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Interaction of water with poly‐α‐amino acids. II. Relationships between counter‐ion and relaxation processes
Author(s) -
Fenton M.,
Hiltner A.
Publication year - 1978
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.1978.360171003
Subject(s) - chemistry , salt (chemistry) , side chain , relaxation (psychology) , bound water , crystallography , ion , differential scanning calorimetry , strontium , glutamic acid , amino acid , molecule , thermodynamics , organic chemistry , polymer , psychology , social psychology , physics , biochemistry
The effect of hydration on the solid‐state conformation and relaxation behavior of the alkaline earth salts of poly ( L ‐glutamic acid) has been examined. The calcium and strontium salts take the β‐conformation and the magnesium salt takes the α‐form. No hydration‐dependent conformational transitions were observed. The amount of bound water, as measured by differential scanning calorimetry, appears to depend on the size of the cation, while conformation has little or no effect. A relative measure of the barrier to side‐chain reorientation was obtained from the temperature of the side‐chain (β 1 ) relaxation. It was found that the barrier is determined by electrostatic forces and increases with increasing cation surface charge density. Side‐chain motion also appears to be more hindered in the β‐conformation than in the α‐conformation.