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Further evidence of the protonation of the C‐terminal of the poly‐γ‐benzyl‐ L ‐glutamate helix by acids
Author(s) -
Watanabe Hiroshi,
Yoshioka Koshiro
Publication year - 1966
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.1966.360040106
Subject(s) - dichloroacetic acid , chemistry , protonation , trifluoroacetic acid , formic acid , glutamic acid , trichloroacetic acid , medicinal chemistry , ethylene oxide , tetranitromethane , amino acid , organic chemistry , polymer , biochemistry , ion , nitration , copolymer
The change of the specific Kerr constant upon the addition of several acids to poly‐γ‐benzyl‐ L ‐glutamate solution in ethylene dichloride has been measured by the rectangular pulse method. The addition of a small amount of strong acid (trifluoroacetic acid, trichloroacetic acid, monochloroacetic acid, or hydrogen chloride) caused a rapid decrease of the specific Kerr constant. On the other hand, the effect of weak acids (formic acid, acetic acid, and propionic acid) was small. These facts show that the apparent dipole moment of a helical poly‐γ‐benzyl‐ L ‐glutamate molecule is considerably diminished by the protonation of terminal peptide groups. The electric conductivity of poly‐γ‐benzyl‐ L ‐glutamate solution in ethylene dichloride–dichloroacetic acid mixtures has been measured. It was found that the specific conductivity per unit concentration of poly‐γ‐benzyl‐ L ‐glutamate increased considerably at small fractions of dichloroacetic acid. This shows that poly‐γ‐benzyl‐ L ‐glutamate can react as a base (proton acceptor) with dichloroacetic acid. This result also confirms the previous conclusion.