Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA.
J Phys Chem B. 2011 Mar 31;115(12):3226-32. doi: 10.1021/jp111680p. Epub 2011 Mar 8.
Photosynthetic reaction centers (RC) convert light into electrical potential via a series of electron transfers between protein-bound, redox-active cofactors. Direct voltammetry was used to characterize the RC protein from Rhodobacter sphaeroides and mutants with focus on the primary electron donor (P) cofactor. Cyclic voltammetry (CV) and square wave voltammetry (SWV) of lipid and polyion films of RCs revealed similar chemically irreversible processes, and starting, switching, or preconditioning potential of -0.15 V was required to observe a well-defined P/P(+) oxidation peak at ∼0.95 V versus normal hydrogen electrode. An irreversible chemical reaction following voltammetric oxidation led to peak decreases upon multiple scans. Mutant RCs with site-directed amino acid modifications in the vicinity of P displayed shifts of oxidation peak potential correlated with those reported from redox titrations. These studies illustrate the utility of thin film voltammetry in characterizing redox properties of bound cofactors in RC proteins.
光合作用反应中心（RC）通过一系列在蛋白结合的氧化还原活性辅因子之间的电子转移将光转化为电势能。我们使用直接伏安法来表征来自球形红杆菌的 RC 蛋白及其突变体，重点关注主要电子供体（P）辅因子。RC 的脂质和聚离子薄膜的循环伏安法（CV）和方波伏安法（SWV）揭示了相似的化学不可逆过程，并且需要起始、切换或预处理电位为-0.15 V，才能在相对于标准氢电极约 0.95 V 处观察到定义明确的 P/P(+)氧化峰。伏安氧化后的不可逆化学反应导致在多次扫描时峰下降。在 P 附近进行定点氨基酸修饰的突变 RC 显示氧化峰电位的偏移与来自氧化还原滴定的报告结果相关。这些研究说明了薄膜伏安法在表征 RC 蛋白中结合辅因子的氧化还原性质方面的实用性。
