The reduction potential of nitric oxide (NO) and its importance to NO biochemistry
The reduction potential of nitric oxide (NO) and its importance to NO biochemistry
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DOI：
10.1073/pnas.162095599
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发表时间：
2002-08-20
影响因子：
11.1
通讯作者：
Houk, KN
中科院分区：
文献类型：
--
作者：
Bartberger, MD;Liu, W;Houk, KN
用量子力学计算、循环伏安法和化学还原实验相结合的方法，确定了一氧化氮（NO）还原成单电子还原态硝酰基阴离子（（NO-）-N-3）的电位约为-0.8（+/-0.2）V（在1 M氢电极上）.该值与一些但不是最普遍接受的先前涉及NO的电化学测量值雅阁。NO还原为（NO-）-N-1是非常不利的，在1 M下相对于正常氢电极的预测还原电位为约-1.7（+/-0.2）V。这些结果分别代表了NO/（NO-）-N-3和NO/（NO-）-N-1电对的+0.39 V和-0.35 V的推导值和广泛引用值的实质性修订，并为先前通过电化学和光电化学方法获得的测量提供了支持。由于这种高度负的还原电位，与将分子氧还原成超氧化物的生理事件相比，NO对还原是惰性的。根据这些还原电位，（NO-）-N-3的pKa重新评估为11.6（3.4）。因此，硝酰基在生理条件下几乎完全以其质子化形式HNO存在。硝酰基阴离子（NO-）-N-1的单重态在生理上是不可接近的。这些潜力的生理和病理生理过程涉及NO和O-2还原条件下的意义进行了讨论。
A potential of about -0.8 (+/-0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion ((NO-)-N-3) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous electrochemical measurements involving NO. Reduction of NO to (NO-)-N-1 is highly unfavorable, with a predicted reduction potential of about -1.7 (+/-0.2) V at 1 M versus normal hydrogen electrode. These results represent a substantial revision of the derived and widely cited values of +039 V and -0.35 V for the NO/(NO-)-N-3 and NO/(NO-)-N-1 couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means. With such highly negative reduction potentials, NO is inert to reduction compared with physiological events that reduce molecular oxygen to superoxide. From these reduction potentials, the pKa of (NO-)-N-3 has been reevaluated as 11.6 ( 3.4). Thus, nitroxyl exists almost exclusively in its protonated form, HNO, under physiological conditions. The singlet state of nitroxyl anion, (NO-)-N-1, is physiologically inaccessible. The significance of these potentials to physiological and pathophysiological processes involving NO and O-2 under reductive conditions is discussed.