Determination of dehydroalanine residues in proteins and peptides: an improved method.

Dehydroalanine residues in peptides and proteins react with 4-pyridoethanethiol in alkaline solution to form 4-pyridoethyl cysteine residues, which after acid hydrolysis, give the corresponding amino acid. An experimental protocol has been developed, and with simple dehydroalanine derivatives, conversions of 96-99% are achieved. Tests with peptides and proteins show that serine and cysteine/cystine residues do not interfere with this analytical procedure. A sample of wool keratin contained 57 mumol dehydroalanine/g.