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Electric field effect on the helix–coil transition of poly( L ‐α,γ‐diaminobutyric acid hydrochloride) in methanol/water mixtures
Author(s) -
Fujimori Mitsuo,
Kikuchi Kazuo,
Yoshioka Koshiro,
Kubota Shigeo
Publication year - 1979
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.1979.360180813
Subject(s) - chemistry , methanol , solvent , birefringence , electric field , helix (gastropod) , analytical chemistry (journal) , hydrochloride , polymer , field strength , chromatography , organic chemistry , optics , magnetic field , ecology , physics , quantum mechanics , snail , biology
Transient electric birefringence of poly( L ‐α,γ‐diaminobutyric acid hydrochloride) in methanol/water mixtures has been measured over a wide range of field strengths and solvent compositions and at different polymer concentrations and temperatures. The molar ellipticity at 222 nm and the specific Kerr constant underwent an abrupt change between 75 and 80 vol % methanol at 25°C, accompanied by a solvent‐induced helix–coil transition. Anomalous birefringence transients were observed between 78 and 80 vol% methanol above threshold field strengths. The double logarithmic plots of the steady‐state specific birefringence versus the square of field strength for different solvent compositions and polymer concentrations could be superimposed by shifting them horizontally along the abscissa and vertically along the ordinate except for the range where anomalous transients were observed. The threshold field strength could be estimated from the point at which a downward deviation occurred. It increased with increasing polymer concentration and with increasing methanol content on the verge of the transition region. The results were interpreted as indicating that a conformational change from the charged helix to the charged coil is induced by high fields in this system, as in the case of poly( L ‐lysine hydrobromide) in methanol/water mixtures.