IDENTIFICATION OF PHOTOCHEMICAL PRODUCTS OF AMINO-ACIDS, PEPTIDES, AND PROTEINS IN ONLINE, POSTCOLUMN PHOTOLYTIC DERIVATIZATION DETECTION BY HPLC-ELECTROCHEMISTRY

In previous studies we have developed a method for the electrochemical detection of aromatic amino acids, sulfur-containing amino acids, peptides, and proteins in HPLC by using photolytic derivatization approaches. Upon irradiation, nonelectroactive (or even inherently electroactive) amino acids and peptides can be converted to electroactive (or more electroactive) compounds, in an on-line, postcolumn manner, which can be detected electrochemically in HPLC. In the case of proteins, the same method can be used to change the electroactivity of proteins photochemically. It is important to identify these photochemically converted compounds, especially those which are electroactive, in order to understand the detection mechanisms of the method. In this paper the results of identification of electroactive photoproducts for aromatic amino acids, peptides, and proteins are presented. Mainly, these studies were carried out by HPLC and direct electrochemical detection of off-line photolyzed analytes.