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Solution properties of synthetic polypeptides. XVIII: Helix–coil transition of poly‐ N 5 ‐(2‐hydroxyethyl) L ‐glutamine
Author(s) -
Miyake Michihisa,
Akita Shuichi,
Teramoto Akio,
Norisuye Takashi,
Fumita Hiroshi
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.1974.360130609
Subject(s) - cooperativity , chemistry , optical rotatory dispersion , solvent , aqueous solution , intrinsic viscosity , helix (gastropod) , enthalpy , viscosity , viscometer , analytical chemistry (journal) , crystallography , thermodynamics , organic chemistry , polymer , circular dichroism , ecology , biochemistry , physics , snail , biology
Abstract The helix–coil transition of poly‐ N 5 ‐(2‐hydroxyethyl) L ‐glutamine (PHEG) in aqueous isopropanol was examined by means of optical rotatory dispersion (ORD) and intrinsic viscosity [η] measurements. The Zimm–Bragg parameters σ and s for the transition were determined from the ORD data as a function of molecular weight. It was found that the transition was characterized by a relatively low cooperativity; the values of \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt \sigma $\end{document} were in the range from 0.039 to 0.066, depending on the solvent composition. These σ values are much larger than those reported for other polypeptide–solvent systems. The transition enthalpy was negative and its magnitude varied with the solvent composition, with a maximum of 620 cal/mol at 40 wt% isopropanol. The curve of [η] versus helical content for a high‐molecular‐weight sample exhibited a very broad minimum, and this behavior was attributed to the low cooperativity of the transition.