Nedospasov Andrei A
Institute of Molecular Genetics, Moscow, Russia.
J Biochem Mol Toxicol. 2002;16(3):109-20. doi: 10.1002/jbt.10029.
The widespread opinion that N(2)O(3) as a product of NO oxidation is the only nitros(yl)ating agent under aerobic conditions is based on experiments in homogeneous buffered water solutions. In vivo NO is oxidized in heterogeneous media and this opinion is not correct. The equilibrium in the system being dependent on temperature and DeltaG((sol)) for NO, NO(2), isomers of both N(2)O(3), and N(2)O(4). For polar solvents including water, DeltaG((sol)) for N(2)O(3) is high enough, and a stationary concentration of N(2)O(3) in the mixture with other oxides is sufficient to guarantee the hydrolysis of N(2)O(3) to nitrite. In heterogeneous media, the mixture contains solvates NO(2(sol)), N(2)O(3(sol)), and N(2)O(4(sol)) at stationary nonequilibrium concentrations. As far as DeltaG((sol)) is decreased in heterogeneous mixtures with low polar solvents and/or at increased temperatures, the equilibrium in such a system shifts to NO(2). Although NO(2) is a reactive free radical, it almost does not react with water. In contrast, the reaction with most functional protein groups efficiently proceeds by a radical type with the formation of nitrite and new radicals (X) further stabilized in various forms. Therefore, the ratio of the nitrosylated and nitrated products yields depends on actual concentrations of all NO(x).
认为一氧化二氮（N₂O₃）作为一氧化氮（NO）氧化产物是有氧条件下唯一的亚硝基化剂这一普遍观点，是基于在均相缓冲水溶液中的实验得出的。而在体内，NO是在非均相介质中被氧化的，所以这个观点并不正确。该体系中的平衡取决于温度以及NO、NO₂、N₂O₃的异构体和N₂O₄的溶解吉布斯自由能（ΔG(sol)）。对于包括水在内的极性溶剂，N₂O₃的ΔG(sol)足够高，并且与其他氧化物混合时N₂O₃的稳定浓度足以保证N₂O₃水解为亚硝酸盐。在非均相介质中，混合物包含处于稳定非平衡浓度的溶剂化物NO₂(sol)、N₂O₃(sol)和N₂O₄(sol)。在与低极性溶剂的非均相混合物中以及/或者在温度升高时，由于ΔG(sol)降低，这样一个体系中的平衡会向NO₂移动。尽管NO₂是一种活性自由基，但它几乎不与水反应。相反，它与大多数功能性蛋白质基团的反应通过自由基类型高效进行，生成亚硝酸盐和新的自由基（X），这些自由基会以各种形式进一步稳定下来。因此，亚硝基化产物和硝化产物的产率之比取决于所有NOₓ的实际浓度。
