Resonant inelastic X-ray scattering determination of the electronic structure of oxyhemoglobin and its model complex.
Fiche publication
Date publication
février 2019
Journal
Proceedings of the National Academy of Sciences of the United States of America
Auteurs
Membres identifiés du Cancéropôle Est :
Dr DECREAU Richard
Tous les auteurs :
Yan JJ, Kroll T, Baker ML, Wilson SA, Decréau R, Lundberg M, Sokaras D, Glatzel P, Hedman B, Hodgson KO, Solomon EI
Lien Pubmed
Résumé
Hemoglobin and myoglobin are oxygen-binding proteins with S = 0 heme {FeO} active sites. The electronic structure of these sites has been the subject of much debate. This study utilizes Fe K-edge X-ray absorption spectroscopy (XAS) and 1s2p resonant inelastic X-ray scattering (RIXS) to study oxyhemoglobin and a related heme {FeO} model compound, [(pfp)Fe(1-MeIm)(O)] (pfp = meso-tetra(α,α,α,α--pivalamido-phenyl)porphyrin, or TpivPP, 1-MeIm = 1-methylimidazole) (pfpO), which was previously analyzed using L-edge XAS. The K-edge XAS and RIXS data of pfpO and oxyhemoglobin are compared with the data for low-spin Fe and Fe [Fe(tpp)(Im)] (tpp = tetra-phenyl porphyrin) compounds, which serve as heme references. The X-ray data show that pfpO is similar to Fe, while oxyhemoglobin is qualitatively similar to Fe, but with significant quantitative differences. Density-functional theory (DFT) calculations show that the difference between pfpO and oxyhemoglobin is due to a distal histidine H bond to O and the less hydrophobic environment in the protein, which lead to more backbonding into the O A valence bond configuration interaction multiplet model is used to analyze the RIXS data and show that pfpO is dominantly Fe with 6-8% Fe character, while oxyhemoglobin has a very mixed wave function that has 50-77% Fe character and a partially polarized Fe-O π-bond.
Mots clés
DFT, X-ray spectroscopy, electronic structure, oxyhemoglobin, resonant inelastic X-ray scattering
Référence
Proc. Natl. Acad. Sci. U.S.A.. 2019 Feb 4;: