Direct EPR Detection of a Hydrogen-Bonded Complex between a Semiquinone Radical Anion and a Protonated Amino Acid, and Electron Transfer Driven by Hydrogen Bonding

摘要

In the photosynthetic reaction center (RC), two quinones denoted QA and QB act as electron acceptors. The RC catalyzes light-induced two-electron reduction of QB with two protons to yield hydroquinone QBH2, which is released from the RC and replaced by another quinone molecule from the pool.[2] Although the first electron transfer, QA·-→QB, does not involve direct protonation of QB·-, the electron transfer (ET) is coupled with protonation of a nearby amino acid residue through hydrogen-bond formation with QB·-.