Spectroscopic properties of photosynthetic reaction centers. 2. Application of the theory to Rhodopseudomonas viridis

Journal Article · Wed Sep 30 00:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00254a040· OSTI ID:6061648

Parson, W W; Warshel, A

In the preceding paper (Warshel and Parson, companion paper), a nonphenomenological molecular theory is developed to calculate the spectroscopic properties of the reaction centers of photosynthetic bacteria. They here apply the theory to the reaction center of Rhodopseudomonas viridis, whose structure is known from recent X-ray crystallographic studies. Optical absorption, linear dichroism, and circular dichroism spectra are calculated and are compared with the spectra observed experimentally. Intermolecular charge-transfer (CT) transitions between the two bacteriochlorophylls (BChls) of the photochemically reactive special pair (BChl/sub LP/ and BChl/sub MP/) appear to make major contributions to the spectroscopic properties. Estimates of the energies of the CT transitions are obtained. Good agreement with the observed spectra is obtained by placing the lowest energy CT transition from BChl/sub MP/ to BChl/sub LP/ near 14,000 cm/sup -1/, well above the reaction center's lowest excited state (10,400 cm/sup -1/), and placing the corresponding CT transition from BChl/sub LP/ to BChl/sub MP at a substantially higher energy. Charge-transfer transitions involving the other two BChls (BChl/sub LA/ and BChl/sub MA/) are found not to contribute significantly to the spectra. To model the absorption changes that occur when the special pair of BChls is photooxidized, or when one of the two bacteriopheophytins is reduced, calculations are performed in which one or more of the molecules are omitted from the structure. The absorption changes that occur in the region from 790 to 860 nm reflect a strong mixing of the transitions of all six pigments.

• Research Organization: Univ. of Washington, Seattle
• OSTI ID: 6061648
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 109:20
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
PHOTOSYNTHETIC REACTION CENTERS
EXCITED STATES
GROUND STATES
RHODOPSEUDOMONAS
DICHROISM
CHARGE TRANSPORT
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
PHOTOSYNTHETIC BACTERIA
THEORETICAL DATA
WAVE FUNCTIONS
BACTERIA
DATA
ENERGY LEVELS
FUNCTIONS
INFORMATION
MICROORGANISMS
NUMERICAL DATA
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)