title: Importance of many-body effects in the Kernel of hemoglobin for ligand binding.
abstract: We propose a mechanism for binding of diatomic ligands to heme based on a dynamical orbital selection process. This scenario may be described as bonding determined by local valence fluctuations. We support this model using linear-scaling first-principles calculations, in combination with dynamical mean-field theory, applied to heme, the kernel of the hemoglobin metalloprotein central to human respiration. We find that variations in Hund's exchange coupling induce a reduction of the iron 3d density, with a concomitant increase of valence fluctuations. We discuss the comparison between our computed optical absorption spectra and experimental data, our picture accounting for the observation of optical transitions in the infrared regime, and how the Hund's coupling reduces, by a factor of 5, the strong imbalance in the binding energies of heme with CO and O(2) ligands.
authors.affiliation: King's College London, Theory and Simulation of Condensed Matter, The Strand, London WC2R 2LS, United Kingdom.
authors.forename: Cédric
authors.initials: C
authors.lastname: Weber
authors.forename: David D
authors.initials: DD
authors.lastname: O'Regan
authors.forename: Nicholas D M
authors.initials: ND
authors.lastname: Hine
authors.forename: Peter B
authors.initials: PB
authors.lastname: Littlewood
authors.forename: Gabriel
authors.initials: G
authors.lastname: Kotliar
authors.forename: Mike C
authors.initials: MC
authors.lastname: Payne
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D013055:Spectrophotometry, Infrared; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D006454:Hemoglobins; D008024:Ligands; D006418:Heme; D002248:Carbon Monoxide; D010100:Oxygen