Experimental and theoretical study on the 1:1 supramolecular complexes of formamide with adrenaline

Gene 496 (2012) 136–140

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Experimental and theoretical study on the 1:1 supramolecular complexes of formamide with adrenaline Tao Liu a, c, Zhangyu Yu b,⁎, Lingli Han a, Xueliang Wang b, Chengbu Liu c a b c

Department of Chemistry and Chemical Engineering, Jining University, Qufu 273155, Shandong, China Department of Chemistry and Chemical Engineering, Heze University, Heze 274015, Shandong, China School of Chemistry and Chemical Engineering, Shandong University, Jinan 250010, Shandong, China

a r t i c l e

i n f o

Article history: Accepted 18 January 2012 Available online 28 January 2012 Keywords: Cyclic voltammetry Supramolecular complex Hydrogen bond

a b s t r a c t The electron transfer properties were investigated for supramolecular complexes of formamide (FA) with adrenaline (Ad) at graphite electrode and paraffine soaked graphite electrode using cyclic voltammetry (CV). The experimental results show that FA affected the electron transfer properties of Ad. The formed supramolecular complexes by hydrogen bond (H-bond) interaction between FA and Ad slowed down the diffusion ability of adrenaline, which makes it hard to donate electron and be oxidized. The H-bond interaction energies calculation for the supramolecular complexes of FA with Ad at MP2/6-311+ G(d,p)//B3LYP/6-311+G(d,p) level have also been performed. The calculational results confirm the experimental fact that FA can form stable supramolecular complexes with Ad. © 2012 Elsevier B.V. All rights reserved.

1. Introduction The importance of the amide linkage is demonstrated by the fact that the amide peptide bond is the basic linkage in peptides and proteins. Its duality to function as both hydrogen bond (H-bond) donor and acceptor makes the linkage versatile in molecular assembly and recognition. For examples, the H-bonds among peptide bonds in proteins are the key driving forces for forming the organized α-helix and β-sheet secondary structures. The linkage also plays important roles in the pharmacophores of the antibacterial agents such as penicillins and carbacephems and has been utilized in designing enzyme inhibitors (Boyd, 1993; Greenberg et al., 2000; Hu et al., 2011; Mandal et al., 2012). Formamide (FA) is one of the simplest molecules usually chosen as a model for studying biological systems exhibiting the peptide type of bonding and DNA structures. Since formamide complexes such as formamide–water and formamide–methanol can serve as model systems for protein–water and protein–solvent interactions, numerous experimental and theoretical studies have been reported (Besley and Hirst, 1999; Contador et al., 1996; Hinton and Harpool, 1977; Lovas et al., 1988; Shi et al., 2004). However, the report is seldom on the characterization of the hydrogen bond interaction between formamide and adrenaline. Adrenaline (Ad) is a hormone secreted from the adrenal medulla, as an important catecholamine neurotransmitter in the mammalian central nervous system, which Abbreviations: CV, cyclic voltammetry; FA, formamide; Ad, adrenaline; H-bond, hydrogen bond. ⁎ Corresponding author. Tel.: + 86 5374458563. E-mail address: [email protected] (Z. Yu). 0378-1119/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.gene.2012.01.032

has important functions in regulating the physiological process (Xie et al., 2006). The lack or excess of adrenaline in nervous system will cause some diseases. Therefore, the investigation of the H-bond interaction between formamide and adrenaline will be helpful to seek the action rules of DNA in the living body, and to provide instructive information for the new drug design with adrenaline as the target. In this paper, we will investigate the electron transfer properties for supramolecular complexes of FA with Ad by using cyclic voltammetry (CV) and theoretical calculations. 2. Experimental and calculation details 2.1. Materials and instruments The pH 7.4 Krebs–Ringer phosphate buffer (KRPB) solution (Zheng, 2003), consisting of 0.025 mol/L Na2HPO4, 0.13 mol/L NaCl, 4.9 × 10 − 3 mol/L KCl, and 2.5 × 10 − 3 mmol/L MgSO4, simulated biological environment of human body. The reagent of adrenaline (>97%) was purchased by Fluka Co. (Sweden). The concentration of adrenaline aqueous solution was 3.0 × 10 − 4 mol/L. Other employed solutions were prepared with analytic grade reagents and doubly distilled water. The electrochemical experiments were performed on an EG&G PAR M398 electrochemical impedance system with an M283 potentiostat/ galvanostat. The three-electrode-system was used to carry out electrochemical tests. Graphite electrode and paraffine soaked graphite electrode served as working electrodes, a platinum wire served as a counter electrode, and a saturation calomel electrode (SCE) served as a reference electrode. A luggin capillary was used to connect the reference and working electrodes in order to reduce the solution resistance.

