- Email: [email protected]
The optical rotatory dispersion of the β structure of poly-l-lysine and poly-l-serine
BIOCHEMICAL
Vol. 23, No. 2, 1966
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
THE OPTICAL ROTATORY DISPERSION OF THE 6 STRUCTURE OF POLY-L-LYSINE Betty
Davidson,
AND POLY-L-SERINEl and Gerald
Nancy Tooney2
D. Fasman3
Graduate Department of Biochemistry Brandeis University, Waltham, Massachusetts (Publication No. 416)
Received
March
17, 1966
Optical technique
rotatory
dispersion
among those
(ORD) has become an important
used to study
the
conformation
and synthetic
polypeptides
in solution
(Blout,
DOW r 1961;
Fasman, 1963).
Although
the a-helical
conformations
have been characterized
ultraviolet
ORD (Blout
and Yang, visible 1960; ton,
1965),
the
et al., --
1963;
Ikeda
et -- al.,
measurements
are far
ponsible
the Cotton
for
ORD spectrum Shechter,
1962;
1964;
removed
has been reported
regions
et al., --
1962;
1965; only
Harrap
and Yahara,
The solid
by farIizuka
in the
(Fasman and Blout,
from the electronic
for
and random
has been studied
Imahori
effects.
Urnes and
Yang and McCabe,
spectral
1961; Bradbury
Wada et al.,
1960;
in aqueous solution
%-conformation
and near ultraviolet
of proteins
state
one B-structure
and Staple-
1964).
These
transitions far
res-
ultraviolet
(Blout
and
1963).
1 For the previous paper in this series see Sage, H. J. and Fasman, G. D., Biochemistry 2, 286 (1966). 2 U. S. Public Health Service Predoctoral Fellow 3This work was done during the tenure of an Established Investiqatorship of the American heart Association. Inquiries should be addressed to Gerald D. Fasman
156
Vol. 23, No. 2, 1966
We wish
BIOCHEMICAL
to describe
ORD parameters
of the
of poly-L-lysine X-ray
ultraviolet
% conformation
state
studies
1962;
Imahori
Yahara
et .- al., -
1963).
an oriented
reported of
I
I 210
and Shechter
%-structure
220
the
in the
is seen in Fig.
by Blout
200
provide
film
and
and
evidence
that
1960; Bradbury
and Imahori,
200-290
1.
This
(1963)
as
for
1963;
rnv region, curve
is simi
the ORD of
of poly-L-isoleucine.
1
I
1
230
240
250
WAVE
(Imahori
f3 conformation
1964; Yahara
The ORD curve,
the
data
(Fasman and Blout,
and Yahara,
of poly-L-serine
film
1963) possesses
derivatives
et al., --
to that
185 rnp)
of a poly-L-serine
and infrared
poly-L-serine
O-blocked
of a film
(280 to
in aqueous solution.
diffraction
solid
does its
lar
far
1964; Bohak and Katchalski,
Yahara, in the
the
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
LENGTH
1 260
270
I 260
IN rnp
Fig. 1. Poly-L-serine (#NT-2-374-27) cast on a quartz disc from trifluoroacetic acid. The polymer was prepared by unblocking poly-0-tertiary-butyl-L-serine, with anhydrous HCl Specific viscosity of blocked polymer and HBr in benzene. in dichloroacetic acid (0.2%) is 0.52.
.
157
Vol. 23, No. 2, 1966
Previous and infrared and Doty, fraction
BIOCHEMICAL
studies,
1962;
(Shmueli
conditions
utilizing
spectroscopy 1958,
the
(Blout
techniques
and Lenormant,
Rosenheck and Doty,
and Traub,
poly-L-lysine
to a B conformation.
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
1965),
1957; Applequist
1961) and X-ray
have shown that
undergoes In the work
of ultraviolet
a transition reported
here,
under
difcertain
from an cc-helical the
ct + B transi-
60.000
70,000
60,000
50,000
40,000
‘E
30,000
20.000
10,000
0
- 10.000
-20,000 180
200 Wovelength
Figure
2.
