Observation of a bacteriochlorophyll anion radical during the primary charge separation in a reaction center

Holzapfel, W. B.; Finkele, Ulrich; Kaiser, W.; Oesterhelt, Dieter; Scheer, Hugo; Stilz, Hans Ulrich; Zinth, Wolfgang

doi:10.1016/0009-2614(89)87543-8

Cited by 276 publications

(157 citation statements)

References 26 publications

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“…The results for A, , = 665 nm and parallel polarizations are not shown. With this polarization the wild-type RC exhibits the 0.9-ps absorption kinetic (Holzapfel et a]., 1989, which has been assigned to the transfer of an electron from P' BA-to P' HA-. In both mutants we do not observe a related absorption kinetic.…”

Section: Resultsmentioning

confidence: 92%

“…The role of the accessory Bchl located between P and HA (referred to as BA) has not been definitely assigned. Recently, we have shown that at room temperature an additional kinetic (7 = 0.9 ps) component is detectable (Holzapfel et al, 1989). The spectral properties and the kinetic constants lead to the conclusion that the corresponding intermediate is the radical pair P' BA- .…”

Section: Sfb 143mentioning

confidence: 92%

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Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Finkele¹,

Lauterwasser²,

Zinth³

et al. 1990

Biochemistry

133

113

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ABSTRACT:Femtosecond spectroscopy was used in combination with site-directed mutagenesis to study the influence of tyrosine M210 (YM210) on the primary electron transfer in the reaction center of Rhodobacter sphaeroides. The exchange of YM210 to phenylalanine caused the time constant of primary electron transfer to increase from 3.5 f 0.4 ps to 16 f 6 ps while the exchange to leucine increased the time constant even more to 22 f 8 ps. The results suggest that tyrosine M210 is important for the fast rate of the primary electron transfer.x e primary photochemical event during photosynthesis of bacteriochlorophyll-(Bchl-) containing organisms is a lightinduced charge separation within a transmembrane protein complex called the reaction center (RC). The crystal structures of RC's from Rhodopseudomonas (Rps.) viridis and Rhodobacter (Rb.) sphaeroides have been solved to high resolution [reviewed in Deisenhofer and Michel (1989), Chang et al. (1986), Tiede et al. (1988), andRees et al. (1989)l. The RC from Rb. sphaeroides contains three protein subunits referred to as L, M, and H, according to their respective mobilities in SDS-polyacrylamide gels. Associated with the L and M subunits are the cofactors, consisting of four Bchl a, two bacteriopheophytin (Bph) a, one atom of non-heme ferrous iron, two quinones (QA and Qe), and in some species one carotenoid [reviewed in Parson (1987) and Feher et al.' Financial support was from the Deutsche Forschungsgemeinschaft,

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Section: Resultsmentioning

confidence: 92%

Section: Sfb 143mentioning

confidence: 92%

Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Finkele¹,

Lauterwasser²,

Zinth³

et al. 1990

Biochemistry

133

113

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“…The species-associated difference spectra (SADS) ( Figure 6) were consistent with the expected spectral properties of the intermediate states specified in the scheme. In particular, Figure 6C shows the 810 and 860 nm bleach, together with the positive band at 1020 nm, that would be expected for the radical pair state P + B L - (5,8,9,12,18). Note the difference of the 1020 nm band with the SADS of Figure 6D,E in the overlay Figure 6F.…”

Section: Target Analysis Of the Wt Rc Data With A Reaction Scheme Invmentioning

confidence: 82%

“…The most favourable fit to the full set of experimental data from 690-1060 nm required five lifetimes. A combination of the model for RC kinetics from (5,6,8,9,12,18) and the idea of radical pair relaxation (5,18,(38)(39)(40) gave a five-component kinetic scheme ( Figure 5) that offered a satisfactory description of the data. The SADS of the two excited states and three radical pair states involved in this scheme were consistent with what is known about the spectra of these states.…”

