Unlocking Fluorescence

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Science  04 Feb 2005:
Vol. 307, Issue 5710, pp. 646
DOI: 10.1126/science.307.5710.646c

The power of fluorescent probes can be enhanced by controlling how and when the probe becomes excitable. Chandran et al. describe an approach for masking fluorescence from a xanthene fluorophore until it is cleaved by esterases within a cell. They coupled rhodamine 110 to two o-hydroxycinnamic acid derivatives via amide linkages. In their acetylated form, these side chains force the rhodamine core to adopt a nonfluorescing lactonized configuration. Ester cleavage causes the side chains to form a hydrocoumarin, which is favored by steric interaction of the methyl groups, and liberates the fluorescent acid form of rhodamine 110. The authors followed the uptake of the latent fluorophore into HeLa cells, where they observed strong fluorescence from the cytosol and lysosomes but not from the nucleus. — PDS

J. Am. Chem. Soc. 10.1021/ja043736v (2005).

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