A D-band (130 GHz) EPR study of the primary electron donor triplet state in photosynthetic reaction centers ofRhodobacter sphaeroides R26

Paschenko, S. V.; Gast, P.; Hoff, A.J.

doi:10.1007/bf03162411

Cited by 14 publications

(11 citation statements)

References 37 publications

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“…The polarized triplet state detected in PTB7:C 60 -PCBM blend (Figure b) is strikingly similar to that detected in quinone prereduced photosynthetic reaction center (RC) protein from purple bacterium Rhodobacter sphaeroides (Figure a). This provides further evidence that ET in OPV material is a sequential process.…”

Section: Results and Discussionsupporting

confidence: 63%

“…The S−T 0 triplet polarization pattern is considered to be a fingerprint of longlived intermediate RP states and, as a consequence, a measure of efficiency of charge separation. The polarized triplet state detected in PTB7:C 60 -PCBM blend (Figure 4b) is strikingly similar to that detected in quinone prereduced photosynthetic reaction center (RC) protein from purple bacterium Rhodobacter sphaeroides 92 (Figure 4a). This provides further evidence that ET in OPV material is a sequential process.…”

Section: ■ Experimental Sectionsupporting

confidence: 63%

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Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions

et al. 2015

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Understanding charge separation and charge transport is crucial for improving the efficiency of organic solar cells. Their active media are based on organic molecules and polymers, serving as both light-absorbing and transport layers. The charge-transfer (CT) states play an important role, being intermediate for free carrier generation and charge recombination. Here, we use light-induced electron paramagnetic resonance spectroscopy to study the CT dynamics in blends of the polymers P3HT, PCDTBT, and PTB7 with the fullerene derivative C60-PCBM. Time-resolved EPR measurements show strong spin-polarization patterns for all polymer-fullerene blends, confirming predominant generation of singlet CT states and partial orientation ordering near the donor-acceptor interface. These observations allow a comparison with charge separation processes in molecular donor-acceptor systems and in natural and artificial photosynthetic assemblies, and thus the elucidation of the initial steps of sequential CT in organic photovoltaic materials.

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Section: Results and Discussionsupporting

confidence: 63%

Section: ■ Experimental Sectionsupporting

confidence: 63%

Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions

et al. 2015

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“…Most quasioptical EPR studies of RCs have focused on radical ions in different organisms. − Another paramagnetic state that has yielded much information about the photodynamics of the RC at conventional EPR frequencies is the primary donor triplet state 3 P*, − which is formed by back-reaction of the primary radical pair (P + BPh - ) in RCs when secondary electron transfer beyond the bacteriopheophytin (BPh) acceptor is blocked. We have reported preliminary observations of 3 P* by 240 GHz EPR and two groups have subsequently published spectra of 3 P* at the significantly lower frequencies of 95 GHz and 130 GHz . In this work we present high-frequency (240 GHz) EPR spectra of the primary donor triplet state 3 P from photosynthetic reaction centers of Rhodobacter sphaeroides R26.1 as a function of temperature.…”

Section: Introductionmentioning

confidence: 89%

“…We have reported preliminary observations of 3 P* by 240 GHz EPR 17 and two groups have subsequently published spectra of 3 P* at the significantly lower frequencies of 95 GHz 18 and 130 GHz. 19 In this work we present high-frequency (240 GHz) EPR spectra of the primary donor triplet state 3 P from photosynthetic reaction centers of Rhodobacter sphaeroides R26.1 as a function of temperature. The spectra exhibit several striking new features in comparison with spectra of 3 P at lower frequencies, including a pronounced asymmetry of the spectrum, a difference in the spin polarization pattern, and an unusual variation in intensity across the spectrum.…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of the Primary Donor Triplet State g-Tensor in Photosynthetic Reaction Centers of Rhodobacter sphaeroides R-26 Observed by Transient 240 GHz Electron Paramagnetic Resonance

et al. 2003

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We report time-resolved 240 GHz EPR spectra of the primary donor triplet state 3P from photosynthetic reaction centers of Rhodobacter sphaeroides R26.1 as a function of temperature in the range 10−230 K. The data allow the determination of the principal g-tensor values and the principal axes directions of the 3P g-tensor with respect to its zero-field axes. The g-tensor measured at 240 GHz differs appreciably from previous measurements of 3P at lower frequencies and also differs from that of the cation radical state P+, which has previously been characterized at high frequencies. In contrast to P+, the 3P state exhibits significant temperature dependence in its g-tensor, particularly in the directions of the principal axes, which appear to rotate by about 30° around the x principal axis over the temperature range studied. The 3P yield anisotropy first observed by Boxer and co-workers at high field using photoselection methods is also evident in the high-field EPR spectrum as a significant variation of intensity across the spectrum. This variation is analyzed in terms of two models. The first model explicitly includes the evolution of the precursor radical pair but leads to significant ambiguities in the assignment of radical pair structural parameters. The second model utilizes only two ad hoc parameters to account for the yield anisotropy, which greatly reduces fitting parameter correlations and improves the accuracy and reliability with which the 3P magnetic parameters are determined.

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“…viridis, which could only be resolved at 670 GHz microwave frequency and 24 T magnetic field strength (Bratt et al 2003). HF-EPR measurements performed on the triplet state of the chlorophyll dimer molecule allowed the extraction of the G-tensor values of this molecular state from the spectra, which are dominated by the strong ZFS interaction of the two unpaired electron spins (Pashenko et al 2001). The G-tensor anisotropy leads to spectra that are no more antisymmetric to their centre.…”

Section: Photosynthetic Proteinsmentioning

confidence: 99%

New developments in high field electron paramagnetic resonance with applications in structural biology

Bennati

Prisner²

2005

Rep. Prog. Phys.

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Recent developments in microwave technologies have led to a renaissance of electron paramagnetic resonance (EPR) due to the implementation of new spectrometers operating at frequencies 90 GHz. EPR at high fields and high frequencies (HF-EPR) has been established up to THz (very high frequency (VHF) EPR) in continuous wave (cw) operation and up to about 300 GHz in pulsed operation. To date, its most prominent application field is structural biology. This review article first gives an overview of the theoretical basics and the technical aspects of HF-EPR methodologies, such as cw and pulsed HF-EPR, as well as electron nuclear double resonance at high fields (HF-ENDOR). In the second part, the article illustrates different application areas of HF-EPR in studies of protein structure and function. In particular, HF-EPR has delivered essential contributions to disentangling complex spectra of radical cofactors or reaction intermediates in photosynthetic reaction centres, radical enzymes (such as ribonucleotide reductase) and in metalloproteins. Furthermore, HF-EPR combined with site-directed spin labelling in membranes and soluble proteins provides new methods of investigating complex molecular dynamics and intermolecular distances.

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A D-band (130 GHz) EPR study of the primary electron donor triplet state in photosynthetic reaction centers ofRhodobacter sphaeroides R26

Cited by 14 publications

References 37 publications

Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions

Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions

Temperature Dependence of the Primary Donor Triplet State g-Tensor in Photosynthetic Reaction Centers of Rhodobacter sphaeroides R-26 Observed by Transient 240 GHz Electron Paramagnetic Resonance

New developments in high field electron paramagnetic resonance with applications in structural biology

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