T. Liu et al. / Gene 496 (2012) 136–140

Highly pure nitrogen was passed through the solution for 15 min to remove dissolved oxygen in solution before measurements, and all measurements were carried out under nitrogen atmosphere at room temperature.

137

a 0.1mA

b

2.2. Calculation methods All structures in the work were fully optimized at the B3LYP/6-311+ G(d,p) level, and characterized to be minima (no imaginary frequency) by frequency analyses at the same level of theory. All the calculations were carried out using the Gaussian 03 suite of programs (Frisch et al., 2003). The H-bond interaction energies between Ad and FA were calculated with Eq. (1). ΔE ¼ Ecomplex −ðEAd þ EFA Þ þ ΔEZPE þ EBSSE

ð1Þ

where Ecomplex, EAd, and EFA are the MP2/6-311+G(d,p)//B3LYP/6311+G(d,p) single-point energies of FA–Ad, Ad, and FA, respectively. ΔEZPE is the calculated zero point energy (ZPE) correction at the B3LYP/6-311+G(d,p) level, and EBSSE calculated at the MP2/6-311+ G(d,p)//B3LYP/6-311+G(d,p) level is the basis set superposition error (BSSE) estimated using the standard counterpoise method (Boys and Bernardi, 1970) implemented in Gaussian 03(Frisch et al., 2003). In order to evaluate H-bond interaction energies for the complexes in aqueous solution, we performed MP2/6-311+G(d,p) energy calculations for the complexes, Ad, and FA in aqueous solution at their gas-phase B3LYP/6-311+G(d,p) optimized geometries, and we used the PCM model (polarizable continuum model) (Cossi et al., 2002; Mennucci et al., 1997; Miertus et al., 1981; Vanommeslaeghe et al., 2005) of the self-consistent reaction field theory to simulate solution effects. The B3LYP/6-311+G(d,p) geometries and the MP2/6-311 +G(d,p)//B3LYP/6-311+G(d,p) energies based on Eq. (1) are used in the following discussions. 3. Results and discussion 3.1. Characterization of the electron transfer properties of adrenaline using cyclic voltammetry The CV curves of adrenaline at graphite electrode in the solution with different concentration of FA are presented in Fig. 1. Peak 1 of curve (a) corresponds to the oxidation peak of adrenaline. It can be seen that, with the addition of FA, the anodic peak current of peak 1

-0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6

E / V(vs.SCE) Fig. 2. Cyclic voltammograms of 3.0× 10− 4 mol/L adrenaline in KRPB(pH =7.4)buffer solution with graphite electrode and paraffine soaked graphite electrode as working electrodes using a scan rate of 100 mV/s. The curves of a and b denote the cyclic voltammograms with graphite electrode and paraffine soaked graphite electrode respectively.

increases and reaches the maximum at 1:1 concentration ration of Ad and FA. To continue adding FA, the current of peak 1 will decrease instead. The phenomena can be interpreted as follows: the graphite electrode surface is loose and porous, which will provide strong absorption strength and big active surface area for electro-redox reactions, so small molecule, such as FA, will be absorbed into the micropores. With the addition of FA at the beginning, the anodic peak current of peak 1 increases, which because the formation of the complex between Ad and FA combining with H-bonds brings more Ad molecules into the micropores and makes the electroredox reaction be easier. However, with the increase of the concentration of FA further, the H-bonds between Ad and FA will protect the phenolic hydroxyl group effectively and make it hard to donate proton, resulting in the anodic peak current of peak 1 decreases. In order to prove above explication, the CVs of Ad on the graphite electrode (curve a) and paraffine soaked graphite electrode (curve b) in KRPB are conducted and the results are shown in Fig. 2. The paraffine soaked graphite electrode was fabricated according to the literature (Szucs et al., 1989). It can be seen that the peak currents on paraffine soaked graphite electrode decrease obviously compared with those on graphite electrode, which can attributed to the blocking of micropores by paraffine wax. The CVs of adrenaline on the paraffine soaked graphite electrode in KRPB buffer solution containing different concentration of FA are also studied (Fig. 3). From Fig. 3, we can find that the anodic peak currents of peaks 1, 3, and 4 decrease a little with the addition of FA. The

