
0.04
0.03
Water 0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
0.1942 Tartaric Acid 0.3773 Tartaric Acid 0.5504 Tartaric Acid 0.7142 Tartaric Acid
0.085
0.080
0.075
0.070
0.065
0.060 0.02 295
300
305
310
315
320
295
T/ K
300
305
310
315
320
T/ K
244 245
Figure 1 Plots of limiting apparent molar expansions, (! 0), versus temperature (T) for (a) glycine and (b) glycylglycine in water and in
246
0.1942, 0.3773, 0.5504 and 0.7142 mol kg-1 aqueous tartaric acid solutions
247 248
3.3 Viscosity studies
249
Here, we have analysed viscosity data in terms of semi empirical Jones-Dole equation [39]
250
ηrelative = η/η0 = 1+ A√m+Bm
251
ηr = 1+ A√m +Bm
252
ηspecific = (ηrel– 1) = A√m +Bm
253
(ηspecific/√m) = (ηr -1)/ √m = (η/η0 -1)/√m = A+B√m
(11)
(12)
254
Where η and η0 are the viscosities of solution and solvents, m is the molal
255
concentration, A and B are Falkenhagen [40,41] and Jones-Dole coefficients [42],
256
respectively. We know, coefficient A accounts for the solute-solute interaction and B is a
257
measure of structural modifications induced by the solute –solvent interactions [43]. The
258
values of A and B have been obtained as the intercept and slope from linear regression of [(ηr
259
-1)/√m] Vs √m curves.
17
Water Water
(a) 0.28
0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
0.1942 Tartaric Acid
0.50
0.3773 Tartaric Acid
0.5504 Tartaric Acid 0.7142 Tartaric Acid
0.5504 Tartaric Acid
0.26
0.45
0.7142 Tartaric Acid
0.24
0.40
B * 103 / m3 mol-1
0.20
.
0.18
.
B * 103 / m3 mol-1
0.22
0.16 0.14 0.12 0.10
260 261 262
0.30 0.25 0.20 0.15
0.08 0.06 295
0.35
300
305
310
315
0.10 295
320
300
305
T/K
310
315
320
T/ K
Figure 2 Plots of Jones-Dole coefficient (B) versus temperature (T) for (a) glycine and (b) glycylglycine in water and in 0.1942, 0.3773, 0.5504 and 0.7142 mol kg-1 aqueous tartaric acid solutions
263
The values of A-coefficients are smaller in magnitude or even negative, showing weak
264
solute-solute interactions. Here, it has been noticed from table 5, that there is decrease in
265
values of A with temperature. The decrease of A with rising temperature is probably due to
266
the greater thermal agitation and reduction of attractive forces between the ions [44]. The B-
267
coefficient is a measure of order or disorder introduced by the ions into the solvent. It is
268
observed from table 5 that there are larger and positive values of B-coefficients in both
269
systems i.e. in glycine and glycylglycine systems as compared to A-coefficient support the
270
behaviour of $ 0 and Sv, respectively, both indicating stronger solute-solvent interaction as
271
compared to solute-solute interactions [12]. Also, in present studied systems, the positive B-
272
coefficient values systematically increases with increase in the hydrophobicity of the amino
273
acid side chain i.e. glycine to glycylglycine. Therefore, the hydrophobic side chain enhances
274
the solute-water interactions even though they affect the structure of solvent-water locally via
275
hydrophobic hydration [45]. The temperature derivatives of B-coefficient (dB/dT) have also
276
been calculated. The sign of dB/dT values provide important information regarding structure
277
making or structure breaking ability of the solute in solvent system [46,47]. In present systems
278
i.e. in glycine and glycylglycine systems, dB/dT is positive, which indicate solute is having
279
structure breaking ability in solvent system, thus supporting our earlier conclusion obtained
280
from Hepler’s constant.
281
3.4 Transfer parameters
282
The transfer parameters, $ 0 and 0 for glycine and glycylglycine in water and in
283
aqueous solution of tartaric acid have been calculated (∆tr $ 0 and (∆tr 0) by following
284
relation [48]:
285
(∆tr % 0)= ∆tr % 0(solution) - % 0 (water) 18
(13)
286
The calculated results are given in table 6 and illustrated in figure 3 and 4. The values of
287
(∆tr $ 0) are by definition free from solute-solute interactions and therefore, provide
288
information regarding solute-solvent interactions. The sign of the (∆tr $ 0) is often
289
interpreted in terms of strength of the solute-co-solute interactions [49]. Here, we have
290
studied partial of volumes is having positive values i.e. (∆tr $ 0) > 0, which indicate ionic-
291
hydrophilic and hydrophilic-hydrophilic interactions are predominant i.e. strong solute-co-
292
solute interactions are present in both systems i.e. in glycine and glycylglycine systems. We
293
also studied that the type of interactions in the ternary systems depend both on the nature of
294
side chain as well as type of the additive [50,51]. As can be seen in Figure 3, the values of
295
(∆tr $ 0) for both glycine and glycylglycine increases gradually with the molality of tartaric
296
acid, showing that high ionic strength dehydrates amino acid/peptide, and almost decreases
297
with temperature. According to the co-sphere overlap model regarding the values of (∆tr $ 0),
298
there is negligible contribution from solute–solute interactions and hence, they provide
299
information regarding solute–solvent interactions [52-57]. The types of interaction that occur
300
between amino acids and tartaric acid molecules can be classified as:
301
(i)
and the zwitterionic centers of the amino acid/peptide.
302 303
(ii)
(iii)
308
Ion-hydrophobic group interactions between the -COOH group of the tartaric acid and the non-polar group of the amino acid/peptide.
306 307
Hydrophilic–hydrophilic group interactions between the -COOH group of the tartaric acid and the -NH2 group of the amino acid/peptide.
304 305
Ion-hydrophilic group interactions between the-COOH group of the tartaric acid
(iv)
Hydrophobic–hydrophobic group interactions between the non-polar group of the tartaric acid and the non-polar group of the amino acid/peptide.
309
Ion-hydrophobic interactions and hydrophobic–hydrophobic interactions contribute
310
negatively based on co-sphere overlap model [58,59] whereas ion-hydrophilic and
311
hydrophilic–hydrophilic interactions contribute positively to the (∆tr $ 0) values. Here, we
312
can easily conclude that ion-hydrophilic and hydrophilic–hydrophilic interactions are much
313
stronger than ion– hydrophobic and hydrophobic–hydrophobic interactions. So, in both
314
systems, there are strong interactions between the (NH3+, COO-) charged ends of amino
315
acid/peptide and ions of the co-solute (solvent), which leads to effective overlap of amino
316
acid/peptide and co-solute ions. The observed higher values of (∆tr $ 0) of glycine than
317
glycylglycine in different molal concentrations of aqueous tartaric acid are due to release of 19
318
more number of water molecules from glycine due to domination of ionic-hydrophilic and
319
hydrophilic-hydrophilic interactions. Further, the observed decrease in (∆tr $ 0) values for
320
glycine/glycylglycine in different molal concentrations of aqueous tartaric acid with an
321
increase in temperature may be attributed to the corresponding decrease in the number of
322
electrostricted water molecules [26].
323
Table 6 shows that (∆tr 0) values are positive and increases with increase in concentration
324
of tartaric acid in all the cases. The increasing (∆tr 0) values in both system i.e. glycine and
325
glycylglycine suggest that there is disruption of the hydration sphere of charged end centres,
326
which implies dominance of ion-hydrophilic interactions [60,61]. The decrease in (∆tr 0)
327
values for glycine/glycylglycine in different molal concentrations of tartaric acid with an
328
increase in temperature indicate that the release of water molecules from the secondary
329
solvation layer of glycine and glycylglycine zwitter ions into the bulk water at higher
330
temperature [26]. The variations of (∆tr $ 0) are consistent with variation in (∆tr 0). 0.1942 Tartaric Acid 0.3773 Tartaric Acid
(a)
0.5504 Tartaric Acid 0.7142 Tartaric Acid
4.0
0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
3.5
0.5504 Tartaric Acid 0.7142 Tartaric Acid
3.0
2.4 2.2 1
2.5
. mol-
2.0 1.8
3
2.0
6
∆ trφ v * 10 / m
1.5
0
.
∆ trφ v0 * 106 / m3 mol-1
2.6
1.0
1.6 1.4 1.2 1.0 0.8 0.6
0.5 295
0.4
300
305
310
315
320
295
300
305
T/K
331
310
315
320
T/K 298.15K 303.15K 308.15K 313.15K 318.15K
(c) 4.0
298.15K 303.15K 308.15K 313.15K 318.15K
(d) 3.0
3.5
1
. mol∆ trφ v * 10 / m
0
1.0
0
1.5 1.0
0.2
333 334
1.5
6
2.0
0.5
332
2.0
3
2.5
6
∆ trφ v * 10 / m
3
. mol-
1
2.5
3.0
0.3
0.4
0.5
0.6
0.7
0.5
0.0
0.8
0.2
mTartaric Acid / mol kg-1
.
0.3
0.4
0.5
0.6
0.7
0.8
mTartaric Acid / mol kg-1
.
Figure 3 Partial volumes of transfer at different molality’s of aqueous tartaric acid solutions and temperatures in (a), (c) glycine and (b), (d) glycylglycine.
20
0.1942 Tartaric Acid 0.3773 Tartaric Acid 0.5504 Tartaric Acid
(a)
0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
0.7142 Tartaric Acid
0.5504 Tartaric Acid
12
0.7142 Tartaric Acid
3.0
∆ trφ k0 * 106 / m3 mol-1
2.0
8
.
.
∆ trφ k0 * 106 / m3 mol-1
10
2.5
1.5
1.0
6
4
2
0.5 295
300
305
310
315
0 295
320
300
305
335 3.5
1
298.15K 303.15K 308.15K 313.15K 318.15K
10
8
.
. mol6
3
∆ trφ k * 10 / m
320
12
∆ trφ k0 * 106 / m3 mol-1
3.0
2.0
315
(d)
298.15K 303.15K 308.15K 313.15K 318.15K
(c)
2.5
310
T/K
T/K
0
1.5
1.0
6
4
2
0.5
0 0.2
0.3
0.5
0.6
0.7
0.2
0.8
0.3
0.4
0.5
0.6
0.7
0.8
mTartaric Acid / mol . kg-1
mTartaric Acid / mol . kg-1
336 337 338
0.4
Figure 4 Partial molar isentropic compressibility of transfer at different molality’s of aqueous tartaric acid solutions and temperatures in (a), (c) glycine and (b), (d) glycylglycine.
339 340 341 342
Table 6 Partial volumes of transfer (∆tr $ 0) and Partial molar isentropic compressibility of transfer (∆tr 0) for glycine and glycylglycine from water to different molality’s of tartaric acid solutions at different temperatures (T = 298.15–318.15) K and at pressure P = 0.1 MPa. From volume molality (tartaric acid)
0.1942
From compressibility 0.3773
0.5504
0.7142
0.1942
0.3773
0.5504
0.7142
/ mol٠kg-1 T (K)
Glycine
Glycine
298.15
1.17
2.24
3.75
3.90
1.23
1.75
2.37
3.19
303.15
1.11
2.13
3.60
3.78
1.12
1.67
2.22
3.08
308.15
0.95
1.94
3.37
3.57
1.02
1.56
2.16
3.01
313.15
0.86
1.77
3.19
3.41
0.85
1.48
1.91
2.96
318.15
0.73
1.59
2.97
3.19
0.54
1.46
1.90
2.89
T (K)
Glycylglycine
Glycylglycine
298.15
0.61
1.02
1.65
2.68
2.95
5.33
8.36
11.36
303.15
0.58
0.97
1.62
2.64
2.49
4.81
8.05
10.93
308.15
0.51
0.98
1.57
2.59
2.45
4.51
7.46
10.38
313.15
0.43
0.91
1.52
2.51
1.64
3.68
6.54
9.62
318.15
0.41
0.87
1.47
2.51
1.10
2.91
5.73
8.32
343 344 345 21
346
3.5 Hydration Number:
347
The hydration numbers, (nh) explicitly reveal the hydration degree of a solute in
348
water; which usually increases with the size of the amino acid/peptide in water, or solution.
349
The partial molar volume of amino acid can be investigated by a simple model using
350
following equation [62]:
351
0 (amino acid/peptide) = 0 (int) + 0 (elect)
(14)
352
where 0 (elect) is the electrostriction partial molar volume due to the hydration of
353
the amino acid/peptide (glycine/glycylglycine) and can be calculated from experimentally
354
measured values of the 0 (amino acid/peptide) (glycine / glycylglycine) and 0 (int) is the
355
intrinsic partial molar volume of the amino acid/peptide (glycine / glycylglycine) and has
356
been estimated by the help of following equation [62]:
357
0 (int) = (0.7/0.6) 0 (cryst.)
358
and
359
0 (int) = (0.7/0.634) 0 (cryst.)
(15)
(16)
360
where 0 (cryst.) (= mol wt/dcryst) is the crystal molar volume, 0.7 is the packing
361
density for the molecules in organic crystals and 0.634 is the packing density for random
362
packing spheres. The values of 0 (int) for the glycine and glycylglycine have been
363
calculated from equations (15) and (16) using dcryst values for glycine and glycylglycine
364
(1.598 [63] and 1.534 g cm-3 [37]) taken from the references.
