Vibrational spectra of N-acetylglycine oligomers. Part 2. - Raman scattering study of selectively C-deuteriated oligomers with polyglycine I- and II-type structures

Article abstract of DOI:10.1039/a605741a

Selectively C-deuteriated N-acetylglycine trimer and tetramer acid types have been synthesized, and their two crystalline modifications, solid-A and solid-B [which correspond in structure to polyglycine (PG) II and I, respectively] have been prepared. Raman scattering spectra have been measured for a series of these glycine oligomers, and the CH₂- and CD₂-characteristic modes have been investigated in detail. Assignment of the CH₂-characteristic bands to each CH₂ group in the oligomers has been carried out successfully. In particular, the results obtained from the CD₂ stretch region show that N- and C-terminal glycine residues for the PGI- and PGII-type trimers and tetramers are all in very similar environments and that the glycine residues which are sandwiched between the two terminal residues are also in a similar environment for both the trimers and the tetramers.

Full text of DOI:10.1039/a605741a

View Article Online / Journal Homepage / Table of Contents for this issue
Vibrational spectra of N-acetylglycine oligomers
Part 2.¤ÈRaman scattering study of selectively C-deuteriated oligomers with
polyglycine I- and II-type structures
Hideki Etori,a Keijiro Taga,a Hirofumi Okabayashia and Kunihiro Ohshimab
a Department of Applied Chemistry, Nagoya Institute of T echnology, Gokiso-cho, Showa-ku,
Nagoya 466, Japan
b T echnical Research L aboratory, Kurabo Industries L td., 14-5, Shimokida-cho, Neyagawa,
Osaka 572, Japan
Selectively C-deuteriated N-acetylglycine trimer and tetramer acid types have been synthesized, and their two crystalline modiÐ-
cations, solid-A and solid-B [which correspond in structure to polyglycine (PG) II and I, respectively] have been prepared.
Raman scattering spectra have been measured for a series of these glycine oligomers, and the CH - and CD -characteristic modes
2
2
have been investigated in detail. Assignment of the CH -characteristic bands to each CH group in the oligomers has been
2
2
carried out successfully. In particular, the results obtained from the CD stretch region show that N- and C-terminal glycine
residues for the PGI- and PGII-type trimers and tetramers are all in very similar environments and that the glycine residues
2
which are sandwiched between the two terminal residues are also in a similar environment for both the trimers and the tetramers.
Polyglycine (PG) exists in two crystalline forms known as the
I- (PGI) and II-types (PGII).1 According to X-ray and elec-
tron di†raction studies, PGI takes up an antiparallel-chain
rippled sheet structure2h6 while PGII takes up an antiparallel
PGII.7h11,15 In particular, the e†ects of N- and C-terminal
glycine residues on the vibrational spectra have been dis-
cussed. Vibrational bands characteristic of PGI13,14 and
PGII15 have also been used as references for interpretation of
the Raman scattering spectra of these oligomers.
chain structure with a 3 -helix.7h10
1
Suzuki et al.11 have prepared Ðve isotopic polyglycines,
(undeuteriated, N-deuteriated, C-deuteriated, completely deu-
teriated and 15N-substituted PG), and made a detailed investi-
gation of the IR spectra of these samples. Their results
provided an almost complete data set of IR absorption
spectra of PGI and PGII. The vibrational spectra of PGI,
PGII and their deuteriated derivatives have also been investi-
gated in detail.12,13 Most of the observed frequencies have
been successfully assigned by normal coordinate analysis
using force constants associated with the intermolecular
hydrogen bonds.14,15
Conformational studies of the glycine oligomers have been
made in order to determine the critical size for formation of
the secondary structure of polypeptides.16h19 In our previous
study,20 we demonstrated, by the use of X-ray powder di†rac-
tion patterns and vibrational spectra, that two crystalline
modiÐcations (solid-A and solid-B) are obtained for the N-
acetylglycine trimer, tetramer and pentamer acid types and
that a solid-A 7 solid-B conversion which is similar to the
PGII 7 PGI conversion is possible for these oligomers.
However, for N-acylglycine oligomers with long acyl
chains,21 it has been shown that the chains induce formation
of a further PGII-like structure in the solid state. The reason
why such a PGII-like conformation shows preferential stabil-
ization by the long acyl chain derivatives remains unresolved.