0.1mA

a a

1

1

0.02mA e

e 4

3 -0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

-0.4

-0.2

0.0

0.2

0.4

0.6

E / V(vs.SCE)

E / V(vs.SCE)

Fig. 1. Cyclic voltammograms of 3.0 × 10− 4 mol/L adrenaline in KRPB(pH = 7.4)buffer solution using graphite electrode as a working electrode. The voltammograms are obtained with a scan rate of 100 mV/s in the solution of adrenaline containing different concentration of FA. The curves of a, b, c, d, and e corresponds to the FA concentration of 3.0 × 10− 4, 6.0 × 10− 4, 0, 9.0 × 10− 4, and 1.2 × 10− 3 mol/L, respectively. The peak 1 denotes the anodic peak.

Fig. 3. Cyclic voltammograms of 3.0 × 10− 4 mol/L adrenaline in KRPB(pH = 7.4)buffer solution with paraffine soaked graphite electrode as a working electrode. The voltammograms are obtained in the solution with different concentration of FA and using a scan rate of 100 mV/s. The curves of a, b, c, d, and e denote the FA concentration of 0, 3.0 × 10− 4, 6.0 × 10− 4, 9.0 × 10− 4, and 1.2 × 10− 3 mol/L, respectively. The peak 1 denotes the anodic peak.

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results demonstrate that FA inhibits the electron transfer of Ad weakly, which is consistent with the calculational result (see below) that there are weak H-bond interaction between FA and Ad, and the Hbonds will protect the phenolic hydroxyl group of Ad effectively and resulting in the oxidation ability of Ad decrease. 3.2. The geometries and H-bond interaction energies of the supramolecular complexes of adrenaline with formamide We have performed the full geometry optimization calculations and get the most conformations of Ad (Liu et al., 2006) and FA (Liu et al., 2008) monomers. The supramolecular complexes of Ad with FA were obtained by geometry optimization calculations at the staring geometries of the complexes, which were tried from FA part approaching to the phenolic hydroxyl, alcoholic hydroxyl and amino group of Ad part, respectively. Ad can form supramolecular complex with FA at different ratio, while in this section, we will only discuss the important stable conformations of 1:1 supramolecular complex and compare the calculational results with the experimental phenomena we list above.

We have calculated ten conformations of the complex between Ad and FA monomers. Five of these are cyclic double-H-bonded structure and the other five are one-H-bonded structure. The geometries of the ten complexes and the corresponding parameters of H-bonds are displayed in Fig. 4. In FA–Ad1, FA–Ad2, FA–Ad3, and FA–Ad4, FA prefers as H-bond donor to form stable H-bonded complex with Ad. With respect to the structure FA–Ad1 and FA–Ad2, the H-bond is formed between the amino group in FA and the phenolic hydroxyl groups in Ad. The H-bond lengths are 2.116 and 2.038 Å in the two complexes, and the corresponding H-bond angles are 175.4° and 174.4°, respectively. For the configuration of FA–Ad3 and FA–Ad4, the H-bond is formed between the amino group in FA and the alcoholic hydroxyl group in Ad. The H-bond lengths (1.972 and 1.937 Å) in the two complexes are shorter than those in FA–Ad1 and FA–Ad2, which indicates that the structures of FA–Ad3 and FA–Ad4 are more stable. In FA–Ad5, FA prefers as H-bond acceptor to form stable H-bonded complex with Ad, and the H-bond is formed between the carbonyl group in FA and the phenolic hydroxyl group in Ad. The H-bond

NF 174.4 2.038 O1

O2

2.116 175.4

NF

FA-Ad1

FA-Ad2

NF 174.1 1.972 O3

O3

165.7

1.937

NF

FA-Ad3

FA-Ad4

O2 170.0

H1

2.307 1.792

O1 H1

OF

131.4 NF 156.7 1.791 OF

FA-Ad5

FA-Ad6

Fig. 4. The B3LYP/6-311+G(d,p) optimized geometry of the FA–Ad complexes (the 1:1 supramolecular complexes of FA with Ad).

