Helix-coil transition of polo-L-glutamic acid film

✍ Scribed by Hajime Noguchi; Jen Tsi Yang

• Publisher: Wiley (John Wiley & Sons)
• Year: 1964
• Tongue: English
• Weight: 480 KB
• Volume: 2
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1964.360020209

✦ Synopsis

Water-insoluble films (m. 0.04 X 3 X 30 mm.3 in dried state) of poly-Lglutamic acid (PGA), crosslinked with glycerol or polyvinyl alcohol at pH 4.8, were suspended in aqueous media and their relative lengths meaaured as a function of pH. The film 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 waa observed in the pH range which corresponded with that observed in PGA solutions by other physical methods.

In NaCl, KC1, and K F solutions the coiled form of the PGA film shrinks with increasing salt concentration. A notable exception is LiBr, which extends the film after a brief, rapid contraction and eventually causes it to disintegrate. Eight molar urea also caused a small elongation of film.

Cupric ion has a drastic effect on the stability of the PGA helices. As low aa 0.001M Cu(CH&00)2 at p H 6.6 converted the coiled form 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.