220
240
m/.~
The ORD of ci and B poly-L-lysine
CL: Poly-L-lysine*HCl (Sample BD-1-10-28, intrinsic viscosity in 1M NaCl at pH 4.0 = 0.67) was dissolved in water and the pH adjusted to 11.06 with NaOH. The 0.0123% solution was filtered through an alkali resistent millipore filter into a water jacketed cell of 1 mm path length. The ORD was determined at 22.%OC. obtaining curve Q, the sample was heated, 51°C, in 6: After situ for about 15 minutes. When no further decrease in [rnv was noted, the cell and contents were cooled to 22.5' and CL&% mU i3 was obtained. A Cary 60 spectropolarimeter was used for the measurements. The solvent reference solution was water adjusted to pH 11.08. Polymer concentration was. determined by a modified micro-biuret procedure (Zamenhof and Chargaff, 1963).
158
BIOCHEMICAL
Vol. 23, No. 2, 1966
tion
was accomplished
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
by heating
(Applequist
and Doty,
Rosenheck
and Doty,
1961) an aqueous solution
at around
50'
no further
this
point
initial
until
the transition
a and final
The experimental of
was judged
conditions
temperature
or concentration
observation
might
parameters film
of
for
the
cross-B
B poly-L-serine.
The wavelength is similar reported
(Townend et -- al.,
for
(Table
190 mu region
violet
that
1961; Tinoco
the
ORD film
et
agree well for
of the
with
circular
random form of,poly-L-lysine
acid
in magnitude
(Blout
over
et -- al.,
points
to the reported
positions
1962)(Table are slightly
I).
than
1962;
that
Iizuka
at wavelengths
and 6 forms of the
parameters
the
the same preparation.
different
The cross
al.,
an
of the ORD peak and trough
1966)
the a-helical
than
and a
perhaps
correspond
maxima for
and Doty,
I).
B rather
of ~1and 6 poly-L-lysine
random poly-L-qlutamic
1965)
The latter
the ORD
of the ORD trough but
the
I summarizes
The positions
in position,
and Yang, the
Table
2.
The rate
either
solution.
At
of the
legend.
by increasing
a and B forms of poly-L-lysine data
ORD curves
an intermolecular
structure.
mu was noted.
in the
of the polymer
indicate
polymer
are shown in Fig.
are described
of aqueous solutions
dichroism
[m'llgg
complete.
was increased
1962;
of the helical
$ form of poly-L-lysine
the 11 + 8 transition
intramoleoular
change in
1958,
of the ultra-
polymer
It
should
displaced
in
(Rosenheck be noted
from those
in
solution. The a0 and b. values (Moffitt,
1956;
to evaluate
Moffitt
varied
and Yang,
the various
the b. and a0 values
obtained
of the
W'ada et al.,
1963;
Ikeda
1961;
et al., --
the wavelength
region
1964).
conformations.
B-structure,
using
and a0 = 350 to
Bradbury
et al., --
The values
460-278
equation
1956) have frequently
polypeptide
from b 0 = 0 to +420,
1960;
from the Moffitt
mu are b.
159
Estimates
of
A0 = 212 mu, have
840 (Fasman and Blout,
1962;
found
been used
Harrap
in this
= -241*17
and Stapleton, study
using
and a0 = -62k5.
s 0
c1
B
Poly-L-lysine,
Poly-L-lysine,
1 Rosenheck 2 Tinoco et
of
rotation;
1961
determinations
and Doty, al., 1962
eight
mean residue
205 rnp
(Holzwarth and Doty r 1965) ORD, calculated from circular dichroism
a Reduced b Average
204 mu
and Yang,
mu
204 mu
204.5
230 mu
233 mu
2233 mu
(Iizuka 1965)
Poly-L-glutamate random conformation (Blout et al., 1962 1
Poly-L-lysine*HCl random conformation
film
Poly-L-serine,
position hula
Fasman,
=-22,000
E-17,500
=-16,000
1963
-25.000'300
-6,220'590b
-15,700*870b
ORD Trough
I
[m’la
+29,200'1380b
+74,900*2470b
ORD Peak
mu
205 mu
198.6
210 rnp
position
Table
L
mu
194 rnp
190 rnp
mu
~202 rnp
c197.5
=198 rnv
196-197
220 mu,
223 mu,
222 mu,
Cross-over wavelengths
192 rnpl
190 mu 1,2 1 194 mu
Reported U.V. Maximum
Vol. 23, No. 2, 1966
From the wide various yield
BIOCHEMICAL
range of values
6 structures, different
mation
parallel,
is
dynamic
stability
the
not
in the
present
hydrogen
bonds of
hydrophobic
side
should at
the
it
degree
the
may of B for-
of overlap
the helical
structure,
that
are also
Acknowledgments -
Science
of Health, Society
to break
work was supported
U. S. Public
content
Health
(Massachusetts
in part
to the
extent
structure. by grants
the National of
Service
Division)
the
of proteins
secondary
(GB-2921), Diseases
the
process.
