| Abstract
| - Nitrosyl hydride, HNO, also commonly termed nitroxyl, is a transient species that has beenimplicated in the biological activity of nitric oxide, NO. Herein, we report the first generation of a stableHNO−metal complex by direct trapping of free HNO. Deoxymyoglobin (Mb−Fe(II)) rapidly reacts with HNOproduced from the decomposition of methylsulfonylhydroxylamine (MSHA) or Angeli's salt (AS) in aqueoussolutions from pH 7 to pH 10, forming an adduct, Mb−HNO. The unique 1H NMR signal of the Fe-boundHNO at 14.8 ppm allows definitive proof of its formation. The generation of Mb−HNO and quantification ofvarious myoglobin byproducts were accomplished by correlation of 1H NMR, UV−vis, and EPR spectroscopies. Typically, the maximum Mb−HNO yield obtained is 60−80%; competitive side reactions withbyproducts as well as the further reactivity of the Mb−HNO decrease the overall yield. At pH 10, the observedrate of Mb−HNO generation by trapping HNO from MSHA is close to that for MSHA decomposition; kineticsimulations give a lower limit to the bimolecular rate of trapping as 1.4 × 104 M-1 s-1. The binding of HNOto deoxymyoglobin is rapid and essentially irreversible, which suggests that the biological activity of nitroxylmay be mediated by its reactivity with ferrous heme proteins such as myoglobin and hemoglobin.
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