Coil-helix transition in poly(L-glutamic acid): Evidence for a 3-state non-cooperative process.
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 the presence of short and long PEG chains suggest a direct interaction of PEG and PGA rather than an osmotic effect.
Service de Physique de l'Etat Condensé, CEA Saclay, 91191, Gif-sur-Yvette cedex, France. Gilbert.Zalczer@cea.fr
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D011092:Polyethylene Glycols / Q000737:chemistry; D011099:Polyglutamic Acid / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013696:Temperature
D011099:Polyglutamic Acid; D011092:Polyethylene Glycols