365
The
number
of
water
molecules
hydrated
to
the
amino
acid/peptide
366
(glycine/glycylglycine) due to electrostriction causes decrease in volume can be related to the
367
hydration number by following expression [64-66]
368
nH = 0 (elect) / (,& 0 - ,' 0)
369
where ,& 0 is the molar
(17) volume of electrostricted water and ,' 0 is the molar
370
volume of the bulk water. If one mol of water molecules moves from the bulk water to the
371
solvation sphere of the amino acid/peptide, the volume is decreased by (,& 0 - ,' 0). The
372
(,& 0 - ,' 0)values, ie. -3.3 * 10-6 m3 mol-1 at T = 298.15 K, and -4.0 * 10-6 m3 mol-1 at T =
373
308.15 K, have been taken from the literature [62,67,68]. The values of hydration number
374
calculated by using both the two methods from these equations (15) and (16) have been 22
375
shown in table 7. Hydration number (nH) of amino acid and its peptide i.e. glycine and
376
glycylglycine decreases with increasing tartaric acid concentrations are smaller than that of
377
water, indicating that ion-hydrophilic group interactions between the -COOH group of the
378
tartaric acid and the zwitterionic centers of the amino acid/peptide (glycine/glycylglycine)
379
becomes stronger which further weaken the electrostriction of the charged centres with water
380
molecules and strengthen the interactions between ions and the charged centers of the amino
381
acid/peptide (glycine/glycylglycine) [37,38]. The 0 values increases with increasing
382
temperature from (298.15 to 318.15) K as shown in table 3. An increase in temperature
383
reduces the electrostriction which leads to increase in values of 0. The reduction in the
384
electrostriction in present ternary system with increasing temperature is confirmed by the
385
decreased hydration number (nH) values with temperature.
386 387 388
Table 7 Hydration number, nH of glycine and glycylglycine in aqueous tartaric acid solutions for the different molal concentrations at T = (298.15 and 308.15) K. m (tartaric acid) / mol٠kg-1
nH From volume Using (Eq. (15))
Using (Eq. (16))
From compressibility Using (Eq. (20)) At 298.15 K
Using (Eq. (15))
Using (Eq. (16))
From compressibility Using (Eq. (20))
From volume
Glycine 0.0000
2.93
3.82
3.29
Glycylglycine 5.82
7.46
4.83
0.1942
2.58
3.47
3.14
5.64
7.27
4.46
0.3773
2.25
3.14
3.08
5.51
7.15
4.17
0.5504
1.79
2.68
3.00
5.32
6.96
3.80
0.7142
1.75
2.64
2.90
5.01
6.64
3.43
At 308.15 K Glycine 0.0000
2.74
3.63
2.94
Glycylglycine 5.60
7.23
4.24
0.1942
2.45
3.34
2.81
5.44
7.08
3.93
0.3773
2.15
3.04
2.74
5.30
6.93
3.68
0.5504
1.72
2.61
2.67
5.12
6.76
3.32
0.7142
1.66
2.55
2.57
4.81
6.45
2.96
389 390
In addition to this, the number of water molecules hydrated to amino acid/peptide
391
(glycine/glycylglycine) can be calculated by using following equation [62,69]
392
nH = -
0
(elect) / ,' 0 Kb0
(18)
23
where, Kb0 is the isothermal compressibility of the bulk water. The estimated value of
393 394
,' 0 Kb0 is 8.1 * 10-5 m3 mol-1 GPa-1. The electrostriction partial molar compressibility
395
(elect) can be calculated experimentally measured values of
396
0
(elect) =
0
(amino acid/peptide) -
As the value of
397
0
0
(int)
many organic solutes in water. So, we can assume
399
the reduced form of equation (19) becomes
400
(elect) =
0
(amino acid) from (19)
(int) is less than 5 * 10-6 m3 mol-1 GPa-1 for ionic crystals and
398
0
0
0
(amino acid/peptide)
0
(int) value to be zero [62]. Therefore,
(20)
401
The values of hydration number calculated by using these equations (20) have been
402
shown in table 7. The hydration number (nH) values decreases with increase in concentration
403
of tartaric acid and are smaller than that of water, this indicates the presence of strong ion-
404
hydrophilic interaction between –COOH group of tartaric acid and zwitter ions of amino
405
acid/peptide (glycine/glycylglycine) with increase in concentration of tartaric acid. With
406
increase in the concentration of tartaric acid , water molecules present in the solution are
407
replaced by tartaric acid molecules due to dehydration effect on glycine/glycylglycine
408
[50,70]. The hydration number (nH) values also decreases with increase in temperature of
409
solution, this results decrease in electrostriction with increase in temperature. These
410
variations are consistent with the variation in values of 0, as 0 values increases with
411
increasing temperature from (298.15 to 318.15) K as shown in table 3. An increase in
412
temperature reduces the electrostriction and hence increases 0. Further, the values of
413
hydration number (nH) shown in table 7, based on volumetric and compressibility models are
414
in good agreement.
415 416
3. Conclusion
417
In present work, the apparent molar volume ($ ), partial molar volume ($ 0), limiting
418
apparent molar expansibility (! 0), transfer volume (∆tr $ 0), Falkenhagen’s coefficient (A),
419
Jones-Dole coefficient (B) and apparent molar isentropic compressibility ( ), partial molar
420
isentropic compressibility ( 0), transfer parameter (∆tr 0) have been studied for glycine
421
and glycylglycine in water and in aqueous tartaric acid between (298.15 and 318.15) K.
422
The ($ ), ($ 0) and (∆tr $ 0) have been obtained which are positive and increases with 24
423
increase in temperature as well as with increase in concentration of tartaric acid. This
424
indicates that there are solute-solvent interactions. It was obtained from Hepler’s criterion
425
and dB/dT values that glycine and glycylglycine act as structure breaker in water and in
426
aqueous tartaric acid solution at different temperatures. The negative values of ( ) and
427
( 0) support our volumetric data. The glycylglycine being dipeptide of glycine has higher
428
values of (! 0). The (! 0) gives information relating to the size of the solute and its
429
hydrophobicity and also tells that there is absence of caging in present system. With the help
430
of transfer parameters, it has been concluded that ion-hydrophilic and hydrophilic-
431
hydrophilic interactions are prominent between the ions of tartaric acid and the zwitterions of
432
glycine and glycylglycine respectively. The hydration number calculated from volumetric
433
and compressibility data shows the presence of interaction between the ions of tartaric acid
434
and glycine/glycylglycine.
435
Acknowledgements
436
The authors are grateful to Himachal Pradesh University, Shimla for providing lab
437
facilities and Abhishek Thakur is thankful to Ministry of Human Resource Development for
438
their support.
439 440 441 442
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HIGHLIGHTS:
• • • •
Molecular interactions between glycine and glycylglycine in water and in aqueous tartaric acid solutons are studied. The Volumetric, Compressibility, Acoustic and Viscometric methods are used to interpret results. Solute-Solvent interactions predominate over solute-solute interactions glycine and glycylglycine behaves as a structure breaker in water and in aqueous tartaric acid solutions.
Conflict of Interest
•
The author is not having any conflict of interest with this publication
With regards,
Prof. Dr. Shashi Kant Sharma Department of Chemistry Himachal Pradesh University, Shimla, India-171005 Email: [email protected] Tel: +919418382396
S0167-7322(19)33218-0
DOI:
https://doi.org/10.1016/j.molliq.2019.111941
Reference:
MOLLIQ 111941
To appear in:
Journal of Molecular Liquids
Received Date: 7 June 2019 Revised Date:
18 September 2019
Accepted Date: 14 October 2019
Please cite this article as: S.K. Sharma, A. Thakur, D. Kumar, V. Nathan, Thermophysical properties of glycine and glycylglycine in aqueous tartaric acid at different temperatures: Volumetric, acoustic and viscometric studies, Journal of Molecular Liquids (2019), doi: https://doi.org/10.1016/ j.molliq.2019.111941. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.
1
Thermophysical properties of glycine and glycylglycine in aqueous tartaric acid at
2
different temperatures: volumetric, acoustic and viscometric studies
3
Shashi Kant Sharma*, Abhishek Thakur, Dinesh Kumar, Vikas Nathan
4
Department of Chemistry, Himachal Pradesh University, Shimla 171005, India
5
Email id: [email protected]
6
Abstract
7
Thermophysical properties like density, ultrasonic velocity and viscosity of glycine,
8
glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 aqueous tartaric
9
acid solutions as a function of concentration at different temperatures ranging between
10
(298.15 and 318.15) K have been determined. These data have been utilized to calculate
11
apparent molar volume ( ), apparent molar isentropic compressibility ( ), and viscosity
12
B-coefficient values of the studied solutions. The partial molar volumes ( 0), partial molar
13
isentropic compressibility ( 0) and experimental slopes (Sv* and Sk*) derived from the
14
Mason equations have been interpreted in terms of solute-solute and solute -solvent
15
interactions. The viscosity coefficients A and B have been determined from the Jones-Dole
16
equation. From the volumetric and viscometric data, hydration number (nH) has been
17
calculated and further, the structural effects of glycine, glycylglycine in tartaric acid solution
18
has been discussed. The results were explained in terms of structure making and structure
19
breaking properties.
20
Keywords: apparent molar volume; apparent molar isentropic compressibility; partial molar
21
volumes; partial molar isentropic compressibility; structural effects.
22
1. Introduction
23
Life began with advanced and continuous series of chemically synthesized reactions
24
which raised the organization of inanimate matter to successively higher levels. Atoms
25
first accumulated to simple compounds, then these metamorphosed into more complex
26
ones and finally, the most complex of them ultimately became organized as living cells.
27
Water is present in these living cells, and is responsible in maintaining electrolytic
28
balance of the body and further small portions in between living cells are also deposited
29
in conjunction with protein and carbohydrate. So, protein having large molecular size
30
plays an important role in the exchange of fluids between the circulating blood and the 1
31
interstitial fluid [1]. So, having knowledge, how these proteins interact with water and
32
their properties vary with temperature and different composition of solvent and solute;
33
became a topic of interest for many researchers. Because of the complex nature of
34
protein, it becomes tedious and quite challenging to get viable information for proteins
35
with water and to study their thermophysical properties [2] so, it’s been worth to use
36
amino acids and peptides, as these are model compounds for understanding the solvation
37
of proteins and by this, we can easily render our discussion on proteins by studying
38
aqueous amino acid/peptide system. In fact, extensive work have been done related to
39
volumetric, acoustic behaviour of aminoacids/peptides in aqueous solutions and in
40
different solvents [3-7], but their study in organic acids are scant. Amino acids, the
41
biologically important compounds is of immense importance as their behaviour in
42
aqueous and mixed aqueous solutions in different temperature range determines how the
43
proteins tends to behave in living cells and this leads to open field of curious research [8-
44
11]. The solution structure of amino acids/peptides is because of the intermolecular
45
interactions and the understanding of these intermolecular interactions have a decisive
46
role for determining the outcome in biological systems and even these are in close contact
47
with the thermodynamic properties of liquids, solids and gases. A change in temperature
48
or concentration significantly affects the charge distribution in molecules, which also
49
influence the different types of molecular interactions (H-bonding, ion-dipole, dipole-
50
dipole etc.) [12].
51
The amino acid used is glycine, a natural osmolyte that can act as osmoprotectants
52
and are of immensely important in the renal medulla. Glycine is used for treating
53
schizophrenia, strokes and other uses in cancer therapy, memory enhancement. Studies
54
shows that glycine may help people with type 2 diabetes by controlling their blood sugar,
55
and got the ability to protect the liver and kidney from damage caused by chemicals such
56
as alcohols. Research are going on the subject that glycine acts in a way to promote the
57
healing of overworked or damaged muscles, soothe an upset stomach, stress reliever,
58
boost the immune system and increase human growth hormone. Glycylglycine, is
59
dipeptide of glycine and because of its low toxicity, act as a buffer for biological systems
60
at different pH [13]. The solvent chosen was tartaric acid, a white crystalline dicarboxylic
61
organic acid found in plants, particularly in tamarinds and grapes. Tartaric acid is used to
62
generate carbon dioxide through interaction with sodium bicarbonate following oral
63
administration. Carbon dioxide, thus produced extends the stomach and provides a 2
64
negative medium during double contrast radiography.
It is also used for protein
65
precipitation and curiously hardly ever studied and a better knowledge of its interactions
66
with different amino acid/peptide is certainly an interesting point for further studies on
67
protein purification and precipitation. [14]. In present study, we will report the densities
68
(ρ), speeds of sound (u) and viscosities (η) of glycine and its peptide (glycylglycine)
69
(0.05 to 0.40) mol kg-1 in pure water to (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 of
70
tartaric acid at (298.15 and 318.15) K. These data have been utilized to calculate apparent
71
molar volume ( ), apparent molar isentropic compression ( ), limiting apparent molar
72
volumes ( 0), limiting apparent molar isentropic compression ( 0) and experimental
73
slopes (Sv* and Sk*) derived from the Mason equations, A and Jone-Dole coefficient B,
74
hydration number (nH). All these parameters give a deep insight into the solute-solvent
75
interactions and structure making/breaking behaviour of glycine and glycylglycine in
76
aqueous solutions of tartaric acid at temperatures (298.15 and 318.15) K.
77
Experimental
78
2.1 Materials
79
The amino acids (glycine and glycylglycine) and solvent (tartaric acid) were used after
80
drying over anhydrous calcium chloride for more than 24 hours and then, weighed using
81
electronic balance SHIMADZU A X 200 (model no D432613208, Japan) a digital balance
82
having a precision of ±0.1 mg. Triply distilled and deionised water with specific conductance
83
< 10-6 ohm-1 cm-1 was used.
