Effect of hydrogen bonds on the energetics of macromolecules in the course of electron transfer

For a model system consisting of a bacteriochlorophyll dimer (P) and a primary quinone with the nearest environment (Q_A), which are the electron donor and acceptor in the recombination reaction in the Rhodobacter spheroides reaction center, the energies of states P⁺Q _A ^? and PQ_A have been calculated at several stable conformations of Q_A that differ in the positions of the proton involved in the hydrogen bond. It is shown that the position of the proton has a considerable influence on the energy of vertical transition P⁺Q _A ^? → PQ_A.