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Solution properties of synthetic polypeptides. XVII. Stability of the α‐helical conformation of poly(γ‐benzyl L ‐glutamate) in helicogenic solvents
Author(s) -
Matsumoto Tadao,
Teramoto Akio
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.1974.360130706
Subject(s) - chemistry , dimethylformamide , solvent , intrinsic viscosity , helix (gastropod) , amide , crystallography , thermal stability , cresol , dipole , optical rotatory dispersion , stereochemistry , organic chemistry , circular dichroism , phenol , polymer , ecology , snail , biology
The Zimm–Bragg parameters s and σ were determined for poly(γ‐benzyl L ‐glutamate) (PBLG) in m ‐cresol and in dimethylformamide (DMF) from ORD data as a function of molecular weight. It was found that, within the temperature range between 10 and 55°C and on the average, s = 1.6 1 ± 0.1 and √σ = 0.04 ± 0.01 in m ‐cresol and s = 1.6 5 ± 0.05 and √σ = 0.045 ± 0.015 in DMF. The values of s in m ‐cresol decreased with increasing temperature, while the values of σ in the same solvent increased. This result for s suggests that PBLG in m ‐cresol will undergo a thermal helix–coil transition of normal type. The parameters in DMF showed no appreciable trend to vary with temperature. Aside from the difference between the two solvents, our results are consistent with existing data for various conformation‐dependent properties such as light‐scattering radius, intrinsic viscosity, and dipole moment, each indicating that the polypeptide chain has some flexibility in helicogenic solvents.