A Reductant-Resistant and Metal-Free Fluorescent Probe
for Nitroxyl Applicable to Living Cells
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Abstract
Nitroxyl
(HNO) is a one-electron reduced and protonated derivative
of nitric oxide (NO) and has characteristic biological and pharmacological
effects distinct from those of NO. However, studies of its biosynthesis
and activities are restricted by the lack of versatile HNO detection
methods applicable to living cells. Here, we report the first metal-free
and reductant-resistant HNO imaging probe available for use in living
cells, P-Rhod. It consists of a rhodol derivative moiety as the fluorophore,
linked via an ester moiety to a diphenylphosphinobenzoyl group, which
forms an aza-ylide upon reaction with HNO. Intramolecular attack of
the aza-ylide on the ester carbonyl group releases a fluorescent rhodol
derivative. P-Rhod showed high selectivity for HNO in the presence
of various biologically relevant reductants, such as glutathione and
ascorbate, in comparison with previous HNO probes. We show that P-Rhod
can detect not only HNO enzymatically generated in the horseradish
peroxidase-hydroxylamine system <i>in vitro</i> but also
intracellular HNO release from Angeli’s salt in living cells.
These results suggest that P-Rhod is suitable for detection of HNO
in living cells