84
Table 1 Specification of chemical samples. Chemical name
Molar mass
Provenance
(g mol-1)
Initial Mass fraction
Purification
Final
purity
method
fraction purity
Tartaric Acid
150.087
Merck Specialities Pvt. Ltd. India
>0.99
None
>0.99
Glycine
75.07
Merck Specialities Pvt. Ltd., India
>0.99
None
>0.99
Glycylglycine
132.12
Merck Specialities Pvt. Ltd., India
>0.99
None
>0.99
Mass
85 86
2.2 Density measurements
87
The density (ρ) and speeds of sound (u) were measured with the help of apparatus
88
DSA (i.e. Density and Sound Analyzer) 5000 supplied by Anton Paar GmbH, Garz, Austria. 3
89
DSA 5000 is the first oscillating U-tube density and velocity of sound meter, which measures
90
to the highest accuracy in wide viscosity and temperature ranges. The studies were carried
91
out at atmospheric pressure P = 0.1 MPa at five different temperatures T = (298.15, 303.15,
92
308.15, 313.15 and 318.15) K with an accuracy of ± 0.01 K. The calibration of DSA (i.e.
93
Density and Sound Analyzer) 5000 was internal realized before in hand, by measuring the
94
density and speed of sound through dried air and triple distilled and deionized water. For
95
water, the measured values of density and speeds of sound are given in table 2 along with
96
corresponding literature values. The average reproducibility in density and speed of sound
97
data from experimental data was ± 0.01 kg m-3and ± 0.1 m s-1 respectively.
98 99
2.3 Viscosity measurements
100
The viscosity measurements were carried out with a modified capillary type
101
viscometer, which is thoroughly cleaned with chromic acid and the subsequently wash
102
with water and acetone followed with drying by vacuum pump. While performing the
103
measurements, the solution in the viscometer is allowed to attain the temperature of the
104
water thermostat for about 20-25 minutes. Stop watch was used for noting the time of
105
flow. The viscosity measurements at different temperatures was determined by using the
106
following equation [15]
107
ƞ⁄ƞ = ⁄
108
where ƞ, , and ƞ , , are the viscosity, density and time of flow of the solutions and
109
water respectively. The viscometer is calibrated with triply distilled and deionized water, the
110
values of relative viscosity (ƞ⁄ƞ ) so obtained is compared with literature values as shown in
111
table 2.
112 113
(1)
3. Results and discussion 3.1 Partial Molar Volumes & Partial Molar Compressibility’s
114
Values of the experimental density (ρ), viscosity (ƞ) and speed of sound (u) of
115
glycine, glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 aqueous
116
solutions of tartaric acid at T = (298.15, 303.15, 308.15, 313.15 and 318.15) K are reported in
117
table 2.The apparent molar volume ( ), apparent molar isentropic compression ( ) were
4
118
calculated from the experimental densities, and speeds of sound by the following standard
119
equations [16, 17]:
120
= ⁄ − 1000( − )⁄
(2)
121
= ( ⁄ ) − (1000( − )⁄ )
(3)
122
With the assumption that the absorption of the acoustic wave is negligible, the
123
isentropic compressibility, () can be calculated using the Newton-Laplace’s equation [18]
124
= 1⁄(u2 )
(4)
125
where m is the molality (mol kg-1) of amino acid/peptide in water and in different
126
molal concentration of aqueous tartaric acid solution, M is the molar mass of the solute
127
(kg mol-1) and , , , and are the densities (kg m-3) and isentropic compressibility’s
128
(Pa-1) of solvent and solution, respectively. The resulting values of , and the different
129
molal concentrations (m) of amino acids in water and in different concentrations of tartaric
130
acid at various temperatures are given in table 2.
5
Table 2 Values of density ( ), speed of sound (u), apparent molar volume ( ), apparent molar isentropic compression ( ), relative viscosity (η/η0) at different molal concentration (m) of glycine, glycylglycine in aqueous solutions of tartaric acid at different temperatures (T = 298.15-318.15) K and at pressure fP = 0.1 MPa with corresponding literature values. ma /
b * 10-3 / kg٠m-3
uc
d * 106 / -1
/ m٠s
m
3
-1
mol
e * 10 3
6
m mol-1
mol٠kg1
ma
Relative /
Viscosity
/
η/η0
mol٠kg-
b * 10-3 / kg٠m-3
uc
d * 106 / -1
/ m٠s
m
3
-1
mol
Relative
m3 mol-1
Viscosity
* 10
6
GPa-1
1
-
e
η/η0
GPa 1
g
Glycine + water 1497.5 (1497.6)[33] (1495.85)[17] (1496.98)[50]
T = 298.15 K Glycylglycine + water
0.0000
0.99708 (0.99702)[33] (0.997047)[17] (0.997045)[71] (0.997080)[50]
0.0496
0.99871 (0.99832)[33] (0.99874)[17] (0.998625)[46]
1500.0 (1500.28)[33] (1500.06)[17] (1500.32)[46]
42.41 (42.65)[17] (43.09)[46]
-26.44
1.0054 (1.0055)[33]
0.0493
0.99987 (0.99926)[33] (0.99982)[37] (0.99984)[6] (0.999656)[29]
1501.5 (1499.28)[33] (1500.53)[29]
76.09 (76.11)[33] (76.37)[37] (76.41)[6] (76.56)[29]
-38.92 (40.02)[29]
1.0114 (1.0065)[33] (1.017)[37]
0.0985
1.00031 (1.00025)[33] (1.000392)[17] (1.000403)[71] (1.000206)[46]
1502.6 (1503.01)[33] (1502.3)[17] (1502.73)[46]
42.59 42.75[33] (42.71)[17] (43.83)[71] (43.15)[46]
-26.25
1.0096 (1.0139)[33]
0.0974
1.00262 (1.00256)[33] (1.002044)[50] (1.002592)[37] (1.002740)[29]
1505.4 (1503.98)[33] (1504.20)[50] (1505.15)[29]
76.29 (76.43)[33] (76.40)[50] (76.48)[37] (76.68)[29]
-38.06 (38.86)[50] (39.3)[29]
1.0188 (1.0162)33] (1.031)[37]
0.1467
1.00189 (1.001899)[71] (1.001777)[46]
1505.2 (1505.14)[46]
42.81 (43.59)[71]
-26.04
1.0136
0.1443
1.00533 (1.00520)[6] (1.005168)[29]
1509.3 (1508.78)[29]
76.50 (76.55)[6] (76.78)[29]
-37.51 (38.6)[29]
1.0254
0.1942
1.00345 (1.003567)[17] (1.003401)[71] (1.003341)[46]
1507.8 (1507.23)[17] (1507.55)[46]
42.97 (42.82)[17] (43.65)[71] (43.28)[46]
-25.89
1.0174
0.1900
1.00497 1510.4 43.18 -25.66 1.00647 1513.0 43.37 -25.49 1.00795 1515.6 43.56 -25.24 1.00941 1518.3 43.73 -25.05 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.01020 1503.8 1.01177 1506.5 43.42 -25.22 1.01334 1509.2 43.47 -24.99 1.01488 1512.0 43.52 -24.84 1.01642 1514.7 43.57 -24.57 1.01795 1517.5 43.61 -24.32 1.01947 1520.3 43.65 -24.12 1.02097 1523.1 43.70 -23.94 1.02246 1526.0 43.76 -23.82 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02266 1511.6 1.02417 1514.4 44.48 -24.61 1.02567 1517.3 44.53 -24.28 1.02716 1520.1 44.57 -23.96 1.02863 1523.0 44.61 -23.62 1.03010 1525.8 44.65 -23.35 1.03155 1528.7 44.69 -23.02 1.03299 1531.6 44.73 -22.80
1.0211 1.0248 1.0286 1.0323
0.2345 0.2780 0.3204 0.3618
0.9322 1.0064 1.0119 1.0172 1.0223 1.0276 1.0327 1.0379 1.0428
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.9765 1.0073 1.0137 1.0197 1.0256 1.0316 1.0374 1.0428
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204
1.00801 1513.3 76.65 -37.22 (1.007894)[37] (1513.58)[50] (76.80)[37] ((1.00838)[50] (1512.95)[29] (76.67)[50] 37.93)[50] (1.00784)[6] (76.65)[6] ((1.007933)[29] (76.96)[29] 37.8)[29] 1.01065 1517.2 76.84 -36.86 1.01325 1521.1 77.03 -36.42 1.01581 1525.1 77.21 -36.08 1.01833 1529.0 77.40 -35.72 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.01020 1503.8 1.01295 1507.8 76.80 -35.69 1.01564 1511.7 77.07 -34.81 1.01829 1515.6 77.32 -34.11 1.02089 1519.4 77.59 -33.47 1.02345 1523.2 77.85 -32.92 1.02595 1527.0 78.14 -32.41 1.02842 1530.8 78.36 -31.91 1.03083 1534.5 78.65 -31.37 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02266 1511.6 1.02536 1515.6 77.37 -33.15 1.02799 1519.6 77.84 -32.22 1.03056 1523.5 78.27 -31.35 1.03305 1527.4 78.71 -30.67 1.03551 1531.4 79.08 -30.01 1.03787 1535.3 79.54 -29.33 1.04018 1539.2 79.95 -28.67
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325
0.8903 (0.8926)[33]
6
1.0317 (1.061)[37]
1.0377 1.0437 1.0494 1.0551 0.9322 1.0120 1.0230 1.0341 1.0449 1.0556 1.0659 1.0765 1.0865 0.9765 1.0133 1.0257 1.0378 1.0500 1.0614 1.0732 1.0849
0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.03443 1534.4 44.77 -22.43 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03526 1518.9 1.03668 1521.9 45.99 -23.84 1.03809 1524.9 46.03 -23.53 1.03949 1527.9 46.06 -23.22 1.04087 1530.9 46.10 -22.74 1.04225 1533.9 46.13 -22.34 1.04361 1536.8 46.17 -21.97 1.04497 1539.8 46.20 -21.60 1.04631 1542.7 46.24 -21.29 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04606 1526.2 1.04746 1529.3 46.15 -22.87 1.04885 1532.3 46.18 -22.32 1.05022 1535.3 46.23 -21.80 1.05158 1538.2 46.27 -21.20 1.05294 1541.0 46.32 -20.61 1.05428 1543.8 46.35 -20.09 1.05561 1546.6 46.40 -19.51 1.05693 1549.3 46.44 -19.06
1.0485
0.3618
1.0379 1.0082 1.0154 1.0224 1.0295 1.0364 1.0430 1.0499 1.0566
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
1.0878 0.0000 1.0095 0.0493 1.0180 0.0974 1.0265 0.1443 1.0344 0.1900 1.0424 0.2345 1.0506 0.2780 1.0586 0.3204 1.0663 0.3618 T = 303.15 K
1.04244 1543.2 80.36 -28.12 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03526 1518.9 1.03791 1522.8 78.08 -30.07 1.04048 1526.7 78.57 -29.21 1.04297 1530.5 79.08 -28.29 1.04539 1534.3 79.61 -27.42 1.04776 1538.2 80.03 -26.87 1.05004 1541.9 80.51 -26.20 1.05225 1545.7 81.00 -25.59 1.05441 1549.3 81.47 -24.86 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04606 1526.2 1.04863 1530.1 79.12 -27.17 1.05113 1534.0 79.62 -26.22 1.05354 1537.8 80.15 -25.30 1.05589 1541.5 80.64 -24.48 1.05816 1545.3 81.12 -23.96 1.06037 1549.0 81.58 -23.27 1.06250 1552.7 82.09 -22.66 1.06457 1556.4 82.54 -22.11
1.0966 1.0379 1.0140 1.0271 1.0408 1.0542 1.0672 1.0808 1.0940 1.1064 1.0878 1.0150 1.0293 1.0439 1.0583 1.0730 1.0872 1.1013 1.1154
0.0000
0.99568 (0.99566)[33]
Glycine + water 1509.4 (1509.87)[33]
0.0496
0.99730 (0.99696)[33] (0.997207)[46]
1512.0 (1515.36)[33] (1512.56)[46]
42.68 (42.68)[33] (43.41)[46]
-25.20
1.0057 (1.0060)[33]
0.0493
0.99846 (0.99789)[33] (0.998240)[29]
1513.3 (1512.6)[33] (1512.80)[29]
76.46 (76.26)[33] (76.98)[29]
-36.41 (37.1)[29]
1.0120 (1.0069)[33]
0.0985
0.99889 (0.99888)[33] (0.998773)[46]
1514.5 (1515.3)[33] (1514.92)[46]
42.87 (42.78)[33] (43.47)[46]
-24.90
1.0103 (1.0149)[33]
0.0974
