A general assay for antibody catalysis using acridone as a fluorescent tag

A simple and highly sensitive catalysis assay is demonstrated based on analyzing reactions with acridone-tagged compounds by thin-layer chromatography. As little as 1 pmol of product is readily visualized by its blue fluorescence under UV illumination and identified by its retention factor (R(f)). Each assay requires only 10 mu l of solution. The method is reliable, inexpensive, versatile, and immediately applicable in repetitive format for screening catalytic antibody libraries. Three examples are presented: (i) the epoxidation of acridone labeled (S)-citronellol. The pair of stereoisomeric epoxides formed is resolved on the plate, which provides a direct selection method for enantioselective epoxidation catalysts. (ii) Oxidation of acridone-labeled 1-hexanol to 1-hexanal. The activity of horse liver alcohol dehydrogenase is detected. (iii) Indirect product labeling of released aldehyde groups by hydrazone formation with an acridone-labeled hydrazide. Activity of catalytic antibodies for hydrolysis of enol ethers is detected.