Saturday, April 17, 2010

Click chemistry assembled HNO sensor in live cells

Joel Rosenthal, Stephen J Lippard
J. Am. Chem. Soc. 
DOI: 10.1021/ja909148v
First published: March 31, 2010

Unlike nitric oxide (NO) which earned prominent position in biological and medical world, other RNS (reactive nitrogen species) received less attention - least in the case of nitroxyl (HNO). However, HNO displays important biological roles with potential pharmacological applications related to K+ channels in mammalian vascular systems. A biologically compatible probe fo HNO would help the current status significantly. 

The authors came up with the Cu(2+)-complex shown in the figure. BODIPY dye - azide and tridentate amine - alkyne undergoes the click chemistry to form the triazole linkage which holds the sensing fluorophore and chelating metal complex in close proximity. One nitrogen atom from the triazole ring participates in the chelation of Cu(2+) as well. The molecules was characterizaed by ESI MS, titration, and spectroscopy.

HNO, when present in aqueous buffer or live HeLa cells, reduces Cu2+ to Cu1+ (EPR evidence and others) and fluorescence rises significantly at 526nm (4-fold) by removing Cu2+ quenching of BODIPY dye. Controls demonstrate that the other RNSs do not interfere: NO3(3-), NO2(1-), ONO2(1-), OCl(1-), H2O2, NO, SNOC. 

Interesting case where click chemistry and triazole moiety are ued in fluorogenic detection, fluorophore - quencher linker, metal-chelation, probing molecules of biological or pharmocological significance, etc.                           

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