Section: Implications Of Our Findings For the Mechanism Of Primary Chmentioning

confidence: 99%

“…The second mechanism involves the formation of the radical pair P + B L -as a discrete, but short-lived, intermediate in a two-step reaction from P* to P + H L -. The complexity of the optical changes accompanying primary electron transfer has lent much support to the idea that such intermediate charge separated states play a role in the reaction, and direct evidence for the formation of the P + B L -radical pair state has been presented (6,8,9,12,18,21,22).…”

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confidence: 99%

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Primary Electron Transfer Kinetics in Membrane-Bound Rhodobacter sphaeroides Reaction Centers: A Global and Target Analysis

et al. 1997

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Absorbance difference kinetics were measured on quinone-reduced membrane-bound wild type Rhodobacter sphaeroides reaction centers in the wavelength region from 690 to 1060 nm using 800 nm excitation. Global analysis of the data revealed five lifetimes of 0.18, 1.9, 5.1, and 22 ps and a long-lived component for the processes that underlie the spectral evolution of the system. The 0.18 ps component was ascribed to energy transfer from the excited state of the accessory bacteriochlorophyll (B*) to the primary donor (P*). The 1.9 ps component was associated with a state involving a BChl anion absorbing in the 1020 nm region. This led to the conclusion that primary electron transfer is best described by a model in which the electron is passed from P* to the acceptor bacteriopheophytin (H L ) via the monomeric bacteriochlorophyll (B L ), with the formation of the radical pair state P + B L-. An analysis assuming partial direct charge separation from B* [Van Brederode, M. E., Jones, M. R., and Chem. Phys. Lett. 268,[143][144][145][146][147][148][149] was also consistent with the data. Within the framework of a five component model, the 5.1 and 22 ps lifetimes were associated with charge separation and relaxation of the P + H L -radical pair state respectively, providing a description which adequately accounted for the complex kinetics of decay of P*. Alternatively, by assuming that the 5.1 and 22 ps components originate from a single component with a multi-exponential decay, a simpler analysis with only four components could be employed, resulting in only a small increase (7%) in the weighted root mean square error of the fit. In both descriptions part of the decay of P* proceeds with a lifetime of about 2 ps. The relative merits of these alternative descriptions of the primary events in light-driven electron transfer are discussed. Similar measurements on YM210H mutant reaction centers revealed four lifetimes of 0.2, 3.1, and 12 ps and a long-lived component. The 3.1 and 12 ps lifetimes are ascribed to multi-exponential decay of the P* state. The differences with the WT data are discussed.The reaction center (RC) of purple bacteria is responsible for the conversion of light energy into a transmembrane electrical potential. The structures of the RC from two species of purple bacteria, Rhodopseudomonas (Rps.) Viridis and Rhodobacter (Rb.) sphaeroides, have been solved to high resolution (1, 2). They reveal an assembly of protein subunits and redox cofactors that are arranged around an axis of approximate 2-fold symmetry. The primary donor of electrons (P) is a pair of excitonically-coupled bacteriochloropyll a (BChl) molecules positioned close to the periplasmic face of the protein. The remaining redox cofactors, two monomeric BChls (B), two molecules of bacteriopheophytin a (H), and two ubiquinones (Q), are arranged around the symmetry axis in two branches that span the membrane dielectric. Excitation of P initiates a sequence of electron transfer reactions that result in the separation of charge across the ...

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Photosynthetic Reaction Centers of Purple Bacteria

Lancaster¹,

Michel²

2004

Handbook of Metalloproteins

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Observation of a bacteriochlorophyll anion radical during the primary charge separation in a reaction center

Cited by 276 publications

References 26 publications

Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Primary Electron Transfer Kinetics in Membrane-Bound Rhodobacter sphaeroides Reaction Centers: A Global and Target Analysis

Photosynthetic Reaction Centers of Purple Bacteria

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