Seminaphtharhodafluor or SNARF is a

fluorescent dye A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with sev ...

that changes color with pH. It can be used to construct optical

biosensor A biosensor is an analytical device, used for the detection of a chemical substance, that combines a biological component with a physical chemistry, physicochemical detector. The ''sensitive biological element'', e.g. tissue, microorganisms, or ...

s that use

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

s that change pH. The

absorption peak A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with sev ...

of the

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. ...

carboxy-SNARF at pH 6.0 is at

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

(515 and) 550 nm, while that at pH 9.0 is at 575 nm. The

emission peak A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with sev ...

of carboxy-SNARF at pH 6.0 is at

585 nm, while that at pH 9.0 is at 640 nm. SNARF-1 can serve as a substrate for the MRP1 (multidrug resistance-associated protein-1) drug transporter, to measure the activity of the MRP1 transporter. For this purpose, an acetomethoxyester group is added to SNARF-1. Cellular esterases cleave off SNARF-1, and its transport out of the cells can be measured by following the loss of fluorescence from the cells.

References

Fluorone dyes Spiro compounds Lactones {{biochem-stub