Influence of electronic asymmetry on the spectroscopic and photodynamic properties of the primary electron donor in the photosynthetic reaction center
- Washington Univ., St. Louis, MO (United States)
- Univ. of California, Riverside, CA (United States)
- Colorado State Univ., Fort Collins, CO (United States)
Resonance Raman and subpicosecond resolution transient absorption data are presented on the reaction center (RC) from the Rb. sphaeroides (M)H202L/(L)L131H double mutant. This RC contains a bacteriochlorophyll/bacteriopheophytin heterodimer primary electron donor (D), as a result of introducing a Leu at M subunit residue 202, as well as a hydrogen bond to the ring-V keto group of he BChl component, as a result of introducing a His at L subunit residue 131. The double mutant shows a longer lifetime (40ps) for the lowest excited singlet state and a lower quantum yield of change separation (25%) than observed perviously for the heterodimer single mutants (M)H202L and (L)H173L. These changes are ascribed in large measure to a decrease in the contribution of the accessory pigment BChl{sub L} to the initial stage of charge separation. Both the rate of internal conversion of the excited primary donor and the characteristics of the near-infrared ground state absoption of the dimer appear to be intermediate between those found for the (M)H202L single mutant and wild type RCs. Resonance Raman profiles obtained via excitation at several wavelengths across the heterodimer absorption band suggest that there is a change in the nature and perhaps ordering of the two lowest excited states of the heterodimer in the double mutant compared with the single mutant. 44 refs., 13 figs., 1 tab.
- OSTI ID:
- 420706
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 44; Other Information: PBD: 31 Oct 1996
- Country of Publication:
- United States
- Language:
- English
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