Initial electron transfer in photosynthetic reaction centers of Rhodobacter capsulatus mutants

Chan, Chi Kin; Chen, Lin X-Q; DiMagno, Theodore J.; Hanson, Deborah K.; Nance, Sharron L.; Schiffer, M.; Norris, James R.; Fleming, Graham R.

doi:10.1016/0009-2614(91)90045-b

Cited by 103 publications

(84 citation statements)

References 19 publications

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“…Similar time constants were observed at 660 nm, which is the probing wavelength for the formation of the charge-separated P+~A state (data not shown). Comparing the charge-separation rates with those of previously reported, analogous mutants , Nagarajan et al 1990, Chan et al 1991, the (M)Y210W mutant appears to have the slowest charge-separation rate component of all reported mutants to date. A similar result (a time constant of 35-+ 3 ps) was reported by Nagarajan et al (1992) for the same mutation.…”

Section: Charge-separation Kineticsmentioning

confidence: 55%

“…capsulatus mutants in which tyrosine-(M)210 had been exchanged by phenylalanine , Chan et al 1991, and leucine . But for most mutations on the tyrosine-(M)210 site, the kinetics at room temperature were fitted with single exponentials (Nagarajan et al 1990, Chan et al 1991. Recent studies on femtosecond spontaneous-and stimulated-emission studies have shown that for all RCs studied (Rb.…”

Section: Charge-separation Kineticsmentioning

confidence: 99%

“…Considering the charge-separation rate in different mutants of Rb. capsulatus, Chan et al (1991) concluded that both the hydroxyl group and the aromatic ring of the tyrosine are important for efficient electron transfer through the A-branch. Using Raman spectroscopy, Mattioli et al (1991) concluded that the tyrosine is not hydrogen bonded to P, contrary to a suggestion based on the X-ray structure (Allen et al 1987a).…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic characterization of reaction centers of the (M)Y210W mutant of the photosynthetic bacterium Rhodobacter sphaeroides

et al. 1994

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The tyrosine-(M)210 of the reaction center of Rhodobacter sphaeroides 2.4.1 has been changed to a tryptophan using site-directed mutagenesis. The reaction center of this mutant has been characterized by low-temperature absorption and fluorescence spectroscopy, time-resolved sub-picosecond spectroscopy, and magnetic resonance spectroscopy. The charge separation process showed bi-exponential kinetics at room temperature, with a main time constant of 36 ps and an additional fast time constant of 5.1 ps. Temperature dependent fluorescence measurements predict that the lifetime of P* becomes 4-5 times slower at cryogenic temperatures. From EPR and absorbance-detected magnetic resonance (ADMR, LD-ADMR) we conclude that the dimeric structure of P is not significantly changed upon mutation. In contrast, the interaction of the accessory bacteriochlorophyll B A with its environment appears to be altered, possibly because of a change in its position.

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Section: Charge-separation Kineticsmentioning

confidence: 55%

Section: Charge-separation Kineticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spectroscopic characterization of reaction centers of the (M)Y210W mutant of the photosynthetic bacterium Rhodobacter sphaeroides

et al. 1994

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“…There it was found that replacement of the M210 tyrosine residue on the active side by phenylalanine leads to an increased efficiency of formation (BPh anion on the inactive B-side). This mutation is known to slow down the forward ET rate (191)(192)(193). However, it may also slow down the recombination rate, thus allowing the primary donor to be reduced more efficiently while is still trapped, with the possibility for a new charge separation proceeding along the normally inactive chain and formation of @g (190).…”

Section: Chlorin and Bchl Radicalsmentioning

confidence: 99%

Radicals and Radical Pairs in Photosynthesis

Angerhofer

Bittl

1996

Photochem & Photobiology

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“…The molecular interpretation given above is related to the one used to explain the slowing down of the primary ET rate in genetically mutated RCs where the polar tyrosine M210 was replaced by nonpolar amino acids. Here the slowing down of the reaction speed was also attributed to the changed energetics (34)(35)(36)(37). The somewhat weaker slowing down of the decay of P* in mutated RCs (compared to the [3-vinyl]RCs) suggests that the [3-vinyl] modification yields a stronger increase in the energy of the intermediate P+B-A ttThis amplitude ratio deviates slightly from the average exchange rate mentioned above, indicating that the exchange yields of the BChl-a molecules are different on the two pigment branches.…”

Section: P+b P+h-p+q- This Model Ismentioning

confidence: 99%

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

Finkele

Lauterwasser

Struck

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

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The primary electron transfer has been investigated by femtosecond time-resolved absorption spectroscopy in two chemically modified reaction centers (RC) of Rhodobacter sphaeroides, in which the monomeric bacteriochlorophylls BA and BB have both been exchanged by 132-hydroxybacteriochlorophyll a or [3-vinylJ-132-hydroxybac-teriochlorophyll a. The kinetics of the primary electron transfer are not influenced by the 132-hydroxy modification. In RCs containing [3-vinyl]-132-hydroxybacteriochlorophyll a the primary rate is reduced by a factor of 10. HThe three known x-ray structures of bacterial reaction centers (RCs) show basically the same arrangement of the cofactors (see refs. 1-4). They form two branches [A (active) and B (inactive)], which are arranged in an approximate twofold symmetry. Surprisingly, the electron transfer (ET) has been found to proceed exclusively along the A branch (5-7). From the primary donor, P870 or P960, an electron is transferred to the acceptor quinone (QA) The structural arrangement of the chromophores suggests an ET via the two intervening pigments-i.e., the monomeric bacteriochlorophyll (BChl) BA and the bacteriopheophytin (BPhe) HAWhile there is general agreement that the BPhe HA is an intermediate electron acceptor (5-9), the role of the BChl BA located between the BChl dimer P and the BPhe HA is still controversially discussed. First studies with sufficient time resolution and an appropriate excitation wavelength led to the conclusion that the state P+B-(P, primary donor) is not a real intermediate in the ET (5,10,11). However, a direct ET from P* to HA over an edge-to-edge distance of '10 A can be accounted for only by a "superexchange" transfer via a virtual intermediate P+B-(12-15 Kinetic measurements were performed at T 298 K in cuvettes of 1-mm path length under stirring. The sample volume was 0.2-0.3 ml. The transmission was between T 10%o and 50% at A = 860 nm (80-25 ,uM The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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Initial electron transfer in photosynthetic reaction centers of Rhodobacter capsulatus mutants

Cited by 103 publications

References 19 publications

Spectroscopic characterization of reaction centers of the (M)Y210W mutant of the photosynthetic bacterium Rhodobacter sphaeroides

Spectroscopic characterization of reaction centers of the (M)Y210W mutant of the photosynthetic bacterium Rhodobacter sphaeroides

Radicals and Radical Pairs in Photosynthesis

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

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