Van Brederode M E, Jones M R, Van Mourik F, Van Stokkum I H, Van Grondelle R
Department of Physics and Astronomy, Free University of Amsterdam, The Netherlands.
Biochemistry. 1997 Jun 10;36(23):6855-61. doi: 10.1021/bi9703756.
It is generally accepted that electron transfer in bacterial photosynthesis is driven by the first singlet excited state of a special pair of bacteriochlorophylls (P*). We have examined the first steps of electron transfer in a mutant of the Rhodobacter sphaeroides reaction center in which charge separation from P* is dramatically slowed down. The results provide for the first time clear evidence that excitation of the monomeric bacteriochlorophyll in the active branch of the reaction center (B(A)) drives ultrafast transmembrane electron transfer without the involvement of P*, demonstrating a new and efficient mechanism for solar energy transduction in photosynthesis. The most abundant charge-separated intermediate state probably is P+B(A)-, which is formed within 200 fs from B(A)* and decays with a lifetime of 6.5 ps into P+H(A)-. We also see evidence for the involvement of a B(A)+H(A)- state in the alternative pathway.
人们普遍认为，细菌光合作用中的电子转移是由一对特殊的细菌叶绿素（P*）的第一单线态激发态驱动的。我们研究了球形红杆菌反应中心突变体中电子转移的第一步，在该突变体中，从P进行的电荷分离显著减慢。结果首次提供了明确的证据，即反应中心活性分支（B(A)）中单体细菌叶绿素的激发驱动超快跨膜电子转移，而无需P的参与，这证明了光合作用中太阳能转换的一种新的有效机制。最丰富的电荷分离中间态可能是P+B(A)-，它在200飞秒内从B(A)*形成，并以6.5皮秒的寿命衰变为P+H(A)-。我们还看到了B(A)+H(A)-态参与替代途径的证据。
