%0 Journal Article %A van Brederode, Marion E. %A H. M. van Stokkum, Ivo %A Katilius, Evaldas %A Mourik, Frank van %A Jones, Michael R. %A Grondelle, Rienk van %D 1999 %T Primary Charge Separation Routes in the BChl:BPhe Heterodimer Reaction Centers of Rhodobacter sphaeroides %U https://acs.figshare.com/articles/journal_contribution/Primary_Charge_Separation_Routes_in_the_BChl_BPhe_Heterodimer_Reaction_Centers_of_i_Rhodobacter_sphaeroides_i_sup_sup_/3588804 %R 10.1021/bi9829128.s001 %2 https://acs.figshare.com/ndownloader/files/5674740 %K excitation wavelength %K B excitation %K bacteriochlorophyll homodimer %K pathway B %K 880 nm excitation light results %K charge separation process %K HL 173L reaction center %K 812 nm %K state D %K 43 ps decay %K B B %K 798 nm excitation light %K excitation energy %K charge separation %K excitations results %K Rhodobacter sphaeroides %K ground state %K monomeric bacteriochlorophylls %K U.S.A %K absorption spectra %K Primary Charge Separation Routes %K HM 202L heterodimer reaction center %X Energy transfer and the primary charge separation process are studied as a function of excitation wavelength in membrane-bound reaction centers of Rhodobacter sphaeroides in which the excitonically coupled bacteriochlorophyll homodimer is converted to a bacteriochlorophyll-bacteriopheophytin heterodimer, denoted D [Bylina, E. J., and Youvan, D. C. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 7226]. In the HM202L heterodimer reaction center, excitation of D using 880 nm excitation light results in a 43 ps decay of the excited heterodimer, D*. The decay of D* results for about 30% in the formation of the charge separated state D+QA- and for about 70% in a decay directly to the ground state. Upon excitation of the monomeric bacteriochlorophylls using 798 nm excitation light, approximately 60% of the excitation energy is transferred downhill to D, forming D*. Clear evidence is obtained that the other 40% of the excitations results in the formation of D+QA- via the pathway BA* → BA+HA- → D+HA- → D+QA-. In the membrane-bound “reversed” heterodimer reaction center HL173L, the simplest interpretation of the transient absorption spectra following B excitation is that charge separation occurs solely via the slow D*-driven route. However, since a bleach at 812 nm is associated with the spectrum of D* in the HL173L reaction center, it cannot be excluded that a state including BB is involved in the charge separation process in this complex. %I ACS Publications