One-bond C-α,H coupling constants in amino acids and peptides pH dependence and substituent increments

One-bond C-α,H coupling constants are reported for glycine, alanine, sarcosine and related di- and tripeptides. A detailed study of the pH dependence of ¹J(C-α,H) has led to a determination of additive increments, ζ, for the functional groups NH₃, NHCO? , COO^?, and CONH? which can be used, together with known values for NH₂, COOH and alkyl substituents, to calculate ¹J(C-α,H) in amino acids and peptides.