Issue Date: July 11, 2011
Iridium Illuminates Nuclei Of Living Cells
An iridium complex turns on and lights up the nuclei of living cells by binding to histidine rather than to DNA, unlike other nuclear imaging agents, reports Fuyou Li and colleagues of China’s Fudan University (J. Am. Chem. Soc., DOI: 10.1021/ja202344c). The complex, [Ir(polypyridyl)2(dimethylsulfoxide)2]PF6, demonstrates little fluorescence as a solid or alone in solution. But when the complex binds to free histidine or histidine-containing proteins and is excited by 488-nm light, it fluoresces intensely. Although the complex can react with cytoplasmic proteins, an active transport mechanism—possibly a transport protein—spontaneously brings it into living cells and segregates it to the nucleus. The complex stains cellular nuclei within a few minutes and has low toxicity, the researchers note.
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