pK values and reactivity to nitrous acid of some glutamine and asparagine dipeptides

Abstract

Determinations are reported of the pK values of the amino- and carboxyl groups of the following peptides : glycyl-, L-leucyl-, and L-cysteinyl-L-asparagine, L-asparaginylglycine, glycyl-DL-glutamine, and L-leucyl-L-glutamine. It was observed that the pK of the amino-groups tended to be markedly reduced by the adjacent amide group. The reaction of these peptides (except L-cysteinyl-L-asparagine) with nitrous acid has also been investigated. The results are discussed in the light of recent suggestions on the structure of asparagine.