The solution may be linked with the reason why the
PGI 7 PGII type conversion is possible for very simple N-
acetylglycine oligomers. Probably, both C- and N-terminal
groups play an important role in the mechanism of such an
interconversion.
Experimental
Materials
Selectively
C-deuteriated
N-acetylglycine
trimers
[AcG*G G , AcG G*G and AcG G G* (the asterisk shows
1
2
3
1
2
3
1
2
2
3
the residue for location of CD -glycine)] and tetramers
(AcG*G G G ,
AcG G*G G ,
AcG G G*G
and
1
2
3
4
1
2
3
4
1 2 3 4
AcG G G G*) were prepared by acetylation of the corre-
1
2 3 4
sponding C-deuteriated triglycines (G*G G , G G*G and
1
2
2
3
3
4
1 2 3
1 2 3 4
G G G*) and tetraglycines (G*G G G , G G*G G ,
1
2
3
1
G G G*G and G G G G*) with acetic anhydride, respec-
1
2
3
4
1 2 3 4
tively.22 The selectively C-deuteriated triglycines and tetra-
glycines were prepared by a stepwise procedure as follows.
The glycine-2,2,d (G*; 98 atom % D, Aldrich) was treated
with carbobenzoxy chloride (ZwCl) to protect the N-
2
terminus.23 The product, carbobenzoxy C-deuteriated glycine
(ZwG*) was then condensed with glycine p-nitrobenzyl ester
(GwONb), which was prepared by esteriÐcation of glycine
with p-nitrobenzyl alcohol in benzene,24 to obtain
ZwG*GwONb using a method similar to that described by
Anderson et al.25 The Z-group of ZwG*GwONb was
removed in 25% HBrÈacetic acid solution in order to obtain
G*GwONb. The G*GwONb thus obtained was further con-
densed with ZwG to prepare ZwGG*GwONb and GG*G
was obtained by removing the Zw and wONb groups by
catalytic reduction with Pd. The other C-deuteriated trimers
and tetramers were prepared similarly. G*wONb was used
for preparation of GGG* and GGGG*.
In order to understand the role of the C- and N-terminal
residues, selectively C-deuteriated N-acetylglycine trimer and
tetramer acid types were prepared. X-Ray powder di†raction
patterns and vibrational spectra of these oligomers were mea-
sured and compared with those for PGI2h6,11,13,14 and
These oligomers were treated with an aqueous solution of
LiBr or with dichloroacetic acid (DCA) as described pre-
viously.20 The samples treated with an aqueous solution of
LiBr and with DCA are termed the A-series and B-series
samples, respectively. The abbreviations for the two crystalline
modiÐcations of these C-deuteriated N-acetylglycine trimer
and tetramer acid types are listed in Table 1.
¤ Part 1: ref. 20.
J. Chem. Soc., Faraday T rans., 1997, 93(2), 313È319
313

View Article Online
Table 1 Abbreviations for A- and B-series of selectively C-deuteriated N-acetylgycine trimer and tetramer acid types
N-acetylgycine oligomer acid typea
AcG*G G
A-series
B-series
G1D3-A
G2D3-A
G3D3-A
G1D3-B
G2D3-B
G3D3-B
1 2
AcG G*G
3
3
trimer
1
2
AcG G G*
1
2
3
AcG*G G G
G1D4-A
G2D4-A
G3D4-A
G4D4-A
G1D4-B
G2D4-B
G3D4-B
G4D4-B
1
2
3
4
4
4
AcG G*G G
tetramer
1
2 3
AcG G G*G
1
2 3
AcG G G G*
1
2
3
4
a An asterisk-marked G denotes a C-deuteriated glycine residue.
Samples were identiÐed by elemental analysis and the
agreement between the calculated and observed values was
within 0.5%. Isotopic purity of each C-deuteriated oligomer,
determined by 1H NMR, was 98%.
For these C-deuteriated oligomers, it has been found that
the observed band frequencies of the NH stretch mode, the
CxO stretch mode of the terminal CO H group, and the
2
amide I and amide II modes are virtually invariant upon
selective C-deuteriation. Therefore, discussion is focussed on
the amide III, CH - and CD -characteristic modes.
Methods
2
2
Raman spectra below 3600 cm~1 were obtained with a
Nicolet 950 Fourier transform Raman spectrometer using the
Nd : YAG laser (excitation wavelength of 1064 nm) with a
resolution of 4 cm~1 at room temperature. The Raman
spectra of the solid samples were obtained from pressed solid
samples using a laser power of 500 mW.
