SPIN-RESOLVED X-RAY-ABSORPTION NEAR-EDGE STRUCTURE (XANES) SIMULATIONOF METMYOGLOBIN

Spin resolved multiple scattering (MS) calculations of Fe K-edge X-ray Absorption Near Edge Structure (XANES) of myoglobin are reported for the first time. The observed differences of the Fe K-edge XANES spectr a of sperm whale metmyoglobin under spin transition as a function of t emperature have been studied. The method allows one to compute separat ely spin effects and local structural effects. The results show that s pin effects are confined in the absorption rising edge in the range 71 11-7130 eV, while purely structural effects are dominant in the range 7130-7170 eV. Symmetry changes of the Fe coordination sphere mainly re lated to its movement towards the heme plane, coupled to an increase o f axial asymmetry, can explain the XANES changes observed above 7130 e V without an appreciable change of the Fe-Np distance.