Fluorophore-labeled S-nitrosothiols

A series of fluorophore-labeled S-nitrosothiols were synthesized, and their fluorescence enhancements upon removal of the nitroso (NO) group were eval uated either by transnitrosation or by photolysis. It was shown that, with a suitable alkyl linker, the fluorescence intensity of dansyl-labeled S-nit rosothiols could be enhanced up to 30-fold. The observed fluorescence enhan cement was attributed to the intramolecular energy transfer from fluorophor e to the SNO moiety. Ab initio density functional theory (DFT) calculations indicated that the "overlap" between the SNO moiety and the dansyl ring is favored because of their stabilizing interaction, which was in turn affect ed by both the length of the alkyl linker and the rigidity of the sulfonami de unit. In addition, one of the dansyl-labeled S-nitrosothiols was used to explore the kinetics of S-nitrosothiol/thiol transnitrosation and was eval uated as a fluorescence probe of S-nitrosothiol-bound NO transfer in human umbilical vein endothelial cells.