title: Bonding of heme Fe(III) with dioxygen: observation and characterization of an incipient bond.
abstract: While ferrous heme (Fe(II)) within hemoproteins binds dioxygen efficiently, it has not yet been possible to observe the analog complex with ferric heme (Fe(III)). We present the first observation and characterization of the latter complex in a cooled ion trap. The bond formation enthalpy of ferric heme-O2 has been derived from the Van't Hoff equation by means of temperature dependent measurements. The binding energy of the [heme Fe(III)-O2](+) ionic complex is rather strong as compared to that of [heme Fe(III)-N2](+), showing the formation of an incipient Fe-O bond, which is confirmed by the electronic absorption spectra of the two complexes. This first observation of the [heme Fe(III)-O2](+) complex lays the basis for the precise description of its electronic states.
authors.affiliation: ISMO, Univ Paris-Sud, CNRS UMR 8214, bat 210 Univ Paris-Sud 91405, Orsay Cedex, France. niloufar.shafizadeh@u-psud.fr.
authors.forename: Léa
authors.initials: L
authors.lastname: Ferrand
authors.forename: Satchin
authors.initials: S
authors.lastname: Soorkia
authors.forename: Gilles
authors.initials: G
authors.lastname: Grégoire
authors.forename: Michel
authors.initials: M
authors.lastname: Broquier
authors.forename: Benoît
authors.initials: B
authors.lastname: Soep
authors.forename: Niloufar
authors.initials: N
authors.lastname: Shafizadeh
mesh_terms: D001665:Binding Sites; D005290:Ferric Compounds / Q000737:chemistry*; D006418:Heme / Q000737:chemistry*; D006420:Hemeproteins / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D005290:Ferric Compounds; D006420:Hemeproteins; D006418:Heme; D007501:Iron; D010100:Oxygen