be in error
of the protein
the
has significant
of helical
and Metabolic
of
and to associate
B-conformation
Foundation
mechanism
interactions
necessary
[m'1233 will part
- This
of Arthritis
Cancer
of
final
thermo-
following
from the heating
estimates
Thus,
based on the measurement
the
As the
hydrophobic
The enthalpy
233 mu.
from the National
chain
is derived
the
chain
The added stability
cc-form.
chains
polypeptide
must have a greater
+ 8.
from side
be noted
B-structures
a single
CL. We propose
a + random chain may result
American
extent
one conformation.
6 conformation,
B structure
Institutes
the
length,
that
more than
than
of formation:
Institute
on chain
that
and cross+,
Moreover,
illustrate
of assuming
structure
that
becomes evident
etc.
is capable
rotation
it
anti-parallel
be dependent
These experiments
It
reported
b. and a0 values.
must also
of chains,
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
the National (A5852)
and the
Inc.
References 133rd Nat'1 Meeting Amer. Applequist, J. and Doty, P., Abstracts, Chem. Sot., p. 32Q (1958). Applequist, J. and Doty, P. in "Polyamino Acids, Polypeptides and Proteins" Ed. M. Stahmann, Univ. of Wisconsin Press, p. 161 (1962) . Blout, 1~. R. in "Optical Rotatory Dispersion" Ed. C. Djerassi, McGraw Hill, (1960). Blout, E. R. and Lenormant, H., Nature 179, 960 (1957). Blout, I~. R., Schmier, I. and Simmons, N. S., J. Amer. Chem. Sot. 3193 (1962). a4 -'
161
Vol. 23, No. 2, 1966
BIOCHEMICAL
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Blout, E. R. and Shechter, E., Biopolymers I, 568 (1963). Bohak, Z. and Katchalski, E., Biochemistry 2, 228 (1963). Bradbury, E. M., Elliott, A. and Hanby, W. E., J. Mol. Biol. 5, 487 (1962). Fasman, G. D. in "Methods in Enzymology" 6, 928 (1963). Fasman, G. D. and Blout, E. R., J. Amer. Chem. Sot. 82, 2262 (1960). B. S. and Stapleton, I. W., Biochim. Biophys. Acta -75, 31 Harrap, (1963). Holzwarth, G. and Doty, P., J. Amer. Chem. Sot. 87, 218 (1965). Iizuka, E. and Yang, J. T., Biochemistry 4, 1249 (1965). Ikeda, S., Maeda, H. and Isemura, T., J. Mol. Biol. 10, 223 (1964). Imahori, K. and Yahara, I., Biopolymers Symp. #l, 421(1964). Moffitt, W., J. Chem. Phys. 25, 467 (1956). Moffitt, W. and Yang, J. T.,Proc. Natl. Acad. Sci. U.S. 42, 596 (1956). Rosenheck, K. and Doty, P., Proc. Natl. Acad. Sci. U.S. 47, 1775 (1961). Shmueli, U. and Traub, W., J. Mol. Biol. 12, 205 (1965). Tinoco, Jr., I., Halpern, A. and Simpson, W. T. in "Polyamino Acids, Polypeptides and Proteins," Ed. M. Stahmann, Univ. of Wisconsin Press, p. 147 (1962). Townend, R., Kumosinski, T. F., Timasheff, S. N., Fasman, G. D. and Davidson, B., Biochem. Biophys. Res. Comm., following paper. Chem. 16, 401 (1961). Urnes, P. and Doty, P., Advances in Prot. Wada, A., Tsuboi, M. and Konishi, E., J. Phys. Chem. 65, 1119 (1961). Yahara, I. and Imahori, K., J. Amer. Chem. Sot. 85, 230 (1963). Yahara, I., Imahori, K., Iitaka, Y. and Tsuboi, M., J. Polymer Sci. B -- 1, 47 (1963). 3, 209 (1965). Yang, J. T. and McCabe, W. J., Biopolymers Zamenhof, S. and Chargaff, E. in "Methods iii Enzymology" 2, 702 (1963). Data of Sarkar, the values
