253 results found
Zhao Z, Rutherford AW, Moser CC, et al., 2013, Photosynthetic Reaction Center Performance under Physiologically Relevant Energetic Changes, 57th Annual Meeting of the Biophysical-Society, Publisher: CELL PRESS, Pages: 489A-489A, ISSN: 0006-3495
Saito K, Rutherford AW, Ishikita H, 2013, Mechanism of proton-coupled quinone reduction in Photosystem II, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 110, Pages: 954-959, ISSN: 0027-8424
Guerrero F, Sedoud A, Kirilovsky D, et al., 2013, A new value for the redox potential of cytochrome c550 in photosystem II from thermosynechococcus elongatus, Advanced Topics in Science and Technology in China, Pages: 71-74
© Zhejiang University Press, Hangzhou and Springer-Verlag Berlin Heidelberg 2013. Cytochrome c550 (cyt c550), which is one of the extrinsic proteins of photosystem II (PSII), is only present in cyanobacteria and red algae. Although this cytochrome has been reported to stabilize the binding of Ca2+ and Cl− ions, which are essential for activity of PSII, the specific function of heme is not yet clear. The reported negative values of the midpoint redox potential (Em) of cyt c550 (−300 mV in the soluble state and −80 mV when associated with PSII) appear to be incompatible with a redox function in PSII. It has been reported that the Em of QA in PSII-enriched membranes was affected by the presence of redox mediators at low ambient potentials. We have carried out new measurements of Em of cyt c550 associated to PSII changing the type and number of redox mediators used. We have determined that the Em of cyt c550 is about +200 mV in the absence of mediators or in the presence of a very limited number of mediators. Our results suggest that the highly reducing conditions reached in the presence of mediators, favor the reduction of a PSII component, most likely the Mn cluster, thereby inducing alterations in protein, the heme environment and consequently the Em of the heme. The new value of Em of cyt c550 opens the possibility of a redox function for this protein.
Thapper A, Styring S, Saracco G, et al., 2013, Artificial photosynthesis for solar fuels - An evolving research field within AMPEA, a joint programme of the European energy research alliance, Green, Vol: 3, Pages: 43-57, ISSN: 1869-876X
On the path to an energy transition away from fossil fuels to sustainable sources, the European Union is for the moment keeping pace with the objectives of the Strategic Energy Technology-Plan. For this trend to continue after 2020, scientific breakthroughs must be achieved. One main objective is to produce solar fuels from solar energy and water in direct processes to accomplish the efficient storage of solar energy in a chemical form. This is a grand scientific challenge. One important approach to achieve this goal is Artificial Photosynthesis. The European Energy Research Alliance has launched the Joint Programme "Advanced Materials & Processes for Energy Applications" (AMPEA) to foster the role of basic science in Future Emerging Technologies. European researchers in artificial photosynthesis recently met at an AMPEA organized workshop to define common research strategies and milestones for the future. Through this work artificial photosynthesis became the first energy research sub-field to be organised into what is designated "an Application" within AMPEA. The ambition is to drive and accelerate solar fuels research into a powerful European field - in a shorter time and with a broader scope than possible for individual or national initiatives. Within AMPEA the Application Artificial Photosynthesis is inclusive and intended to bring together all European scientists in relevant fields. The goal is to set up a thorough and systematic programme of directed research, which by 2020 will have advanced to a point where commercially viable artificial photosynthetic devices will be under development in partnership with industry.