T. Liu et al. / Gene 496 (2012) 136–140

O2

139

165.3 H2

H3

NF

O3

2.215

2.200 147.7

OF

129.6 109.8 2.532

2.100

O1 H1

FA-Ad7

FA-Ad8

N

N H3 156.0

O3

1.927

2.180 OF

140.4

NF 2.597

O3 171.5

171.4 H3 1.861 OF

FA-Ad9

FA-Ad10 Fig. 4 (continued).

length is 1.792 Å and the departure of the H-bond angle from the linearity is 10.0°. FA–Ad6 exhibits a cyclic conformation, with FA accepting a proton from phenolic hydroxyl group while donating a proton to the phenolic hydroxyl group. In both FA–Ad5 and FA–Ad6, the H-bonds between the hydrogen atom at oxygen atom of phenolic hydroxyl group in Ad and oxygen atom in FA will protect the phenolic hydroxyl groups and make them hard to donate proton and be oxidized, which is consistent with experimental results we stated above. For structure of FA–Ad7, it is a cyclic configuration too. FA is not only the hydrogen acceptor but also the hydrogen donor; which accepts the H proton from one of the phenolic hydroxyl group of Ad and offers the H proton to another phenolic hydroxyl group of Ad, respectively. The two H-bond lengths are 2.200 and 2.100 Å, respectively. The ∠HNCH dihedral angle of FA moiety in FA–Ad7 is 176.2°, while the corresponding value of FA monomer and FA moiety in other FA–Ad complex is nearly 180.0°. The phenomena can be interpreted by the negative two-way effects we stated in our previous study (Liu et al., 2008). The H-bonded complex formed by the amino group of FA as Hbond acceptor will weaken the resonance effect of FA, affect the geometrical and electronic structure of FA, and make the amino groups tend to be more unplanarized.

As to the configuration FA–Ad8, FA accepts a proton from alcoholic hydroxyl group and donates a proton to the alcoholic hydroxyl group. Though the weak bond CF-H•••O3 is not the traditional H-bond, the Hbond length 2.532 Å is only a little longer than the traditional H-bond length of O3-H3•••OF (2.215 Å). Therefore, the untraditional H-bond also plays an important role in the H-bonded complexes and cannot be neglected comparing with the traditional H-bond. FA–Ad9 also shows a cyclic structure in which the H at the N atom of Ad bonded to the carbonyl group of FA and the H at the C atom of FA bonded to the alcoholic hydroxyl group of Ad. The two H-bond lengths are 2.180 and 2.597 Å, respectively. With respect to the last structure FA–Ad10, there are two H-bonds too. One H-bond is (NF)-H•••NAd with the H-bond length of 1.927 Å and H-bond angle of 171.5°, another is (O3)-H3•••OF with the Hbond length of 1.861 Å and H-bond angle of 171.4°. Comparing the ten H-bonded complexes we discussed above, we can find that the different stabilities of the H-bonded complexes studied depend on the different donor–acceptor character of the groups involved and the oxygen atom of the hydroxyl group is worse acceptor than the oxygen atom of the carbonyl group in FA, which is in a similar way as occurs in the previous work (Torrent-Sucarrat and Anglada, 2004). The MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) H-bond interaction energies

Table 1 The MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) H-bond interaction energies (in kcal/mol) for the FA–Ad complexes in the gas-phase and in aqueous solution (ΔEs)a.

FA–Ad1 FA–Ad2 FA–Ad3 FA–Ad4 FA–Ad5 FA–Ad6 FA–Ad7 FA–Ad8 FA–Ad9 FA–Ad10 a

ΔEint

ΔEint + ΔEZPE

ΔEint + ΔEBSSE

ΔEint + ΔEZPE + ΔEBSSE

ΔEs

− 5.33 − 6.42 − 8.42 − 10.23 − 11.75 − 11.73 − 5.04 − 4.49 − 7.62 − 11.07

− 4.24 − 5.41 − 7.31 − 8.77 − 10.04 − 9.83 − 3.91 − 4.16 − 6.62 − 9.41

− 3.55 − 4.92 − 6.62 − 8.10 − 8.84 − 9.21 − 3.30 − 2.95 − 5.39 − 7.39

− 2.46 − 3.91 − 5.51 − 6.64 − 7.13 − 7.31 − 2.18 − 2.61 − 4.39 − 5.73

− 4.11 − 4.38 − 6.57 − 7.30 − 9.19 − 8.88 − 2.41 − 3.51 − 4.58 − 7.89

Based on the PCM-MP2/6-311+G(d,p) energy calculations in aqueous solution at the gas-phase B3LYP/6-311+G(d,p) optimized geometries.