P. K. and Doty, reported herein
P. are in reasonable (personal COmmUniCatiOn).
162
agreement
with
Vol. 23, No. 2, 1966
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
THE OPTICAL ROTATORY DISPERSION OF THE 6 STRUCTURE OF POLY-L-LYSINE Betty
Davidson,
AND POLY-L-SERINEl and Gerald
Nancy Tooney2
D. Fasman3
Graduate Department of Biochemistry Brandeis University, Waltham, Massachusetts (Publication No. 416)
Received
March
17, 1966
Optical technique
rotatory
dispersion
among those
(ORD) has become an important
used to study
the
conformation
and synthetic
polypeptides
in solution
(Blout,
DOW r 1961;
Fasman, 1963).
Although
the a-helical
conformations
have been characterized
ultraviolet
ORD (Blout
and Yang, visible 1960; ton,
1965),
the
et al., --
1963;
Ikeda
et -- al.,
measurements
are far
ponsible
the Cotton
for
ORD spectrum Shechter,
1962;
1964;
removed
has been reported
regions
et al., --
1962;
1965; only
Harrap
and Yahara,
The solid
by farIizuka
in the
(Fasman and Blout,
from the electronic
for
and random
has been studied
Imahori
effects.
Urnes and
Yang and McCabe,
spectral
1961; Bradbury
Wada et al.,
1960;
in aqueous solution
%-conformation
and near ultraviolet
of proteins
state
one B-structure
and Staple-
1964).
These
transitions far
res-
ultraviolet
(Blout
and
1963).
1 For the previous paper in this series see Sage, H. J. and Fasman, G. D., Biochemistry 2, 286 (1966). 2 U. S. Public Health Service Predoctoral Fellow 3This work was done during the tenure of an Established Investiqatorship of the American heart Association. Inquiries should be addressed to Gerald D. Fasman
156
Vol. 23, No. 2, 1966
We wish
BIOCHEMICAL
to describe
ORD parameters
of the
of poly-L-lysine X-ray
ultraviolet
% conformation
state
studies
1962;
Imahori
Yahara
et .- al., -
1963).
an oriented
reported of
I
I 210
and Shechter
%-structure
220
the
in the
is seen in Fig.
by Blout
200
provide
film
and
and
evidence
that
1960; Bradbury
and Imahori,
200-290
1.
This
(1963)
as
for
1963;
rnv region, curve
is simi
the ORD of
of poly-L-isoleucine.
1
I
1
230
240
250
WAVE
(Imahori
f3 conformation
1964; Yahara
The ORD curve,
the
data
(Fasman and Blout,
and Yahara,
of poly-L-serine
film
1963) possesses
derivatives
et al., --
to that
185 rnp)
of a poly-L-serine
and infrared
poly-L-serine
O-blocked
of a film
(280 to
in aqueous solution.
diffraction
solid
does its
lar
far
1964; Bohak and Katchalski,
Yahara, in the
the
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
LENGTH
1 260
270
I 260
IN rnp
Fig. 1. Poly-L-serine (#NT-2-374-27) cast on a quartz disc from trifluoroacetic acid. The polymer was prepared by unblocking poly-0-tertiary-butyl-L-serine, with anhydrous HCl Specific viscosity of blocked polymer and HBr in benzene. in dichloroacetic acid (0.2%) is 0.52.
.
157
Vol. 23, No. 2, 1966
Previous and infrared and Doty, fraction
BIOCHEMICAL
studies,
1962;
(Shmueli
conditions
utilizing
spectroscopy 1958,
the
(Blout
techniques
and Lenormant,
Rosenheck and Doty,
and Traub,
poly-L-lysine
to a B conformation.
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
1965),
1957; Applequist
1961) and X-ray
have shown that
undergoes In the work
of ultraviolet
a transition reported
here,
under
difcertain
from an cc-helical the
ct + B transi-
60.000
70,000
60,000
50,000
40,000
‘E
30,000
20.000
10,000
0
- 10.000
-20,000 180
200 Wovelength
Figure
2.
