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Jeffrey R Reimers - One of the best experts on this subject based on the ideXlab platform.
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synthetically tuneable biomimetic artificial Photosynthetic Reaction Centres that closely resemble the natural system in purple bacteria
Chemical Science, 2016Co-Authors: Saiho Lee, Shunichi Fukuzumi, Kei Ohkubo, Iain M Blake, Allan G Larsen, James A Mcdonald, Jeffrey R ReimersAbstract:Porphyrin-based Photosynthetic Reaction Centre (PRC) mimics, ZnPQ-Q2HP-C60 and MP2Q-Q2HP-C60 (M = Zn or 2H), designed to have a similar special-pair electron donor and similar charge-separation distances, redox processes and photochemical Reaction rates to those in the natural PRC from purple bacteria, have been synthesised and extensive photochemical studies performed. Mechanisms of electron-transfer Reactions are fully investigated using femtosecond and nanosecond transient absorption spectroscopy. In benzonitrile, all models show picosecond-timescale charge-separations and the final singlet charge-separations with the microsecond-timescale. The established lifetimes are long compared to other processes in organic solar cells or other organic light harvesting systems. These rigid, synthetically flexible molecules provide the closest mimics to the natural PRC so far synthesised and present a future direction for the design of light harvesters with controllable absorption, redox, and kinetics properties.
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non adiabatic effects in thermochemistry spectroscopy and kinetics the general importance of all three born oppenheimer breakdown corrections
Physical Chemistry Chemical Physics, 2015Co-Authors: Jeffrey R Reimers, Laura K Mckemmish, Ross H Mckenzie, Noel S HushAbstract:Using a simple model Hamiltonian, the three correction terms for Born–Oppenheimer (BO) breakdown, the adiabatic diagonal correction (DC), the first-derivative momentum non-adiabatic correction (FD), and the second-derivative kinetic-energy non-adiabatic correction (SD), are shown to all contribute to thermodynamic and spectroscopic properties as well as to thermal non-diabatic chemical Reaction rates. While DC often accounts for >80% of thermodynamic and spectroscopic property changes, the commonly used practice of including only the FD correction in kinetics calculations is rarely found to be adequate. For electron-transfer Reactions not in the inverted region, the common physical picture that diabatic processes occur because of surface hopping at the transition state is proven inadequate as the DC acts first to block access, increasing the transition state energy by (ℏω)2λ/16J2 (where λ is the reorganization energy, J the electronic coupling and ω the vibration frequency). However, the rate constant in the weakly-coupled Golden-Rule limit is identified as being only inversely proportional to this change rather than exponentially damped, owing to the effects of tunneling and surface hopping. Such weakly-coupled long-range electron-transfer processes should therefore not be described as “non-adiabatic” processes as they are easily described by Born–Huang ground-state adiabatic surfaces made by adding the DC to the BO surfaces; instead, they should be called just “non-Born–Oppenheimer” processes. The model system studied consists of two diabatic harmonic potential-energy surfaces coupled linearly through a single vibration, the “two-site Holstein model”. Analytical expressions are derived for the BO breakdown terms, and the model is solved over a large parameter space focusing on both the lowest-energy spectroscopic transitions and the quantum dynamics of coherent-state wavepackets. BO breakdown is investigated pertinent to: ammonia inversion, aromaticity in benzene, the Creutz–Taube ion, the bacterial Photosynthetic Reaction Centre, BNB, the molecular conductor Alq3, and inverted-region charge recombination in a ferrocene–porphyrin–fullerene triad Photosynthetic model compound. Throughout, the fundamental nature of BO breakdown is linked to the properties of the cusp catastrophe: the cusp diameter is shown to determine the magnitudes of all couplings, numerical basis-set and trajectory-integration requirements, and to determine the transmission coefficient κ used to understand deviations from transition-state theory.
Gergely Katona - One of the best experts on this subject based on the ideXlab platform.