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for the FA–Ad complexes in the gas-phase are shown in Table 1. It can be seen from Table 1 that the most stable structure is FA–Ad6 with the Hbond interaction energy of −7.31 kcal/mol, and the second is FA–Ad5 (−7.13 kcal/mol). Comparing the two structures with others, we can find that the H-bonds in the two complexes are both formed between the hydrogen atom at oxygen atom of phenolic hydroxyl group in Ad and oxygen atom in FA, which will protect the phenolic hydroxyl group and make it hard to donate proton and become more stable as we stated above. FA–Ad7 is the most unstable structure in all complexes (the H-bond interaction energy is only −2.18 kcal/mol), which can also be interpreted by the negative two-way effects (Liu et al., 2008) that the resonance effect of FA weaken the H-bond when the amino group of FA as H-bond acceptor. The H-bond interaction energies (without ZPE and BSSE corrections) of FA–Ad complexes (except FA–Ad1, FA–Ad7, and FA–Ad8) are larger than H-bond interaction energy (−6.11 kcal/mol) of FA–water (Liu et al., 2008) at the MP2/6-311+G(d,p) level. H-bond interaction energies for the FA–Ad complexes based on the PCM-MP2/6-311+G(d,p) energy calculations in aqueous solution at the gas-phase B3LYP/6-311+G(d,p) optimized geometries are also given in Table 1. From it we can see that either in the gas phase or in aqueous solution, FA–Ad5 and FA–Ad6 are the two most stable conformations, which proves further that FA can form H-bonds with phenolic hydroxyl group of Ad and protect the phenolic hydroxyl group effectively as the CV results. The H-bond interaction energies in aqueous solution are –9.19 and –8.88 kcal/mol for the two complexes. However, the H-bond interaction energies of FA–Ad5 and FA–Ad6 are − 7.13 and − 7.31 kcal/mol in the gas phase, respectively. The phenomenon can be interpreted by the competition between the two complexes in the two phases. The FA–Ad6 is more stable in the gas phase while FA–Ad5 is more stable in aqueous solution. FA– Ad7 in aqueous solution is more stable than in the gas phase and the H-bond interaction energy in aqueous solution is –0.23 kcal/mol lower than that in the gas phase (without ZPE and BSSE corrections). 4. Conclusion The electron transfer properties of supramolecular complexes of FA with Ad at graphite electrode and paraffine soaked graphite electrode using CV have been investigated in this paper. The experimental data show that FA affects the electron transfer properties of adrenaline. The supramolecular complexes of FA–Ad formed by H-bond interaction between FA and Ad will protect the phenolic hydroxyl groups of adrenaline and make them hard to donate electron and be oxidized. The H-bond interaction energies for the supramolecular complexes of FA–Ad in the gas phase and aqueous solution calculated at MP2/6311+G(d,p)//B3LYP/6-311+G(d,p) level confirm the experimental results that FA can form stable supramolecular complexes with Ad. Acknowledgments This work was supported by the China Postdoctoral Science Foundation Funded Project (No. 2011M500724), the Natural Science

