Passing a Blood Test

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Science  31 Jan 2003:
Vol. 299, Issue 5607, pp. 627-629
DOI: 10.1126/science.299.5607.627e

Almost all of us have undergone one of the basic laboratory procedures: a measurement of blood chemistry, sometimes referred to as an SMA (sequential multiple analyzer)-12 test for the 12 components (cholesterol, glucose, etc.) analyzed. Unlike experimental measurements under optimized conditions, real-life quantitation of the critical electrolyte K+ should be independent of other variables such as pH and Na+. Another desirable quality for a K+ sensor would be a highly sensitive fluorescent readout, which would require placing both the excitation and emission wavelengths outside those of the endogenous chromophores in whole blood. He et al. describe the synthesis of a molecule that passes these tests; it contains a fluorophore (absorbing at 470 nm; emitting at 540 nm) linked to a K+-binding (Kd ∼ 5 mM) crown ether derivative. In the absence of K+, the fluorescence is quenched via intramolecular electron transfer, which is nullified when the tertiary amine binds K+. Similarly, He et al. have designed a Na+ sensor (Kd ∼ 80 mM) that fluoresces in a pH- and K+-independent manner. — GJC

J. Am. Chem. Soc. 10.1021/ja0284761 (2003); Anal. Chem. 10.1021/ac0205107 (2003).

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