10.1021/bi9829128.s001
Marion E. van Brederode
Marion E.
van Brederode
Ivo H. M. van Stokkum
Ivo
H. M. van Stokkum
Evaldas Katilius
Evaldas
Katilius
Frank van Mourik
Frank van
Mourik
Michael R. Jones
Michael R.
Jones
Rienk van Grondelle
Rienk van
Grondelle
Primary Charge Separation Routes in the BChl:BPhe Heterodimer Reaction Centers
of <i>Rhodobacter sphaeroides</i><sup>†</sup>
American Chemical Society
1999
excitation wavelength
B excitation
bacteriochlorophyll homodimer
pathway B
880 nm excitation light results
charge separation process
HL 173L reaction center
812 nm
state D
43 ps decay
B B
798 nm excitation light
excitation energy
charge separation
excitations results
Rhodobacter sphaeroides
ground state
monomeric bacteriochlorophylls
U.S.A
absorption spectra
Primary Charge Separation Routes
HM 202L heterodimer reaction center
1999-05-19 00:00:00
Journal contribution
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
Energy transfer and the primary charge separation process are studied as a function of excitation
wavelength in membrane-bound reaction centers of <i>Rhodobacter</i> <i>sphaeroides</i> in which the excitonically
coupled bacteriochlorophyll homodimer is converted to a bacteriochlorophyll-bacteriopheophytin heterodimer, denoted D [Bylina, E. J., and Youvan, D. C. (1988) <i>Proc. Natl. Acad. Sci. U.S.A.</i> <i>85</i>, 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<sup>+</sup>Q<sub>A</sub><sup>-</sup> 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<sup>+</sup>Q<sub>A</sub><sup>-</sup> via the pathway B<sub>A</sub>* → B<sub>A</sub><sup>+</sup>H<sub>A</sub><sup>-</sup> → D<sup>+</sup>H<sub>A</sub><sup>-</sup> → D<sup>+</sup>Q<sub>A</sub><sup>-</sup>. 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 B<sub>B</sub> is involved in the charge separation process
in this complex.