Publications
277 results found
Messant M, Timm S, Fantuzzi A, et al., 2018, Glycolate Induces Redox Tuning Of Photosystem II in Vivo: Study of a Photorespiration Mutant, PLANT PHYSIOLOGY, Vol: 177, Pages: 1277-1285, ISSN: 0032-0889
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- Citations: 17
Nuernberg DJ, Morton J, Santabarbara S, et al., 2018, Photochemistry beyond the red limit in chlorophyll f-containing photosystems, Science, Vol: 360, Pages: 1210-1213, ISSN: 0036-8075
Photosystems I and II convert solar energy into the chemical energy that powers life. Chlorophyll a photochemistry, using red light (680 to 700 nm), is near universal and is considered to define the energy “red limit” of oxygenic photosynthesis. We present biophysical studies on the photosystems from a cyanobacterium grown in far-red light (750 nm). The few long-wavelength chlorophylls present are well resolved from each other and from the majority pigment, chlorophyll a. Charge separation in photosystem I and II uses chlorophyll f at 745 nm and chlorophyll f (or d) at 727 nm, respectively. Each photosystem has a few even longer-wavelength chlorophylls f that collect light and pass excitation energy uphill to the photochemically active pigments. These photosystems function beyond the red limit using far-red pigments in only a few key positions.
Boussac A, Ugur I, Marion A, et al., 2018, The low spin - high spin equilibrium in the S2-state of the water oxidizing enzyme, Biochim Biophys Acta, Vol: 1859, Pages: 342-356, ISSN: 0006-3002
In Photosystem II (PSII), the Mn4CaO5-cluster of the active site advances through five sequential oxidation states (S0to S4) before water is oxidized and O2is generated. Here, we have studied the transition between the low spin (LS) and high spin (HS) configurations of S2using EPR spectroscopy, quantum chemical calculations using Density Functional Theory (DFT), and time-resolved UV-visible absorption spectroscopy. The EPR experiments show that the equilibrium between S2LSand S2HSis pH dependent, with a pKa ≈ 8.3 (n ≈ 4) for the native Mn4CaO5and pKa ≈ 7.5 (n ≈ 1) for Mn4SrO5. The DFT results suggest that exchanging Ca with Sr modifies the electronic structure of several titratable groups within the active site, including groups that are not direct ligands to Ca/Sr, e.g., W1/W2, Asp61, His332 and His337. This is consistent with the complex modification of the pKaupon the Ca/Sr exchange. EPR also showed that NH3addition reversed the effect of high pH, NH3-S2LSbeing present at all pH values studied. Absorption spectroscopy indicates that NH3is no longer bound in the S3TyrZstate, consistent with EPR data showing minor or no NH3-induced modification of S3and S0. In both Ca-PSII and Sr-PSII, S2HSwas capable of advancing to S3at low temperature (198 K). This is an experimental demonstration that the S2LSis formed first and advances to S3via the S2HSstate without detectable intermediates. We discuss the nature of the changes occurring in the S2LSto S2HStransition which allow the S2HSto S3transition to occur below 200 K. This work also provides a protocol for generating S3in concentrated samples without the need for saturating flashes.
Zhang JZ, Bombelli P, Sokol KP, et al., 2018, Photoelectrochemistry of Photosystem II &ITin Vitro&IT vs&IT in Vivo&IT, Journal of the American Chemical Society, Vol: 140, Pages: 6-9, ISSN: 1520-5126
Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp. PCC 6803 cells. The mediated photocurrent densities generated by the biofilm were 2 orders of magnitude lower than those of the protein-film. This was partly attributed to a lower photocatalyst loading as the rate of mediated electron extraction from PSII in vitro is only double that of PSII in vivo. On the other hand, the biofilm exhibited much greater longevity (>5 days) than the protein-film (<6 h), with turnover numbers surpassing those of the protein-film after 2 days. The mechanism of biofilm electrogenesis is suggested to involve an intracellular redox mediator, which is released during light irradiation.
