N-(7-dimethylamino-4-methylcoumarinyl)-maleimide (DACM): an alternative label for fluorescence tracing

N-(7-dimethylamino-4-methylcoumarinyl)maleimide (DACM), a fluorescent thiol reagent, has a high molar extinction coefficient and a high quantum yield when it reacts with protein sulphhydryl bonds. DACM proved to be effective as a fluorescent probe when used for labelling rabbit immunoglobulin G anti-human gamma-chain (IgG). DACM-labelled rabbit immunoglobulin G anti-human gamma-chain conjugates (DACM-IgG) can be purified efficiently by Sephadex G-50 gel chromatography. The immunological properties of the IgG are not altered appreciably by conjugation. As a label DACM has advantages with regard to ease of preparation, specific immunofluorescence and strong photoresistance.