title: Photochemical reduction of cytochrome c by a 1,4,5,8-naphthalenediimide radical anion.
abstract: Steady-state UV irradiation of aqueous solutions containing cytochrome c (cyt c) and N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (BPNDI), a water-soluble aromatic imide, resulted in the reduction of the heme iron from the Fe(III) to the Fe(II) oxidation state. The reaction kinetics were followed by the increase of the ferrocytochrome c absorbance band at 549 nm. The rate of the photochemical reaction was pH dependent, reaching its maximum values over the pH range 4-7. Addition of electrolyte (NaCl) at pH 5 resulted in a decrease in the reaction rate, as expected for reactions between oppositely charged species. Flash photolysis studies revealed that the actual reductant in the reaction was a photogenerated BPNDI radical anion, which transferred an electron to the cyt c heme iron. The participation of imide radicals in the process was confirmed by the ready reduction of cyt c by BPNDI radicals chemically generated with sodium dithionite.
authors.affiliation: Centro Interdisciplinar de Investigação Bioquímica, Universidade de Mogi das Cruzes, Mogi das Cruzes, SP, Brazil.
authors.forename: Ivana B
authors.initials: IB
authors.lastname: Campos
authors.forename: Iseli L
authors.initials: IL
authors.lastname: Nantes
authors.forename: Mario J
authors.initials: MJ
authors.lastname: Politi
authors.forename: Sergio
authors.initials: S
authors.lastname: Brochsztain
mesh_terms: D000838:Anions / Q000737:chemistry / Q000494:pharmacology; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism*; D005609:Free Radicals / Q000737:chemistry / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009994:Osmolar Concentration; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D010618:Phenanthrolines; D010777:Photochemistry; D012965:Sodium Chloride / Q000494:pharmacology; D013057:Spectrum Analysis
chemical_list: D000838:Anions; D005609:Free Radicals; C514821:N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide; D010618:Phenanthrolines; D012965:Sodium Chloride; D045304:Cytochromes c