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Raman spectral changes induced by side‐chain interactions in racemic poly‐γ‐benzyl glutamate
Author(s) -
Wilser Walter T.,
Fitchen D. B.
Publication year - 1974
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1974.360130714
Subject(s) - chemistry , raman spectroscopy , amide , spectral line , polymer , intensity (physics) , side chain , crystallography , stereochemistry , organic chemistry , optics , physics , astronomy
Laser Raman spectra are reported for solid films cast from a series of solutions containing mixtures of right‐ and left‐handed α‐helices of poly‐γ‐benzyl‐ L ‐ and D ‐glutamate. Procedures were established for producing spectra that were reproducible in position to ±0.3 cm −1 and in relative intensity to a few percent for features of interest. Spectra for the pure L and pure D polymers were identical, as expected. Several small but definite spectral changes appear in the mixtures, reaching a maximum for the racemic 50:50 mixture. The changes are a shift of −1.4 cm −1 in the amide I peak at 1650.5 cm −1 ; a shift of about −5 cm −1 in the partially resolved amide III peak at 1291 cm −1 ; a shift of +2.5 cm −1 in the benzyl peak at 3062.5 cm −1 ; changes in relative intensity of as much as 50% in several regions; and the marked enhancement of several peaks, particularly that at 254 cm −1 . These changes are discussed in terms of side‐chain interactions in the packing of right‐ and left‐handed helices.