Coil-helix transition in poly(L-glutamic acid) : Evidence for a 3-state non-cooperative process

TL;DR

This study reveals that poly(L-glutamic acid) undergoes a three-state, non-cooperative coil-helix transition, with evidence of a third state influenced by PEG interactions, challenging traditional two-state models.

Contribution

The paper introduces a three-state model for PGA's coil-helix transition, incorporating a third state and demonstrating non-cooperative behavior influenced by PEG.

Findings

Identification of a third conformational state in PGA

Evidence for non-cooperative transition process

PEG interactions affect PGA conformational states

Abstract

A careful analysis of measurements of circular dichroism of poly(L-glutamic acid) (PGA) shows that the data can be very accurately described by introducing a third state for the PGA configuration, in addition to the helix and coil ones, and considering a simple equilibrium between these three states, without cooperativity. The third state is more conspicuous when high molecular weight polyethyleneglycol (PEG) is added. Excluded volume effects shown by differences in presence of short and long PEG chains indicate a direct interaction of PEG and PGA rather than an osmotic effect.