Institute of Physico-Chemical Biology, Moscow State University, Leninsky Gory, 119992, Moscow, Russia.
Chemphyschem. 2011 Feb 25;12(3):681-8. doi: 10.1002/cphc.201000830. Epub 2011 Feb 14.
We explain the transient absorption kinetics (E. Romero, I. H. M. van Stokkum, V. I. Novoderezhkin, J. P. Dekker, R. van Grondelle, Biochemistry 2010, 49, 4300) measured for isolated reaction centers of photosystem II at 77 K upon excitation of the primary donor band (680 nm). The excited-state dynamics is modeled on the basis of the exciton states of 6 cofactors coupled to 4 charge-transfer (CT) states. One CT state (corresponding to charge separation within the special pair) is supposed to be strongly coupled with the excited states, whereas the other radical pairs are supposed to be localized. Relaxation within the strongly coupled manifold and transfer to localized CT's are described by the modified Redfield and generalized Förster theories, respectively. A simultaneous and quantitative fit of the 680, 545, and 460 nm kinetics (corresponding to respectively the Q(y) transitions of the red-most cofactors, Q(x) transition of pheophytin, and pheophytin anion absorption) enables us to define the pathways and time scales of primary electron transfer. A consistent modeling of the data is only possible with a Scheme where charge separation occurs from both the accessory chlorophyll and from the special pair, giving rise to fast and slow components of the pheophytin anion formation, respectively.
我们解释了在 77 K 下测量到的分离的光合系统 II 反应中心在激发原初供体带（680nm）时的瞬态吸收动力学（E. Romero，I. H. M. van Stokkum，V. I. Novoderezhkin，J. P. Dekker，R. van Grondelle，生物化学 2010，49，4300）。激发态动力学是基于与 4 个电荷转移（CT）态耦合的 6 个辅助因子的激子态建模的。一个 CT 态（对应于特殊对内的电荷分离）被假定与激发态强烈耦合，而其他自由基对被假定为局域化的。强耦合流形内的弛豫和到局域化 CT 的转移分别由修正的 Redfield 和广义 Förster 理论描述。680nm、545nm 和 460nm 动力学（分别对应于最红辅助因子的 Q(y)跃迁、叶绿素 pheophytin 的 Q(x)跃迁和 pheophytin 阴离子吸收）的同时和定量拟合使我们能够定义初级电子转移的途径和时间尺度。只有在一种方案中，数据的一致建模才是可能的，该方案假设电荷分离既来自辅助叶绿素，也来自特殊对，从而分别导致 pheophytin 阴离子形成的快和慢组分。
