The reaction of fluorodinitrobenzene with the α- and ∈-amino groups of collagen

Abstract

The reaction of fluorodinitrobenzene with amino groups of collagen, modified collagen and procollagen was studied. Only 55-60% of the lysine could be recovered as the epsilon-dinitrophenyl (DNP) derivative from collagen, modified collagen or gelatin which had been treated with fluorodinitrobenzene. Only small amts. of free amino N and unchanged lysine were found in the DNP proteins leaving approx. 30% of the lysine unaccounted for. The possibility of decomposition of epsilon-DNP-lysine during hydrolysis, and of the presence of acid-resistant epsilon-DNP-lysine peptides is considered. No terminal resiudes were detected in collagen, and possible reasons for this are discussed. Small amts. of various end groups were found in procollagen, the modified collagens, and gelatin. Aspartic acid was most frequently found as a terminal residue, followed by glutamic acid, glycine, alanine and threonine. With the possible exception of aspartic acid these are considered to arise from hydrolysis of peptide bonds during the treatments. Aspartic acid is either a terminal residue which is inaccessible to fluorodinitrobenzene or the peptide bond involving its alpha-amino groups is especially labile.