1.00119 (1.00118)[33] (1.001301)[29]
1517.1 (1517.69)[33] (1517.23)[29]
76.64 (76.58)[33] (77.11)[29]
-35.71 (36.3)[29]
1.0201 (1.0172)[33]
0.1467
1.00045 (1.000329)[46]
1517.0 (1517.26)[46]
43.08 (43.54)[46]
-24.58
1.0147
0.1443
1.00388 (1.003709)[29]
1521.0 (1520.73)[29]
76.88 (77.23)[29]
1.0274
0.1942
1.00199 (1.001878)[46]
1519.5 (1519.61)[46]
43.27 (43.60)[46]
-24.31
1.0188
0.1900
1.00655 (1.006453)[29]
1524.8 (1524.82)[29]
77.04 (77.41)[29]
-35.19 (35.6)[29] -34.76 (-35)[29]
1.00351 1522.0 43.45 -24.10 1.00499 1524.6 43.66 -23.86 1.00646 1527.1 43.84 -23.62 1.00791 1529.6 44.02 -23.42 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00866 1515.4 1.01023 1518.0 43.63 -23.98 1.01178 1520.6 43.68 -23.75 1.01331 1523.2 43.74 -23.51 1.01484 1525.7 43.80 -23.22 1.01635 1528.2 43.85 -22.91 1.01786 1530.7 43.88 -22.64 1.01935 1533.2 43.93 -22.43 1.02084 1535.6 43.98 -22.14 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02100 1522.3 1.02250 1525.1 44.64 -23.28 1.02400 1527.8 44.67 -22.91 1.02548 1530.4 44.72 -22.46 1.02694 1533.1 44.76 -22.14 1.02840 1535.6 44.79 -21.65 1.02985 1538.0 44.84 -21.25 1.03129 1540.4 44.87 -20.77 1.03272 1542.9 44.91 -20.52 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03358 1529.1 1.03499 1532.0 46.11 -22.71
1.0231 1.0271 1.0311 1.0353
0.2345 0.2780 0.3204 0.3618
1.0416 1.0483 1.0549 1.0614
0.8367 1.0070 1.0131 1.0188 1.0244 1.0303 1.0357 1.0413 1.0465
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.8735 1.0078 1.0146 1.0209 1.0273 1.0339 1.0400 1.0464 1.0524
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.9206 1.0089
0.0000 0.0493
1.00916 1528.6 77.26 -34.35 1.01174 1532.3 77.43 -33.92 1.01429 1536.2 77.61 -33.65 1.01680 1539.9 77.77 -33.23 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00866 1515.4 1.01139 1519.3 77.13 -33.72 1.01407 1523.1 77.44 -32.66 1.01670 1526.8 77.70 -31.97 1.01929 1530.5 77.95 -31.33 1.02182 1534.2 78.24 -30.66 1.02431 1537.8 78.51 -30.01 1.02675 1541.4 78.78 -29.50 1.02916 1545.0 79.01 -28.93 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.02100 1522.3 1.02369 1526.2 77.70 -31.23 1.02630 1530.1 78.17 -30.22 1.02884 1533.9 78.64 -29.33 1.03133 1537.7 79.08 -28.54 1.03374 1541.5 79.52 -27.80 1.03610 1545.3 79.94 -27.14 1.03840 1549.1 80.35 -26.48 1.04063 1552.8 80.79 -25.80 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03358 1529.1 1.03621 1532.9 78.41 -28.08
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496
Glycylglycine + water 0.7975 (0.8007)[33]
7
1.0346
0.8367 1.0126 1.0248 1.0370 1.0484 1.0606 1.0722 1.0835 1.0947 0.8735 1.0143 1.0277 1.0407 1.0537 1.0666 1.0795 1.0923 1.1049 0.9206 1.0147
0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.03639 1534.9 46.15 -22.10 1.03779 1537.7 46.18 -21.62 1.03917 1540.4 46.21 -21.14 1.04054 1543.0 46.24 -20.54 1.04190 1545.5 46.28 -20.12 1.04325 1548.0 46.31 -19.60 1.04460 1550.4 46.35 -19.18 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04416 1535.7 1.04555 1538.7 46.30 -21.61 1.04694 1541.5 46.34 -20.76 1.04831 1544.2 46.38 -19.91 1.04967 1546.8 46.41 -19.18 1.05101 1549.2 46.47 -18.37 1.05234 1551.4 46.52 -17.62 1.05367 1553.7 46.56 -17.04 1.05499 1555.7 46.59 -16.28 Glycine + water 1520.1 (1520.6)[33] (1519.14)[17]
1.0168 1.0245 1.0318 1.0398 1.0469 1.0544 1.0619
0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.9696 0.0000 1.0099 0.0493 1.0197 0.0974 1.0289 0.1443 1.0381 0.1900 1.0475 0.2345 1.0564 0.2780 1.0654 0.3204 1.0743 0.3618 T = 308.15 K
1.03875 1536.7 78.97 -26.91 1.04123 1540.4 79.50 -26.06 1.04363 1544.0 80.02 -25.27 1.04596 1547.7 80.50 -24.57 1.04822 1551.2 81.00 -23.85 1.05041 1554.8 81.49 -23.15 1.05255 1558.4 81.92 -22.63 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04416 1535.7 1.04672 1539.5 79.43 -25.14 1.04919 1543.2 80.01 -24.00 1.05159 1546.9 80.54 -23.22 1.05391 1550.4 81.05 -22.36 1.05617 1554.0 81.55 -21.64 1.05835 1557.5 82.04 -20.91 1.06046 1561.0 82.55 -20.25 1.06252 1564.4 82.98 -19.62
1.0297 1.0444 1.0590 1.0735 1.0877 1.1020 1.1167 0.9696 1.0161 1.0323 1.0483 1.0643 1.0797 1.0957 1.1110 1.1264
Glycylglycine + water
0.0000
0.99407 (0.99405)[33] (0.994031)[17] (0.994030)[71]
0.0496
0.99567 (0.995676)[17] (0.99534)[33] (0.995577)[46]
1522.6 (1522.89)[17] (1523.32)[33] (1523.08)[46]
43.03 (43.61)[17] (42.65)[33] (43.65)[41]
-23.57
1.0061 (1.0065)[33]
0.0493
0.99683 (0.99627)[33] (0.996748)[37]
1523.9 (1523.51)[33]
76.83 (76.42)[33] (77.30)[37]
-33.99
1.0125 (1.0075)[33] (1.016)[37]
0.0985
0.99725 (0.99727)[33] (0.997281)[17] (0.997108)[71] (0.997132)[46]
1525.0 (1525.9)[33] (1524.73)[17] (1525.37)[46]
43.20 (42.79)[33] (43.67)[17] (44.31)[71] (43.72)[46]
-23.23
1.0110 (1.0164)[33]
0.0974
0.99954 (0.99955)[33] (0.999518)[37] (0.998949)[50]
1527.6 (1528.14)[33] (1526.64)[50]
77.09 (76.76)[33] (77.48)[37] (77.21)[50]
-33.20
1.0214 (1.0187)[33] (1.030)[37]
0.1467
0.99880 (0.998680)[71] (0.998677)[46]
1527.4 (1527.65)[46]
43.39 (44.17)[71] (43.78)[46]
-22.95
1.0156
0.1443
1.00222
1531.2
77.28
-32.69
1.0296
0.1942
1.00032 (1.000371)[17] (1.000296)[71] (1.000216)[46]
1529.9 (1529.67)[17] (1529.95)[46]
43.59 (43.74)[17] (44.20)[71] (43.84)[46]
-22.66
1.0202
0.1900
1.00485 (1.004768)[37] (1.005201)[50]
1534.9 (1535.58)[50]
77.49 (77.80)[37] (77.49)[50]
-32.17
1.0375 (1.057)[37]
1.00183 1532.3 43.76 -22.40 1.00331 1534.7 43.93 -22.15 1.00476 1537.1 44.12 -21.90 1.00619 1539.6 44.29 -21.75 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00691 1525.6 1.00847 1528.1 43.83 -22.45 1.01001 1530.6 43.89 -22.11 1.01154 1533.0 43.94 -21.85 1.01306 1535.5 44.00 -21.50 1.01456 1537.8 44.04 -21.16 1.01605 1540.2 44.10 -20.88 1.01754 1542.5 44.14 -20.63 1.01901 1544.8 44.19 -20.31 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01914 1531.7 1.02063 1534.4 44.81 -21.77 1.02212 1537.0 44.84 -21.30 1.02359 1539.5 44.88 -20.83 1.02506 1541.9 44.92 -20.34 1.02651 1544.3 44.95 -19.87 1.02795 1546.6 44.99 -19.38 1.02939 1548.9 45.02 -19.02 1.03081 1551.1 45.06 -18.65
1.0247 1.0292 1.0336 1.0381
0.2345 0.2780 0.3204 0.3618
0.7533 1.0074 1.0139 1.0200 1.0263 1.0323 1.0383 1.0445 1.0502
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7864 1.0083 1.0154 1.0225 1.0294 1.0361 1.0429 1.0495 1.0561
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
0.7195 (0.7234)[28]
8
1.00745 1538.5 77.68 -31.73 1.01000 1542.1 77.90 -31.21 1.01253 1545.7 78.08 -30.88 1.01500 1549.4 78.29 -30.57 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00691 1525.6 1.00963 1529.3 77.43 -31.42 1.01230 1532.9 77.71 -30.41 1.01491 1536.5 78.04 -29.52 1.01748 1540.1 78.30 -29.02 1.02000 1543.6 78.56 -28.31 1.02247 1547.1 78.86 -27.73 1.02490 1550.5 79.12 -27.17 1.02730 1554.0 79.35 -26.74 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01914 1531.7 1.02181 1535.5 78.10 -29.11 1.02440 1539.2 78.57 -28.12 1.02693 1542.9 79.03 -27.23 1.02939 1546.6 79.47 -26.41 1.03178 1550.2 79.95 -25.61 1.03412 1553.8 80.39 -24.92 1.03641 1557.4 80.77 -24.27 1.03862 1561.1 81.19 -23.69
1.0452 1.0525 1.0600 1.0672 0.7533 1.0133 1.0267 1.0400 1.0533 1.0664 1.0792 1.0920 1.1047 0.7864 1.0153 1.0295 1.0437 1.0580 1.0721 1.0858 1.0993 1.1135
0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03091 1537.8 1.03232 1540.6 46.24 -21.06 1.03372 1543.3 46.27 -20.40 1.03511 1545.9 46.30 -19.89 1.03648 1548.5 46.33 -19.39 1.03785 1551.0 46.37 -18.91 1.03921 1553.3 46.41 -18.32 1.04056 1555.6 46.44 -17.78 1.04190 1557.7 46.47 -17.13 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04209 1543.8 1.04348 1546.6 46.45 -20.07 1.04485 1549.3 46.49 -18.98 1.04622 1551.8 46.53 -18.07 1.04757 1554.1 46.57 -17.21 1.04891 1556.3 46.62 -16.36 1.05024 1558.4 46.66 -15.60 1.05156 1560.4 46.70 -14.84 1.05287 1562.2 46.74 -14.15
0.8235 1.0093 1.0183 1.0262 1.0345 1.0427 1.0510 1.0588 1.0668
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.8645 0.0000 1.0104 0.0493 1.0208 0.0974 1.0319 0.1443 1.0422 0.1900 1.0529 0.2345 1.0632 0.2780 1.0738 0.3204 1.0842 0.3618 T = 313.15 K
Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.03091 1537.8 1.03352 1541.5 78.77 -26.11 1.03606 1545.1 79.26 -25.03 1.03851 1548.6 79.86 -24.13 1.04089 1552.1 80.40 -23.14 1.04321 1555.5 80.89 -22.37 1.04545 1558.9 81.39 -21.63 1.04763 1562.3 81.86 -20.92 1.04975 1565.6 82.32 -20.26 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.04209 1543.8 1.04463 1547.4 79.79 -23.22 1.04709 1551.0 80.36 -22.07 1.04947 1554.4 80.89 -21.15 1.05179 1557.9 81.39 -20.34 1.05402 1561.2 81.91 -19.57 1.05616 1564.5 82.48 -18.69 1.05827 1567.7 82.93 -17.89 1.06030 1571.1 83.41 -17.42
0.8235 1.0154 1.0319 1.0476 1.0635 1.0795 1.0958 1.1118 1.1277 0.8645 1.0177 1.0354 1.0530 1.0700 1.0882 1.1054 1.1220 1.1392
0.0000
0.99225 (0.99223)[33]
Glycine + water 1529.2 (1529.86)[33]
0.0496
0.99384 (0.99353)[33] (0.993753)[46]
1531.5 (1532.15)[33] (1532.06)[46]
43.31 (42.72)[33] (43.90)[46]
-21.91
1.0064 (1.0070)[33]
0.0493
0.99499 (0.99445)[33]
1532.8 (1532.56)[33]
77.30 (76.53)[33]
-31.15
1.0133 (1.0070)[33]
0.0985
0.99540 (0.99545)[33] (0.995297)[46]
1533.9 (1535.17)[33] (1534.30)[46]
43.49 (42.82)[33] (43.96)[46]
-21.62
1.0117 (1.0174)[33]
0.0974
0.99769 (0.99773)[33]
1536.2 (1537.08)[33]
77.50 (76.86)[33]
-30.37
1.0227 (1.0197)[33]
0.1467
0.99695 (0.996832)[46]
1536.2 (1536.51)[46]
43.67 (44.02)[46]
-21.32
1.0167
0.1443
1.00035
1539.7
77.70
-29.78
1.0316
0.1942
0.99846 (0.998361)[46]
1538.5 (1538.73)[46]
43.87 (44.08)[46]
-20.98
1.0217
0.1900
1.00296
1543.2
77.94
-29.30
1.0401
0.99995 1540.8 44.04 -20.77 1.00142 1543.1 44.21 -20.53 1.00287 1545.5 44.36 -20.37 1.00429 1547.8 44.54 -20.18 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00498 1534.2 1.00653 1536.6 44.06 -20.92 1.00806 1539.0 44.12 -20.58 1.00958 1541.4 44.16 -20.23 1.01109 1543.6 44.22 -19.86 1.01258 1545.9 44.28 -19.57 1.01406 1548.1 44.34 -19.16 1.01553 1550.4 44.39 -18.98 1.01699 1552.5 44.44 -18.61 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01708 1539.6 1.01857 1542.1 44.94 -20.19 1.02005 1544.6 44.97 -19.58 1.02151 1546.9 45.02 -19.02 1.02297 1549.3 45.06 -18.60 1.02442 1551.4 45.09 -17.97 1.02585 1553.6 45.14 -17.57 1.02728 1555.7 45.17 -17.16 1.02870 1557.7 45.20 -16.70 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.02947 1545.0 1.03087 1547.7 46.36 -19.51 1.03227 1550.3 46.39 -18.72
