Evidence from Model Peptides relating to the Denaturation of Proteins by Lithium Salts

Abstract

IN an earlier communication¹ we reported that mixtures of N-methylacetamide (NMA) or N,N-dimethylacetamide (DMA) with strong aqueous lithium bromide show viscosities much higher than those calculated on the assumption of ideal mixing. This was termed ‘relative viscosity’, which is different from the usual use of this term. It was proposed that the high viscosity is caused by aggregation arising from carbonyl–lithium (I) and carbonyl–water–lithium (II) associations. Dots indicate hydrogen bonds, and dashes ion-dipole interactions. These associations were also considered to occur in protein denaturation. We now report evidence for the existence of both types of association, as well as peptide-anion associations.