Deuterium Exchange in Polypeptides

Abstract

OBSERVATIONS on the rate of deuteration of the NH groups in solutions of proteins in heavy water (see, for example, ref. 1) have shown that in some proteins there is both a fast and a slow exchange, and it has been conjectured that those NH groups which exchange slowly are hydrogen-bonded in α-helix arrangements, whereas the fast reaction is associated with solvated NH groups. This possibility can be more profitably examined in solutions of a simple polypeptide such as poly-γ-benzyl-L-glutamate, where the conditions for α-helical or random, solvated coil forms are now well-known^2,3. Doty and Yang³ have shown that in mixtures of dichloracetic acid and ethylene dichloride, samples of poly-γ-benzyl-L-glutamate of high molecular weight may exist either in α-helix or in random coil forms, according to the composition of the solvent.