Electronic couplings and energy transfer dynamics in the oxidized primary electron donor of the bacterial reaction center

被引:40
作者
Jordanides, XJ
Scholes, GD
Shapley, WA
Reimers, JR
Fleming, GR
机构
[1] Lawrence Berkeley Lab, Phys Biosci Div, Berkeley, CA 94720 USA
[2] Univ Sydney, Sch Chem, Sydney, NSW 2006, Australia
[3] Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA
关键词
D O I
10.1021/jp036516x
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
It has been known for 30 years that the oxidized special pair radical cation P+ is as efficient as the neutral ground-state species P in quenching excitation from the neighboring accessory bacteriochlorophylls B-L and B-M, but the mechanism for this process has remained elusive. Indeed, simple treatments based on application of standard Forster theory to the most likely acceptor candidate fails by 5 orders of magnitude in the prediction of the energy transfer rates to P+. We present a qualitative description of the electronic energy transfer (EET) dynamics that involves mixing of the strongly allowed transitions in P+ with a manifold of exotic lower-energy transitions to facilitate EET on the observed time scale of 150 fs. This description is obtained using a three-step procedure. First, multireference configuration-interaction (MRCI) calculations are performed using the semiempirical INDO/S Hamiltonian to depict the excited states of P+. However, these calculations are qualitatively indicative but of insufficient quantitative accuracy to allow for a fully a priori simulation of the EET and so, second, the INDO results are used to establish a variety of scenarios, empirical parameters that are then fitted to describe a range of observed absorption and circular dichroism data. Third, EET according to these scenarios is predicted using a generalized Forster theory that uses donor and acceptor transition densities, which together account for the large size of the chromophores in relation to the interchromophore spacings. The spectroscopic transitions of P+ that facilitate the fast EET are thus unambiguously identified.
引用
收藏
页码:1753 / 1765
页数:13
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