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Structure of a Photosynthetic Reaction Centre determined by serial femtosecond crystallography
2016Co-Authors: Linda C. Johansson, Gergely Katona, David Arnlund, Thomas A. White, Daniel P. Deponte, Robert L. Shoeman, Anton Barty, Cecilia Wickstr, Amit Sharma, Garth J. WilliamsAbstract:Serial femtosecond crystallography is an X-ray free-electron-laser-based method with considerable potential to have an impact on challenging problems in structural biology. Here we present X-ray diffraction data recorded from microcrystals of the Blastochloris viridis Photosynthetic Reaction Centre to 2.8Å resolution and determine its serial femtosecond crystallography structure to 3.5Å resolution. Although every microcrystal is exposed to a dose of 33MGy, no signs of X-ray-induced radiation damage are visible in this integra
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Local contact(s):
2014Co-Authors: Edward Mitchell, Gergely Katona, Ulf Andreasson, Larserik Andreasson, Stéphanie Monaco, Joanne Mccarthy, Pontus Gourdon, Arjan Snijder, Ehud L, Richard NeutzeAbstract:Structural studies of light-driven conformational changes in a Photosynthetic Reaction Centre
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Structure of a Photosynthetic Reaction Centre determined by serial femtosecond crystallography
Nature communications, 2013Co-Authors: Linda C. Johansson, Gergely Katona, David Arnlund, Cecilia Wickstrand, Thomas A. White, Daniel P. Deponte, Robert L. Shoeman, Anton Barty, Amit Sharma, Garth J. WilliamsAbstract:Serial femtosecond crystallography is an X-ray free-electron-laser-based method with considerable potential to have an impact on challenging problems in structural biology. Here we present X-ray diffraction data recorded from microcrystals of the Blastochloris viridis Photosynthetic Reaction Centre to 2.8 A resolution and determine its serial femtosecond crystallography structure to 3.5 A resolution. Although every microcrystal is exposed to a dose of 33 MGy, no signs of X-ray-induced radiation damage are visible in this integral membrane protein structure.
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lipidic cubic phase crystal structure of the Photosynthetic Reaction Centre from rhodobacter sphaeroides at 2 35a resolution
Journal of Molecular Biology, 2003Co-Authors: Gergely Katona, Ulf Andreasson, Ehud M Landau, Larserik Andreasson, Richard NeutzeAbstract:Abstract Well-ordered crystals of the bacterial Photosynthetic Reaction Centre from Rhodobacter sphaeroides were grown from a lipidic cubic phase. Here, we report the type I crystal packing that results from this crystallisation medium, for which 3D crystals grow as stacked 2D crystals, and the Reaction Centre X-ray structure is refined to 2.35 A resolution. In this crystal form, the location of the membrane bilayer could be assigned with confidence. A cardiolipin-binding site is found at the protein–protein interface within the membrane-spanning region, shedding light on the formation of crystal contacts within the membrane. A chloride-binding site was identified in the membrane-spanning region, which suggests a putative site for interaction with the light-harvesting complex I, the cytochrome bc1 complex or PufX. Comparisons with the X-ray structures of this Reaction Centre deriving from detergent-based crystals are drawn, indicating that a slight compression occurs in this lipid-rich environment.
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lipidic cubic phase crystal structure of the Photosynthetic Reaction Centre from rhodobacter sphaeroides at 2 35 a resolution
Journal of Molecular Biology, 2003Co-Authors: Gergely Katona, Ulf Andreasson, Ehud M Landau, Larserik Andreasson, Richard NeutzeAbstract:Abstract Well-ordered crystals of the bacterial Photosynthetic Reaction Centre from Rhodobacter sphaeroides were grown from a lipidic cubic phase. Here, we report the type I crystal packing that results from this crystallisation medium, for which 3D crystals grow as stacked 2D crystals, and the Reaction Centre X-ray structure is refined to 2.35 A resolution. In this crystal form, the location of the membrane bilayer could be assigned with confidence. A cardiolipin-binding site is found at the protein–protein interface within the membrane-spanning region, shedding light on the formation of crystal contacts within the membrane. A chloride-binding site was identified in the membrane-spanning region, which suggests a putative site for interaction with the light-harvesting complex I, the cytochrome bc1 complex or PufX. Comparisons with the X-ray structures of this Reaction Centre deriving from detergent-based crystals are drawn, indicating that a slight compression occurs in this lipid-rich environment.
Richard Neutze - One of the best experts on this subject based on the ideXlab platform.
