Holzwarth Alfred R, Müller Marc G, Niklas Jens, Lubitz Wolfgang
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim a.d. Ruhr, Germany.
J Phys Chem B. 2005 Mar 31;109(12):5903-11. doi: 10.1021/jp046299f.
The fluorescence kinetics of photosystem I core particles from Chlamydomonas reinhardtii have been measured with picosecond resolution in order to test a previous hypothesis suggesting a charge recombination mechanism for the early electron-transfer steps and the fluorescence kinetics (Müller et al. Biophys. J. 2003, 85, 3899-3922). Performing global target analyses for various kinetic models on the original fluorescence data confirms the "charge recombination" model as the only acceptable one of the models tested while all of the other models can be excluded. The analysis allowed a precise determination of (i) the effective charge separation rate constant from the equilibrated reaction center excited state (438 ns(-1)) confirming our previous assignment based on transient absorption data (Müller et al. Biophys. J. 2003, 85, 3899-3922), (ii) the effective charge recombination rate constant back to the excited state (52 ns(-1)), and (iii) the intrinsic secondary electron-transfer rate constant (80 ns(-1)). The average energy equilibration lifetime core antenna/RC is about 1 ps in the "charge recombination" model, in agreement with previous transient absorption data, vs the 18-20 ps energy transfer lifetime from antenna to RC within "transfer-to-the-trap-limited" models. The apparent charge separation lifetime in the recombination model is about three times faster than in the "transfer-to-the-trap-limited" model. We conclude that the charge separation kinetics is trap-limited in PS I cores devoid of red antenna states such as in C. reinhardtii.
为了验证之前提出的关于早期电子转移步骤和荧光动力学的电荷复合机制的假设（Müller等人，《生物物理学杂志》，2003年，85卷，3899 - 3922页），已使用皮秒分辨率测量了莱茵衣藻光系统I核心颗粒的荧光动力学。对原始荧光数据上的各种动力学模型进行全局目标分析，证实“电荷复合”模型是所测试模型中唯一可接受的模型，而所有其他模型均可排除。该分析允许精确确定：(i) 从平衡反应中心激发态的有效电荷分离速率常数（438 ns⁻¹），这证实了我们之前基于瞬态吸收数据的赋值（Müller等人，《生物物理学杂志》，2003年，85卷，3899 - 3922页）；(ii) 回到激发态的有效电荷复合速率常数（52 ns⁻¹）；以及(iii) 内在二次电子转移速率常数（80 ns⁻¹）。在“电荷复合”模型中，核心天线/反应中心的平均能量平衡寿命约为1 ps，这与之前的瞬态吸收数据一致，而在“转移到陷阱限制”模型中，从天线到反应中心的能量转移寿命为18 - 20 ps。复合模型中的表观电荷分离寿命比“转移到陷阱限制”模型快约三倍。我们得出结论，在没有红色天线状态的光系统I核心中，如在莱茵衣藻中，电荷分离动力学是陷阱限制的。
