Sonolytic hydrolysis of peptides in aqueous solution upon addition of catechol

The sonolytic hydrolysis of peptides with addition of phenolic reagents to aqueous solutions is described. Sonolysis of an aqueous solution of peptides to which catechol (o-dihydroxybenzene) had been added resulted in hydrolytic products reflecting the amino acid sequence without any side reactions, while sonolysis without any additives resulted in oxidation analytes and degradation products caused by side reactions. Although the use of additives such as resorcinol (m-dihydroxybenzene), hydroquinone (p-dihydroxybenzene) and phenol was also effective in producing sequence related products, several degradation products were produced by side reactions. A characteristic of the sonolysis of peptides is that the N-terminal side of proline, Xxx-Pro, is more susceptible than other amino acid residues to the process. This characteristic of sonolysis is superior to that of acid hydrolysis in which cleavage at the C-terminal side of proline, Pro-Xxx is difficult, and where dehydration products result due to side reactions.