The binuclear nickel center in the A-cluster of acetyl-CoA synthase (ACS) and two biomimetic dinickel complexes studied by X-ray absorption and emission spectroscopy

16th International Conference on X-ray Absorption Fine Structure

Schrapers, P.^1 ; Mebs, S.^1 ; Ilina, Y.^2 ; Warner, D.S.^3 ; Wörmann, C.^2 ; Schuth, N.^1 ; Kositzki, R.^1 ; Dau, H.^1 ; Limberg, C.^3 ; Dobbek, H.^2 ; Haumann, M.^1

Department of Physics, Freie Universität Berlin, Berlin

14195, Germany^1

Department of Biology, Humboldt-Universität zu Berlin, Berlin

10115, Germany^2

Department of Chemistry, Humboldt-Universität zu Berlin, Berlin

12489, Germany^3

关键词: Biomimetic compounds;    DFT calculation;    Electronic differences;    Emission features;    Experimental spectra;    Square-planar nickel;    Synthetic compounds;    X-ray absorption and emission spectroscopy;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/712/1/012029/pdf
DOI  :  10.1088/1742-6596/712/1/012029

来源: IOP

【 摘 要 】

Acetyl-CoA synthase (ACS) is involved in the bacterial carbon oxide conversion pathway. The binuclear nickel sites in ACS enzyme and two biomimetic synthetic compounds containing a Ni(II)Ni(II) unit (1 and 2) were compared using XAS/XES. EXAFS analysis of ACS proteins revealed similar Ni-N/O/S bond lengths and Ni-Ni/Fe distances as in the crystal structure in oxidized ACS, but elongated Ni-ligand bonds in reduced ACS, suggesting more reduced nickel species. The XANES spectra of ACS and the dinickel complexes showed overall similar shapes, but less resolved pre-edge and edge features in ACS, attributed to more distorted square-planar nickel sites in particular in reduced ACS. DFT calculation of pre-edge absorption and Kβ2,5emission features reproduced the experimental spectra of the synthetic complexes, was sensitive even to the small geometry differences in 1 and 2, and indicated low-spin Ni(II) sites. Comparison of nickel sites in proteins and biomimetic compounds is valuable for deducing structural and electronic differences in response to ligation and redox changes.