scholarly journals Electron Transfer Routes in Oxygenic Photosynthesis: Regulatory Mechanisms and New Perspectives

10.5772/55339 ◽  
2013 ◽  
Author(s):  
Snjeana Juri ◽  
Lea Vojta ◽  
Hrvoje Fulgosi
Keyword(s):  
Electron Transfer ◽  
Regulatory Mechanisms ◽  
Oxygenic Photosynthesis

scholarly journals Mediator-assisted water oxidation by the ruthenium “blue dimer” cis,cis-[(bpy)2(H2O)RuORu(OH2)(bpy)2]4+

2008 ◽  
Vol 105 (46) ◽  
pp. 17632-17635 ◽  
Author(s):  
Javier J. Concepcion ◽  
Jonah W. Jurss ◽  
Joseph L. Templeton ◽  
Thomas J. Meyer
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Renewable Energy ◽  
Photosystem Ii ◽  
Water Splitting ◽  
Water Oxidation ◽  
Oxygenic Photosynthesis ◽  
Reduced Water ◽  
Insight Into ◽  
Recent Insight

Light-driven water oxidation occurs in oxygenic photosynthesis in photosystem II and provides redox equivalents directed to photosystem I, in which carbon dioxide is reduced. Water oxidation is also essential in artificial photosynthesis and solar fuel-forming reactions, such as water splitting into hydrogen and oxygen (2 H2O + 4 hν → O2 + 2 H2) or water reduction of CO2 to methanol (2 H2O + CO2 + 6 hν → CH3OH + 3/2 O2), or hydrocarbons, which could provide clean, renewable energy. The “blue ruthenium dimer,” cis,cis-[(bpy)2(H2O)RuIIIORuIII(OH2)(bpy)2]4+, was the first well characterized molecule to catalyze water oxidation. On the basis of recent insight into the mechanism, we have devised a strategy for enhancing catalytic rates by using kinetically facile electron-transfer mediators. Rate enhancements by factors of up to ≈30 have been obtained, and preliminary electrochemical experiments have demonstrated that mediator-assisted electrocatalytic water oxidation is also attainable.

Proton-Coupled Electron Transfer in a Biomimetic Peptide as a Model of Enzyme Regulatory Mechanisms

2007 ◽  
Vol 129 (14) ◽  
pp. 4393-4400 ◽  
Author(s):  
Robin Sibert ◽  
Mira Josowicz ◽  
Fernando Porcelli ◽  
Gianluigi Veglia ◽  
Kevin Range ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Regulatory Mechanisms ◽  
Proton Coupled Electron Transfer

scholarly journals Structure of plant PSI-plastocyanin complex reveals strong hydrophobic interactions

2021 ◽  
Author(s):  
Ido Caspy ◽  
Mariia Fadeeva ◽  
Sebastian Kuhlgert ◽  
Anna Borovikova-Sheinker ◽  
Daniel Klaiman ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Genetic Engineering ◽  
Hydrophobic Interactions ◽  
Structural Data ◽  
Oxygenic Photosynthesis ◽  
Water Molecules ◽  
Major Step ◽  
Ferredoxin Oxidoreductase ◽  
Complex Forms ◽  
Oxidized Pc

AbstractPhotosystem I is defined as plastocyanin-ferredoxin oxidoreductase. Taking advantage of genetic engineering, kinetic analyses and cryo-EM, our data provide novel mechanistic insights into binding and electron transfer between PSI and Pc. Structural data at 2.74 Å resolution reveals strong hydrophobic interactions in the plant PSI-Pc ternary complex, leading to exclusion of water molecules from PsaA-PsaB / Pc interface once the PSI-Pc complex forms. Upon oxidation of Pc, a slight tilt of bound oxidized Pc allows water molecules to accommodate the space between Pc and PSI to drive Pc dissociation. Such a scenario is consistent with the six times larger dissociation constant of oxidized as compared to reduced Pc and mechanistically explains how this molecular machine optimized electron transfer for fast turnover.One Sentence SummaryGenetic engineering, kinetics and cryo-EM structural data reveal a mechanism in a major step of oxygenic photosynthesis

scholarly journals Occurrence, Evolution and Specificities of Iron-Sulfur Proteins and Maturation Factors in Chloroplasts from Algae

2021 ◽  
Vol 22 (6) ◽  
pp. 3175
Author(s):  
Jonathan Przybyla-Toscano ◽  
Jérémy Couturier ◽  
Claire Remacle ◽  
Nicolas Rouhier
Keyword(s):  
Electron Transfer ◽  
Molecular Mechanisms ◽  
Chlorophyll Synthesis ◽  
Oxygenic Photosynthesis ◽  
Terrestrial Plants ◽  
Iron Sulfur ◽  
Isoprenoid Metabolism ◽  
Metabolic Reactions ◽  
Photosynthetic Electron Transfer ◽  
S Proteins

