ELECTRIC FIELD EFFECTS ON PHOTOSYSTEM II ELECTRON TRANSFER

我们已经开发出测量电子转移动力学的方法， 由膜结合反应中心制成的特殊设计的电容器 蛋白 这就要求设计关键的耦合协议 飞秒脉冲和跨 结构 从光谱学的观点来看， 为了改善FS实验中的信噪比 不能移动或流动。 此外，这样的耦合 脉冲电场实验及有关演示 瞬态场的存在是不平凡的。 的自由能 细菌光合反应中的初始电荷分离 中心已被修改，通过放置取向的朗缪尔-布洛杰特膜 在平面中的外部电极之间的纯化的蛋白质 电容器并施加接近106 V/cm的场。 近红外 瞬态吸收变化与受激 细菌叶绿素二聚体的状态和初始电荷 以300 fs的时间分辨率测量分离， 应用领域 令人惊讶的是， 定向系统与无定向系统的比较表明， 激发的细菌叶绿素二聚体之间的能隙的调制 与细菌叶绿素单体的电荷分离态 降低了电场对速率的主要影响。 的 在较长时间尺度上观察到的场致量子产额失效 似乎与细菌脱镁叶绿素的调节有关， 细菌叶绿素二聚体电荷重组。

We have developed ways of measuring electron transfer dynamics in specially designed capacitors made from membrane bound reaction center protein. This has demanded the design of critical coupling protocols between femtosecond pulses and the creation of fields across the structure. From the spectroscopic standpoint the great challenge is to improve the signal-to noise in fs experiments where the sample cannot be moved or flowed. Furthermore, the coupling of such experiments to pulsed electric fields and concerning demonstrations of the presence of transient fields is nontrivial. The free energy of the initial charge separation in bacterial photosynthetic reaction centers has been modified by placing oriented Langmuir-Blodgett films of the purified protein between external electrodes in a planar capacitor and applying a field of nearly 106 V/cm. The near-infrared transient absorption changes associated with the decay of the excited state of the bacteriochlorophyll d imer and t he initial charge separation was measured with 300 fs time resolution with and without applied field. The surprisingly small field induced rate changes of the oriented systems compared to unoriented systems suggest that modulation of the energy gap between excited bacteriochlorophyll dimer and the charge separated state with bacteriochlorophyll monomer reduced is the principal influence of electric field on rate. The field induced quantum yield failure observed at longer timescales appears to be associated with modulation of the bacteriopheophytin to bacteriochlorophyll dimer charge recombination.