Deng Lan, Wang Hongxin, Dapper Christie H, Newton William E, Shilov Sergey, Wang Shunlin, Cramer Stephen P, Zhou Zhao-Hui
State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
SETI Institute, Mountain View, CA 94043, USA.
Commun Chem. 2020;3. doi: 10.1038/s42004-020-00392-z. Epub 2020 Oct 28.
Protonation of FeMo-cofactor is important for the process of substrate hydrogenation. Its structure has been clarified as Δ-MoFeSC(-homocit)(cys)(Hhis) for the efforts of nearly 30 years, while it remains controversial whether FeMo-cofactor is protonated or deprotonated with chelated ≡C-O(H) homocitrate. We have used protonated molybdenum(V) lactates and its enantiomer as model compounds for -homocitrate in FeMo-cofactor of nitrogenase. Vibrational circular dichroism (VCD) spectrum of at 1051 cm is attributed to ≡C-O vibration, and molybdenum(VI) -lactate at 1086 cm is assigned as ≡C-O vibration. These vibrations set up labels for the protonation state of coordinated -hydroxycarboxylates. The characteristic VCD band of NMF-extracted FeMo-cofactor is assigned to ν(C-O), which is based on the comparison of molybdenum(VI) -homocitrate. Density Functional Theory calculations are in consistent with these assignments. To the best of our knowledge, this is the first time that protonated -homocitrate in FeMo-cofactor is confirmed by VCD spectra.
铁钼辅因子的质子化对于底物氢化过程很重要。经过近30年的努力，其结构已被阐明为Δ-Mo*FeSC(-高柠檬酸)(半胱氨酸)(组氨酸)，而铁钼辅因子与螯合的≡C-O(H)高柠檬酸是质子化还是去质子化仍存在争议。我们使用质子化的钼(V)乳酸盐及其对映体作为固氮酶铁钼辅因子中-高柠檬酸的模型化合物。1051 cm处的振动圆二色性(VCD)光谱归因于≡C-O振动，1086 cm处的钼(VI)-乳酸盐被指定为≡C-O振动。这些振动为配位的-羟基羧酸盐的质子化状态建立了标记。NMF提取的铁钼辅因子的特征VCD带被指定为ν(C-O)，这是基于钼(VI)-高柠檬酸的比较。密度泛函理论计算与这些归属一致。据我们所知，这是首次通过VCD光谱证实铁钼辅因子中质子化的-高柠檬酸。
