Does slow energy transfer limit the observed time constant for radical pair formation in photosystem II reaction centers

摘要: We have used spectrally photoselective femtosecond transient absorption spectroscopy on photosystem II reaction centers to show that there are at least two pools of chlorin molecules/states which can transfer excitation energy P680, the primary electron donor in II. It has previously been shown one pool equilibrates with P680 100 fs [Durrant et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 11632-11636], and we report here observation from a second more weakly coupled pool. The effect is increase apparent time constant for radical pair formation 21 ps when selectively excited 27 accessory chlorins excited. conclude it possible observe both somewhat slowed by an step not limited this slow transfer, depending upon chromophores initially These observations provide evidence using observed step.