Quantitative Analysis of X-Ray Absorption Near Edge Structure Data by a Full Multiple Scattering Procedure: The Fe-CO Geometry in Photolyzed Carbonmonoxy-Myoglobin Single Crystal

We report the first quantitative analysis of the Fe K-edge polarized x-ray absorption near edge structure of the iron protein carbonmonoxy-myoglobin (MbCO) single crystal and of its cryogenic photoproduct ${\mathrm{Mb}}^{*}\mathrm{CO}$. The CO-Fe-heme local structure has been determined using a novel fitting procedure based on the full multiple scattering approach. The extracted local structure of ${\mathrm{Mb}}^{*}\mathrm{CO}$ includes a Fe-CO distance of $(3.08\pm 0.07)Å$, with a tilting angle between the heme normal and the Fe-C vector of $(37\pm 7)°$, and a bending angle between the Fe-C vector and the C-O bond of $(31\pm 5)°$.