In photosynthetic bacteria, the absorbed light drives the canonical cyclic electron transfer between the reaction center and the cytochrome bc₁ complexes via the pools of mobile electron carriers. If kinetic or structural barriers hinder the participation of the bc₁ complex in the cyclic flow of electrons, then the pools of mobile redox agents must supply the electrons for the multiple turnovers of the reaction center. These conditions were achieved by continuous high light excitation of intact cells of bacterial strains Rba. sphaeroides and Rvx. gelatinosus with depleted donor side cytochromes c₂ (cycA) and tetraheme cytochrome subunit (pufC), respectively. The gradual oxidation by ferricyanide further reduced the availability of electron donors to pufC. Electron transfer through the reaction center was tracked by absorption change and by induction and relaxation of the fluorescence of the bacteriochlorophyll dimer. The rate constants of the electron transfer (~ 3 × 10³ s^‒1) from the mobile donors of Rvx. gelatinosus bound either to the RC (pufC) or to the tetraheme subunit (wild type) were similar. The electrons transferred through the reaction center dimer were supplied entirely by the donor pool; their number amounted to about 5 in wild type Rvx. gelatinosus and decreased to 1 in pufC oxidized by ferricyanide. Fluorescence yield was measured as a function of the oxidized fraction of the dimer and its complex shape reveals the contribution of two competing processes: the migration of the excitation energy among the photosynthetic units and the availability of electron donors to the oxidized dimer. The experimental results were simulated and rationalized by a simple kinetic model of the two-electron cycling of the acceptor side combined with aperiodic one-electron redox function of the donor side.

在光合细菌中，吸收的光通过移动电子载体池驱动反应中心和细胞色素bc ₁复合物之间的典型循环电子转移。如果动力学或结构障碍阻碍了bc ₁配合物参与电子的循环流动，则移动氧化还原剂池必须为反应中心的多次周转提供电子。这些条件是通过连续强光激发细菌菌株Rba 的完整细胞来实现的。球状体和Rvx。分别具有耗尽供体侧细胞色素 c ₂ ( cycA ) 和四血红素细胞色素亚基 ( pufC ) 的明胶。铁氰化物的逐渐氧化进一步降低了pufC的电子供体可用性。通过吸收变化以及细菌叶绿素二聚体荧光的诱导和弛豫来跟踪通过反应中心的电子转移。Rvx移动供体的电子转移速率常数 (~ 3 × 10 ³  s ^{−1 )} 。明胶与 RC ( pufC ) 或四血红素亚基（野生型）的结合是相似的。通过反应中心二聚体转移的电子完全由供体池提供；在野生型 Rvx 中，它们的数量约为 5 个。明胶并在被铁氰化物氧化的pufC中减少至 1 。荧光产量作为二聚体氧化部分的函数进行测量，其复杂的形状揭示了两个竞争过程的贡献：光合单元之间激发能的迁移和氧化二聚体的电子供体的可用性。通过受体侧双电子循环的简单动力学模型结合供体侧非周期性单电子氧化还原函数对实验结果进行了模拟和合理化。