Iron-containing proteins, including iron-sulfur (Fe-S) proteins, are essential for numerous electron transfer and metabolic reactions. They are present in most subcellular compartments. In plastids, in addition to sustaining the linear and cyclic photosynthetic electron transfer chains, Fe-S proteins participate in carbon, nitrogen, and sulfur assimilation, tetrapyrrole and isoprenoid metabolism, and lipoic acid and thiamine synthesis. The synthesis of Fe-S clusters, their trafficking, and their insertion into chloroplastic proteins necessitate the so-called sulfur mobilization (SUF) protein machinery. In the first part, we describe the molecular mechanisms that allow Fe-S cluster synthesis and insertion into acceptor proteins by the SUF machinery and analyze the occurrence of the SUF components in microalgae, focusing in particular on the green alga Chlamydomonas reinhardtii. In the second part, we describe chloroplastic Fe-S protein-dependent pathways that are specific to Chlamydomonas or for which Chlamydomonas presents specificities compared to terrestrial plants, putting notable emphasis on the contribution of Fe-S proteins to chlorophyll synthesis in the dark and to the fermentative metabolism. The occurrence and evolutionary conservation of these enzymes and pathways have been analyzed in all supergroups of microalgae performing oxygenic photosynthesis.

scholarly journals Murburn precepts for the light reaction of oxygenic photosynthesis

2020 ◽  
Author(s):  
Kelath Murali Manoj ◽  
Nikolai Bazhin ◽  
Abhinav Parashar ◽  
Daniel Andrew Gideon ◽  
Vivian David Jacob ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Red Light ◽  
Oxygenic Photosynthesis ◽  
Systemic Resistance ◽  
Connected Components ◽  
Ps Ii ◽  
Light Reaction ◽  
Simultaneous Excitation ◽  
Parallel Reactions ◽  
Original Observation

Robert Emerson’s original observation (1957) that “oxygenesis occurs even with far-red light excitation of Photosystem I” is incompatible with the extant Kok-Joliot cycle’s foundation that “photolysis occurs only at red-light stimulated Photosystem II harboring MnComplex”. Further, the Z-scheme of electron transfer cannot account for Emerson’s observations of enhanced oxygenesis by simultaneous excitation of the two photosystems with both red and far-red light because serially connected components would surely increase systemic resistance to flow of charges, impeding the overall electron transfer process from water to NADP+. To address such discrepancies, we propose that the photo-excitation of various pigments leads to the formation of aquated electrons (eaq) and diffusible reactive oxygen species (DROS) in milieu, which are stabilized by a pool of redox-active elements within chloroplasts. Subsequently, the ‘eaq+DROS’ pool is utilized and routed via disordered and parallel reactions by the ‘photosystem switches’ for NADP reduction, O2 liberation and ADP phosphorylation. The stochastic ‘murburn’ model is thermodynamically and kinetically favorable and evidenced by the identification of multiple ADP-binding sites on PS II/Cytochrome b6f, and structure/distribution of the concerned proteins, complexes and pigments. The new model also explains the observed synergy in functioning of photosystems and plants’ photosynthetic spectral range of 400-700 nm.

scholarly journals Electrostatically Constrained Pathway of Intra-Monomer Electron Transfer in the Cytochrome B6F Complex of Oxygenic Photosynthesis

2013 ◽  
Vol 104 (2) ◽  
pp. 488a
Author(s):  
Stanislav D. Zakharov ◽  
Syed Saif Hasan ◽  
Adrien Chauvet ◽  
Sergei Savikhin ◽  
William A. Cramer
Keyword(s):  
Electron Transfer ◽  
Oxygenic Photosynthesis ◽  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
B6f Complex

scholarly journals Oxygenic photosynthesis: Critiquing the standing explanations and proposing explorative solutions based in murburn concept

2019 ◽  
Author(s):  
Kelath Murali Manoj
Keyword(s):  
Electron Transfer ◽  
Oxygenic Photosynthesis ◽  
Light Reaction ◽  
Mechanistic Explanations ◽  
Interactive Dynamics

The available explanations for oxygenic photosynthesis for the light reaction of photolysis and photophosphorylation (Pl-Pp) are critically analyzed. Based on the structure cum distribution of protagonist molecules and the new mechanistic explanations in redox biochemistry, the interactive dynamics of key reactants are re-assessed for viability. The Z-scheme for electron transfer and Kok-Joliot cycle for water-lysis are found to be physiologically non-viable. Further, mechanistic explorations based on murburn concept are advocated for Pl-Pp.

A light optical diffractometer for electron microscopical images operating in line

1978 ◽  
Vol 36 (1) ◽  
pp. 86-87
Author(s):  
P. Bonhomme ◽  
A. Beorchia
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Electron Microscope ◽  
Image Converter ◽  
Coherent Light ◽  
Spatial Filters ◽  
Electron Image ◽  
Electron Microscopical ◽  
Working Parameters ◽  
Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

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