Influence of an amino-acid residue on the optical properties and electron transfer dynamics of a photosynthetic reaction centre complex

Bylina, Edward J.; Kirmaier, Christine; McDowell, Lynda M.; Holten, Dewey; Youvan, Douglas C.

doi:10.1038/336182a0

Cited by 164 publications

(134 citation statements)

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“…[98][99][100][101] The Q X bleaching of H M in D LL -FY L F M has a full width at halfmaximum (fwhm) about 2 nm larger than that of the Q X band of H L in wild type (11 vs 9 nm). These width differences are consistent with the ground-state absorption features at 77 K, which have estimated fwhms of 11 nm (for H M in D LL -FY L F M ) and 8.5 nm (for H L in wild type).…”

Section: Time Evolution Of Visible Spectra For D Ll -Fy L F M In Derimentioning

confidence: 99%

Temperature Dependence of Electron Transfer to the M-Side Bacteriopheophytin in Rhodobacter capsulatus Reaction Centers

et al. 2008

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-lauryl-N,N-dimethylamine-N-oxide (LDAO) is used to suspend the RCs, the excited state of the primary electron donor (P*) decays to the ground state with an average lifetime at 77 K of 330 or 170 ps, respectively; however, in both cases the time constant obtained from single-exponential fits varies markedly as a function of the probe wavelength. These findings on the D LL RC are most easily explained in terms of a heterogeneous population of RCs. Similarly, the complex results for D LL -FY L F M in Deriphatglycerol glass at 77 K are most simply explained using a model that involves (minimally) two distinct populations of RCs with very different photochemistry. Within this framework, in 50% of the D LL -FY L F M RCs in Deriphat-glycerol glass at 77 K, P* deactivates to the ground state with a time constant of ∼400 ps, similar to the deactivation of P* in the D LL mutant at 77 K. In the other 50% of D LL -FY L F M RCs, P* has a 35 ps lifetime and decays via electron transfer to the M branch, giving P + H M -in high yield (g80%). This result indicates that P* f P + H M -is roughly a factor of 2 faster at 77 K than at 295 K. In alternative homogeneous models the rate of this M-side electron-transfer process is the same or up to 2-fold slower at low temperature. A 2-fold increase in rate with a reduction in temperature is the same behavior found for the overall L-side process P* f P + H L -in wild-type RCs. Our results suggest that, as for electron transfer on the L side, the M-side electron-transfer reaction P* f P + H M -is an activationless process.

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Section: Time Evolution Of Visible Spectra For D Ll -Fy L F M In Derimentioning

confidence: 99%

Temperature Dependence of Electron Transfer to the M-Side Bacteriopheophytin in Rhodobacter capsulatus Reaction Centers

et al. 2008

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“…The transient absorption changes at 757 nm that arise from an electrochromic shift associated with k AB (1) (9,21,25,26) were measured in native as well as in all hybrid RCs. The data were fitted with a biexponential function and were in general agreement with the results obtained by the other methods.…”

Section: Determination Of Electron Transfer Rates Q Amentioning

confidence: 99%

Conformational gating of the electron transfer reaction Q _A ⁻ ^⋅ Q _B → Q _A Q _B ⁻ ^⋅ in bacterial reaction centers of Rhodobacter sphaeroides determined by a driving force assay

Graige

Fehér

Okamura

1998

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

211

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The mechanism of the electron transfer reaction, Q A ؊ ⅐ Q B 3 Q A Q B ؊ ⅐ , was studied in isolated reaction centers from the photosynthetic bacterium Rhodobacter sphaeroides by replacing the native Q 10 in the Q A binding site with quinones having different redox potentials. These substitutions are expected to change the intrinsic electron transfer rate by changing the redox free energy (i.e., driving force) for electron transfer without affecting other events that may be associated with the electron transfer (e.g., protein dynamics or protonation). The electron transfer from Q A ؊ ⅐ to Q B was measured by three independent methods: a functional assay involving cytochrome c 2 to measure the rate of Q A ؊ ⅐ oxidation, optical kinetic spectroscopy to measure changes in semiquinone absorption, and kinetic near-IR spectroscopy to measure electrochromic shifts that occur in response to electron transfer. The results show that the rate of the observed electron transfer from Q A ؊ ⅐ to Q B does not change as the redox free energy for electron transfer is varied over a range of 150 meV. The strong temperature dependence of the observed rate rules out the possibility that the reaction is activationless. We conclude, therefore, that the independence of the observed rate on the driving force for electron transfer is due to conformational gating, that is, the rate limiting step is a conformational change required before electron transfer. This change is proposed to be the movement, controlled kinetically either by protein dynamics or intermolecular interactions, of Q B by Ϸ5 Å as observed in the x-ray studies of Stowell et al.

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“…The results received by X-ray analysis of crystals of the reaction centers of the purple bacteria showed [48] that the pigment and cofactors (bacteriochlorophyll of the special pairs, monomeric bacteriochlorophylls, monomers of bacteriopheophytin and two quinones) are located symmetrically along L and M subunits of protein complex RC. However, in the kinetic experiments it was shown that the electron transfer along L subunit occurred about five times quicker than along M subunit [172]. Why the electron chooses one of two similar paths is not clear?…”

Section: Amentioning

confidence: 99%

Role of quantum chemical calculations in molecular biophysics with a historical perspective

Kukushkin

Jalkanen

2009

Theor Chem Acc

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We discuss how the basic principles of quantum chemistry and quantum mechanics can be and have been applied to a variety of problems in molecular biophysics. First, the historical development of quantum concepts in biophysics is discussed. Next, we describe a series of interesting applications of quantum chemical methods for studying biologically active molecules, molecular structures and some of the important processes which play a role in living organisms. We discuss the application of quantum chemistry to such processes as energy storage and transformation, and the transmission of genetic information. Quantum chemical approaches are essential to comprehend and understand the molecular nature of these processes. To conclude our work, we present a short discussion of the perspectives of quantum chemical methods in modern biophysics, the field of experimental and theoretical chiral vibrational and electronic spectroscopy.

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Influence of an amino-acid residue on the optical properties and electron transfer dynamics of a photosynthetic reaction centre complex

Cited by 164 publications

References 20 publications

Temperature Dependence of Electron Transfer to the M-Side Bacteriopheophytin in Rhodobacter capsulatus Reaction Centers

Temperature Dependence of Electron Transfer to the M-Side Bacteriopheophytin in Rhodobacter capsulatus Reaction Centers

Conformational gating of the electron transfer reaction Q _A ⁻ ^⋅ Q _B → Q _A Q _B ⁻ ^⋅ in bacterial reaction centers of Rhodobacter sphaeroides determined by a driving force assay

Role of quantum chemical calculations in molecular biophysics with a historical perspective

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Influence of an amino-acid residue on the optical properties and electron transfer dynamics of a photosynthetic reaction centre complex

Cited by 164 publications

References 20 publications

Temperature Dependence of Electron Transfer to the M-Side Bacteriopheophytin in Rhodobacter capsulatus Reaction Centers

Temperature Dependence of Electron Transfer to the M-Side Bacteriopheophytin in Rhodobacter capsulatus Reaction Centers

Conformational gating of the electron transfer reaction Q A − ⋅ Q B → Q A Q B − ⋅ in bacterial reaction centers of Rhodobacter sphaeroides determined by a driving force assay

Role of quantum chemical calculations in molecular biophysics with a historical perspective

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Conformational gating of the electron transfer reaction Q _A ⁻ ^⋅ Q _B → Q _A Q _B ⁻ ^⋅ in bacterial reaction centers of Rhodobacter sphaeroides determined by a driving force assay