title: Redox chemistry of low-pH forms of tetrahemic cytochrome c3.
abstract: Desulfovibrio vulgaris Hildenborough cytochrome c(3) contains four hemes in a low-spin state with bis-histidinyl coordination. High-spin forms of cytochrome c(3) can be generated by protonation of the axial ligands in order to probe spin equilibrium (low-spin/high-spin). The spin alterations occurring at acid pH, the associated changes in redox potentials, as well as the reactivity towards external ligands were followed by the conjunction of square wave voltammetry and UV-visible, CD, NMR and EPR spectroscopies. These processes may be used for modelling the action of enzymes that use spin equilibrium to promote enzyme activity and reactivity towards small molecules.
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Santos
authors.forename: M M Correia
authors.initials: MM
authors.lastname: Dos Santos
authors.forename: M L Simões
authors.initials: ML
authors.lastname: Gonçalves
authors.forename: C
authors.initials: C
authors.lastname: Costa
authors.forename: J C
authors.initials: JC
authors.lastname: Romão
authors.forename: J J G
authors.initials: JJ
authors.lastname: Moura
mesh_terms: D002942:Circular Dichroism; D003574:Cytochrome c Group / Q000737:chemistry*; D016969:Desulfovibrio vulgaris / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003574:Cytochrome c Group; D006418:Heme; C017165:cytochrome c(3)