X-Ray powder di†raction patterns were obtained by use of
an RAD-RC di†ractometer with countermonochrometer (Cu-
Ka ray; voltage, 60 kV, current, 200 mA).
Raman scattering spectra of selectively C-deuteriated
PGII-type glycine oligomers
Amide III. Fig. 1 shows the Raman spectra of the A-series
oligomers. For undeuteriated oligomers, the Raman bands at
1280È1284 and 1290È1294 cm~1 are assigned to amide III
modes.15 For C-deuteriated A-series oligomers, selective C-
deuteriation a†ects the spectral features in this region, since
amide III modes are heavily mixed with the CawH and CH
2
characteristic modes.15 For the trimers, deuteriation of G1-
Abbreviations
CH brings about the disappearance of the 1284 cmv1 band
2
and on deuteriation of G2-CH the 1290 cm~1 band disap-
The following abbreviations for vibrational assignments are
used: amide I, mainly CxO stretching vibration; amide II,
NH in-plane bending vibration coupled with the amide CN
stretching mode; amide III, amide CN stretching vibration
coupled with NH in-plane bending and CawH bending
modes.26,27
2
pears, indicating that the G1-CH group contributes to the
former band and the G2-CH group to the latter. For the
tetramers, the intensity of the 1280È1282 cm~1 band decreases
on deuteriation of the G1- or G4-residue, while that of the
1292È1298 cm~1 band decreases upon deuteriation of the G2-
or G3-CH group. Thus, the G1- and G4-CH groups con-
2
2
2
2
tribute to the band at 1280È1282 cm~1 and the G2- and G3-
Results and Discussion
X-Ray powder di†raction patterns of N-acetylglycine oligomers
CH groups to those at 1292È1298 cm~1.
2
CH deformational bands. For the undeuteriated A-series
The X-ray powder di†raction patterns of selectively C-
deuteriated N-acetylglycine trimer and tetramer acid types
were measured and compared with those of PGI1,5,6 and
PGII.1,7h10 For the C-deuteriated A-series, very intense reÑec-
tions at 4.18È4.19 A and weak reÑections at 3.15È3.17 A,
which correspond well to the 4.14 and 3.09 A reÑections of
PGII, were observed, while the di†raction patterns of the C-
deuteriated B-series contained very intense reÑections at 3.35È
3.37 A and medium reÑections at 4.35È4.36 A, corresponding
to the reÑections at 3.42 and 4.36 A for PGI. The results indi-
cate that the oligomers of the C-deuteriated A-series take up
the PGII-like helical structure while those of the C-
deuteriated B-series take up a structure similar to the b-sheet
structure of PGI. Thus, the oligomers of the C-deuteriated A-
series can be regarded as PGII-type oligomers and those of
the C-deuteriated B-series as PGI-type oligomers.
2
oligomers, broad and strong bands at 1423È1424 cm~1 are
assigned to the CH bend modes. These bands are split by
2
selective C-deuteriation. For the trimers, when the G1- or G2-
CH group is deuteriated, the intensity of the 1423 cm~1 band
2
decreases and the 1408È1410 cmv1 band appears, while on
deuteriation of the G3-CH group this latter band disappears.
2
Thus, we may assume that both the G1- and G2-CH groups
2
contribute to the 1423 cm~1 band but only the G3-CH
2
group contributes to the 1410 cm~1 band. For the A-series
tetramers, the intensity of the 1422È1425 cm~1 band decreases
on deuteriation of the G1- (or G2- or G3-) methylene, indicat-
ing that all three methylene groups contribute to the 1422È
1425 cm~1 band. Furthermore, since the band at 1412È1415
cm~1 disappears on deuteriation of the G4-CH group, we
2
may assign this band to the G4-CH group.
2
The CH wag modes, which are coupled with an NH in-
2
plane bend mode,15 appear in the 1330È1390 cm~1 region.
For the Raman spectra of undeuteriated A-series oligomers,
Raman scattering spectra of PGII- and PGI-type glycine
oligomers
the bands at 1350È1358 and 1385 cm~1 are assigned to the
The Raman scattering spectra of PGII- and PGI-type N-
acetylglycine trimer and tetramer acid types and their selec-
tively C-deuteriated derivatives were measured in the
100È3600 cm~1 region, and were compared with the data of
isotopic polyglycines11 and with the normal modes of
PGI13,14 and PGII.15 It was also conÐrmed from the Raman
spectra that the A-series samples take up a PGII-like structure
while the B-series samples are in a PGI-like structure.