1.0266 1.0314 1.0361 1.0409
0.2345 0.2780 0.3204 0.3618
0.6829 1.0083 1.0152 1.0219 1.0285 1.0352 1.0418 1.0481 1.0544
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7098 1.0087 1.0165 1.0239 1.0315 1.0387 1.0462 1.0530 1.0604
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7408 1.0100 1.0193
0.0000 0.0493 0.0974
1.00553 1546.6 78.16 -28.89 1.00806 1550.0 78.37 -28.42 1.01058 1553.5 78.52 -28.15 1.01303 1556.9 78.74 -27.77 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid 1.00498 1534.2 1.00768 1537.8 77.79 -29.25 1.01033 1541.3 78.09 -28.36 1.01293 1544.8 78.40 -27.51 1.01548 1548.1 78.69 -26.75 1.01798 1551.5 78.96 -26.17 1.02044 1554.8 79.24 -25.55 1.02286 1558.2 79.49 -25.03 1.02524 1561.4 79.72 -24.50 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01708 1539.6 1.01973 1543.2 78.44 -27.10 1.02230 1546.8 78.97 -25.82 1.02482 1550.3 79.42 -24.90 1.02726 1553.7 79.89 -23.96 1.02964 1557.1 80.34 -23.16 1.03197 1560.5 80.73 -22.46 1.03423 1563.9 81.17 -21.76 1.03642 1567.2 81.61 -21.00 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.02947 1545.0 1.03207 1548.6 79.15 -24.12 1.03458 1552.0 79.70 -23.00
0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985
Glycylglycine + water 0.6535 (0.6579)[33]
9
1.0482 1.0565 1.0645 1.0720 0.6829 1.0139 1.0286 1.0432 1.0579 1.0721 1.0865 1.1008 1.1154 0.7098 1.0163 1.0322 1.0474 1.0631 1.0781 1.0930 1.1081 1.1227 0.7408 1.0162 1.0337
0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.03365 1552.8 46.42 -18.31 1.03503 1555.2 46.45 -17.55 1.03639 1557.4 46.49 -16.89 1.03774 1559.5 46.53 -16.20 1.03909 1561.6 46.56 -15.64 1.04042 1563.4 46.59 -14.95 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03986 1550.5 1.04124 1553.2 46.59 -18.25 1.04261 1555.7 46.63 -17.23 1.04397 1558.0 46.67 -16.25 1.04532 1560.1 46.70 -15.31 1.04665 1562.2 46.76 -14.46 1.04798 1564.0 46.80 -13.52 1.04930 1565.6 46.84 -12.65 1.05060 1567.2 46.87 -11.87
1.0284 1.0373 1.0462 1.0548 1.0640 1.0728
0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.7756 0.0000 1.0111 0.0493 1.0228 0.0974 1.0338 0.1443 1.0451 0.1900 1.0569 0.2345 1.0679 0.2780 1.0796 0.3204 1.0909 0.3618 T = 318.15 K
1.03702 1555.4 80.28 -21.95 1.03938 1558.7 80.80 -20.99 1.04167 1561.9 81.33 -20.13 1.04390 1565.1 81.81 -19.40 1.04606 1568.3 82.29 -18.63 1.04815 1571.4 82.78 -17.94 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03986 1550.5 1.04239 1554.0 80.16 -21.13 1.04483 1557.3 80.71 -19.96 1.04719 1560.6 81.28 -18.98 1.04949 1563.8 81.79 -18.08 1.05169 1567.0 82.38 -17.28 1.05384 1570.1 82.85 -16.57 1.05591 1573.2 83.36 -15.83 1.05792 1576.2 83.84 -15.17
1.0514 1.0683 1.0854 1.1029 1.1202 1.1372 0.7756 1.0189 1.0379 1.0576 1.0767 1.0955 1.1146 1.1333 1.1526
0.0000
0.99024 (0.990141)[17]
Glycine + water 1536.7 (1536.14)[17]
0.0496
0.99182 (0.991747)[17]
1539.0 (1538.94)[17]
43.64 (44.42)[17]
-20.21
1.0067
0.0493
0.99297
1540.1
77.71
-28.33
1.0138
0.0985
0.99337 (0.993309)[17]
1541.2 (1541.13)[17]
43.82 (44.52)[17]
-19.88
1.0122
0.0974
0.99564
1543.4
77.94
-27.54
1.0238
0.1467 0.1942
0.99490 0.99640 (0.996317)[17]
1543.4 1545.6 (1545.80)[17]
43.98 44.13 (44.62)[17]
-19.62 -19.45
1.0176 1.0228
0.1443 0.1900
0.99828 1.00087
1546.6 1549.9
78.14 78.38
-26.97 -26.51
1.0334 1.0425
0.2410 0.2871 0.3325 0.3773
0.99788 1547.8 44.31 -19.21 0.99934 1550.0 44.47 -18.99 1.00078 1552.2 44.64 -18.75 1.00221 1554.5 44.77 -18.61 Glycine + 0.1942 mol٠kg-1 aqueous tartaric acid
1.0280 1.0332 1.0383 1.0432
0.2345 0.2780 0.3204 0.3618
1.00344 1553.1 78.55 -25.98 1.00596 1556.3 78.75 -25.67 1.00843 1559.6 78.97 -25.30 1.01089 1562.9 79.15 -25.07 Glycylglycine + 0.1942 mol٠kg-1 aqueous tartaric acid
1.0513 1.0602 1.0690 1.0775
0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
1.00288 1541.3 1.00441 1543.6 44.26 -19.51 1.00593 1545.9 44.32 -19.08 1.00745 1548.1 44.37 -18.69 1.00894 1550.3 44.44 -18.38 1.01043 1552.4 44.48 -17.94 1.01190 1554.5 44.55 -17.64 1.01336 1556.6 44.60 -17.31 1.01481 1558.6 44.66 -16.98 Glycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01453 1546.0 1.01602 1548.5 45.09 -18.61 1.01749 1550.7 45.13 -17.79 1.01895 1552.9 45.16 -17.16 1.02041 1555.0 45.19 -16.61 1.02185 1557.1 45.23 -16.15 1.02328 1559.0 45.26 -15.68 1.02471 1561.0 45.29 -15.31 1.02613 1562.8 45.32 -14.82 Glycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.02720 1551.0 1.02860 1553.5 46.48 -17.81 1.02999 1555.9 46.50 -16.89 1.03137 1558.2 46.53 -16.26 1.03274 1560.3 46.56 -15.34 1.03410 1562.3 46.60 -14.74 1.03545 1564.2 46.64 -14.00 1.03679 1566.0 46.67 -13.32 1.03812 1567.6 46.71 -12.66 Glycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03826 1555.9
0.6209 1.0090 1.0166 1.0239 1.0312 1.0382 1.0452 1.0521 1.0589
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.6209 1.0147 1.0307 1.0464 1.0624 1.0780 1.0932 1.1089 1.1238
0.6435 1.0090 1.0172 1.0253 1.0333 1.0412 1.0486 1.0563 1.0641
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.6707 1.0106 1.0208 1.0308 1.0406 1.0504 1.0600 1.0692 1.0787
0.0000 0.0493 0.0974 0.1443 0.1900 0.2345 0.2780 0.3204 0.3618
0.6996
0.0000
1.00288 1541.3 1.00556 1544.8 78.18 -27.00 1.00819 1548.1 78.49 -25.96 1.01077 1551.4 78.80 -25.15 1.01330 1554.6 79.09 -24.41 1.01580 1557.8 79.34 -23.85 1.01824 1560.9 79.59 -23.28 1.02064 1564.0 79.86 -22.68 1.02300 1567.1 80.11 -22.13 Glycylglycine + 0.3773 mol٠kg-1 aqueous tartaric acid 1.01453 1546.0 1.01717 1549.5 78.86 -24.99 1.01973 1552.9 79.36 -23.66 1.02222 1556.2 79.82 -22.64 1.02465 1559.4 80.30 -21.73 1.02701 1562.7 80.74 -20.89 1.02931 1565.8 81.19 -20.08 1.03155 1569.1 81.62 -19.30 1.03374 1572.1 82.03 -18.67 Glycylglycine + 0.5504 mol٠kg-1 aqueous tartaric acid 1.027120 1551.0 1.02978 1554.4 79.52 -22.03 1.03228 1557.6 80.09 -20.81 1.03469 1560.8 80.70 -19.75 1.03704 1563.9 81.22 -18.90 1.03931 1567.0 81.75 -18.07 1.04151 1570.0 82.26 -17.15 1.04365 1572.9 82.76 -16.37 1.04573 1575.7 83.21 -15.51 Glycylglycine + 0.7142 mol٠kg-1 aqueous tartaric acid 1.03826 1555.9
0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000 0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773 0.0000
Glycylglycine + water 0.5963
10
0.6435 1.0172 1.0341 1.0511 1.0679 1.0846 1.1013 1.1178 1.1336 0.6707 1.0169 1.0359 1.0553 1.0742 1.0937 1.1129 1.1319 1.1504 0.6996
0.0496 0.0985 0.1467 0.1942 0.2410 0.2871 0.3325 0.3773
131 132 133 134 135 136 137 138 139 140 141
1.03964 1558.4 46.71 -16.57 1.0117 0.0493 1.04077 1559.2 80.58 -19.52 1.04101 1560.7 46.75 -15.32 1.0241 0.0974 1.04319 1562.5 81.17 -18.23 1.04236 1562.9 46.79 -14.40 1.0361 0.1443 1.04554 1565.6 81.71 -17.13 1.04370 1564.8 46.84 -13.37 1.0483 0.1900 1.04781 1568.6 82.24 -16.17 1.04503 1566.6 46.88 -12.40 1.0610 0.2345 1.05001 1571.6 82.74 -15.37 1.04635 1568.1 46.93 -11.36 1.0726 0.2780 1.05213 1574.5 83.26 -14.50 1.04766 1569.6 46.96 -10.50 1.0848 0.3204 1.05418 1577.4 83.78 -13.76 1.04896 1570.8 47.00 -9.59 1.0969 0.3618 1.05617 1580.1 84.27 -12.97 a Standard uncertainties in molality are with in u (m) = ± 2 * 10-3 / mol٠ kg-1 b Standard uncertainties in density are with in u ( ) = ± 1*10-2 / kg٠m-3 c Standard uncertainties in ultrasonic velocity are with in u (u) = ±0.1 m٠s-1 d Standard uncertainties in apparent molar volume are with in u ( ) = ± (0.1 and 0.02) * 10-5 / m3 ٠ mol-1 for low & high concentration of amino acids e Standard uncertainties in apparent molar isentropic compression are with in u ( ) = ± (0.3–0.04) * 10-6 / m3 ٠ mol-1 ٠ GPa-1 for low and high concentration of amino acids. f Standard uncertainties in pressure are with in u (P) = ± 0.01 MPa. g Standard uncertainties in temperature are with in u (T) = ± 0.01 K.
From table 2, it is observed that the values of are positive which increase with
142
increase in temperature for all tartaric acid concentrations. The positive values indicate the
143
presence of solute-solvent interactions, which increase with increase of peptide bond from
144
glycine to glycylglycine. This effect is because of dissociation of amino acids into amino
145
(NH3+) and carboxyl group (COO-) in solutions [19].
146
The values of as obtained from equation (3) and reported in table 3 are negative.
147
The negative values of decreases with increase in concentration and with temperature.
148
The negative values shows that water molecules around solute are less compressible than
149
water molecules in the bulk because it is assumed that amino acid and ions are not pressure
150
dependent and electrostricted water molecules are already compressed to its maximum extent
151
by the charge on the ions and the amino acids. Therefore, the compressibility of a solution is
152
mainly due to the effect of pressure on the bulk water molecules [20]. Further, these
153
negative values as mentioned above predicts that water molecules around solute are less
154
compressible than water molecules in the bulk which is attributed to strong solute-solvent
155
interactions between ions of amino acid/peptide and ions of tartaric acid.
156
The apparent molar volumes ( ) have been found to vary linearly with molal
157
concentration (m) for glycine and glycylglycine in (0.1942, 0.3773, 0.5504 and 0.7142)
158
mol kg-1 aqueous tartaric acid solutions in accordance with Masson’s equation [21-22] given
159
below:
160
= 0 + Sv* m
161 162
(5)
Here, 0is the apparent molar volume at infinite dilution of the respective amino acid and ∗ is the experimental slope and m is the molal concentration of solution.
