When peptides containing the Asn-Gly sequence, such as H in the equation given in Fig. P26.69, are stored in aqueous solution at neutral or slightly basic solution, ammonia is liberated and a derivative I is formed. On continued storage, species 1 reacts to give two new peptides: J and K. Peptide J is the same as peptide H except that Asn is replaced by Asp, and peptide K is an isomer of peptide J. Propose structures for peptides ,J and K, and rationalize their formation using the curved-arrow notation. (These reactions are believed to be a major source of deterioration associated with aging in naturally occurring peptides and proteins.)
P26.69