CH wag modes.
2
For the C-deuteriated trimers, deuteriation of the G1- or
G2-CH group results in a decrease in intensity of the 1380È
2
1381 cm~1 band while on deuteriation of the G3-CH group
2
the 1357È1358 cm~1 band disappears. Therefore, it may be
assumed that the G1- and G2-CH groups predominantly
2
contribute to the 1380È1385 cm~1 band while the G3-CH
2
group contributes to the 1357È1358 cm~1 band. For the C-
314
J. Chem. Soc., Faraday T rans., 1997, V ol. 93

View Article Online
deuteriated tetramers, similar observations were made: on
deuteriation of the G2- or G3-CH group the intensity of the
2
band at 1381È1385 cm~1 decreases, while on deuteriation of
G4-CH the 1350È1357 cm~1 band disappears. Thus, it is
2
evident that both G2- and G3-CH groups contribute to the
2
1381È1385 cm~1 band and the G4-CH group contributes to
2
the 1350È1357 cm~1 band.
For the Raman spectra of G1D3-A and G2D3-A, the bands
at 1308È1309 and 1315È1316 cm~1 are observed in common,
and may be assigned to the CH wag modes coupled with the
2
CH twist modes. On deuteriation of the G3-CH group the
2
2
latter band disappears, indicating that the 1315È1316 cm~1
band arises from the G3-residue. For the C-deuteriated tetra-
mers, the 1307È1313 cm~1 bands observed in common may
arise from all CH groups and the 1318È1325 cm~1 bands
2
from the G4-CH group.
2
For undeuteriated oligomers, the CH twist modes, which
2
are heavily mixed with CH wag and NH in-plane bend
2
modes,15 appear at 1250È1252 and 1263 cm~1. Selective C-
deuteriation markedly a†ects the Raman band features in this
region; for the trimers the intensity of the 1252 cmv1 band
decreases upon deuteriation of the G1- or G2-CH group,
2
showing the contribution of G1- and G2-CH groups to this
2
band. Similar results were obtained for the tetramers.
The CH rock modes, which are heavily mixed with skeletal
2
CwC stretch and CwN stretch modes, are observed in the
800È1000 cm~1 region. For the undeuteriated trimer, a domi-
nant Raman band at 889 cm~1 (in addition to shoulders at
863, 875 and 904 cm~1) is observed, and is assigned to the
CH rock mode. For the C-deuteriated trimers, the 875 cm~1
2
band disappears on deuteriation of the G1-CH group, indi-
2
cating that the G1-CH group contributes to this band. On
deuteriation of the G2-CH group the 889 cm~1 band disap-
pears, while deuteriation of G3-CH group results in a disap-
2
2
2
pearance of the 863 cm~1 band. Therefore, the G2- and G3-
CH groups contribute to the 889 and 863 cm~1 bands,
2
respectively. Since the 893È898 cm~1 bands (which corre-
sponds to the 904 cmv1 band in the undeuteriated trimer) are
observed in common for all these C-deuteriated trimers, all
the CH groups contribute to these bands.
2
For the undeuteriated tetramer, a predominant Raman
band at 887 cm~1 is observed, in addition to very weak shoul-
der bands at 864, 875 and 901 cm~1, and is assigned to the
CH rock mode. When the CH group of the tetramer is selec-
2
2
tively deuteriated, splitting of the rock mode also occurs, as
shown in Fig. 1(B). On deuteriation of the G1-CH group the
2
875 cm~1 band disappears while deuteriation of the G4-CH
2
group brings about disappearance of the 864 cm~1 band.
These results are similar to those obtained for G1D3-A and
G3D3-A. Thus, we may assume that the 875 cm~1 band arises
from the CH group of the N-terminal glycine residue, while
2
the 864È866 cm~1 band arises from that of the C-terminal
glycine. When the G2-CH group is deuteriated, the intensities
2
of the 879 and 886 cm~1 bands decrease, while deuteriation of
the G3-CH group results in a decrease in intensity of the 885
2
cm~1 band. Thus, for the tetramers, both the G2- and G3-
CH groups predominantly contribute to the 887 cm~1 band
2
and the G2-CH group also contributes to the 879 cm~1
2
band.