Lohmiller T, Krewald V, Sedoud A, et al., 2017, The First State in the Catalytic Cycle of the Water-Oxidizing Enzyme: Identification of a Water-Derived mu-Hydroxo Bridge, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 139, Pages: 14412-14424, ISSN: 0002-7863
Davis GA, Rutherford AW, Kramer DM, 2017, Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Delta psi and Delta pH, Philosophical Transactions of the Royal Society of London: Biological Sciences, Vol: 372, ISSN: 0962-8436
There is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the ‘energy-dependent' form of non-photochemical quenching (qE), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce field recombination-induced photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δψ) induce photosystem II recombination reactions that produce damaging singlet oxygen (1O2). Both qE and FRIP are directly linked to the thylakoid proton motive force (pmf), and in particular, the slow kinetics of partitioning pmf into its ΔpH and Δψ components. Using a series of computational simulations, we explored the possibility of ‘hacking' pmf partitioning as a target for improving photosynthesis. Under a range of illumination conditions, increasing the rate of counter-ion fluxes across the thylakoid membrane should lead to more rapid dissipation of Δψ and formation of ΔpH. This would result in increased rates for the formation and decay of qE while resulting in a more rapid decline in the amplitudes of Δψ-spikes and decreasing 1O2 production. These results suggest that ion fluxes may be a viable target for plant breeding or engineering. However, these changes also induce transient, but substantial mismatches in the ATP : NADPH output ratio as well as in the osmotic balance between the lumen and stroma, either of which may explain why evolution has not already accelerated thylakoid ion fluxes. Overall, though the model is simplified, it recapitulates many of the responses seen in vivo, while spotlighting critical aspects of the complex interactions between pmf components and photosynthetic processes. By making the programme available, we hope to enable t
Kornienko N, van Grondelle R, Rutherford AW, et al., 2017, Quantitatively probing photosystem II with a rotating ring disk electrode assembly, 254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Kaucikas M, Nurnberg D, Dorhliac G, et al., 2017, Femtosecond visible transient absorption spectroscopy ofChlorophyll f-containing Photosystem I, Biophysical Journal, Vol: 112, Pages: 234-249, ISSN: 1542-0086
Photosystem I (PSI) from Chroococcidiopsis thermalis PCC 7203 grown under far-red light (FRL; >725 nm) contains both chlorophyll a and a small proportion of chlorophyll f. Here, we investigated excitation energy transfer and charge separation using this FRL-grown form of PSI (FRL-PSI). We compared femtosecond transient visible absorption changes of normal, white-light (WL)-grown PSI (WL-PSI) with those of FRL-PSI using excitation at 670 nm, 700 nm, and (in the case of FRL-PSI) 740 nm. The possibility that chlorophyll f participates in energy transfer or charge separation is discussed on the basis of spectral assignments. With selective pumping of chlorophyll f at 740 nm, we observe a final ∼150 ps decay assigned to trapping by charge separation, and the amplitude of the resulting P700+•A1−• charge-separated state indicates that the yield is directly comparable to that of WL-PSI. The kinetics shows a rapid 2 ps time constant for almost complete transfer to chlorophyll f if chlorophyll a is pumped with a wavelength of 670 nm or 700 nm. Although the physical role of chlorophyll f is best supported as a low-energy radiative trap, the physical location should be close to or potentially within the charge-separating pigments to allow efficient transfer for charge separation on the 150 ps timescale. Target models can be developed that include a branching in the formation of the charge separation for either WL-PSI or FRL-PSI.