11
1.0202 1.0407 1.0621 1.0830 1.1030 1.1246 1.1450 1.1652
163
Further, the apparent molar isentropic compression ( ) for glycine and
164
glycylglycine in (0.1942, 0.3773, 0.5504 and 0.7142) mol kg-1 aqueous tartaric acid solutions
165
vary linearly with respective molal concentration according to following equation [23-25]:
166
= 0 + Sk* m
(6)
Here, 0is the apparent molar volume at infinite dilution of the respective amino acid
167 168
and ∗ is the experimental slope and m is the molal concentration of solution.
169 170 171 172 173
Table 3 Limiting apparent molar volumes ( 0), limiting apparent molar isentropic compression ( 0) and experimental slopes (Sv*), (Sk*) for glycine and glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol٠kg-1 aqueous tartaric acid solutions with corresponding standard deviations at different temperatures (aT = 298.15–318.15) K and at pressure bP = 0.1 MPa along with standard deviation and corresponding literature values. Tempera t-ure T /K
Limiting Apparent Molar volume 0 6 3 * 10 / m ٠ mol-1
Limiting Experimenta Apparent l Slopes Molar Sv* 6 3 Isentropic * 10 / m ٠ L1/2٠ mol-3/2 compression 0 6 10 / m3 ٠ * -1 mol GPa-1 Glycine + Water
Experimenta l Slopes Sk* 6 3 * 10 / m ٠ L1/2٠ mol-3/2٠ GPa-1
Limiting Apparent Molar volume 0 6 3 * 10 / m ٠ mol-1
298.15
42.20 (±0.01) (42.58)[33] (42.68)[17] (43.5)[71] (42.81)[46] (42.14)[38] (43.24)[72] (43.19)[3] (42.54)[4] (43.14)[5] (43.19)[2] (43.01)[6] (42.9)[7]
-26.67 (±0.02) (-26.12)[38] (-26.33)[72] (-27.00)[5] (-25.97)[2] (-26.6)[7]
303.15
42.47 (±0.01) (42.61)[33] (44.2)[71] (43.14)[46]
308.15
4.07 (±0.04)
4.24 (±0.09)
75.88 (±0.01) (75.89)[33] (76.22)[72] (76.22)[50] (76.26)[37] (76.23)[3] (76.23)[5] (76.36)[6] (76.27)[52] (76.40)[29]
-39.11 (±0.13) (-39.64)[72] (-39.64)[50] (-40.20)[5] (-40.9)[29]
4.17 (±0.05)
9.61 (±0.55)
-25.42 (±0.03)
4.10 (±0.03)
5.41 (±0.14)
76.25 (±0.01) (76.04)[33] (76.84)[29]
-36.71 (±0.09) (-37.7)[29]
4.26 (±0.06)
9.83 (±0.38)
42.83 (±0.01) (42.62)[33] (43.56)[17] (43.38)[46] (42.21)[38]
-23.79 (±0.04) (-23.98)[38]
3.89 (±0.03)
5.62 (±0.16)
76.62 (±0.01) (76.18)[33] (77.04)[50] (77.19)[37] (77.32)[29]
-34.32 (±0.11) (-35.57)[50] (-35.4)[29]
4.57 (±0.05)
10.81 (±0.45)
313.15
43.13 (±0.01) (42.64)[33] (44.38)[17] (43.66)[46]
-22.11 (±0.05)
3.76 (±0.04)
5.33 (±0.22)
77.06 (±0.01) (76.30)[33]
-31.43 (±0.12)
4.63 (±0.06)
10.51 (±0.52)
318.15
43.47 (±0.01) (42.44)[38]
-20.39 (±0.03) (-21.19)[38]
3.48 (±0.03)
4.84 (±0.14)
77.49 (±0.01)
-28.58 (±0.14)
4.60 (±0.05)
10.29 (±0.59)
12
Limiting Experimenta Apparent l Slopes Molar Sv* 6 3 Isentropic * 10 / m ٠ L1/2٠ mol-3/2 compression 0 6 10 / m3 ٠ mol* 1 ٠ GPa-1 Glycylglycine + Water
Experimenta l Slopes Sk* 6 3 * 10 / m ٠ L1/2٠ mol-3/2٠ GPa-1
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
174 175 176 177
Standard
Glycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid
Glycylglycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid
43.37 -25.44 1.01 4.46 (±0.01) (±0.03) (±0.02) (±0.14) 43.58 -24.30 1.06 5.71 (±0.01) (±0.02) (±0.03) (±0.10) 43.78 -22.77 1.10 6.51 (±0.01) (±0.02) (±0.01) (±0.09) 43.99 -21.26 1.18 7.04 (±0.01) (±0.03) (±0.02) (±0.14) 44.20 -19.85 1.21 7.67 (±0.01) (±0.03) (±0.02) (±0.12) Glycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid
-36.16 13.49 76.49 5.89 (±0.10) (±0.41) (±0.02) (±0.07) -34.22 14.93 76.83 6.02 (±0.11) (±0.46) (±0.01) (±0.06) -31.87 14.71 77.13 6.19 (±0.14) (±0.60) (±0.01) (±0.06) -29.79 15.06 77.49 6.22 (±0.12) (±0.50) (±0.01) (±0.05) -27.48 15.15 77.90 6.14 (±0.13) (±0.56) (±0.01) (±0.06) Glycylglycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid
44.44 -24.92 0.87 6.54 (±0.01) (±0.02) (±0.01) (±0.10) 44.60 -23.75 0.83 8.69 (±0.01) (±0.04) (±0.02) (±0.18) 44.77 -22.23 0.77 9.68 (±0.01) (±0.04) (±0.01) (±0.15) 44.90 -20.63 0.82 10.55 (±0.01) (±0.06) (±0.02) (±0.24) 45.06 -18.93 0.70 11.17 (±0.01) (±0.12) (±0.01) (±0.48) Glycine + 0.5504 mol٠kg-1 Aqueous Tartaric Acid
-33.78 15.96 76.90 9.52 (±0.08) (±0.35) (±0.02) (±0.08) -31.90 17.10 77.22 9.82 (±0.09) (±0.38) (±0.01) (±0.03) -29.81 17.36 77.60 9.94 (±0.10) (±0.41) (±0.01) (±0.06) -27.75 19.02 77.97 10.02 (±0.14) (±0.59) (±0.02) (±0.07) -25.67 19.94 78.36 10.14 (±0.15) (±0.64) (±0.01) (±0.02) Glycylglycine + 0.5504 mol٠kg-1 Aqueous Tartaric Acid
45.95 -24.30 0.77 8.05 (±0.01) (±0.04) (±0.01) (±0.18) 46.07 -23.20 0.72 10.77 (±0.01) (±0.03) (±0.01) (±0.14) 46.20 -21.63 0.71 11.66 (±0.01) (±0.05) (±0.02) (±0.23) 46.32 -20.20 0.71 13.82 (±0.01) (±0.06) (±0.02) (±0.26) 46.44 -18.49 0.70 15.59 (±0.01) (±0.06) (±0.03) (±0.25) Glycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid
-30.75 16.40 77.53 10.82 (±0.10) (±0.42) (±0.02) (±0.09) -28.66 17.17 77.87 11.25 (±0.13) (±0.54) (±0.01) (±0.05) -26.86 18.65 78.19 11.48 (±0.10) (±0.45) (±0.02) (±0.09) -24.89 19.68 78.58 11.61 (±0.12) (±0.53) (±0.01) (±0.05) -22.85 20.41 78.96 11.85 (±0.08) (±0.39) (±0.02) (±0.08) Glycylglycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid
46.10 (±0.01) 46.25 (±0.01) 46.40 (±0.01) 46.54 (±0.01) 46.66 (±0.01)
-23.48 (±0.03) -22.34 (±0.06) -20.78 (±0.09) -19.15 (±0.04) -17.50 (±0.06)
0.90 (±0.02) 0.91 (±0.02) 0.89 (±0.02) 0.89 (±0.01) 0.90 (±0.01)
11.82 (±0.12) 16.18 (±0.23) 17.93 (±0.37) 19.48 (±0.17) 21.14 (±0.25)
-27.75 16.00 78.56 10.97 (±0.13) (±0.54) (±0.01) (±0.06) -25.78 17.38 78.89 11.35 (±0.10) (±0.44) (±0.01) (±0.05) -23.94 18.59 79.21 11.61 (±0.11) (±0.49) (±0.02) (±0.08) -21.81 18.81 79.57 11.83 (±0.13) (±0.54) (±0.01) (±0.06) -20.26 20.54 80.01 11.75 (±0.14) (±0.59) (±0.01) (±0.05) errors for Limiting apparent molar volumes ( 0), Limitng apparent molar isentropic compression ( 0) and experimental slopes
(Sv*), (Sk*) are given in parenthesis. a
Standard uncertainties in temperatures are u(T) = ± 0.01 K.
b
Standard uncertainties in pressures are u(P) = ± 0.01 MPa.
178
From table 3, it is observed that 0 values of glycine and glycylglycine in water and
179
in aqueous tartaric acid solutions are positive and increases with increase in concentration of
180
tartaric acid and temperature. The 0 values are indicative of solute-solvent interactions and
181
it is clear here that positive values of 0, suggesting strong solute-solvent interactions [26].
182
We have studied, when an overlap of co-spheres of two ionic species there is increase in
183
volume and if two hydrophobic-hydrophobic groups and ion-hydrophobic groups overlap,
13
184
there is decrease in volume [27,28]. And here, the observed positive values of 0 are
185
because of ion-hydrophilic interactions which dominate over hydrophobic-hydrophobic and
186
ion-hydrophobic interactions. We have also seen, in table 3 that mostly with the increase in
187
molar mass and hydrophobicity of alkyl side chain, i.e. from glycine to glycylglycine, the
188
0 values increase [29]. And with the increase in concentration, the increases in 0 values
189
are because of increase in solvation of glycine and glycylglycine with ions of tartaric acid.
190
From table 3, the negative values of
0
(loss of compressibility of medium) indicate
191
that the water molecules surrounding the amino acid/peptide would present greater resistance
192
to compression than water molecules present in bulk. With increase in temperature the
193
values become less negative which means that electrostriction reduces and some water
194
molecules are released to bulk. The strong interactions due to hydration of ions produced
195
from the dissociation of tartaric acid induce the dehydration of amino acid/peptide and
196
increase the water molecule in the bulk. Because of formation of ion pairs between the
197
zwitter ions of amino acid/peptide and tartaric acid ions, the electrostriction interaction
198
between amino acid/peptide and water molecules are suppressed. In addition to this, the
199
attractive interaction between the ions of tartaric acid and water molecules induces the
200
dehydration of amino acid/peptide and therefore, at high tartaric acid concentrations, the
201
water molecules around the amino acid/peptide are more compressible than those at lower
202
tartaric acid concentrations [30]. The positive values of Sv* and Sk* respectively are indicative
203
of solute-solute interactions in the system and here, less but positive values of Sv* accounts
204
for weaker solute-solute interactions. Moreover, an irregular trend of Sv* and Sk* values
205
suggest that solute-solute interactions are influenced by number of effects [31].
0
206 207
3.2 Temperature effects
208
The temperature dependence of 0 can be expressed by the following relations [32,33]:
209
0 = a + bT + cT2
(7)
210
Where T is the temperature expressed in Kelvin and a, b and c are constants. On
211
solving this equation for different values of 0 at different temperature, we get values of a,
212
b and c constants. The limiting apparent molar expansion i.e. ! 0 were obtained by
213
differentiating above equation with respect to temperature:
214
! 0 = (δ 0/δΤ)P = b + 2cT
14
(8)
215
And the double derivative of partial molar volumes is shown as
216
(δ2ϕv0/δΤ2)P = 2c
(9)
217
From table 5, (! 0) decreases with increase in temperature, which implies caging
218
effect is absent. The sign of (! 0) values is found to provide important information regarding
219
the size of solute and its hydrophobicity. Here, in present both systems, (! 0) values are
220
positive but having lower values, there by showing weak solute-solute interactions and also
221
indicate that the solute is hydrophilic.
222 223 224 225 226 227 228
The criteria proposed by Hepler (1969) [34], called hydrophobicity criteria, make use of the double derivative of partial molar volume with respect to temperature to explain the hydrophobicity of the solute. From table, in present both systems i.e. glycine and glycylglycine system, (δ2ϕv0/δΤ2)P< 0 as constant c is negative (table 4), indicating thereby the solute is hydrophilic. Qualitative information on hydration of solutes [35-38] could be obtained from the thermal expansion of aqueous solution by using the general thermodynamic expression:
229 230
(δCP0/δP)T = - T (δ2ϕv0/δΤ2)P
(10)
Here, in present studied system, we have
231
(δCP0/δP)T> 0 i.e. (δ2φvο/δΤ2)P< 0, for both glycine and glycylglycine systems which
232
indicates that glycine and glycylglycine behaves as structure-breaker in water as well as in
233
different compositions of tartaric acid at different temperatures.
234 235 236
Table 4 Values of constant c for glycine and glycylglycine in water and in aqueous tartaric acid solutions at different temperatures (aT = 298.15– 318.15) K and at pressure bP = 0.1 MPa. molality (tartaric acid) / mol٠kg-1
237 238 239 240 241
a
Value of c Glycine
Glycylglycine
0.0000
-0.000199
-0.000200
0.1942
-0.000067
-0.000133
0.3773
-0.000133
-0.000199
0.5504
-0.000200
-0.000200
0.7142
-0.000199
-0.000200
Standard uncertainties in temperatures are u(T) = ± 0.01 K.
b
Standard uncertainties in pressures are u(P) = ± 0.01 MPa.
