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Helix‐coil transition of polo‐ L ‐glutamic acid film
Author(s) -
Noguchi Hajime,
Yang Jen Tsi
Publication year - 1964
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.1964.360020209
Subject(s) - chemistry , urea , aqueous solution , elongation , ethylene glycol , polymer , helix (gastropod) , calcium , polyvinyl alcohol , salt (chemistry) , crystallography , nuclear chemistry , organic chemistry , ultimate tensile strength , ecology , materials science , biology , snail , metallurgy
Water‐insoluble films ( ca. 0.04 × 3 × 30 mm. in dried state) of poly‐ L ‐glutamic acid (PGA), crosslinked with glycerol or polyvinyl alcohol at pH 4.8, were suspended in aqueous media and their relative lengths measured as a function of pH. The films elongate in alkaline pH and contract in acidic pH; the process is completely reversible, although the equilibration time usually takes several days at each pH. A sharp transition of the polymer was observed in the pH range which corresponded with that observed in PGA solutions by other physical methods. In NaCl, KCl, and KF solution the coiled from of the PGA film shrinks with increasing salt concentration. A notable exception is LiBr, which extends the film after a broef, rapid contraction and eventually causes it to disintegrate. Eight molar urea also caused a small elongation of film. Curpic ion has a drastic effect on the stability of the PGA helices. As low as 0.001 M Cu(CH 3 COO) 2 at pH 6.6 converted the coiled from the of the film into the helical form. On the other hand, calcium and magnesium ions only reduced the film length, probably without coil‐to‐helix transition.