Design, synthesis and characterization of a novel fluorescent probe for nitric oxide (nitrogen monoxide)

The iron(II) complex of quinoline pendant cyclam was designed as a mimic of the activation site of guanylate cyclase and synthesized as a fluorescent probe for nitric oxide (NO). Fe(II) ion shifted the excitation and emission maxima of the pendant fluorophore to longer wavelengths, and the fluorescence intensity was greatly increased. NO from NO-releasing agents quenched the fluorescence effectively. Nitrite, which is a metabolite of NO, did not affect the fluorescence of the complex. Cyanate also did not affect the spectral change of the complex with NO. NO, as low as μM, can be determined spectrofluorimetrically using 200 μM reagent. This is the first example of a fluorescent probe for NO which recognizes the molecule directly.