title: Parameters controlling the kinetics of ferric and ferrous hemeproteins reduction by hydrated electrons.
abstract: To clarify the processes of hemeproteins reduction, three classes of these proteins (ferric, ferrous and desFe) were reduced by hydrated electrons generated by pulse radiolysis. Spectral and kinetic investigations were made on alpha hemoglobin chain and myoglobin. Human alpha chain has been chosen to avoid all ferric contaminations and horse ferric myoglobin to eliminate all ferrous protein fractions. We have successively studied the influences of: the iron presence, its oxidation state (II and III), the protein charge and the iron-ligand nature (H2O, OH-, N3- and CN-). For alpha human hemoglobin chain without metallic ion or with ferrous iron, the reduction rates are the same: 1.1 +/- 0.2.10(10) M-1.s-1. In the case of horse ferric myoglobin, the reduction rates depend principally on the protein charge (from pH 6.3 to pH 9.5, the reduction rate of Mb(FeIII)N3- decreases from 2.5 +/- 0.5.10(10) M-1.s-1 to 1.2 +/- 0.2.10(10) M-1.s-1) and are also modulated by the equilibrium constant of the hemeprotein-ligand association (1.2 +/- 0.2.10(10) M-1.s-1 for Mb(FeIII)N3- and 0.8 +/- 0.2.10(10) M-1.s-1 for Mb(FeIII)CN-, at pH 9.8).
authors.affiliation: Laboratoire de Biologie Physico-Chimique, Université Paris VII, France.
authors.forename: S
authors.initials: S
authors.lastname: Pin
authors.forename: B
authors.initials: B
authors.lastname: Hickel
authors.forename: B
authors.initials: B
authors.lastname: Alpert
authors.forename: C
authors.initials: C
authors.lastname: Ferradini
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004583:Electrons; D005290:Ferric Compounds; D005296:Ferrous Compounds; D005914:Globins; D006420:Hemeproteins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008786:Metmyoglobin / Q000031:analogs & derivatives; D009211:Myoglobin; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D013053:Spectrophotometry
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D006420:Hemeproteins; D009211:Myoglobin; C007177:cyanometmyoglobin; C292386:metmyoglobin azide; D008786:Metmyoglobin; D005914:Globins