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首页> 外文期刊>RSC Advances >Proton-coupled electron transfer promotes the reduction of ferrylmyoglobin by uric acid under physiological conditions
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Proton-coupled electron transfer promotes the reduction of ferrylmyoglobin by uric acid under physiological conditions

机译：在生理条件下，质子耦合电子转移促进尿酸还原铁血肌红蛋白

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The hypervalent muscle pigment ferrylmyoglobin, MbFe(IV)O, is not reduced by urate monoanions at physiological conditions despite a strong driving force of around ?30 kJ mol?1 while for low pH, uric acid was found to reduce protonated ferrylmyoglobin, MbFe(IV)O,H+, efficiently in a bimolecular reaction with k1 = 1.1 ± 0.1 × 103 L mol?1 s?1, ΔH? = 66.1 ± 0.1 kJ mol?1 and ΔS? = 35.2 ± 0.2 J mol?1 K?1. For intermediate pH, like for anaerobic muscles and for meat, proton-coupled electron transfer occurs in a transition state, {MbFe(IV)O?H+?urate}?, which is concluded to be formed from uric acid and MbFe(IV)O rather than from urate and MbFe(IV)O,H+ with k3 = 9.7 ± 0.6 × 102 L mol?1 s?1, ΔH? = 59.2 ± 0.1 kJ mol?1 and ΔS? = 11.5 ± 0.3 J mol?1 K?1. The activation parameters as calculated from the temperature dependence of the pH-reduction profile in aqueous 0.067 mol L?1 NaCl (from 25 °C up to 40 °C), support a mechanism for reduction of hypervalent heme iron, where initial proton transfer to oxo-iron initiates the intermolecular electron transfer from urate to ferrylmyoglobin. The concentration of the powerful prooxidant ferrylmyoglobin increases strongly during digestion of red meat in the stomach. A concomitant increase in uric acid concentration may serve as an inherent protection against radical formation by ferrylmyoglobin.
机译：尽管在生理条件下尿酸一酸一阴离子仍不会将高价肌色素铁血肌红蛋白MbFe（ IV ）O还原，尽管其驱动力约为30 kJ mol ？1 而对于低pH值，发现尿酸可以有效地还原质子化的铁蛋白铁蛋白，MbFe（ IV ）O，H + 在 k 1 = 1.1±0.1×10 3 L的双分子反应中mol ？1 s ？1 ，Δ H ？ = 66.1±0.1 kJ mol ？1 和Δ S ？ = 35.2±0.2 J mol ？1 K ？1 。对于中等pH值（如厌氧肌肉和肉类），质子耦合电子转移以过渡态发生，{MbFe（ IV ）O？H + < / small>？urate} ？ ，其结论是由尿酸和MbFe（ IV ）O而不是由尿酸盐和MbFe形成（ IV ）O，H + 与 k 3 = 9.7±0.6×10 2 L mol ？1 s ？1 ，Δ H ？ = 59.2±0.1 kJ mol ？1 和Δ S ？ = 11.5±0.3 J mol ？1 K ？1 。根据0.067 mol L ？1 NaCl水溶液（从25°C到40°C）中pH还原曲线的温度依赖性计算的活化参数一种还原高价血红素铁的机制，其中质子最初转移到氧代铁会引发分子间电子从尿酸盐转移到铁血红蛋白。在胃中的红肉消化过程中，强氧化剂前铁血肌红蛋白的浓度会大大增加。随之而来的尿酸浓度的增加可作为固有的保护，以防止铁肌红蛋白形成自由基。

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