Energy Trapping and Detrapping in Reaction Center Mutants from Rhodobacter sphaeroides

Katiliene, Zivile; Katilius, Evaldas; Woodbury, Neal W.

doi:10.1016/s0006-3495(03)70048-4

Cited by 12 publications

(20 citation statements)

References 40 publications

(81 reference statements)

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“…Interestingly, approximately the same transfer times as in PSII are found between the LH1 core antenna and the RC in purple bacteria (upper part of Fig. 1, Bergström et al (1989); Visscher et al (1989); Sundström et al (1999); Katiliene et al (2003)) despite the different organization of the antenna. A common property of both photosystems, which is responsible for this behavior, is the relatively large distance between the pigments in the RC and those in the antennae.…”

Section: Purple Bacteriasupporting

confidence: 52%

“…Transmembrane helices (red and yellow cylinders) are depicted together with the macrocycles of bacteriochlorophyll a pigments (green). The energy levels of excited states of LH1 and RC and the transfer times between them, as obtained from an analysis of time-resolved spectra by Katiliene et al (2003) are shown below the structure. kT denotes the thermal energy at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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Structure-based modeling of energy transfer in photosynthesis

et al. 2013

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We provide a minimal model for a structure-based simulation of excitation energy transfer in pigment-protein complexes (PPCs). In our treatment, the PPC is assembled from its building blocks. The latter are defined such that electron exchange occurs only within, but not between these units. The variational principle is applied to investigate how the Coulomb interaction between building blocks changes the character of the electronic states of the PPC. In this way, the standard exciton Hamiltonian is obtained from first principles and a hierarchy of calculation schemes for the parameters of this Hamiltonian arises. Possible extensions of this approach are discussed concerning (i) the inclusion of dispersive site energy shifts and (ii) the inclusion of electron exchange between pigments. First results on electron exchange within the special pair of photosystem II of cyanobacteria and higher plants are presented and compared with earlier results on purple bacteria. In the last part of this mini-review, the coupling of electronic and nuclear degrees of freedom is considered. First, the standard exciton-vibrational Hamiltonian is parameterized with the help of a normal mode analysis of the PPC. Second, dynamical theories are discussed that exploit this Hamiltonian in the study of dissipative exciton motion.

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Section: Purple Bacteriasupporting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Structure-based modeling of energy transfer in photosynthesis

et al. 2013

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“…Furthermore, the third component was small in amplitude but required to obtain a better fitting to the decay profile 27 and was assigned to relaxation of the nearequilibrium mixture of excited and charge-separated states. 31 A recent study of Stark absorption spectroscopy 9 indicated that relatively large changes in the dipole moment and polarizability in Tch. tepidum arise from mixing of a charge transfer state into the lowest exciton state of the special pair 40 and LH1 41 as a result of closely packed and excitonically coupled BChl a molecules.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Biochemical and Spectroscopic Characterizations of a Hybrid Light-Harvesting Reaction Center Core Complex

et al. 2018

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The light-harvesting 1 reaction center (LH1-RC) complex from Thermochromatium tepidum exhibits a largely red-shifted LH1 Q absorption at 915 nm due to binding of Ca, resulting in an "uphill" energy transfer from LH1 to the reaction center (RC). In a recent study, we developed a heterologous expression system (strain TS2) to construct a functional hybrid LH1-RC with LH1 from Tch. tepidum and the RC from Rhodobacter sphaeroides [Nagashima, K. V. P., et al. (2017) Proc. Natl. Acad. Sci. U. S. A. 114, 10906]. Here, we present detailed characterizations of the hybrid LH1-RC from strain TS2. Effects of metal cations on the phototrophic growth of strain TS2 revealed that Ca is an indispensable element for its growth, which is also true for Tch. tepidum but not for Rba. sphaeroides. The thermal stability of the TS2 LH1-RC was strongly dependent on Ca in a manner similar to that of the native Tch. tepidum, but interactions between the heterologous LH1 and RC became relatively weaker in strain TS2. A Fourier transform infrared analysis demonstrated that the Ca-binding site of TS2 LH1 was similar but not identical to that of Tch. tepidum. Steady-state and time-resolved fluorescence measurements revealed that the uphill energy transfer rate from LH1 to the RC was related to the energy gap in an order of Rba. sphaeroides, Tch. tepidum, and strain TS2; however, the quantum yields of LH1 fluorescence did not exhibit such a correlation. On the basis of these findings, we discuss the roles of Ca, interactions between LH1 and the RC from different species, and the uphill energy transfer mechanisms.

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“…Also, the rates of fast ET steps can be very sensitive to protein dynamics and conformation (28,49,50). Such protein relaxation is well known for bacterial RCs (27,29,49,51,52) and isolated PSII RCs (37)(38)(39)(53)(54)(55). Protein dynamic processes span a huge range of time, from picoseconds to hours (32,(56)(57)(58).…”

Section: Protein Dynamicsmentioning

confidence: 99%

Charge Separation, Stabilization, and Protein Relaxation in Photosystem II Core Particles with Closed Reaction Center

Szczepaniak

Sander

Nowaczyk

et al. 2009

Biophysical Journal

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The fluorescence kinetics of cyanobacterial photosystem II (PSII) core particles with closed reaction centers (RCs) were studied with picosecond resolution. The data are modeled in terms of electron transfer (ET) and associated protein conformational relaxation processes, resolving four different radical pair (RP) states. The target analyses reveal the importance of protein relaxation steps in the ET chain for the functioning of PSII. We also tested previously published data on cyanobacterial PSII with open RCs using models that involved protein relaxation steps as suggested by our data on closed RCs. The rationale for this reanalysis is that at least one short-lived component could not be described in the previous simpler models. This new analysis supports the involvement of a protein relaxation step for open RCs as well. In this model the rate of ET from reduced pheophytin to the primary quinone Q(A) is determined to be 4.1 ns(-1). The rate of initial charge separation is slowed down substantially from approximately 170 ns(-1) in PSII with open RCs to 56 ns(-1) upon reduction of Q(A). However, the free-energy drop of the first RP is not changed substantially between the two RC redox states. The currently assumed mechanistic model, assuming the same early RP intermediates in both states of RC, is inconsistent with the presented energetics of the RPs. Additionally, a comparison between PSII with closed RCs in isolated cores and in intact cells reveals slightly different relaxation kinetics, with a approximately 3.7 ns component present only in isolated cores.

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Energy Trapping and Detrapping in Reaction Center Mutants from Rhodobacter sphaeroides

Cited by 12 publications

References 40 publications

Structure-based modeling of energy transfer in photosynthesis

Structure-based modeling of energy transfer in photosynthesis

Biochemical and Spectroscopic Characterizations of a Hybrid Light-Harvesting Reaction Center Core Complex

Charge Separation, Stabilization, and Protein Relaxation in Photosystem II Core Particles with Closed Reaction Center

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