Anion and cation radicals of bacteriochlorophyll and bacteriopheophytin b: their role in the primary charge separation of Rhodopseudomonas viridis

Journal Article · Thu Dec 27 04:00:00 EST 1979 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100489a005· OSTI ID:5578240

Davis, M S; Forman, A; Hanson, L K; Thornber, J P; Fajer, J

Optical, ESR, ENDOR, and redox characteristics of anion and cation radicals of bacteriochlorophyll b (BChl) and bacteriopheophytin b (BPh) have been obtained in nonaqueous solvents. The radicals exhibit properties similar to those of BChl a derivatives, as expected from extended Huckel and Pariser-Parr-Pople MO calculations. The electronic configurations of the radicals have been assigned on the basis of the MO calculations and by analogy with BChl a and BPh a results. Oxidized reaction centers of Rhodopseudomonas viridis do not display the ..sqrt..2 narrowing of the ESR line width nor the 50% decrease in ENDOR splittings expected for a symmetric cation dimer, when compared to BChl b/sup +/. Nonetheless, computer simulations indicate that a dimeric model for P960, the primary donor of R. viridis, can be rationalized by imposing a torsional angle on ring IV different from that found in crystals of Chl a, i.e., P960 may be a dimer with a twist. Comparison of the resolved ESR spectra and ENDOR splittings of the primary acceptor (I/sup -/) of R. viridis with in-vitro results indicates that I/sup -/ is a monomeric anion. Optical and redox data favor BPh over BChl as the primary acceptor. These results allow a description of the electronic profile of the species which evolve within a picosecond time domain in the primary conversion of light into chemical energy at approx. 1000 nm.

• Research Organization: Brookhaven National Lab., Upton, NY
• OSTI ID: 5578240
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 83:26; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
550700* -- Microbiology
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
CHEMICAL REACTIONS
DATA
DATA FORMS
ELECTRON SPIN RESONANCE
ENDOR
EXPERIMENTAL DATA
INFORMATION
ISOLATED VALUES
MAGNETIC RESONANCE
MICROORGANISMS
NUMERICAL DATA
PHOTOCHEMICAL REACTIONS
RESONANCE
RHODOPSEUDOMONAS