Rutherford AW, 2012, Redox tuning in bioenergetics: Compromising efficiency to survive life in O-2, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1817, Pages: S2-S2, ISSN: 0005-2728
Kato M, Cardona T, Rutherford AW, et al., 2012, Photoelectrochemical Water Oxidation with Photosystem II Integrated in a Mesoporous; Indium Tin Oxide Electrode, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 134, Pages: 8332-8335, ISSN: 0002-7863
Rutherford AW, Osyczka A, Rappaport F, 2012, Back-reactions, short-circuits, leaks and other energy wasteful reactions in biological electron transfer: Redox tuning to survive life in O(2)., FEBS Lett, Vol: 586, Pages: 603-616
The energy-converting redox enzymes perform productive reactions efficiently despite the involvement of high energy intermediates in their catalytic cycles. This is achieved by kinetic control: with forward reactions being faster than competing, energy-wasteful reactions. This requires appropriate cofactor spacing, driving forces and reorganizational energies. These features evolved in ancestral enzymes in a low O(2) environment. When O(2) appeared, energy-converting enzymes had to deal with its troublesome chemistry. Various protective mechanisms duly evolved that are not directly related to the enzymes' principal redox roles. These protective mechanisms involve fine-tuning of reduction potentials, switching of pathways and the use of short circuits, back-reactions and side-paths, all of which compromise efficiency. This energetic loss is worth it since it minimises damage from reactive derivatives of O(2) and thus gives the organism a better chance of survival. We examine photosynthetic reaction centres, bc(1) and b(6)f complexes from this view point. In particular, the evolution of the heterodimeric PSI from its homodimeric ancestors is explained as providing a protective back-reaction pathway. This "sacrifice-of-efficiency-for-protection" concept should be generally applicable to bioenergetic enzymes in aerobic environments.
Cardona T, Sedoud A, Cox N, et al., 2012, Charge separation in Photosystem II: A comparative and evolutionary overview, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1817, Pages: 26-43, ISSN: 0005-2728
Hideg E, Deak Z, Hakala-Yatkin M, et al., 2011, Pure forms of the singlet oxygen sensors TEMP and TEMPD do not inhibit Photosystem II, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1807, Pages: 1658-1661, ISSN: 0005-2728
Cox N, Rapatskiy L, Su J-H, et al., 2011, Effect of Ca2+/Sr2+ Substitution on the Electronic Structure of the Oxygen-Evolving Complex of Photosystem II: A Combined Multifrequency EPR, Mn-55-ENDOR, and DFT Study of the S-2 State (vol 133, pg 3635, 2011), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 133, Pages: 14149-14149, ISSN: 0002-7863
Sedoud A, Cox N, Sugiura M, et al., 2011, Semiquinone-iron complex of photosystem II: EPR signals assigned to the low-field edge of the ground state doublet of QA•-Fe2+ and QB•-Fe2+., Biochemistry, Vol: 50, Pages: 6012-6021
The quinone-iron complex of the electron acceptor complex of Photosystem II was studied by EPR spectroscopy in Thermosynechococcus elongatus. New g ∼ 2 features belonging to the EPR signal of the semiquinone forms of the primary and secondary quinone, i.e., Q(A)(•-)Fe(2+) and Q(B)(•-)Fe(2+), respectively, are reported. In previous studies, these signals were missed because they were obscured by the EPR signal arising from the stable tyrosyl radical, TyrD(•). When the TyrD(•) signal was removed, either by chemical reduction or by the use of a mutant lacking TyrD, the new signals dominated the spectrum. For Q(A)(•-)Fe(2+), the signal was formed by illumination at 77 K or by sodium dithionite reduction in the dark. For Q(B)(•-)Fe(2+), the signal showed the characteristic period-of-two variations in its intensity when generated by a series of laser flashes. The new features showed relaxation characteristics comparable to those of the well-known features of the semiquinone-iron complexes and showed a temperature dependence consistent with an assignment to the low-field edge of the ground state doublet of the spin system. Spectral simulations are consistent with this assignment and with the current model of the spin system. The signal was also present in Q(B)(•-)Fe(2+) in plant Photosystem II, but in plants, the signal was not detected in the Q(A)(•-)Fe(2+) state.
