PRIMARY STRUCTURE EFFECTS ON PEPTIDE GROUP HYDROGEN-EXCHANGE

The rate of exchange of peptide group NH hydrogens with the hydrogens of aqueous solvent is sensitive to neighboring side chains. To evaluat e the effects of protein side chains, all 20 naturally occurring amino acids were studied using dipeptide models. Both inductive and steric blocking effects are apparent. The additivity of nearest-neighbor bloc king and inductive effects was tested in oligo- and polypeptides and, surprisingly, confirmed. Reference rates for alanine-containing peptid es were determined and effects of temperature considered. These result s provide the information necessary to evaluate measured protein NH to ND exchange rates by comparing them with rates to be expected for the same amino acid sequence is unstructured oligo- and polypeptides. The application of this approach to protein studies is discussed. (C) 199 3 Wiley-Liss, Inc.