CD deformational bands. For the G1D3-A and G1D4-A
2
samples, in which each G1-CH group was deuteriated, the
2
band arising from the CD rock modes appears at a lower
2
frequency [804 (trimer) and 807 (tetramer) cm~1], compared
with those of the oligomers C-deuteriated at other positions,
as seen in Table 2. For the G3D3-A and G4D4-A samples, in
which the C-terminal CH group was deuteriated, the CD
bend modes are clearly observed at a lower frequency and
splitting of the bend and wag modes also occurs.
Fig. 1 Raman spectra of undeuteriated and selectively C-deuteriated
PGII-type N-acetylglycine oligomers in the solid state in the 800È
1700 cm~1 region. [A, Trimers: (a) undeuteriated; (b) G1D3-A; (c)
G2D3-A; (d) G3D3-A. B Tetramers: (a) undeuteriated; (b) G1D4-A;
(c) G2D4-A; (d) G3D4-A; (e) G4D4-A].
2
2
J. Chem. Soc., Faraday T rans., 1997, V ol. 93
315

View Article Online
Table 2 CD characteristic band frequencies (cm~1) for selectively C-deuteriated PGII-type trimers and tetramers
2
trimer
G2D3-A
1186
tetramer
G1D3-A
1189
G3D3-A
G1D4-A
1188
G2D4-A
1182
G3D4-A
G4D4-A
tentative assignmenta
1185
1159
1133
n
1170
1153
1134
1084
1049
1170
t
1136
CD bend
o
p
1112
1076
2
t
1078
1052
1090
1061
1071
967
1080
970
1066
970H
966
969
971
942
967
CD wag
942
2
918
920
836
918
807
919
837
919
837
CD twist
2
838H
839
CD rock
804
2
a Ref. 11.
Skeletal stretch bands. For the undeuteriated trimer and
tetramer, the Raman bands observed in the 1000È1150 cm~1
region are assigned to the skeletal stretch modes. In particu-
lar, C-deuteriation does not a†ect the frequency of the 1034È
1038 cm~1 band which is characteristic of the PGII-type
structure.15
sandwiched between the two terminal residues are also in a
similar environment for both the trimers and the tetramers.
Raman scattering spectra of selectively C-deuteriated PGI-type
glycine oligomers
Fig. 3 shows the Raman spectra of the B-series oligomers. For
the undeuteriated trimer and tetramer, the Raman bands at
1014È1015 and 1154 cm~1 are assigned to the skeletal stretch
modes, which are characteristic of a PGI-type structure.13,14
For the C-deuteriated oligomers, selective C-deuteriation
strongly a†ects the Raman bands in this region in both fre-
quency and intensity. Indeed, from the results of normal mode
analysis for isotopic PGI,13,14 one may assume that bands
CD stretch bands. Fig. 2 shows the Raman spectra of selec-
2
tively C-deuteriated A-series oligomers in the CD stretch
2
region. For the C-deuteriated PGII-type trimers, the Raman
bands at 2110È2117, 2166È2169 and 2245È2248 cm~1 corre-
spond closely to the IR bands at 2117, 2172 and 2244 cm~1
which were observed for C-deuteriated PGII.11 The Raman
spectral features in this region reÑect the environment of the
selectively C-deuteriated glycine residue. We may compare the
coupled between the CD wag and bend modes and those for
2
the skeletal stretch modes appear in this region. In this study,
Raman band features of the CD stretch modes for the three
2
detailed discussion of these spectral features is omitted, since it
is difficult at present explicitly to interpret them.
selectively-C-deuteriated trimers with those of the four C-
deuteriated tetramers. In this region the features of the G1-
and G3-deuteriated trimers are very similar to those of the
G1- and G4-deuteriated tetramers, respectively. This observ-
ation implies that the environments of the N- and C-terminal
glycine residues in both the trimer and the tetramer are very
similar. The spectral feature of the G2D3-A sample is approx-
imately similar to those of the G2D4-A and G3D4-A samples.
Therefore, we may assume that the glycine residues which are
CH deformational bands. For the B-series samples, the
2
Raman bands arising from the CH bend, wag and rock
2
modes are listed in Table 3 (A, trimers; B, tetramers). It is
found that the Raman bands arising from these modes vary
markedly both in frequency and intensity upon C-
deuteriation.