Table 5 Values of limiting apparent molar expansiona(! 0),Falkenhagen’s Coefficient (A), Jones-Dole Coefficient (B) for glycine and glycylglycine in water and in (0.1942, 0.3773, 0.5504 and 0.7142) mol٠kg-1 aqueous tartaric acid solutions at different temperatures (bT = 298.15–318.15)
15
242
K and at pressure cP = 0.1 MPa along with standard deviation and corresponding literature values. Temperature T /K
Limiting apparent molar expansion, # 0∗ 106 / m3 ٠ mol-1٠ K-1
298.15
0.0650 (0.00790)[33]
303.15
0.0630 (0.00390)[33]
0.0074 (±0.0003)
0.0810 (±0.0006)
0.0910 (0.094)[29] (0.0289)[33]
0.0246 (±0.0010)
0.1274 (±0.0021)
308.15
0.0610 (-0.00002)[33]
0.0073 (±0.0006)
0.0883 (±0.0012)
0.0890 (0.079)[29] (0.0269)[33]
0.0233 (±0.0009)
0.1456 (±0.0019)
313.15
0.0590 (-0.0041)[33]
0.0071 (±0.0003)
0.0962 (±0.0008)
0.0870 (0.0249)[33]
0.0236 (±0.0011)
0.1586 (±0.0023)
318.15
0.0570
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15 318.15
298.15 303.15 308.15 313.15
Falkenhagen’s Coefficient, A * 103/2 / m3/2 ٠ mol-1/2 Glycine + Water 0.0079 (±0.0003)
Jones-Dole Coefficient, B * 103 / m3 ٠ mol-1
0.0722 (±0.0006)
0.0065 0.1036 (±0.0003) (±0.0008) Glycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid 0.0423 0.0050 0.1046 (±0.0005) (±0.0011) 0.0417 0.0061 0.1131 (±0.0004) (±0.0009) 0.0410 0.0053 0.1239 (±0.0005) (±0.0012) 0.0403 0.0072 0.1318 (±0.0006) (±0.0013) 0.0397 0.0086 0.1416 (±0.0004) (±0.0009) Glycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid 0.0327 0.0066 0.1174 (±0.0002) (±0.0005) 0.0313 0.0061 0.1284 (±0.0006) (±0.0014) 0.0300 0.0059 0.1384 (±0.0004) (±0.0008) 0.0287 0.0049 0.1514 (±0.0004) (±0.0009) 0.0273 0.0038 0.1630 (±0.0003) (±0.0007) Glycine + 0.5504 mol٠kg-1 Aqueous Tartaric Acid 0.0290 0.0059 0.1345 (±0.0004) (±0.0009) 0.0270 0.0059 0.1480 (±0.0006) (±0.0012) 0.0250 0.0053 0.1620 (±0.0006) (±0.0013) 0.0230 0.0038 0.1793 (±0.0004) (±0.0010) 0.0210 0.0031 0.1971 (±0.0003) (±0.0007) Glycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid 0.0330 0.0049 0.1672 (±0.0006) (±0.0013) 0.0310 0.0013 0.1944 (±0.0004) (±0.0009) 0.0290 -0.0057 0.2315 (±0.0007) (±0.0015) 0.0270 -0.0065 0.2498 (±0.0012) (±0.0025)
16
Limiting Falkenhagen’s apparent molar Coefficient, expansion, A * 103/2 / m3/2 ٠ # 0∗ 106 / m3٠ mol-1/2 mol-1 ٠ K-1 Glycylglycine + Water 0.0930 0.0270 (0.099)[29] (±0.0008) (0.0309)[33]
0.0850
Jones-Dole Coefficient, B * 103 / m3 ٠ mol-1
0.1061 (±0.0018)
0.0217 0.1761 (±0.0013) (±0.0027) Glycylglycine + 0.1942 mol٠kg-1 Aqueous Tartaric Acid 0.0687 0.0001 0.2377 (±0.0011) (±0.0024) 0.0673 -0.0033 0.2657 (±0.0012) (±0.0025) 0.0660 -0.0081 0.3008 (±0.0012) (±0.0026) 0.0647 -0.0143 0.3394 (±0.0017) (±0.0037) 0.0633 -0.0165 0.3677 (±0.0012) (±0.0027) Glycylglycine + 0.3773 mol٠kg-1 Aqueous Tartaric Acid 0.0790 -0.0002 0.2648 (±0.0015) (±0.0032) 0.0770 -0.0019 0.2903 (±0.0018) (±0.0040) 0.0750 -0.0032 0.3156 (±0.0021) (±0.0045) 0.0730 -0.0045 0.3442 (±0.0016) (±0.0034) 0.0710 -0.0097 0.3830 (±0.0019) (±0.0042) Glycylglycine in 0.5504 mol٠kg-1 Aqueous Tartaric Acid 0.0830 -0.0068 0.3035 (±0.0021) (±0.0045) 0.0810 -0.0095 0.3349 (±0.0016) (±0.0036) 0.0790 -0.0160 0.3758 (±0.0025) (±0.0054) 0.0770 -0.0193 0.4078 (±0.0021) (±0.0046) 0.0750 -0.0279 0.4594 (±0.0020) (±0.0044) Glycylglycine + 0.7142 mol٠kg-1 Aqueous Tartaric Acid 0.0670 -0.0082 0.3297 (±0.0021) (±0.0046) 0.0650 -0.0097 0.3628 (±0.0016) (±0.0036) 0.0630 -0.0114 0.4006 (±0.0022) (±0.0048) 0.0610 -0.0163 0.4443 (±0.0024) (±0.0053)
318.15
0.0250
-0.0077 0.2681 0.0590 -0.0200 (±0.0008) (±0.0018) (±0.0029) Standard errors for Falkenhagen’s Coefficient (A), Jones-Dole Coefficient (B) are given in parenthesis. a Standard uncertainties in limiting apparent molar volumes expansion, u(! ) = ± (0.0001-0.0004) ∗ 106 / m3٠ mol-1٠ K-1. b Standard uncertainties in temperatures are u(T) = ± 0.01 K. c Standard uncertainties in pressures are u(P) = ± 0.01 MPa.
0.4861 (±0.0063)
243 Water
(a)
0.5504 Tartaric Acid 0.7142 Tartaric Acid
0.090
φE0 * 106/ m3. mol-1. K-1
φ E0 * 106/ m3. mol-1. K-1
0.07
0.06
0.05
0.04
0.03
Water 0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
0.1942 Tartaric Acid 0.3773 Tartaric Acid 0.5504 Tartaric Acid 0.7142 Tartaric Acid
0.085
0.080
0.075
0.070
0.065
0.060 0.02 295
300
305
310
315
320
295
T/ K
300
305
310
315
320
T/ K
244 245
Figure 1 Plots of limiting apparent molar expansions, (! 0), versus temperature (T) for (a) glycine and (b) glycylglycine in water and in
246
0.1942, 0.3773, 0.5504 and 0.7142 mol kg-1 aqueous tartaric acid solutions
247 248
3.3 Viscosity studies
249
Here, we have analysed viscosity data in terms of semi empirical Jones-Dole equation [39]
250
ηrelative = η/η0 = 1+ A√m+Bm
251
ηr = 1+ A√m +Bm
252
ηspecific = (ηrel– 1) = A√m +Bm
253
(ηspecific/√m) = (ηr -1)/ √m = (η/η0 -1)/√m = A+B√m
(11)
(12)
254
Where η and η0 are the viscosities of solution and solvents, m is the molal
255
concentration, A and B are Falkenhagen [40,41] and Jones-Dole coefficients [42],
256
respectively. We know, coefficient A accounts for the solute-solute interaction and B is a
257
measure of structural modifications induced by the solute –solvent interactions [43]. The
258
values of A and B have been obtained as the intercept and slope from linear regression of [(ηr
259
-1)/√m] Vs √m curves.
17
Water Water
(a) 0.28
0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
0.1942 Tartaric Acid
0.50
0.3773 Tartaric Acid
0.5504 Tartaric Acid 0.7142 Tartaric Acid
0.5504 Tartaric Acid
0.26
0.45
0.7142 Tartaric Acid
0.24
0.40
B * 103 / m3 mol-1
0.20
.
0.18
.
B * 103 / m3 mol-1
0.22
0.16 0.14 0.12 0.10
260 261 262
0.30 0.25 0.20 0.15
0.08 0.06 295
0.35
300
305
310
315
0.10 295
320
300
305
T/K
310
315
320
T/ K
Figure 2 Plots of Jones-Dole coefficient (B) versus temperature (T) for (a) glycine and (b) glycylglycine in water and in 0.1942, 0.3773, 0.5504 and 0.7142 mol kg-1 aqueous tartaric acid solutions
263
The values of A-coefficients are smaller in magnitude or even negative, showing weak
264
solute-solute interactions. Here, it has been noticed from table 5, that there is decrease in
265
values of A with temperature. The decrease of A with rising temperature is probably due to
266
the greater thermal agitation and reduction of attractive forces between the ions [44]. The B-
267
coefficient is a measure of order or disorder introduced by the ions into the solvent. It is
268
observed from table 5 that there are larger and positive values of B-coefficients in both
269
systems i.e. in glycine and glycylglycine systems as compared to A-coefficient support the
270
behaviour of $ 0 and Sv, respectively, both indicating stronger solute-solvent interaction as
271
compared to solute-solute interactions [12]. Also, in present studied systems, the positive B-
272
coefficient values systematically increases with increase in the hydrophobicity of the amino
273
acid side chain i.e. glycine to glycylglycine. Therefore, the hydrophobic side chain enhances
274
the solute-water interactions even though they affect the structure of solvent-water locally via
275
hydrophobic hydration [45]. The temperature derivatives of B-coefficient (dB/dT) have also
276
been calculated. The sign of dB/dT values provide important information regarding structure
277
making or structure breaking ability of the solute in solvent system [46,47]. In present systems
278
i.e. in glycine and glycylglycine systems, dB/dT is positive, which indicate solute is having
279
structure breaking ability in solvent system, thus supporting our earlier conclusion obtained
280
from Hepler’s constant.
281
3.4 Transfer parameters
282
The transfer parameters, $ 0 and 0 for glycine and glycylglycine in water and in
283
aqueous solution of tartaric acid have been calculated (∆tr $ 0 and (∆tr 0) by following
284
relation [48]:
285
(∆tr % 0)= ∆tr % 0(solution) - % 0 (water) 18
(13)
286
The calculated results are given in table 6 and illustrated in figure 3 and 4. The values of
287
(∆tr $ 0) are by definition free from solute-solute interactions and therefore, provide
288
information regarding solute-solvent interactions. The sign of the (∆tr $ 0) is often
289
interpreted in terms of strength of the solute-co-solute interactions [49]. Here, we have
290
studied partial of volumes is having positive values i.e. (∆tr $ 0) > 0, which indicate ionic-
291
hydrophilic and hydrophilic-hydrophilic interactions are predominant i.e. strong solute-co-
292
solute interactions are present in both systems i.e. in glycine and glycylglycine systems. We
293
also studied that the type of interactions in the ternary systems depend both on the nature of
294
side chain as well as type of the additive [50,51]. As can be seen in Figure 3, the values of
295
(∆tr $ 0) for both glycine and glycylglycine increases gradually with the molality of tartaric
296
acid, showing that high ionic strength dehydrates amino acid/peptide, and almost decreases
297
with temperature. According to the co-sphere overlap model regarding the values of (∆tr $ 0),
298
there is negligible contribution from solute–solute interactions and hence, they provide
299
information regarding solute–solvent interactions [52-57]. The types of interaction that occur
300
between amino acids and tartaric acid molecules can be classified as:
301
(i)
and the zwitterionic centers of the amino acid/peptide.
302 303
(ii)
(iii)
308
Ion-hydrophobic group interactions between the -COOH group of the tartaric acid and the non-polar group of the amino acid/peptide.
306 307
Hydrophilic–hydrophilic group interactions between the -COOH group of the tartaric acid and the -NH2 group of the amino acid/peptide.
304 305
Ion-hydrophilic group interactions between the-COOH group of the tartaric acid
(iv)
Hydrophobic–hydrophobic group interactions between the non-polar group of the tartaric acid and the non-polar group of the amino acid/peptide.
309
Ion-hydrophobic interactions and hydrophobic–hydrophobic interactions contribute
310
negatively based on co-sphere overlap model [58,59] whereas ion-hydrophilic and
311
hydrophilic–hydrophilic interactions contribute positively to the (∆tr $ 0) values. Here, we
312
can easily conclude that ion-hydrophilic and hydrophilic–hydrophilic interactions are much
313
stronger than ion– hydrophobic and hydrophobic–hydrophobic interactions. So, in both
314
systems, there are strong interactions between the (NH3+, COO-) charged ends of amino
315
acid/peptide and ions of the co-solute (solvent), which leads to effective overlap of amino
316
acid/peptide and co-solute ions. The observed higher values of (∆tr $ 0) of glycine than
317
glycylglycine in different molal concentrations of aqueous tartaric acid are due to release of 19
318
more number of water molecules from glycine due to domination of ionic-hydrophilic and
319
hydrophilic-hydrophilic interactions. Further, the observed decrease in (∆tr $ 0) values for
320
glycine/glycylglycine in different molal concentrations of aqueous tartaric acid with an
321
increase in temperature may be attributed to the corresponding decrease in the number of
322
electrostricted water molecules [26].
