SEQUENCE ANALYSIS OF ARGINYL PEPTIDES BY MASS SPECTROMETRY

The problem of modifying arginine-containing peptides to form volatile derivatives suitable for mass spectrometry has recently been solved in two general ways. Treatment of arginine-containing peptides with hydrazine yields ornithine residues (1, 2) while treatment with various dicarbonyl reagents results in the formation of a heterocyclic ring (1, 3). In this communication we report the use of 1,2-cyclohexanedione (CHD) in modifying arginine residues for mass spectrometry. This reagent has been shown to react quantitatively with arginine residues of proteins (Fig. 1) without significant side reactions or peptide bond cleavage (4). By combining this modification of arginine residues with acylation and permethylation (2, 5, 6) volatile compounds were obtained from several peptides. The mass spectra of these compounds combined with knowledge of the amino acid composition of the parent peptide yielded considerable sequence information for each of the arginine-containing peptides studied, including the nonapeptide bradykinin. © 1969.