Jablonsky Jiri, Lazar Dusan
Palacky University, Faculty of Science, Laboratory of Biophysics, Olomouc, Czech Republic.
Biophys J. 2008 Apr 1;94(7):2725-36. doi: 10.1529/biophysj.107.122861. Epub 2008 Jan 4.
We have analyzed flash-induced period-four damped oscillation of oxygen evolution and chlorophyll fluorescence with the aid of a kinetic model of photosystem II. We have shown that, for simulation of the period-four oscillatory behavior of oxygen evolution, it is essential to consider the so-called intermediate S-state as an initial phase of each of the S(n)-S(n+1), (n = 0, 1, 2, 3) transitions. The intermediate S-states are defined as [S(n)Y(Z)(ox)]-states (n = 0, 1, 2, 3) and are formed with rate constant k(iSn) approximately 1.5 x 10(6) s(-1), which was determined from comparison of theoretical predictions with experimental data. The assumed intermediate S-states shift the equilibrium in reaction P680(+)Y(Z)<-->P680Y(Z)(ox) more to the right and we suggest that kinetics of the intermediate S-states reflects a relaxation process associated with changes of the redox equilibrium in the above reaction. The oxygen oscillation is simulated without the miss and double-hit parameters, if the intermediate S-states, which are not the source of the misses or the double-hits, are included in the simulation. Furthermore, we have shown that the intermediate S-states, together with S(2)Q(A)(-) charge recombination, are prerequisites for the simulation of the period-four oscillatory behavior of the chlorophyll fluorescence.
我们借助光系统II的动力学模型，分析了闪光诱导的氧气释放和叶绿素荧光的四周期阻尼振荡。我们已经表明，为了模拟氧气释放的四周期振荡行为，将所谓的中间S态视为每个S(n)-S(n+1)（n = 0, 1, 2, 3）转变的初始阶段至关重要。中间S态被定义为[S(n)Y(Z)(ox)]态（n = 0, 1, 2, 3），其形成速率常数k(iSn)约为1.5 x 10(6) s(-1)，这是通过理论预测与实验数据的比较确定的。假定的中间S态使反应P680(+)Y(Z)<-->P680Y(Z)(ox)中的平衡更多地向右移动，并且我们认为中间S态的动力学反映了与上述反应中氧化还原平衡变化相关的弛豫过程。如果在模拟中包括不是漏失或双击来源的中间S态，则可以在不使用漏失和双击参数的情况下模拟氧气振荡。此外，我们已经表明，中间S态与S(2)Q(A)(-)电荷复合一起，是模拟叶绿素荧光四周期振荡行为的先决条件。