Su J-H, Cox N, Ames W, et al., 2011, The electronic structures of the S-2 states of the oxygen-evolving complexes of photosystem II in plants and cyanobacteria in the presence and absence of methanol, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1807, Pages: 829-840, ISSN: 0005-2728
Herrero C, Quaranta A, Leibl W, et al., 2011, Artificial photosynthetic systems. Using light and water to provide electrons and protons for the synthesis of a fuel, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 4, Pages: 2353-2365, ISSN: 1754-5692
Ido K, Gross CM, Guerrero F, et al., 2011, High and low potential forms of the Q(A) quinone electron acceptor in Photosystem II of Thermosynechococcus elongatus and spinach, JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY, Vol: 104, Pages: 154-157, ISSN: 1011-1344
Herrero C, Quaranta A, Protti S, et al., 2011, Light-Driven Activation of the [H2O(terpy)Mn-III-mu-(O-2)-Mn-IV(terpy)OH2] Unit in a Chromophore-Catalyst Complex, CHEMISTRY-AN ASIAN JOURNAL, Vol: 6, Pages: 1335-1339, ISSN: 1861-4728
Cox N, Rapatskiy L, Su J-H, et al., 2011, Effect of Ca2+/Sr2+ Substitution on the Electronic Structure of the Oxygen-Evolving Complex of Photosystem II: A Combined Multifrequency EPR, Mn-55-ENDOR, and DFT Study of the S-2 State, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 133, Pages: 3635-3648, ISSN: 0002-7863
Guerrero F, Sedoud A, Kirilovsky D, et al., 2011, A High Redox Potential Form of Cytochrome c(550) in Photosystem II from Thermosynechococcus elongatus, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 286, Pages: 5985-5994, ISSN: 0021-9258
Sedoud A, Kastner L, Cox N, et al., 2011, Effects of formate binding on the quinone-iron electron acceptor complex of photosystem II., Biochim Biophys Acta, Vol: 1807, Pages: 216-226, ISSN: 0006-3002
EPR was used to study the influence of formate on the electron acceptor side of photosystem II (PSII) from Thermosynechococcus elongatus. Two new EPR signals were found and characterized. The first is assigned to the semiquinone form of Q(B) interacting magnetically with a high spin, non-heme-iron (Fe²(+), S=2) when the native bicarbonate/carbonate ligand is replaced by formate. This assignment is based on several experimental observations, the most important of which were: (i) its presence in the dark in a significant fraction of centers, and (ii) the period-of-two variations in the concentration expected for Q(B)(•-) when PSII underwent a series of single-electron turnovers. This signal is similar but not identical to the well-know formate-modified EPR signal observed for the Q(A)(•-)Fe²(+) complex (W.F.J. Vermaas and A.W. Rutherford, FEBS Lett. 175 (1984) 243-248). The formate-modified signals from Q(A)(•-)Fe²(+) and Q(B)(•-)Fe²(+) are also similar to native semiquinone-iron signals (Q(A)(•-)Fe²(+)/Q(B)(•-)Fe²(+)) seen in purple bacterial reaction centers where a glutamate provides the carboxylate ligand to the iron. The second new signal was formed when Q(A)(•-) was generated in formate-inhibited PSII when the secondary acceptor was reduced by two electrons. While the signal is reminiscent of the formate-modified semiquinone-iron signals, it is broader and its main turning point has a major sub-peak at higher field. This new signal is attributed to the Q(A)(•-)Fe²(+) with formate bound but which is perturbed when Q(B) is fully reduced, most likely as Q(B)H₂ (or possibly Q(B)H(•-) or Q(B)(²•-)). Flash experiments on formate-inhibited PSII monitoring these new EPR signals indicate that the outcome of charge separation on the first two flashes is not greatly modified by formate. However on the third flash and subsequent flashes, the modified Q(A)(•-)Fe²(+)Q(B)H₂ sign
Hughes JL, Cox N, Rutherford AW, et al., 2010, D1 protein variants in Photosystem II from Thermosynechococcus elongatus studied by low temperature optical spectroscopy, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1797, Pages: 11-19, ISSN: 0005-2728
Herrero C, Hughes JL, Quaranta A, et al., 2010, Intramolecular light induced activation of a Salen-Mn-III complex by a ruthenium photosensitizer, CHEMICAL COMMUNICATIONS, Vol: 46, Pages: 7605-7607, ISSN: 1359-7345
Cox N, Hughes J, Rutherford AW, et al., 2010, On the assignment of PSHB in D1/D2/cytb(559) reaction centers, PROCEEDINGS OF THE TENTH INTERNATIONAL MEETING ON HOLE BURNING, SINGLE MOLECULE AND RELATED SPECTROSCOPIES, Vol: 3, Pages: 1601-1605, ISSN: 1875-3892
Vittadello M, Gorbunov MY, Mastrogiovanni DT, et al., 2010, Photoelectron Generation by Photosystem II Core Complexes Tethered to Gold Surfaces, CHEMSUSCHEM, Vol: 3, Pages: 471-475, ISSN: 1864-5631