220
240
m/.~
The ORD of ci and B poly-L-lysine
CL: Poly-L-lysine*HCl (Sample BD-1-10-28, intrinsic viscosity in 1M NaCl at pH 4.0 = 0.67) was dissolved in water and the pH adjusted to 11.06 with NaOH. The 0.0123% solution was filtered through an alkali resistent millipore filter into a water jacketed cell of 1 mm path length. The ORD was determined at 22.%OC. obtaining curve Q, the sample was heated, 51°C, in 6: After situ for about 15 minutes. When no further decrease in [rnv was noted, the cell and contents were cooled to 22.5' and CL&% mU i3 was obtained. A Cary 60 spectropolarimeter was used for the measurements. The solvent reference solution was water adjusted to pH 11.08. Polymer concentration was. determined by a modified micro-biuret procedure (Zamenhof and Chargaff, 1963).
158
BIOCHEMICAL
Vol. 23, No. 2, 1966
tion
was accomplished
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
by heating
(Applequist
and Doty,
Rosenheck
and Doty,
1961) an aqueous solution
at around
50'
no further
this
point
initial
until
the transition
a and final
The experimental of
was judged
conditions
temperature
or concentration
observation
might
parameters film
of
for
the
cross-B
B poly-L-serine.
The wavelength is similar reported
(Townend et -- al.,
for
(Table
190 mu region
violet
that
1961; Tinoco
the
ORD film
et
agree well for
of the
with
circular
random form of,poly-L-lysine
acid
in magnitude
(Blout
over
et -- al.,
points
to the reported
positions
1962)(Table are slightly
I).
than
1962;
that
Iizuka
at wavelengths
and 6 forms of the
parameters
the
the same preparation.
different
The cross
al.,
an
of the ORD peak and trough
1966)
the a-helical
than
and a
perhaps
correspond
maxima for
and Doty,
I).
B rather
of ~1and 6 poly-L-lysine
random poly-L-qlutamic
1965)
The latter
the ORD
of the ORD trough but
the
I summarizes
The positions
in position,
and Yang, the
Table
2.
The rate
either
solution.
At
of the
legend.
by increasing
a and B forms of poly-L-lysine data
ORD curves
an intermolecular
structure.
mu was noted.
in the
of the polymer
indicate
polymer
are shown in Fig.
are described
of aqueous solutions
dichroism
[m'llgg
complete.
was increased
1962;
of the helical
$ form of poly-L-lysine
the 11 + 8 transition
intramoleoular
change in
1958,
of the ultra-
polymer
It
should
displaced
in
(Rosenheck be noted
from those
in
solution. The a0 and b. values (Moffitt,
1956;
to evaluate
Moffitt
varied
and Yang,
the various
the b. and a0 values
obtained
of the
W'ada et al.,
1963;
Ikeda
1961;
et al., --
the wavelength
region
1964).
conformations.
B-structure,
using
and a0 = 350 to
Bradbury
et al., --
The values
460-278
equation
1956) have frequently
polypeptide
from b 0 = 0 to +420,
1960;
from the Moffitt
mu are b.
159
Estimates
of
A0 = 212 mu, have
840 (Fasman and Blout,
1962;
found
been used
Harrap
in this
= -241*17
and Stapleton, study
using
and a0 = -62k5.
s 0
c1
B
Poly-L-lysine,
Poly-L-lysine,
1 Rosenheck 2 Tinoco et
of
rotation;
1961
determinations
and Doty, al., 1962
eight
mean residue
205 rnp
(Holzwarth and Doty r 1965) ORD, calculated from circular dichroism
a Reduced b Average
204 mu
and Yang,
mu
204 mu
204.5
230 mu
233 mu
2233 mu
(Iizuka 1965)
Poly-L-glutamate random conformation (Blout et al., 1962 1
Poly-L-lysine*HCl random conformation
film
Poly-L-serine,
position hula
Fasman,
=-22,000
E-17,500
=-16,000
1963
-25.000'300
-6,220'590b
-15,700*870b
ORD Trough
I
[m’la
+29,200'1380b
+74,900*2470b
ORD Peak
mu
205 mu
198.6
210 rnp
position
Table
L
mu
194 rnp
190 rnp
mu
~202 rnp
c197.5
=198 rnv
196-197
220 mu,
223 mu,
222 mu,
Cross-over wavelengths
192 rnpl
190 mu 1,2 1 194 mu
Reported U.V. Maximum
Vol. 23, No. 2, 1966
From the wide various yield
BIOCHEMICAL
range of values
6 structures, different
mation
parallel,
is
dynamic
stability
the
not
in the
present
hydrogen
bonds of
hydrophobic
side
should at
the
it
degree
the
may of B for-
of overlap
the helical
structure,
that
are also
Acknowledgments -
Science
of Health, Society
to break
work was supported
U. S. Public
content
Health
(Massachusetts
in part
to the
extent
structure. by grants
the National of
Service
Division)
the
of proteins
secondary
(GB-2921), Diseases
the
process.
