On the Influence of Multiple Scattering Contributions to the Extended X-Ray Absorption Fine Structure (EXAFS) Spectra of the Photosystem Ⅱ Manganese Complex

摘要

The catalytic center of photosynthetic water oxidation is a tetra-nuclear manganese complex which presumably is covalently bound to the polypeptides of the Photosystem Ⅱ (PS Ⅱ) protein complex. Extended X-ray Absorption Fine Structure (EXAFS) spectra were simulated for various likely structural elements of the PS Ⅱ manganese complex. The influence of multiple scattering contributions to the EXFAS spectra is assessed. It is found that for distances below 3.5 A multiple scattering contributions to the EXAFS spectrum of the PS Ⅱ manganese complex are presumably negligible. However, for distances above 3.5 A multiple scattering contributions to the EXAFS spectrum of the PS Ⅱ manganese complex are likely to be of relevance. We conclude that the amino acid residues (glutamate, aspartate, histidine) which are ligands of the PS Ⅱ manganese complex could give rise to the EXAFS Fourier peak at about 4 A.