Foundation of Shandong Province (Nos. ZR2009BM003, ZR2010BQ031), the Shandong Province Postdoctoral Innovation Foundation Funded Project China (No. 201102019), the Education Department of Shandong Province (No. J09LB54), the Advanced Project for National Fund (No. 2011YYJJ05). References Besley, N.A., Hirst, J.D., 1999. Ab initio study of the electronic spectrum of formamide with explicit solvent. J. Am. Chem. Soc. 121, 8559–8566. Boyd, D.B., 1993. Application of the hypersurface iterative projection method to bicyclic pyrazolidinone antibacterial agents. J. Med. Chem. 36, 1443–1449. Boys, S.F., Bernardi, F., 1970. The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors. Mol. Phys. 19, 553–566. Contador, J.C., Sanchez, M.L., Aguilar, M.A., Olivares del Valle, F.J., 1996. Solvent effects on the potential energy surface of the 1:1 complex of water and formamide: application of the polarizable continuum model to the study of nonadditive effects. J. Chem. Phys. 104, 5539–5546. Cossi, M., Scalmani, G., Rega, N., Barone, V., 2002. New developments in the polarizable continuum model for quantum mechanical and classical calculations on molecules in solution. J. Chem. Phys. 117, 43–54. Frisch, M.J., et al., 2003. Gaussian 03W. Gaussian, Inc., Pittsburgh, PA. Greenberg, A., Breneman, C.M., Liebman, J.F., 2000. The Amide Linkage: Structural Significance in Chemistry, Biochemistry, and Materials Science. Willy, New York. Hinton, J.F., Harpool, R.D., 1977. An ab initio investigation of (formamide)n and formamide-(water)n systems. Tentative models for the liquid state and dilute aqueous solution. J. Am. Chem. Soc. 99, 349–353. Hu, Z.R., Yu, Y., Wang, R., Yao, Y.Y., Peng, H.R., Ni, Z.F., Sun, Q.X., 2011. Expression divergence of TaMBD2 homoeologous genes encoding methyl CpG-binding domain proteins in wheat (Triticum aestivum L.). Gene 471, 13–18. Liu, T., Huang, M.-B., Yu, Z.-Y., Yan, D.-Y., 2006. Theoretical study on the supramolecular complexes of 12-crown-4 with adrenaline. J. Mol. Struct. THEOCHEM 776, 97–104. Liu, T., Li, H., Huang, M.-B., Duan, Y., Wang, Z.-X., 2008. The two-way effects between hydrogen bond and the intra-molecular resonance effect: a computational study on the complexes of formamide and its derivatives with water. J. Phys. Chem. A 112, 5436–5447. Lovas, F.J., Suenram, R.D., Fraser, G.T., Gillies, C.W., Zozom, J., 1988. The microwave spectrum of formamide–water and formamide–methanol complexes. J. Chem. Phys. 88, 722–729. Mandal, A., Rao, D., Karuppaiah, D., Gopalakrishnan, A., Pozhoth, J., Samraj, Y.C.T., Doyle, R.W., 2012. Population genetic structure of Penaeus monodon, in relation to monsoon current patterns in Southwest, East and Andaman coastal waters of India. Gene 491, 149–157. Mennucci, B., Cancès, E., Tomasi, J., 1997. Evaluation of solvent effects in isotropic and anisotropic dielectrics and in ionic solutions with a unified integral equation method: theoretical bases, computational implementation, and numerical applications. J. Phys. Chem. B 101, 10506–10517. Miertus, S., Scrocco, E., Tomasi, J., 1981. Electrostatic interaction of a solute with a continuum. A direct utilizaion of AB initio molecular potentials for the prevision of solvent effects. Chem. Phys. 55, 117–129. Shi, Y., Zhou, Z.Y., Zhang, H.T., 2004. Density functional theory study of the hydrogen bonding interaction of 1:1 complexes of formamide with glycine. J. Phys. Chem. A 108, 6414–6420. Szucs, A., Hitchens, G.D., Bochris, JO'M., 1989. Electrochemical reactions of glucose oxidase at graphite electrodes. J. Electroanal. Chem. Interfacial Electrochem. 275, 133–148. Torrent-Sucarrat, M., Anglada, J.M., 2004. The gas-phase hydrogen bond complexes between formic acid with hydroxyl radical: a theoretical study. Chemphyschem 5, 183–191. Vanommeslaeghe, K., Loverix, S., Geerlings, P., Tourwé, D., 2005. DFT-based ranking of zinc-binding groups in histone deacetylase inhibitors. Bioorg. Med. Chem. 13, 6070–6082. Xie, P.P., Chen, X.X., Wang, F., Hu, C.G., Hu, S.S., 2006. Electrochemical behaviors of adrenaline at acetylene black electrode in the presence of sodium dodecyl sulfate. Colloids Surf. B 48, 17–23. Zheng, H., 2003. Pharmaceutical Chemistry. People's Medical Publishing House, Beijing.