The Raman bands in the 1430È1460 cm~1 region arise from
the CH bend modes. For the undeuteriated trimer, the CH
bend modes consist of the three bands at 1433, 1454 and 1459
2
2
cm~1. We may note that selective deuteriation of G1- or G2-
or G3-CH groups cause the bands at 1450È1455, 1459È1460
2
and 1431È1438 cm~1 to disappear. Therefore, the G1-CH
2
group predominantly contributes to the 1450È1455 cm~1
band and the G2-CH group to the 1459È1460 cm~1 band.
2
Furthermore, the 1431È1438 cm~1 band contains the pre-
dominant contribution of the G3-CH group, although the
2
increased intensity found for the 1438 cm~1 band of G1D3-B
cannot be explained.
The CH wag modes are reÑected in the 1300È1420 cm~1
2
region. For the undeuteriated trimer, the wag modes consist of
four bands at 1337, 1373, 1389 and 1412 cm~1. Deuteriation
of the G1- or G2-CH group causes the band at 1383È1389 or
2
1373È1378 cm~1 to disappear. Moreover, on deuteriation of
the G3-CH group the 1337È1344 and 1411È1414 cm~1 bands
2
also disappear. These results indicate that the G1- and G2-
CH groups contribute mainly to the bands at 1383È1389 and
2
1373È1378 cm~1 while the G3-CH group contributes to the
2
bands at 1337È1346 and 1411È1414 cm~1.
For these trimers, the Raman bands at 1240È1243 and
1268È1269 cm~1 may be assigned to the CH twist modes.
Fig. 2 Raman spectra of selectively C-deuteriated PGII-type N-
2
For the undeuteriated trimer, we may assign the bands at
acetylglycine oligomers in the solid state in the CD stretch region.
2
896, 961 and 985 cmv1 to the CH rock modes. For the selec-
[A, Trimers (a) G1D3-A; (b) G2D3-A; (c) G3D3-A. B, Tetramers: (a)
2
G1D4-A; (b) G2D4-A; (c) G3D4-A; (d) G4D4-A].
tively C-deuteriated trimers, the very weak bands at 895È896,
316
J. Chem. Soc., Faraday T rans., 1997, V ol. 93

View Article Online
Fig. 4 Raman spectra of selectively C-deuteriated PGI-type N-
acetylglycine oligomers in the solid state in the CD stretch region.
2
[A, Trimers: (a) G1D3-B; (b) G2D3-B; (c) G3D3-B. B, Tetramers (a)
G1D4-B; (b) G2D4-B; (c) G3D4-B; (d) G4D4-B]
while upon deuteriation of the G2-CH group, the 895È896
2
cm~1 band disappears, and upon deuteriation of the G3-CH
2
group the 960È961 cm~1 band disappears. Thus, the G1-CH
2
group predominantly contributes to the 985 cm~1 band and
the 895È896 cm~1 band probably arises from the G2-CH
2
group. Furthermore, the G3-CH group predominantly con-
2
tributes to the 960È961 cm~1 band.
For selectively C-deuteriated tetramers similar observations
were made, and tentative assignment of the CH characteristic
2
modes for these PGI-type tetramers is also summarized in
Table 3(a).
CD stretch bands. Fig. 4 shows the Raman spectra of selec-
2
tively C-deuteriated PGI-type oligomers in the CD stretch
2
region.
The Raman spectral features of the C-deuteriated B-series
oligomers in this region reÑect the environment of the selec-
tively C-deuteriated glycine residue in the PGI-type structure.
For the trimers, the spectral features of G1D3-B and G3D3-B
are very similar to those of G1D4-B and G4D4-B. Further-
more, the Raman spectral features of the CD stretch modes
2
for G2D3-B are similar to those of G2D4-B and G3D4-B.
Thus, in the B-series oligomers, we may assume that N- and
C-terminal glycine residues have similar residual environ-
ments and that the G2-glycine residue of the trimer also has a
similar environment to those of the G2- and G3-residues of
the tetramer.
CD deformational bands. The bend, wag, twist and rock
2
modes characteristic of the CD group in the PGI-type struc-
2
ture are listed in Table 4. Note that the CD rock modes of
2
the G3D3-B and G4D4-B are observed at a lower frequency
(843 cm~1). This observation may indicate restriction of the
C-terminal glycine residues of the trimer and the tetramer.
Fig. 3 Raman spectra of undeuteriated and selectively C-deuteriated
PGI-type N-acetylglycine oligomers in the solid state in the 800È1700
cm~1 region. [A, Trimers: (a) undeuteriated; (b) G1D3-B; (c)
G2D3-B; (d) G3D3-B. B, Tetramers: (a) undeuteriated; (b) G1D4-B;
(c) G2D4-B; (d) G3D4-B; (e) G4D4-B].
