Rancova Olga, Jankowiak Ryszard, Kell Adam, Jassas Mahboobe, Abramavicius Darius
Department of Theoretical Physics, Vilnius University , Sauletekio al 9-III, 10222 Vilnius, Lithuania.
J Phys Chem B. 2016 Jun 30;120(25):5601-16. doi: 10.1021/acs.jpcb.6b02595. Epub 2016 Jun 20.
Persistent/transient spectral hole burning (HB) and computer simulations are used to provide new insight into the excitonic structure and excitation energy transfer of the widely studied bacterial reaction center (bRC) of Rhodobacter (Rb.) sphaeroides. We focus on site energies of its cofactors and electrochromic shifts induced in the chemically oxidized (P(+)) and charge-separated (P(+)QM(-)) states. Theoretical models lead to two alternative interpretations of the H-band. On the basis of our experimental and simulation data, we suggest that the bleach near 813-825 nm in transient HB spectra in the P(+)QM(-) state, often assigned to the upper exciton component of the special pair, is mostly due to different electrochromic shifts of the BL/M cofactors. From the exciton compositions in the charge-neutral (CN) bRC, the weak fourth excitonic band near 780 nm can be denoted PY+, that is, the upper excitonic band of the special pair, which in the CN bRC behaves as a delocalized state over PM and PL pigments that weakly mixes with accessory BChls. Thus, the shoulder in the absorption of Rb. sphaeroides near 813-815 nm does not contain the PY+ exciton band.
利用持续/瞬态光谱烧孔（HB）和计算机模拟，对广泛研究的球形红杆菌（Rb.）球形细菌反应中心（bRC）的激子结构和激发能量转移提供了新的见解。我们关注其辅因子的位点能量以及在化学氧化（P(+)）和电荷分离（P(+)QM(-)）状态下诱导的电致变色位移。理论模型对H带给出了两种不同的解释。基于我们的实验和模拟数据，我们认为在P(+)QM(-)状态下瞬态HB光谱中813 - 825 nm附近的漂白，通常被认为是特殊对的上激子成分，主要是由于BL/M辅因子不同的电致变色位移。从电荷中性（CN）bRC中的激子组成来看，780 nm附近较弱的第四激子带可表示为PY +，即特殊对的上激子带，在CN bRC中，它表现为在PM和PL色素上的离域态，并与辅助细菌叶绿素弱混合。因此，球形红杆菌在813 - 815 nm附近吸收光谱中的肩峰不包含PY +激子带。
