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Infrared spectra and molecular conformations of D , L ‐copoly‐γ‐benzylglutamates
Author(s) -
Tsuboi Masamichi,
Mitsui Yukio,
Wada Akiyoshi,
Miyazawa Tatsuo,
Nagashima Nobuya
Publication year - 1963
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.360010403
Subject(s) - polymerization , chemistry , helix (gastropod) , copolymer , degree of polymerization , random coil , infrared spectroscopy , polymer chemistry , infrared , crystallography , polymer , circular dichroism , organic chemistry , ecology , physics , snail , optics , biology
Infrared absorption and x‐ray diffraction measurements have been made of D , L ‐copoly‐γ‐benzylglutamate fibers (cast from dioxane solutions) with various D / L ratios and with various degrees of polymerization. It was found that each chain of these copolymers consists of a random coil portion and an α‐helix portion and that the conformation of the latter is similar to the α‐helix of pure poly‐γ‐benzyl‐ L ‐glutamate. It was also found that the fraction of the α‐helix portion increases with the degree of polymerization of the copolymer. A simplified polymerization mechanism has been proposed for mixtures of D ‐ and L ‐amino acid N ‐carboxyanhydrides. A model of the molecular conformation of the D , L ‐copolypeptide chains derived from this proposed polymerization mechanism is in good agreement with infrared, x‐ray, and other measurements. Based on the results of these observations, we discuss the number of L ‐ or D ‐residues linked in succession that is required for initiating the formation of an α‐helix during the course of polymerization.