Photolysis of the HNO Adduct of Myoglobin: Transient Generation of the Aminoxyl Radical

摘要

Nitroxyl or nitrosyl hydride, HNO, is the one-electron reduced form of nitric oxide in aqueous solution. We have demonstrated that deoxy myoglobin (Mb) traps free HNO to form a stable adduct, HNO-Mb, which has been characterized by ~1HNMR, resonance Raman, and XAS. There remain ambiguities in bonding description of this species as well as in its possible involvement in the observed activities of HNO-releasing compounds on cardiovascular disease. HNO-Mb is very stable, with a half-life of greater than 6 months at 4℃ in the absence of light and air. Prolonged laser excitation at 413 nm during resonance Raman experiments resulted in the appearance of an absorption band at 1373 cm~(-1) attributable to metMb. Likewise, its thermal decomposition to metMb at 37℃ doubles in rate under ambient light (see Supporting Information (SI)).