Rutherford AW, Fantuzzi A, Brinkert K, et al., 2016, Bicarbonate-induced redox tuning in Photosystem II for regulation and protection, Proceedings of the National Academy of Sciences of the United States of America, Vol: 113, Pages: 12144-12149, ISSN: 1091-6490
The midpoint potential (Em) of QA/Q−∙AQA/QA−•, the one-electron acceptor quinone of Photosystem II (PSII), provides the thermodynamic reference for calibrating PSII bioenergetics. Uncertainty exists in the literature, with two values differing by ∼80 mV. Here, we have resolved this discrepancy by using spectroelectrochemistry on plant PSII-enriched membranes. Removal of bicarbonate (HCO3−) shifts the Em from ∼−145 mV to −70 mV. The higher values reported earlier are attributed to the loss of HCO3− during the titrations (pH 6.5, stirred under argon gassing). These findings mean that HCO3− binds less strongly when QA−• is present. Light-induced QA−• formation triggered HCO3− loss as manifest by the slowed electron transfer and the upshift in the Em of QA. HCO3−-depleted PSII also showed diminished light-induced 1O2 formation. This finding is consistent with a model in which the increase in the Em of QA/Q−∙AQA/QA−• promotes safe, direct P+∙Q−∙AP+•QA−• charge recombination at the expense of the damaging back-reaction route that involves chlorophyll triplet-mediated 1O2 formation [Johnson GN, et al. (1995) Biochim Biophys Acta 1229:202–207]. These findings provide a redox tuning mechanism, in which the interdependence of the redox state of QA and the binding by HCO3− regulates and protects PSII. The potential for a sink (CO2) to source (PSII) feedback mechanism is discussed.
Davis GA, Kanazawa A, Schöttler MA, et al., 2016, Limitations to photosynthesis by proton motive force-induced photosystem II photodamage., eLife, Vol: 5, ISSN: 2050-084X
The thylakoid proton motive force (pmf) generated during photosynthesis is the essential driving force for ATP production; it is also a central regulator of light capture and electron transfer. We investigated the effects of elevated pmf on photosynthesis in a library of Arabidopsis thaliana mutants with altered rates of thylakoid lumen proton efflux, leading to a range of steady-state pmf extents. We observed the expected pmf-dependent alterations in photosynthetic regulation, but also strong effects on the rate of photosystem II (PSII) photodamage. Detailed analyses indicate this effect is related to an elevated electric field (Δψ) component of the pmf, rather than lumen acidification, which in vivo increased PSII charge recombination rates, producing singlet oxygen and subsequent photodamage. The effects are seen even in wild type plants, especially under fluctuating illumination, suggesting that Δψ-induced photodamage represents a previously unrecognized limiting factor for plant productivity under dynamic environmental conditions seen in the field.
Brinkert K, Le formal F, Li X, et al., 2016, Photocurrents from photosystem II in a metal oxide hybrid system: electron transfer pathways, Biochimica et Biophysica Acta-Bioenergetics, Vol: 1857, Pages: 1497-1505, ISSN: 0005-2728
We have investigated the nature of the photocurrent generated by Photosystem II (PSII), the water oxidising enzyme, isolated from Thermosynechococcus elongatus, when immobilized on nanostructured titanium dioxide on an indium tin oxide electrode (TiO2/ITO). We investigated the properties of the photocurrent from PSII when immobilized as a monolayer versus multilayers, in the presence and absence of an inhibitor that binds to the site of the exchangeable quinone (QB) and in the presence and absence exogenous mobile electron carriers (mediators). The findings indicate that electron transfer occurs from the first quinone (QA) directly to the electrode surface but that the electron transfer through the nanostructured metal oxide is the rate-limiting step. Redox mediators enhance the photocurrent by taking electrons from the nanostructured semiconductor surface to the ITO electrode surface not from PSII. This is demonstrated by photocurrent enhancement using a mediator incapable of accepting electrons from PSII. This model for electron transfer also explains anomalies reported in the literature using similar and related systems. The slow rate of the electron transfer step in the TiO2 is due to the energy level of electron injection into the semiconducting material being below the conduction band. This limits the usefulness of the present hybrid electrode. Strategies to overcome this kinetic limitation are discussed.
