Detection of Proteins in Polyacrylamide Gels via Prelabeling by Isatoic Anhydride

Fluorescent methods for staining of proteins in polyacrylamide gels are obtaining increasing attention due to their advantages including high sensitivity and rapidness. In the present chapter we describe, step by step, a rapid and inexpensive fluorescent prelabeling method based on derivatization of proteins with isatoic anhydride. This method allows researchers to detect less than 2 ng of standard proteins per band in less than 15 min. Although this method is sensitive, inexpensive, rapid, compatible with most of common biological reagents and is able to detect proteins in crude cell extract, covalent binding of isatoic anhydride to protein lysine residues makes it unsuitable for processes in which post-electrophoresis analysis is required. Moreover, isatoic anhydride derivatization induces a small band broadening.