Anomalous exchange kinetics of peptide amide protons in aqueous solutions.

Reports concerning anomalous rates of exchange of some amides in oxytocin, alumichrome, and gramicidin S are reexamined through systematic analysis of the exchange data as a function of pH and primary structure. It is shown that such an analysis can provide useful information on secondary structure when the degree of hydrogen bonding to both the NH undergoing exchange and the neighboring carbonyl group are taken into consideration.