Nature and dynamics of the charge-separated intermediate in reaction centers in which bacteriochlorophyll replaces the photoactive bacteriopheophytin. 2. The rates and yields of charge separation and recombination
- Washington Univ., St. Louis, MO (United States)
- Colorado State Univ., Fort Collins, CO (United States)
The primary photochemistry of the (M)L214H and (M)L214H/(L)E104V mutant bacterial reaction centers (RCs) from Rhodobacter sphaeroides has been investigated at room and cryogenic temperatures. In both mutants the native bacteriopheophytin electron acceptor (BPh{sub L}) is replaced with a bacteriochlorophyll (BChl) molecule denoted by {Beta}; in the double mutant a hydrogen-bonding interaction of {Beta}-is removed. The initial stage of charge separation, formation of an intermediate P{sup +}I{sup -}, is slowed somewhat in both mutants but without a detectable loss in yield. However, the yield of the subsequent stage of charge separation, P{sup +}I{sup N} {yields} P{sup +}Q{sub A}{sup -}, is significantly reduced due to the combination of slower electron transfer from I{sup -} to Q{sub A} and enhanced charge recombination of P{sup +}I{sup -} to the ground state. Models are considered in which P{sup +}{Beta}{sup -} and P{sup +}BCh1{sub L} are quantum-mechanically mixed or in thermal equilibrium. It is concluded that P{sup +}{Beta}{sup -} and P{sup +}BCh1{sub L} are very close in energy in the mutants and that P{sup +}BCh1{sub L} is very close in energy to the primary electron donor, P{sup *}, in both the mutant and wild-type RCs. 40 refs., 8 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 62462
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 21 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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