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

Journal Article · Thu Dec 27 00:00:00 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), Vol. 83:26
• Country of Publication: United States
• Language: English

Related Subjects

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