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.

TLDR: The first quantitative analysis of the Fe K-edge polarized x-ray absorption near edge structure of the iron protein carbonmonoxy-myoglobin single crystal and of its cryogenic photoproduct Mb(*)CO is reported.

Abstract: 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 $(3.08\ifmmode\pm\else\textpm\fi{}0.07)\phantom{\rule{0ex}{0ex}}\AA{}$, with a tilting angle between the heme normal and the Fe-C vector of $(37\ifmmode\pm\else\textpm\fi{}7)\ifmmode^\circ\else\textdegree\fi{}$, and a bending angle between the Fe-C vector and the C-O bond of $(31\ifmmode\pm\else\textpm\fi{}5)\ifmmode^\circ\else\textdegree\fi{}$.