Conclusion
Selectively C-deuteriated N-acetylglycine trimer and tetramer
acid types have been synthesized, and their two crystalline
modiÐcations, solid-A and solid-B, which correspond to PGII
and PGI in secondary structure, have been prepared.
960 and 985 cm~1 probably correspond to the 896, 961 and
985 cm~1 bands of the undeuteriated trimer. When the G1-
CH group is deuteriated, the 985 cm~1 band disappears,
2
J. Chem. Soc., Faraday T rans., 1997, V ol. 93
317

View Article Online
Table 3(a) CH characteristic mode frequencies (cm~1) for PGI-type trimers and their tentative assignment
2
undeuteriated
trimer
G1D3-B
G2D3-B
G3D3-B
tentative assignment
1459
1454
1433
1460
È
1438
È
1455
1431
1460
1450
È
G2-CH n
2
G1-CH o bend
2
G3-CH p
2
n
1412
1389
1373
1337
1411
È
1378
1341
1414
1383
È
È
1389
1376
È
G3-CH
G1-CH
G2-CH
G3-CH
2
t
wag
2
o
2t
1344
p
2
985
961
896
È
960
896
985
960
È
985
È
895
G1-CH n
2
G3-CH o rock
2
G2-CH p
2
(b) CH characteristic mode frequencies (cm~1) for PGI-type tetramers and their tentative assignment
2
undeuteriated
tetramer
G1D4-B
G2D4-B
G3D4-B
G4D4-B
tentative assignment
1458
1452
1435
1460
È
1439
È
1449
1434
È
1449
1433
1459
1451
È
G2-, G3-CH n
2
G1-CH
G4-CH
o bend
2
2
p
1412
1393
1385
1372
1363
1413
È
1389
1371
È
1411
È
1382
È
1412
1390
È
1370
È
È
G4-CH
n
2
1396
1389
1374
1365
G1-, G2-CH t
2
G3-CH
G2-CH
o wag
2
2
t
1366
G1-, G3-CH p
2
Table 4 CD characteristic band frequencies (cm~1) of selectively C-deuteriated PGI-type trimers and tetramers
2
trimer
G2D3-B
1177
tetramer
G1D3-B
1177
G3D3-B
G1D4-B
G2D4-B
G3D4-B
G4D4-B
tentative assignmenta
1177
1146
1174
1126
1172
1151
n
p
n
1156
1146
1156
1118
oCD wag ] CD bend
2
2
1136
1138
1096
1099
1077
1048
1099
1079
1034
1098
1070
1047
1092
1077
1031
1095
1033
1085
1032
oCD bend ] CD wag
2
2
1038
p
H
928
916
932
916
935
930
925
912
925
915
930
918
935
929
twist ] CD wag
HCD
2
2
855
882
868
887
865
884
882
884
868
887
864
CD wag ] CD rock
2
2
843
843
CD rock
2
a Ref. 14.
Fig. 5 PGII(helical)-type (A) and PGI(b-sheet)-type (B) structural models for the N-acetylglycine tetramer. The dotted lines represent hydrogen
bonding.
318
J. Chem. Soc., Faraday T rans., 1997, V ol. 93

View Article Online
2
W. T. Astbury, C. E. Dalgliesh, S. E. Darmon and G. B. B. M.
Sutherland, Nature (L ondon), 1948, 162, 596.
W. T. Astbury, Nature (L ondon), 1949, 163, 722.
L. Pauling and R. B. Corey, Proc. Natl. Acad. Sci. USA, 1953, 39,
253.
B. Lotz, J. Mol. Biol., 1974, 87, 169.
S. Munoz-Guerra, J. Puiggal•, A. Rodr•guez and J. A. Subirana,
J. Mol. Biol., 1983, 167, 223.
X-Ray powder di†raction patterns of these oligomers have
been measured and compared with those of PGII and PGI.
The results indicate that the oligomers of the selectively C-
deuteriated A-series take up the PGII-type helical structure
while those of the C-deuteriated B-series adopt a b-sheet
structure which is similar to that of PGI.