323
Table 6 shows that (∆tr 0) values are positive and increases with increase in concentration
324
of tartaric acid in all the cases. The increasing (∆tr 0) values in both system i.e. glycine and
325
glycylglycine suggest that there is disruption of the hydration sphere of charged end centres,
326
which implies dominance of ion-hydrophilic interactions [60,61]. The decrease in (∆tr 0)
327
values for glycine/glycylglycine in different molal concentrations of tartaric acid with an
328
increase in temperature indicate that the release of water molecules from the secondary
329
solvation layer of glycine and glycylglycine zwitter ions into the bulk water at higher
330
temperature [26]. The variations of (∆tr $ 0) are consistent with variation in (∆tr 0). 0.1942 Tartaric Acid 0.3773 Tartaric Acid
(a)
0.5504 Tartaric Acid 0.7142 Tartaric Acid
4.0
0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
3.5
0.5504 Tartaric Acid 0.7142 Tartaric Acid
3.0
2.4 2.2 1
2.5
. mol-
2.0 1.8
3
2.0
6
∆ trφ v * 10 / m
1.5
0
.
∆ trφ v0 * 106 / m3 mol-1
2.6
1.0
1.6 1.4 1.2 1.0 0.8 0.6
0.5 295
0.4
300
305
310
315
320
295
300
305
T/K
331
310
315
320
T/K 298.15K 303.15K 308.15K 313.15K 318.15K
(c) 4.0
298.15K 303.15K 308.15K 313.15K 318.15K
(d) 3.0
3.5
1
. mol∆ trφ v * 10 / m
0
1.0
0
1.5 1.0
0.2
333 334
1.5
6
2.0
0.5
332
2.0
3
2.5
6
∆ trφ v * 10 / m
3
. mol-
1
2.5
3.0
0.3
0.4
0.5
0.6
0.7
0.5
0.0
0.8
0.2
mTartaric Acid / mol kg-1
.
0.3
0.4
0.5
0.6
0.7
0.8
mTartaric Acid / mol kg-1
.
Figure 3 Partial volumes of transfer at different molality’s of aqueous tartaric acid solutions and temperatures in (a), (c) glycine and (b), (d) glycylglycine.
20
0.1942 Tartaric Acid 0.3773 Tartaric Acid 0.5504 Tartaric Acid
(a)
0.1942 Tartaric Acid 0.3773 Tartaric Acid
(b)
0.7142 Tartaric Acid
0.5504 Tartaric Acid
12
0.7142 Tartaric Acid
3.0
∆ trφ k0 * 106 / m3 mol-1
2.0
8
.
.
∆ trφ k0 * 106 / m3 mol-1
10
2.5
1.5
1.0
6
4
2
0.5 295
300
305
310
315
0 295
320
300
305
335 3.5
1
298.15K 303.15K 308.15K 313.15K 318.15K
10
8
.
. mol6
3
∆ trφ k * 10 / m
320
12
∆ trφ k0 * 106 / m3 mol-1
3.0
2.0
315
(d)
298.15K 303.15K 308.15K 313.15K 318.15K
(c)
2.5
310
T/K
T/K
0
1.5
1.0
6
4
2
0.5
0 0.2
0.3
0.5
0.6
0.7
0.2
0.8
0.3
0.4
0.5
0.6
0.7
0.8
mTartaric Acid / mol . kg-1
mTartaric Acid / mol . kg-1
336 337 338
0.4
Figure 4 Partial molar isentropic compressibility of transfer at different molality’s of aqueous tartaric acid solutions and temperatures in (a), (c) glycine and (b), (d) glycylglycine.
339 340 341 342
Table 6 Partial volumes of transfer (∆tr $ 0) and Partial molar isentropic compressibility of transfer (∆tr 0) for glycine and glycylglycine from water to different molality’s of tartaric acid solutions at different temperatures (T = 298.15–318.15) K and at pressure P = 0.1 MPa. From volume molality (tartaric acid)
0.1942
From compressibility 0.3773
0.5504
0.7142
0.1942
0.3773
0.5504
0.7142
/ mol٠kg-1 T (K)
Glycine
Glycine
298.15
1.17
2.24
3.75
3.90
1.23
1.75
2.37
3.19
303.15
1.11
2.13
3.60
3.78
1.12
1.67
2.22
3.08
308.15
0.95
1.94
3.37
3.57
1.02
1.56
2.16
3.01
313.15
0.86
1.77
3.19
3.41
0.85
1.48
1.91
2.96
318.15
0.73
1.59
2.97
3.19
0.54
1.46
1.90
2.89
T (K)
Glycylglycine
Glycylglycine
298.15
0.61
1.02
1.65
2.68
2.95
5.33
8.36
11.36
303.15
0.58
0.97
1.62
2.64
2.49
4.81
8.05
10.93
308.15
0.51
0.98
1.57
2.59
2.45
4.51
7.46
10.38
313.15
0.43
0.91
1.52
2.51
1.64
3.68
6.54
9.62
318.15
0.41
0.87
1.47
2.51
1.10
2.91
5.73
8.32
343 344 345 21
346
3.5 Hydration Number:
347
The hydration numbers, (nh) explicitly reveal the hydration degree of a solute in
348
water; which usually increases with the size of the amino acid/peptide in water, or solution.
349
The partial molar volume of amino acid can be investigated by a simple model using
350
following equation [62]:
351
0 (amino acid/peptide) = 0 (int) + 0 (elect)
(14)
352
where 0 (elect) is the electrostriction partial molar volume due to the hydration of
353
the amino acid/peptide (glycine/glycylglycine) and can be calculated from experimentally
354
measured values of the 0 (amino acid/peptide) (glycine / glycylglycine) and 0 (int) is the
355
intrinsic partial molar volume of the amino acid/peptide (glycine / glycylglycine) and has
356
been estimated by the help of following equation [62]:
357
0 (int) = (0.7/0.6) 0 (cryst.)
358
and
359
0 (int) = (0.7/0.634) 0 (cryst.)
(15)
(16)
360
where 0 (cryst.) (= mol wt/dcryst) is the crystal molar volume, 0.7 is the packing
361
density for the molecules in organic crystals and 0.634 is the packing density for random
362
packing spheres. The values of 0 (int) for the glycine and glycylglycine have been
363
calculated from equations (15) and (16) using dcryst values for glycine and glycylglycine
364
(1.598 [63] and 1.534 g cm-3 [37]) taken from the references.
365
The
number
of
water
molecules
hydrated
to
the
amino
acid/peptide
366
(glycine/glycylglycine) due to electrostriction causes decrease in volume can be related to the
367
hydration number by following expression [64-66]
368
nH = 0 (elect) / (,& 0 - ,' 0)
369
where ,& 0 is the molar
(17) volume of electrostricted water and ,' 0 is the molar
370
volume of the bulk water. If one mol of water molecules moves from the bulk water to the
371
solvation sphere of the amino acid/peptide, the volume is decreased by (,& 0 - ,' 0). The
372
(,& 0 - ,' 0)values, ie. -3.3 * 10-6 m3 mol-1 at T = 298.15 K, and -4.0 * 10-6 m3 mol-1 at T =
373
308.15 K, have been taken from the literature [62,67,68]. The values of hydration number
374
calculated by using both the two methods from these equations (15) and (16) have been 22
375
shown in table 7. Hydration number (nH) of amino acid and its peptide i.e. glycine and
376
glycylglycine decreases with increasing tartaric acid concentrations are smaller than that of
377
water, indicating that ion-hydrophilic group interactions between the -COOH group of the
378
tartaric acid and the zwitterionic centers of the amino acid/peptide (glycine/glycylglycine)
379
becomes stronger which further weaken the electrostriction of the charged centres with water
380
molecules and strengthen the interactions between ions and the charged centers of the amino
381
acid/peptide (glycine/glycylglycine) [37,38]. The 0 values increases with increasing
382
temperature from (298.15 to 318.15) K as shown in table 3. An increase in temperature
383
reduces the electrostriction which leads to increase in values of 0. The reduction in the
384
electrostriction in present ternary system with increasing temperature is confirmed by the
385
decreased hydration number (nH) values with temperature.
386 387 388
Table 7 Hydration number, nH of glycine and glycylglycine in aqueous tartaric acid solutions for the different molal concentrations at T = (298.15 and 308.15) K. m (tartaric acid) / mol٠kg-1
nH From volume Using (Eq. (15))
Using (Eq. (16))
From compressibility Using (Eq. (20)) At 298.15 K
Using (Eq. (15))
Using (Eq. (16))
From compressibility Using (Eq. (20))
From volume
Glycine 0.0000
2.93
3.82
3.29
Glycylglycine 5.82
7.46
4.83
0.1942
2.58
3.47
3.14
5.64
7.27
4.46
0.3773
2.25
3.14
3.08
5.51
7.15
4.17
0.5504
1.79
2.68
3.00
5.32
6.96
3.80
0.7142
1.75
2.64
2.90
5.01
6.64
3.43
At 308.15 K Glycine 0.0000
2.74
3.63
2.94
Glycylglycine 5.60
7.23
4.24
0.1942
2.45
3.34
2.81
5.44
7.08
3.93
0.3773
2.15
3.04
2.74
5.30
6.93
3.68
0.5504
1.72
2.61
2.67
5.12
6.76
3.32
0.7142
1.66
2.55
2.57
4.81
6.45
2.96
389 390
In addition to this, the number of water molecules hydrated to amino acid/peptide
391
(glycine/glycylglycine) can be calculated by using following equation [62,69]
392
nH = -
0
(elect) / ,' 0 Kb0
(18)
23
where, Kb0 is the isothermal compressibility of the bulk water. The estimated value of
393 394
,' 0 Kb0 is 8.1 * 10-5 m3 mol-1 GPa-1. The electrostriction partial molar compressibility
395
(elect) can be calculated experimentally measured values of
396
0
(elect) =
0
(amino acid/peptide) -
As the value of
397
0
0
(int)
many organic solutes in water. So, we can assume
399
the reduced form of equation (19) becomes
400
(elect) =
0
(amino acid) from (19)
(int) is less than 5 * 10-6 m3 mol-1 GPa-1 for ionic crystals and
398
0
0
0
(amino acid/peptide)
0
(int) value to be zero [62]. Therefore,
(20)
401
The values of hydration number calculated by using these equations (20) have been
402
shown in table 7. The hydration number (nH) values decreases with increase in concentration
403
of tartaric acid and are smaller than that of water, this indicates the presence of strong ion-
404
hydrophilic interaction between –COOH group of tartaric acid and zwitter ions of amino
405
acid/peptide (glycine/glycylglycine) with increase in concentration of tartaric acid. With
406
increase in the concentration of tartaric acid , water molecules present in the solution are
407
replaced by tartaric acid molecules due to dehydration effect on glycine/glycylglycine
408
[50,70]. The hydration number (nH) values also decreases with increase in temperature of
409
solution, this results decrease in electrostriction with increase in temperature. These
410
variations are consistent with the variation in values of 0, as 0 values increases with
411
increasing temperature from (298.15 to 318.15) K as shown in table 3. An increase in
412
temperature reduces the electrostriction and hence increases 0. Further, the values of
413
hydration number (nH) shown in table 7, based on volumetric and compressibility models are
414
in good agreement.
415 416
3. Conclusion
417
In present work, the apparent molar volume ($ ), partial molar volume ($ 0), limiting
418
apparent molar expansibility (! 0), transfer volume (∆tr $ 0), Falkenhagen’s coefficient (A),
419
Jones-Dole coefficient (B) and apparent molar isentropic compressibility ( ), partial molar
420
isentropic compressibility ( 0), transfer parameter (∆tr 0) have been studied for glycine
421
and glycylglycine in water and in aqueous tartaric acid between (298.15 and 318.15) K.
422
The ($ ), ($ 0) and (∆tr $ 0) have been obtained which are positive and increases with 24
423
increase in temperature as well as with increase in concentration of tartaric acid. This
424
indicates that there are solute-solvent interactions. It was obtained from Hepler’s criterion
425
and dB/dT values that glycine and glycylglycine act as structure breaker in water and in
426
aqueous tartaric acid solution at different temperatures. The negative values of ( ) and
427
( 0) support our volumetric data. The glycylglycine being dipeptide of glycine has higher
428
values of (! 0). The (! 0) gives information relating to the size of the solute and its
429
hydrophobicity and also tells that there is absence of caging in present system. With the help
430
of transfer parameters, it has been concluded that ion-hydrophilic and hydrophilic-
431
hydrophilic interactions are prominent between the ions of tartaric acid and the zwitterions of
432
glycine and glycylglycine respectively. The hydration number calculated from volumetric
433
and compressibility data shows the presence of interaction between the ions of tartaric acid
434
and glycine/glycylglycine.
435
Acknowledgements
436
The authors are grateful to Himachal Pradesh University, Shimla for providing lab
437
facilities and Abhishek Thakur is thankful to Ministry of Human Resource Development for
438
their support.
439 440 441 442
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HIGHLIGHTS:
• • • •
Molecular interactions between glycine and glycylglycine in water and in aqueous tartaric acid solutons are studied. The Volumetric, Compressibility, Acoustic and Viscometric methods are used to interpret results. Solute-Solvent interactions predominate over solute-solute interactions glycine and glycylglycine behaves as a structure breaker in water and in aqueous tartaric acid solutions.
Conflict of Interest
•
The author is not having any conflict of interest with this publication
With regards,
Prof. Dr. Shashi Kant Sharma Department of Chemistry Himachal Pradesh University, Shimla, India-171005 Email: [email protected] Tel: +919418382396