Dias Lúcia, Bekhti Nihel, Kuznetsov Maxim L, Ferreira José A B, Bacariza Maria C, da Silva José Armando L
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001, Lisbon, Portugal.
Chemistry. 2018 Feb 16;24(10):2474-2482. doi: 10.1002/chem.201705385. Epub 2018 Jan 19.
Reactions of two vanadium(IV) complex anions that are homologues of amavadin, [V(HIDPA) ] and [V(HIDA) ] (HIDPA=N-oxyiminodipropionate, HIDA=N-oxyiminodiacetate), with the nitrite ion (NO ) in aqueous solution were investigated by experimental (absorption spectroscopy in the visible range, through measurements of dioxygen formed in solution from water oxidation and identification of nitrogen oxide species of a gaseous atmosphere from nitrite reduction by using an IR analyser) and theoretical methods. Two reactions, mediated by the vanadium complexes, with environmental and biological significance, were observed in this system, namely, reduction of nitrite to N O and oxidation of water to molecular oxygen. The reduction of nitrite, as studied by DFT calculations, occurs through the formation of NO (ΔG =14.3 kcal mol ), which is strongly dependent on pH and slightly endergonic, and is then easily converted into N O, with an overall activation barrier of ΔG =11.8 kcal mol . The later process includes dimerisation of NO assisted by one molecule of the V complex, protonation and oxidation of the formed ONNO ligand by another amavadin molecule or by nitrite, and NO bond cleavage/proton transfer in the ONNOH ligand. The results indicate that amavadin exhibits an unusual nitrite reductase type activity that could be involved in nitrogen metabolism of Amanita muscaria and other fungi containing this vanadium complex.
对两种与阿马瓦丁同系的钒（IV）络合阴离子[V(HIDPA) ]和[V(HIDA) ]（HIDPA = N-氧亚氨基二丙酸酯，HIDA = N-氧亚氨基二乙酸酯）与水溶液中的亚硝酸根离子（NO ）的反应，采用实验方法（可见范围内的吸收光谱法，通过测量水氧化形成的溶液中的氧气以及使用红外分析仪鉴定亚硝酸盐还原产生的气态气氛中的氮氧化物种类）和理论方法进行了研究。在该体系中观察到了由钒络合物介导的两个具有环境和生物学意义的反应，即亚硝酸盐还原为N O以及水氧化为分子氧。通过密度泛函理论计算研究发现，亚硝酸盐的还原是通过形成NO （ΔG =14.3 kcal mol ）发生的，这强烈依赖于pH且略微吸热，然后很容易转化为N O，其总活化能垒为ΔG =11.8 kcal mol 。后续过程包括在一个钒络合物分子的协助下NO 的二聚化、由另一个阿马瓦丁分子或亚硝酸盐对形成的ONNO配体进行质子化和氧化，以及ONNOH配体中的NO键断裂/质子转移。结果表明，阿马瓦丁表现出一种不寻常的亚硝酸还原酶类型的活性，可能参与了毒蝇伞和其他含有这种钒络合物的真菌的氮代谢。
