Møller Jens K S, Skibsted Leif H
Food Chemistry, Department of Food Science, University of Copenhagen, Rolighedsvej 30, 1958, Frederiksberg C, Denmark,
J Biol Inorg Chem. 2014 Aug;19(6):805-12. doi: 10.1007/s00775-014-1112-y. Epub 2014 Feb 13.
Nitrosylmyoglobin, MbFe(II)NO, was found to be oxidized by Fe(CN)6 and HClO/ClO(-), but not by the semistable radical nitrosodisulfonate (anion of Frémy's salt) or NO2 (-) at ambient temperature in aqueous solution with pH 7.0. The oxidation by HClO/ClO(-) was significantly faster than that by Fe(CN)6. With excess Fe(CN)6, MbFe(II)NO was oxidized to metmyoglobin, MbFe(III), in a second-order reaction with k 2 = 1.67 ± 0.10 M(-1) s(-1) at 288 K without detectable intermediates as determined by stopped-flow spectroscopy. The activation parameters were ΔH (‡) = 43 ± 2 kJ mol(-1) and ΔS (‡) = -93 ± 9 J(-1) K(-1) mol(-1). Outer-sphere electron-transfer to Fe(CN)6 was assigned as rate determining rather than NO dissociation from iron(II) followed by electron transfer. Outer-sphere electron transfer from MbFe(II)NO to certain moderate oxidizing agents may thus have a role in labilizing NO association slowly through oxidation of iron(II) to iron(III). In contrast, hypochlorite oxidizes MbFe(II)NO much faster in a complex sequence of processes involving a rate-determining second-order (unidentified) reaction with k 2 = 2.6 ± 0.3 × 10(3) M(-1) s(-1) at 288 K and possibly involving protein degradation.
在pH 7.0的水溶液中，室温下发现亚硝酰肌红蛋白（MbFe(II)NO）可被[Fe(CN)₆]³⁻和HClO/ClO⁻氧化，但不能被亚稳定自由基亚硝基二磺酸盐（弗雷米盐的阴离子）或NO₂⁻氧化。HClO/ClO⁻的氧化速度明显快于[Fe(CN)₆]³⁻。在过量[Fe(CN)₆]³⁻存在下，MbFe(II)NO在288 K下以二级反应被氧化为高铁肌红蛋白（MbFe(III)），k₂ = 1.67 ± 0.10 M⁻¹ s⁻¹，通过停流光谱法测定未检测到中间体。活化参数为ΔH(‡) = 43 ± 2 kJ mol⁻¹和ΔS(‡) = -93 ± 9 J⁻¹ K⁻¹ mol⁻¹。确定从MbFe(II)NO到[Fe(CN)₆]³⁻的外层电子转移是速率决定步骤，而不是NO从铁(II)解离后再进行电子转移。因此，MbFe(II)NO向某些中等氧化剂的外层电子转移可能通过将铁(II)氧化为铁(III)而在缓慢使NO结合不稳定方面发挥作用。相比之下，次氯酸盐在一系列复杂过程中氧化MbFe(II)NO的速度要快得多，这些过程涉及到在288 K下k₂ = 2.6 ± 0.3 × 10³ M⁻¹ s⁻¹的速率决定二级（未确定）反应，并且可能涉及蛋白质降解。