3
4
5
6
Raman scattering spectra were measured for these A- and
B-series oligomers and, in particular, the CH - and CD -
7
8
F. H. C. Crick and A. Rich, Nature (L ondon), 1955, 176, 780.
G. N. Ramachandran, V. Sasisekharan and C. Ramakrishnan,
Biochim. Biophys. Acta, 1966, 112, 168.
2
2
characteristic modes were examined. Selective C-deuteriation
made it possible to assign the CH deformational bands to
9
S. Krimm, Nature (L ondon), 1966, 212, 1482.
2
each CH group.
10 G. N. Ramachandran, C. Ramakrishnan and C. M. Venkatacha-
lam, in Conformation of Biopolymers, ed. G. N. Ramachandran,
Academic Press, New York, 1967, p.429.
2
For the A- and B-series oligomers, in which the N- and
C-terminal glycine CH groups were deuteriated, the CD
bend, twist and rock modes appeared at a lower frequency
than those of the oligomers C-deuteriated in other positions.
2
2
11 S. Suzuki, Y. Iwashita, T. Shimanouchi and M. Tsuboi, Bio-
polymers, 1966, 4, 337.
12 E. W. Small, B. Fanconi and W. L. Peticolas, J. Chem. Phys.,
1970, 52, 4369.
13 Y. Abe and S. Krimm, Biopolymers, 1972, 11, 1817.
14 A. M. Dwivedi and S. Krimm, Macromolecules, 1982, 15, 177.
15 A. M. Dwivedi and S. Krimm, Biopolymers, 1982, 21, 2377.
16 M. Smith, A. G. Walton and J. L. Koenig, Biopolymers, 1969, 8,
29.
17 A. M. Dwivedi and V. D. Gupta, Chem. Phys. L ett., 1971, 8, 220.
18 V. D. Gupta, M. K. Gupta and K. Nath, Biopolymers, 1975, 14,
1987.
From the Raman band features in the CD stretch region, we
2
may assume that the N- and C-terminal glycine residues of the
A- and B-series oligomers are in very similar environments to
one another and that the glycine residues which are sand-
wiched between the two terminal residues are also in a similar
environment to each other.
We have recently studied the 2H spinÈlattice relaxation
times for the samples of selectively C-deuteriated A- and B-
series in the solid state,28 in order to evaluate the mobility of
each glycine residue in these oligomers. The results showed
that for the two series of C-deuteriated oligomers segmental
19 M. Avignon, C. Garrigon-Lagrange, Spectrochim. Acta A, 1971,
27, 297.
20 H. Okabayashi, K. Ohshima, H. Etori, K. Taga, T. Yoshida and
E. Nishio, J. Phys. Chem., 1989, 93, 6638.
21 H. Okabayashi, K. Ohshima, H. Etori, R. Debnath, K. Taga, T.
Yoshida and E. Nishio, J. Chem. Soc., Faraday T rans., 1990, 86,
1561.
mobilities of the CH groups of both the N- and C-terminal
2
residues are more restricted than those of the methylenes
sandwiched between the terminal residues.
Furthermore, in our previous studies,20 we have shown that
the mode of the hydrogen-bonding system is di†erent between
the A- and B-series samples.
Thus, we may assume that such behaviour of the two ter-
minal residues depends on the mode of the hydrogen-bonding
system. The two structural models are shown schematically in
Fig. 5 for the representative tetramer case.
22 R. M. Herbst and D. Shemin, in Organic Syntheses, ed. A. H.
Blatt, Wiley, New York, 1966, vol. 2, p. 11.
23 J. P. Greenstein and M. Winitz, in Chemistry of the Amino Acids,
Wiley, New York, 1961, vol. 2, p. 891.
24 Ref. 23, p. 942.
25 G. W. Anderson, J. E. Zimmerman and F. M. Callahan, J. Am.
Chem. Soc., 1967, 89, 5012
26 J. Bandekar, Biochim. Biophys. Acta, 1992, 1120, 123.
27 M. Diem, O. Lee and G. M. Roberts, J. Phys. Chem., 1992, 96,
548.
28 H. Etori, A. Yoshino, K. Watanabe, H. Okabayashi and K.
Ohshima, J. Chem. Soc., Faraday T rans., 1997, 143.
References
1
C. H. Bamford, L. Brown, E. M. Cant, A. Elliott, W. E. Hanby
and B. R. Malcolm, Nature (L ondon), 1955, 176, 396.
Paper 6/05741A; Received 16th August, 1996
J. Chem. Soc., Faraday T rans., 1997, V ol. 93
319