Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE, 106 91, Sweden.
J Comput Chem. 2018 May 5;39(12):743-747. doi: 10.1002/jcc.25145. Epub 2017 Dec 18.
In the key enzyme for nitrogen fixation in nature, nitrogenase, the active site has a metal cluster with seven irons and one molybdenum bound by bridging sulfurs. Surprisingly, there is also a carbon in the center of the cluster, with a role that is not known. A mechanism has been suggested experimentally, where two hydrides leave as a hydrogen molecule in the critical E state. A structure with two hydrides, two protonated sulfurs and an unprotonated carbon has been suggested for this state. Rather recently, DFT calculations supported the experimental mechanism but found an active state where the central carbon is protonated all the way to CH . Even more recently, another DFT study was made that instead supported the experimentally suggested structure. To sort out the origin of these quite different computational results, additional calculations have here been performed using different DFT functionals. The conclusion from these calculations is very clear and shows no computational support for an unprotonated carbon in E . © 2017 Wiley Periodicals, Inc.
在自然界中固氮的关键酶——氮酶中，活性位点有一个金属簇，由 7 个铁原子和 1 个钼原子通过桥连的硫原子结合而成。令人惊讶的是，簇的中心还有一个碳原子，其作用尚不清楚。实验提出了一种机制，其中两个氢化物作为氢分子离开关键的 E 态。有人提出，在这种状态下，结构中含有两个氢化物、两个质子化的硫原子和一个未质子化的碳原子。最近，DFT 计算支持了实验提出的机制，但发现了一个活性状态，其中中心碳原子被质子化到 CH。更近一些时候，另一项 DFT 研究反而支持了实验提出的结构。为了理清这些截然不同的计算结果的起源，这里使用不同的 DFT 泛函进行了额外的计算。这些计算的结论非常明确，表明在 E 态中没有未质子化的碳的计算支持。© 2017 威利父子公司。