be in error
of the protein
the
has significant
of helical
and Metabolic
of
and to associate
B-conformation
Foundation
mechanism
interactions
necessary
[m'1233 will part
- This
of Arthritis
Cancer
of
final
thermo-
following
from the heating
estimates
Thus,
based on the measurement
the
As the
hydrophobic
The enthalpy
233 mu.
from the National
chain
is derived
the
chain
The added stability
cc-form.
chains
polypeptide
must have a greater
+ 8.
from side
be noted
B-structures
a single
CL. We propose
a + random chain may result
American
extent
one conformation.
6 conformation,
B structure
Institutes
the
length,
that
more than
than
of formation:
Institute
on chain
that
and cross+,
Moreover,
illustrate
of assuming
structure
that
becomes evident
etc.
is capable
rotation
it
anti-parallel
be dependent
These experiments
It
reported
b. and a0 values.
must also
of chains,
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
the National (A5852)
and the
Inc.
References 133rd Nat'1 Meeting Amer. Applequist, J. and Doty, P., Abstracts, Chem. Sot., p. 32Q (1958). Applequist, J. and Doty, P. in "Polyamino Acids, Polypeptides and Proteins" Ed. M. Stahmann, Univ. of Wisconsin Press, p. 161 (1962) . Blout, 1~. R. in "Optical Rotatory Dispersion" Ed. C. Djerassi, McGraw Hill, (1960). Blout, E. R. and Lenormant, H., Nature 179, 960 (1957). Blout, I~. R., Schmier, I. and Simmons, N. S., J. Amer. Chem. Sot. 3193 (1962). a4 -'
161
Vol. 23, No. 2, 1966
BIOCHEMICAL
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Blout, E. R. and Shechter, E., Biopolymers I, 568 (1963). Bohak, Z. and Katchalski, E., Biochemistry 2, 228 (1963). Bradbury, E. M., Elliott, A. and Hanby, W. E., J. Mol. Biol. 5, 487 (1962). Fasman, G. D. in "Methods in Enzymology" 6, 928 (1963). Fasman, G. D. and Blout, E. R., J. Amer. Chem. Sot. 82, 2262 (1960). B. S. and Stapleton, I. W., Biochim. Biophys. Acta -75, 31 Harrap, (1963). Holzwarth, G. and Doty, P., J. Amer. Chem. Sot. 87, 218 (1965). Iizuka, E. and Yang, J. T., Biochemistry 4, 1249 (1965). Ikeda, S., Maeda, H. and Isemura, T., J. Mol. Biol. 10, 223 (1964). Imahori, K. and Yahara, I., Biopolymers Symp. #l, 421(1964). Moffitt, W., J. Chem. Phys. 25, 467 (1956). Moffitt, W. and Yang, J. T.,Proc. Natl. Acad. Sci. U.S. 42, 596 (1956). Rosenheck, K. and Doty, P., Proc. Natl. Acad. Sci. U.S. 47, 1775 (1961). Shmueli, U. and Traub, W., J. Mol. Biol. 12, 205 (1965). Tinoco, Jr., I., Halpern, A. and Simpson, W. T. in "Polyamino Acids, Polypeptides and Proteins," Ed. M. Stahmann, Univ. of Wisconsin Press, p. 147 (1962). Townend, R., Kumosinski, T. F., Timasheff, S. N., Fasman, G. D. and Davidson, B., Biochem. Biophys. Res. Comm., following paper. Chem. 16, 401 (1961). Urnes, P. and Doty, P., Advances in Prot. Wada, A., Tsuboi, M. and Konishi, E., J. Phys. Chem. 65, 1119 (1961). Yahara, I. and Imahori, K., J. Amer. Chem. Sot. 85, 230 (1963). Yahara, I., Imahori, K., Iitaka, Y. and Tsuboi, M., J. Polymer Sci. B -- 1, 47 (1963). 3, 209 (1965). Yang, J. T. and McCabe, W. J., Biopolymers Zamenhof, S. and Chargaff, E. in "Methods iii Enzymology" 2, 702 (1963). Data of Sarkar, the values
P. K. and Doty, reported herein
P. are in reasonable (personal COmmUniCatiOn).
162
agreement
with