Vanin Anatoly F, Poltorakov Alexander P, Mikoyan Vasak D, Kubrina Lioudmila N, van Faassen Ernst
Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, Russia.
Nitric Oxide. 2006 Dec;15(4):295-311. doi: 10.1016/j.niox.2005.11.007. Epub 2006 Jan 5.
The in vivo mechanism of NO trapping by iron-dithiocarbamate complexes is considered. Contrary to common belief, we find that in biological systems the NO radicals are predominantly trapped by ferric iron-dithiocarbamates. Therefore, the trapping leads to ferric mononitrosyl complexes which are diamagnetic and cannot be directly detected with Electron Paramagnetic Resonance spectroscopy. The ferric mononitrosyl complexes are far easily reduced to ferrous state with L-cysteine, glutathione, ascorbate or dithiocarbamate ligands than their non-nitrosyl counterpart. When trapping NO in oxygenated biological systems, the majority of trapped nitric oxide is found in diamagnetic ferric mononitrosyl iron complexes. Only a minority fraction of NO is trapped in the form of paramagnetic ferrous mononitrosyl iron complexes with dithiocarbamate ligands. Subsequent ex vivo reduction of biological samples sharply increases the total yield of the paramagnetic mononitrosyl iron complexes. Reduction also eliminates the overlapping EPR spectrum from Cu(2+)-dithiocarbamate complexes. This facilitates the quantification of yields from NO trapping.
本文探讨了二硫代氨基甲酸盐铁配合物捕获一氧化氮（NO）的体内机制。与普遍看法相反，我们发现，在生物系统中，NO自由基主要被三价铁二硫代氨基甲酸盐捕获。因此，捕获过程会生成抗磁性的三价铁亚硝酰配合物，无法通过电子顺磁共振光谱直接检测到。与非亚硝酰对应物相比，三价铁亚硝酰配合物更容易被L-半胱氨酸、谷胱甘肽、抗坏血酸或二硫代氨基甲酸盐配体还原为二价铁状态。在含氧生物系统中捕获NO时，大部分捕获的一氧化氮存在于抗磁性的三价铁亚硝酰铁配合物中。只有一小部分NO以具有二硫代氨基甲酸盐配体的顺磁性二价铁亚硝酰铁配合物形式被捕获。随后对生物样品进行体外还原，会大幅提高顺磁性亚硝酰铁配合物的总产量。还原还消除了来自铜（2+）-二硫代氨基甲酸盐配合物的重叠电子顺磁共振光谱。这有助于对NO捕获的产量进行定量分析。