Rutherford AW, Prell J, MacKellar D, et al., 2016, Streptomyces thermoautotrophicus does not fix nitrogen, Scientific Reports, Vol: 6, ISSN: 2045-2322
Streptomyces thermoautotrophicus UBT1 has been described as a moderately thermophilic chemolithoautotroph with a novel nitrogenase enzyme that is oxygen-insensitive. We have cultured the UBT1 strain, and have isolated two new strains (H1 and P1-2) of very similar phenotypic and genetic characters. These strains show minimal growth on ammonium-free media, and fail to incorporate isotopically labeled N2 gas into biomass in multiple independent assays. The sdn genes previously published as the putative nitrogenase of S. thermoautotrophicus have little similarity to anything found in draft genome sequences, published here, for strains H1 and UBT1, but share >99% nucleotide identity with genes from Hydrogenibacillus schlegelii, a draft genome for which is also presented here. H. schlegelii similarly lacks nitrogenase genes and is a non-diazotroph. We propose reclassification of the species containing strains UBT1, H1, and P1-2 as a non-Streptomycete, non-diazotrophic, facultative chemolithoautotroph and conclude that the existence of the previously proposed oxygen-tolerant nitrogenase is extremely unlikely.
Ugur I, Rutherford AW, Kaila VR, 2016, Redox-coupled substrate water reorganization in the active site of Photosystem II - the role of calcium in substrate water delivery, Biochimica et Biophysica Acta - Bioenergetics, Vol: 1857, Pages: 740-748, ISSN: 0005-2728
Photosystem II (PSII) catalyzes light-driven water splitting in nature and is the key enzyme for energy input into the biosphere. Important details of its mechanism are not well understood. In order to understand the mechanism of water splitting, we perform here large-scale density functional theory (DFT) calculations on the active site of PSII in different oxidation, spin and ligand states. Prior to formation of the O-O bond, we find that all manganese atoms are oxidized to Mn(IV) in the S3 state, consistent with earlier studies. We find here, however, that the formation of the S3 state is coupled to the movement of a calcium-bound hydroxide (W3) from the Ca to a Mn (Mn1 or Mn4) in a process that is triggered by the formation of a tyrosyl radical (Tyr-161) and its protonated base, His-190. We find that subsequent oxidation and deprotonation of this hydroxide on Mn1 result in formation of an oxyl-radical that can exergonically couple with one of the oxo-bridges (O5), forming an O-O bond. When O2 leaves the active site, a second Ca-bound water molecule reorients to bridge the gap between the manganese ions Mn1 and Mn4, forming a new oxo-bridge for the next reaction cycle. Our findings are consistent with experimental data, and suggest that the calcium ion may control substrate water access to the water oxidation sites.
Saito K, Rutherford AW, Ishikita H, 2015, Energetics of proton release on the first oxidation step in the water-oxidizing enzyme, Nature Communications, Vol: 6, Pages: 1-10, ISSN: 2041-1723
In photosystem II (PSII), the Mn4CaO5 cluster catalyses the water splitting reaction. The crystal structure of PSII shows the presence of a hydrogen-bonded water molecule directly linked to O4. Here we show the detailed properties of the H-bonds associated with the Mn4CaO5 cluster using a quantum mechanical/molecular mechanical approach. When O4 is taken as a μ-hydroxo bridge acting as a hydrogen-bond donor to water539 (W539), the S0 redox state best describes the unusually short O4–OW539 distance (2.5 Å) seen in the crystal structure. We find that in S1, O4 easily releases the proton into a chain of eight strongly hydrogen-bonded water molecules. The corresponding hydrogen-bond network is absent for O5 in S1. The present study suggests that the O4-water chain could facilitate the initial deprotonation event in PSII. This unexpected insight is likely to be of real relevance to mechanistic models for water oxidation.