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Local contact(s):
2014Co-Authors: Edward Mitchell, Gergely Katona, Ulf Andreasson, Larserik Andreasson, Stéphanie Monaco, Joanne Mccarthy, Pontus Gourdon, Arjan Snijder, Ehud L, Richard NeutzeAbstract:Structural studies of light-driven conformational changes in a Photosynthetic Reaction Centre
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lipidic cubic phase crystal structure of the Photosynthetic Reaction Centre from rhodobacter sphaeroides at 2 35a resolution
Journal of Molecular Biology, 2003Co-Authors: Gergely Katona, Ulf Andreasson, Ehud M Landau, Larserik Andreasson, Richard NeutzeAbstract:Abstract Well-ordered crystals of the bacterial Photosynthetic Reaction Centre from Rhodobacter sphaeroides were grown from a lipidic cubic phase. Here, we report the type I crystal packing that results from this crystallisation medium, for which 3D crystals grow as stacked 2D crystals, and the Reaction Centre X-ray structure is refined to 2.35 A resolution. In this crystal form, the location of the membrane bilayer could be assigned with confidence. A cardiolipin-binding site is found at the protein–protein interface within the membrane-spanning region, shedding light on the formation of crystal contacts within the membrane. A chloride-binding site was identified in the membrane-spanning region, which suggests a putative site for interaction with the light-harvesting complex I, the cytochrome bc1 complex or PufX. Comparisons with the X-ray structures of this Reaction Centre deriving from detergent-based crystals are drawn, indicating that a slight compression occurs in this lipid-rich environment.
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lipidic cubic phase crystal structure of the Photosynthetic Reaction Centre from rhodobacter sphaeroides at 2 35 a resolution
Journal of Molecular Biology, 2003Co-Authors: Gergely Katona, Ulf Andreasson, Ehud M Landau, Larserik Andreasson, Richard NeutzeAbstract:Abstract Well-ordered crystals of the bacterial Photosynthetic Reaction Centre from Rhodobacter sphaeroides were grown from a lipidic cubic phase. Here, we report the type I crystal packing that results from this crystallisation medium, for which 3D crystals grow as stacked 2D crystals, and the Reaction Centre X-ray structure is refined to 2.35 A resolution. In this crystal form, the location of the membrane bilayer could be assigned with confidence. A cardiolipin-binding site is found at the protein–protein interface within the membrane-spanning region, shedding light on the formation of crystal contacts within the membrane. A chloride-binding site was identified in the membrane-spanning region, which suggests a putative site for interaction with the light-harvesting complex I, the cytochrome bc1 complex or PufX. Comparisons with the X-ray structures of this Reaction Centre deriving from detergent-based crystals are drawn, indicating that a slight compression occurs in this lipid-rich environment.
Per A Bullough - One of the best experts on this subject based on the ideXlab platform.
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the 8 5a projection structure of the core rc lh1 pufx dimer of rhodobacter sphaeroides
Journal of Molecular Biology, 2005Co-Authors: Pu Qian, Neil C Hunter, Per A BulloughAbstract:Two-dimensional crystals of dimeric Photosynthetic Reaction Centre-LH1-PufX complexes have been analysed by cryoelectron microscopy. The 8.5A resolution projection map extends previous analyses of complexes within native membranes to reveal the alpha-helical structure of two Reaction Centres and 28 LH1 alphabeta subunits within the dimer. For the first time, we have achieved sufficient resolution to suggest a possible location for the PufX transmembrane helix, the orientation of the RC and the arrangement of helices within the surrounding LH1 complex. Whereas low-resolution projections have shown an apparent break in the LH1, our current map reveals a diffuse density within this region, possibly reflecting high mobility. Within this region the separation between beta14 of one monomer and beta2 of the other monomer is approximately 6A larger than the average beta-beta spacing within LH1; we propose that this is sufficient for exchange of quinol at the RC Q(B) site. We have determined the position and orientation of the RC within the dimer, which places its Q(B) site adjacent to the putative PufX, with access to the point in LH1 that appears most easily breached. PufX appears to occupy a strategic position between the mobile alphabeta14 subunit and the Q(B) site, suggesting how the structure, possibly coupled with a flexible ring, plays a role in optimizing quinone exchange during photosynthesis.
