Electron Transfer in <i>Rhodobacter sphaeroides</i> Reaction Centers Containing Zn-Bacteriochlorophylls: A Hole-Burning Study

Neupane, Bhanu; Jaschke, Paul R.; Saer, Rafael G.; Beatty, J. Thomas; Reppert, Mike; Jankowiak, Ryszard

doi:10.1021/jp300304r

Cited by 11 publications

(35 citation statements)

References 49 publications

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“…The average Γ hom ∼ 5.0 ± 0.5 cm –1 corresponds to an average CS time of 1.1 ± 0.1 ps (recall that 2Γ hom = Γ ZPH ). The latter value is similar to that observed previously for the WT bRC and Zn-bRCs, which were also about 1 ps. , …”

Section: Experimental Results and Modeling Studiessupporting

confidence: 91%

“…Although the mutation site of (M)214 is close to H A , which is the primary electron acceptor, and the presence of two distinct bRC subpopulations was demonstrated, it appears that the L → G mutation only weakly altered the primary CS time, which at low temperatures is still on the order of ∼1 ps. Similar ET times in WT, (M)L214G, and the Zn-bRC (containing six Zn-BChls) of Rb. sphaeroides indicate that the CS process is robust in spite of these mutations.…”

Section: Concluding Remarksmentioning

confidence: 76%

“…Weakly frequency-dependent ET times (∼1 ps) were also observed in the Zn-RC and Zn-β-RC (measured from ZPHs in resonant transient P + Q A – HB spectra). Since both the Zn-RC and Zn-β-RC had similar ET times, it was suggested that the difference in coordination state of the H A cofactor was not responsible for preservation of the efficient ET time . However, in the (M)Y210W mutant, the replacement of tyrosine with tryptophan was found to slow down primary CS to ∼50 ps, − tentatively indicating that the local environment of H A , depending on the mutation, can affect the rate of CS.…”

Section: Discussionmentioning

confidence: 99%

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Mutation-Induced Changes in the Protein Environment and Site Energies in the (M)L214G Mutant of the Rhodobacter sphaeroides Bacterial Reaction Center

Jankowiak¹,

Rancova

Chen³

et al. 2016

J. Phys. Chem. B

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This work focuses on the low-temperature (5 K) photochemical (transient) hole-burned (HB) spectra within the P870 absorption band, and their theoretical analysis, for the (M)L214G mutant of the photosynthetic Rhodobacter sphaeroides bacterial reaction center (bRC). To provide insight into system-bath interactions of the bacteriochlorophyll a (BChl a) special pair, i.e., P870, in the mutated bRC, the optical line shape function for the P870 band is calculated numerically. On the basis of the modeling studies, we demonstrate that (M)L214G mutation leads to a heterogeneous population of bRCs with modified (increased) total electron-phonon coupling strength of the special pair BChl a and larger inhomogeneous broadening. Specifically, we show that after mutation in the (M)L214G bRC a large fraction (∼50%) of the bacteriopheophytin (HA) chromophores shifts red and the 800 nm absorption band broadens, while the remaining fraction of HA cofactors retains nearly the same site energy as HA in the wild-type bRC. Modeling using these two subpopulations allowed for fits of the absorption and nonresonant (transient) HB spectra of the mutant bRC in the charge neutral, oxidized, and charge-separated states using the Frenkel exciton Hamiltonian, providing new insight into the mutant's complex electronic structure. Although the average (M)L214G mutant quantum efficiency of P(+)QA(-) state formation seems to be altered in comparison with the wild-type bRC, the average electron transfer time (measured via resonant transient HB spectra within the P870 band) was not affected. Thus, mutation in the vicinity of the electron acceptor (HA) does not tune the charge separation dynamics. Finally, quenching of the (M)L214G mutant excited states by P(+) is addressed by persistent HB spectra burned within the B band in chemically oxidized samples.

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Section: Experimental Results and Modeling Studiessupporting

confidence: 91%

Section: Concluding Remarksmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 99%

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Mutation-Induced Changes in the Protein Environment and Site Energies in the (M)L214G Mutant of the Rhodobacter sphaeroides Bacterial Reaction Center

Jankowiak¹,

Rancova

Chen³

et al. 2016

J. Phys. Chem. B

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“…7-18) by the temperature-dependent lineshape formulas developed by Hayes et al 19 These formulas provide analytical expressions for HB spectra in terms of an assumed spectral density, allowing for the extraction of J(ω) by fitting experimental spectra against calculated lineshapes. 19,20 It has recently come to our attention while modeling transient HB spectra in a bacterial Zn-reaction center (Zn-RC) and its mutant (Zn-β-RC) 21 that the lineshape function formulas in the mean-phonon approximation given in Ref. 19 contain inconsistencies in notation, leading in some cases (i.e., for moderate and strong electron-phonon (el-ph) coupling strengths) to incorrect expressions.…”

Section: Introductionmentioning

confidence: 99%

“…While for simple systems these inconsistencies are insignificant, for cases of strong el-ph coupling like those observed in bacterial RCs 20,22 (where multiple phonon transitions are involved) they lead to significant errors. 21 To clarify the situation, in this work, we derive corrected lineshape formulas under the same assumptions as made by Hayes et al, 19 while focusing on the various approximations appearing in these expressions and their physical significance. For routine analysis of HB spectra, however, we suggest that the lineshape should generally be evaluated numerically without the introduction of the mean-phonon approximation.…”

Section: Introductionmentioning

confidence: 99%

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

Reppert

Kell

Pruitt

et al. 2015

The Journal of Chemical Physics

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The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths. A corrected lineshape function L(ω) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, ωsp, for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers.

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Mechanism of Primary Charge Separation in Photosynthetic Reaction Centers

Savikhin

Jankowiak

2014

The Biophysics of Photosynthesis

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Electron Transfer in Rhodobacter sphaeroides Reaction Centers Containing Zn-Bacteriochlorophylls: A Hole-Burning Study

Cited by 11 publications

References 49 publications

Mutation-Induced Changes in the Protein Environment and Site Energies in the (M)L214G Mutant of the Rhodobacter sphaeroides Bacterial Reaction Center

Mutation-Induced Changes in the Protein Environment and Site Energies in the (M)L214G Mutant of the Rhodobacter sphaeroides Bacterial Reaction Center

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

Mechanism of Primary Charge Separation in Photosynthetic Reaction Centers

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