The strength of the binding interaction of the carboxylate group of peptide cell-wall analogues with ristocetin A is shown, by 1H NMR studies of hydrogen bonded NHs, to increase towards a limiting value as the number of interactions on the same ligand template increases; the carboxylate electrostatic binding energy appears to reflect the whole set of linked weak interactions as a cooperative unit, and this cooperative effect is distinct from the classical chelate effect.