Cox N, Jin L, Jaszewski A, et al., 2009, The Semiquinone-Iron Complex of Photosystem II: Structural Insights from ESR and Theoretical Simulation; Evidence that the Native Ligand to the Non-Heme Iron Is Carbonate, BIOPHYSICAL JOURNAL, Vol: 97, Pages: 2024-2033, ISSN: 0006-3495
The semiquinone-iron complex of photosystem II was studied using electron spin resonance (ESR) spectroscopy and density functional theory calculations. Two forms of the signal were investigated: 1), the native g similar to 1.9 form; and 2), the g similar to 1.84 form, which is well known in purple bacterial reaction centers and occurs in photosystem 11 when treated with formate. The g similar to 1.9 form shows low- and high-field edges at g similar to 3.5 and g < 0.8, respectively, and resembles the g similar to 1.84 form in terms of shape and width. Both types of ESR signal were simulated using the theoretical approach used previously for the BRC complex, a spin Hamiltonian formalism in which the semiquinone radical magnetically interacts (J similar to 1 cm(-1)) with the nearby high-spin Fe(2+). The two forms of ESR signal differ mainly by an axis rotation of the exchange coupling tensor (J) relative to the zero-field tensor (D) and a small increase in the zero-field parameter D (similar to 6 cm(-1)). Density functional theory calculations were conducted on model semiquinone-iron systems to identify the physical nature of these changes. The replacement of formate (or glutamate in the bacterial reaction centers) by bicarbonate did not result in changes in the coupling environment. However, when carbonate (CO(3)(2-)) was used instead of bicarbonate, the exchange and zero-field tensors did show changes that matched those obtained from the spectral simulations. This indicates that 1), the doubly charged carbonate ion is responsible for the g similar to 1.9 form of the semiquinone-iron signal; and 2), carbonate, rather than bicarbonate, is the ligand to the iron.
Cox N, Hughes JL, Steffen R, et al., 2009, Identification of the Q(Y) Excitation of the Primary Electron Acceptor of Photosystem II: CD Determination of Its Coupling Environment, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 113, Pages: 12364-12374, ISSN: 1520-6106
Rutherford AW, 2009, Biological and biomimetic water photolysis, 34th Congress of the Federation-of-European-Biochemical-Societies, Publisher: WILEY-BLACKWELL PUBLISHING, INC, Pages: 65-65, ISSN: 1742-464X
Boussac A, Sugiura M, Rutherford AW, et al., 2009, Complete EPR spectrum of the S3-state of the oxygen-evolving photosystem II., J Am Chem Soc, Vol: 131, Pages: 5050-5051
Despite crystallographic structures now available and intensive work in the past decades, little is known about the higher redox states of the catalytic cycle of Photosystem II, the enzyme responsible for the presence of O(2) on Earth and at the beginning of the process that has produced both the biomass and the fossil fuels. In one of the highest oxidation states, the S(3)-state, only signals at g-values higher than 4 have been detected so far at the X-band. In this work, we report for the first time the complete X-band EPR spectrum for the S(3)-state of Photosystem II. Simulations show that, for a spin state S = 1, as was previously suggested for S(3), it is not possible to account for all the features observed. A satisfactory simulated spectrum was obtained for a spin state S = 3 with zero-field splitting parameters D = 0.175 cm(-1) and E/D = 0.275. The detection of the full EPR signal for S(3) opens the door for new investigations and a better understanding of the catalytic cycle of Photosystem II.
Mackiewicz N, Delaire JA, Rutherford AW, et al., 2009, Carbon Nanotube-Acridine Nanohybrids: Spectroscopic Characterization of Photoinduced Electron Transfer, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 15, Pages: 3882-3888, ISSN: 0947-6539
Hughes JL, Rutherford AW, Sugiura M, et al., 2008, Quantum efficiency distributions of photo-induced side-pathway donor oxidation at cryogenic temperature in photosystem II, PHOTOSYNTHESIS RESEARCH, Vol: 98, Pages: 199-206, ISSN: 0166-8595
Christoforidis KC, Louloudi M, Rutherford AW, et al., 2008, Semiquinone in molecularly imprinted hybrid amino acid-SiO2 biomimetic materials. An experimental and theoretical study, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 112, Pages: 12841-12852, ISSN: 1932-7447
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