Premium
Effect of counterion concentration on the dielectric behavior of a polypeptidic chain in the helix–coil transition
Author(s) -
Bordi F.,
Cametti C.,
Paradossi G.
Publication year - 1993
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.360330705
Subject(s) - counterion , chemistry , dielectric , random coil , polyelectrolyte , polymer , aqueous solution , helix (gastropod) , conductivity , dispersion (optics) , electrical resistivity and conductivity , electromagnetic coil , ion , thermodynamics , chemical physics , materials science , crystallography , organic chemistry , optics , physics , circular dichroism , ecology , optoelectronics , quantum mechanics , biology , snail
On the basis of the two‐state model of a polyelectrolyte solution, the ion concentration in the polymer domain has been calculated by using the spherical Poisson–Boltzmann equation. The ion accumulation in the neighboring of the polyion influences, on different time scales, various electrical properties of the solution, in particular the low‐frequency electrical conductivity and the high‐frequency dielectric dispersion. These predictions have been compared with recent dielectric measurements on poly ( L ‐glutamic acid) aqueous solutions during the conformational transition from the α‐helix to random coil, and a satisfactory agreement has been found. This finding suggests that counterion distribution plays a different role in determining the electrical properties of charged polymer solutions, causing a electrophoretic contribution of the polymer domain to the electrical conductivity and influencing the high‐frequency dielectric dispersion. © 1993 John Wiley & Sons, Inc.