Syntheses and characterizations of novel pyrrolocoumarin probes for SNAP-tag labeling technology

SNAP-tag technology is a revolutionary protein labeling technology employing in various biological studies. Since low signal/noise ratio and severe overlap between the FRET donors/acceptors often occurred in applying present fluorescent probes and thus limited the further applications, development of new fluorescent probes with excellent fluorescent properties is still of request by today’s SNAP-tag technology. In this paper, a number of SNAP-tag protein probes have been developed by incorporating a novel pyrrolocoumarin fluorophore recently developed by our group. Examination of these novel synthetic compounds shows all these materials possess satisfactory fluorescent properties. Among these, probe 7 exhibits the most excellent characters, and its quantum yield, maximum emission wavelength and Stocks shift reach to 0.44, 534 nm and 112 nm, respectively. Further analysis of structure-property relationship indicates that the probes with a longer C3-substituted alkyl (such as pentyl) give stronger fluorescence.