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projection structure of the Photosynthetic Reaction Centre antenna complex of rhodospirillum rubrum at 8 5 a resolution
The EMBO Journal, 2002Co-Authors: Stuart J Jamieson, Peiyi Wang, Pu Qian, John Y Kirkland, Matthew J Conroy, Neil C Hunter, Per A BulloughAbstract:Two‐dimensional crystals of the Reaction‐Centre–light‐harvesting complex I (RC–LH1) of the purple non‐ sulfur bacterium Rhodospirillum rubrum have been formed from detergent‐solubilized and purified protein complexes. Unstained samples of this intrinsic membrane protein complex have been analysed by electron cryomicroscopy (cryo EM). Projection maps were calculated to 8.5 A from two different crystal forms, and show a single Reaction Centre surrounded by 16 LH1 subunits in a ring of ∼115 A diameter. Within each LH1 subunit, densities for the α‐ and β‐polypeptide chains are clearly resolved. In one crystal form the LH1 forms a circular ring, and in the other form the ring is significantly ellipsoidal. In each case, the Reaction Centre adopts preferred orientations, suggesting specific interactions between the Reaction Centre and LH1 subunits rather than a continuum of possible orientations with the antenna ring. This experimentally determined structure shows no evidence of any other protein components in the closed LH1 ring. The demonstration of circular or elliptical forms of LH1 indicates that this complex is likely to be flexible in the bacterial membrane.
Shunichi Fukuzumi - One of the best experts on this subject based on the ideXlab platform.
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synthetically tuneable biomimetic artificial Photosynthetic Reaction Centres that closely resemble the natural system in purple bacteria
Chemical Science, 2016Co-Authors: Saiho Lee, Shunichi Fukuzumi, Kei Ohkubo, Iain M Blake, Allan G Larsen, James A Mcdonald, Jeffrey R ReimersAbstract:Porphyrin-based Photosynthetic Reaction Centre (PRC) mimics, ZnPQ-Q2HP-C60 and MP2Q-Q2HP-C60 (M = Zn or 2H), designed to have a similar special-pair electron donor and similar charge-separation distances, redox processes and photochemical Reaction rates to those in the natural PRC from purple bacteria, have been synthesised and extensive photochemical studies performed. Mechanisms of electron-transfer Reactions are fully investigated using femtosecond and nanosecond transient absorption spectroscopy. In benzonitrile, all models show picosecond-timescale charge-separations and the final singlet charge-separations with the microsecond-timescale. The established lifetimes are long compared to other processes in organic solar cells or other organic light harvesting systems. These rigid, synthetically flexible molecules provide the closest mimics to the natural PRC so far synthesised and present a future direction for the design of light harvesters with controllable absorption, redox, and kinetics properties.
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supramolecular electron transfer by anion binding
Chemical Communications, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Francis Dsouza, Jonathan L SesslerAbstract:Anion binding has emerged as an attractive strategy to construct supramolecular electron donor–acceptor complexes. In recent years, the level of sophistication in the design of these systems has advanced to the point where it is possible to create ensembles that mimic key aspects of the photoinduced electron-transfer events operative in the Photosynthetic Reaction Centre. Although anion binding is a reversible process, kinetic studies on anion binding and dissociation processes, as well as photoinduced electron-transfer and back electron-transfer Reactions in supramolecular electron donor–acceptor complexes formed by anion binding, have revealed that photoinduced electron transfer and back electron transfer occur at time scales much faster than those associated with anion binding and dissociation. This difference in rates ensures that the linkage between electron donor and acceptor moieties is maintained over the course of most forward and back electron-transfer processes. A particular example of this principle is illustrated by electron-transfer ensembles based on tetrathiafulvalene calix[4]pyrroles (TTF-C4Ps). In these ensembles, the TTF-C4Ps act as donors, transferring electrons to various electron acceptors after anion binding. Competition with non-redox active substrates is also observed. Anion binding to the pyrrole amine groups of an oxoporphyrinogen unit within various supramolecular complexes formed with fullerenes also results in acceleration of the photoinduced electron-transfer process but deceleration of the back electron transfer; again, this is ascribed to favourable structural and electronic changes. Anion binding also plays a role in stabilizing supramolecular complexes between sulphonated tetraphenylporphyrin anions ([MTPPS]4−: M = H2 and Zn) and a lithium ion encapsulated C60 (Li+@C60); the resulting ensemble produces long-lived charge-separated states upon photoexcitation of the porphyrins.