Using a variety of synthetic peptides, it was shown that the reaction of o-phthalaldehyde with peptides to yield fluorescent derivatives was dependent upon the presence of the free l -akin0 group of lysine.
Procedures for the analysis of mixtures of amino acids have recently been increased in sensitivity by the introduction of two reagents (o-phthalaldehyde and fluorescamine) capable of forming fluorescent derivatives with primary amines. Since the original description (1) of fluorescamine (FA)' its reaction with primary amines has been well characterized chemically and the fluorophors formed described in detail (2). However, o-phthalaldehyde (OPA) was apparently first utilized empirically (3) and its reaction with primary amines has not yet been clearly elucidated (4).
not comment otherwise, it was presumed that the tracing produced resembled that obtained with ninhydrin detection systems. Following this success, the technique was described in detail ( 8) and commercial solutions of OPA and suitable dilutent buffer were produced (Dun-urn Chemical Corp., Sunnyvale, Calif.) in collaboration with James Benson. Based upon unpublished results (J. Benson, personal communication), the pH of the commercial buffer was produced at 10.4 and RNA tumor virus proteins were compared (9).