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Thermal and charge-induced coil to α-helix transition of poly-L-glutamic acid and random L-glutamic acid–L-alanine copolymers

✍ Scribed by Akira Warashina; Akira Ikegami

Publisher
Wiley (John Wiley & Sons)
Year
1972
Tongue
English
Weight
850 KB
Volume
11
Category
Article
ISSN
0006-3525

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✦ Synopsis

Thermal and charge induced random coil to a-helii transitions of poly-cglutamic acid (PGA) were measured by optical rotatory dispersion in various solvents. The data of PGA in 0.1M NaCl were analyzed by the Zimm-Rice theory. Enthalpy and entropy changes for the coil-to-helix transition in the unionized state were obtained: AH' = -1020 f 100 cal/residue mole; AS" = -3.0 f 0.4 e.u./residue mole. The initiation parameter, u, of the Zimm-Rice theory w&s given by a value of 5 f 1 X Random copolymers of bglutamic acid and calanine containing 10, 30, and 40 molar percents of alanyl residue were synthesized. Stabilities of a-helix of the copolymers were compared to that of PGA. In water and water-ethanol solutions, stabilities of the polymers were almost equal after the simple correction about the ionized charge density of the polymers. In O.1M NaCl solution these copolymers showed some deviations from the transition curve of PGA, which would suggest the hydrophobic contribution of the alanyl residues.

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