Mode of inhibition of electron transport by orthophenanthroline in chromatophores and reaction centers of Rhodopseudomonas sphaeroides

Journal Article · Tue Apr 01 00:00:00 EST 1980 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.77.4.1809· OSTI ID:5125544

Vermeglio, A ^[1]; Martinet, T; Clayton, R K

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1. Center d'Etudes Nucleaires de Saclay, Gif-sur-Yvette, France

In Rhodopseudomonas sphaeroides, light causes the transfer of electrons from bacteriochlorophyll to ubiquinone in the photochemical reaction centers. Electrons from this primary ubiquinone move on to a secondary ubiquinone. We have studied the manner in which o-phenanthroline inhibits the transfer of electrons from primary to secondary ubiquinone in chromatophores (intracytoplasmic membrane fragments) and isolated reaction centers of Rp. sphaeroides. The formation of anionic semiquinones, both primary and secondary, is signaled by an absorption band at 450nm and by band shifts of bacteriopheophytin and bacteriochlorophyll in the near infrared. The pattern of band shifts is different for primary and secondary semiquinone, allowing us to distinguish which quinone has become semireduced. This point was established for isolated reaction centers and is confirmed here for chromatophores. By adding o-phenanthroline at various times during a sequence of actinic light flashes and monitoring the resulting optical absorbance changes, we have found that o-phenanthroline inhibits electron transfer from primary semiquinone to secondary quinone if the latter is in its oxidized form, but not if the latter is semireduced. Our findings can explain the decay kinetics of delayed fluorescence from bacteriochlorophyll in Rp. sphaeroides as measured by R.P. Carithers and W.W. Parson.

• DOE Contract Number: EY-76S-02-3162
• OSTI ID: 5125544
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 77:4
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
59 BASIC BIOLOGICAL SCIENCES
PHENANTHROLINE-ORTHO
TOXICITY
RHODOPSEUDOMONAS
SENSITIVITY
UBIQUINONE
ELECTRON TRANSFER
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
CHLOROPHYLL
INHIBITION
PHOTOCHEMICAL REACTIONS
AROMATICS
BACTERIA
BENZOQUINONES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COENZYMES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
KINETICS
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHENANTHROLINES
PHYTOCHROMES
PIGMENTS
PORPHYRINS
QUINONES
REACTION KINETICS
REAGENTS
560302* - Chemicals Metabolism & Toxicology- Microorganisms- (-1987)
551000 - Physiological Systems
550500 - Metabolism