Multipulse spectroscopy on the wild-type and YM210W Bacterial Reaction Centre uncovers a new intermediate state in the special pair excited state

Abstract

The Bacterial Reaction Centre (BRC) has a complex electronic excited state, P ∗, that evolves into subsequent charge separated product states P +H − and P +B −. Pump–dump–probe spectroscopy on the wild-type BRC and on YM210W, a mutant with a stabilized, long-lived P ∗ excited state, has uncovered a new charge-separated state in both BRC’s. When P ∗ is dumped, a fraction of its population is transferred to this state that has a strong Stark shift in the accessory bacteriochlorophyll (B M) region which serves as a signature for P + and a lifetime highly comparable to the slow phase of P ∗ decay. This lead us propose this intermediate to be P +/P −.