Mersch D, Lee C-Y, Zhang JZ, et al., 2015, Wiring of Photosystem II to Hydrogenase for Photoelectrochemical Water Splitting, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 137, Pages: 8541-8549, ISSN: 0002-7863
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- Citations: 186
Cardona Londono T, Murray JW, Rutherford AW, 2015, Origin and evolution of water oxidation before the last common ancestor of the Cyanobacteria, Molecular Biology and Evolution, Vol: 32, Pages: 1310-1328, ISSN: 1537-1719
Photosystem II, the water oxidizing enzyme, altered the course of evolution by filling the atmosphere with oxygen. Here, we reconstruct the origin and evolution of water oxidation at an unprecedented level of detail by studying the phylogeny of all D1 subunits, the main protein coordinating the water oxidizing cluster (Mn4CaO5) of Photosystem II. We show that D1 exists in several forms making well-defined clades, some of which could have evolved before the origin of water oxidation and presenting many atypical characteristics. The most ancient form is found in the genome of Gloeobacter kilaueensis JS-1 and this has a C-terminus with a higher sequence identity to D2 than to any other D1. Two other groups of early evolving D1 correspond to those expressed under prolonged far-red illumination and in darkness. These atypical D1 forms are characterized by a dramatically different Mn4CaO5 binding site and a Photosystem II containing such a site may assemble an unconventional metal cluster. The first D1 forms with a full set of ligands to the Mn4CaO5 cluster are grouped with D1 proteins expressed only under low oxygen concentrations and the latest evolving form is the dominant type of D1 found in all cyanobacteria and plastids. In addition, we show that the plastid ancestor had a D1 more similar to those in early branching Synechococcus. We suggest each one of these forms of D1 originated from transitional forms at different stages towards the innovation and optimization of water oxidation before the last common ancestor of all known cyanobacteria.
Boussac A, Rutherford AW, Sugiura M, 2015, Electron transfer pathways from the S<sub>2</sub>-states to the S<sub>3</sub>-states either after a Ca<SUP>2+</SUP>/Sr<SUP>2+</SUP> or a Cl<SUP>-</SUP>/I<SUP>-</SUP> exchange in Photosystem II from, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1847, Pages: 576-586, ISSN: 0005-2728
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- Citations: 82
Cotton CA, Douglass JS, De Causmaecker S, et al., 2015, Photosynthetic constraints on fuel from microbes., Frontiers in Bioengineering and Biotechnology, Vol: 3, ISSN: 2296-4185
Rutherford AW, 2014, Redox tuning in biological electron transfer: sacrificing efficiency to survive life in O<sub>2</sub>, 12th European Biological Inorganic Chemistry Conference (EuroBIC), Publisher: SPRINGER, Pages: S704-S704, ISSN: 0949-8257
Sugiura M, Azami C, Koyama K, et al., 2014, Modification of the pheophytin redox potential in <i>Therrnosynechococcus elongatus</i> Photosystem II with PsbA3 as D1, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1837, Pages: 139-148, ISSN: 0005-2728
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- Citations: 29
Kato M, Cardona T, Rutherford AW, et al., 2013, Covalent Immobilization of Oriented Photosystem II on a Nanostructured Electrode for Solar Water Oxidation, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 135, Pages: 10610-10613, ISSN: 0002-7863
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- Citations: 98
Saito K, Rutherford AW, Ishikita H, 2013, Mechanism of tyrosine D oxidation in Photosystem II, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 110, Pages: 7690-7695, ISSN: 0027-8424
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- Citations: 58
Faunce T, Styring S, Wasielewski MR, et al., 2013, Artificial photosynthesis as a frontier technology for energy sustainability, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 6, Pages: 1074-1076, ISSN: 1754-5692
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- Citations: 254
Faunce TA, Lubitz W, Rutherford AWB, et al., 2013, Energy and environment policy case for a global project on artificial photosynthesis, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 6, Pages: 695-698, ISSN: 1754-5692
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- Citations: 231
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
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- Citations: 104
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.
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
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.
Dutton PL, Zhao Z, Rutherford AW, et al., 2012, Electron tunneling in biological energetics, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1817, Pages: S3-S4, ISSN: 0005-2728
Rutherford AW, 2012, Redox tuning in bioenergetics: Compromising efficiency to survive life in O<sub>2</sub>, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1817, Pages: S2-S2, ISSN: 0005-2728
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