Extended conformations of polypeptides and proteins in urea and guanidine hydrochloride

Abstract

By analyzing the effect of urea and guanidine hydrochloride on the circular dichroism of many polypeptides and proteins, it is concluded that under conditions of high concentration of the perturbant and at low temperatures the resultant state approached is that of a local extended helix structure instead of a completely random coil. Intensification by urea and guanidine hydrochloride of the circular dichroism bands of poly- L -proline II leads to the proof that the mechanism of interaction of urea and guanidine hydrochloride with proteins is through hydrogen bonding to the backbone carbonyl group.