Articoli di riviste: "Electron transport Complex I"

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Bose, Himangshu S., Brendan Marshall, Dilip K. Debnath, Elizabeth W. Perry e Randy M. Whittal. "Electron Transport Chain Complex II Regulates Steroid Metabolism". iScience 23, n. 7 (luglio 2020): 101295. http://dx.doi.org/10.1016/j.isci.2020.101295.

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Zhang, Jiecheng, Erik D. Kountz, Kamran Behnia e Aharon Kapitulnik. "Thermalization and possible signatures of quantum chaos in complex crystalline materials". Proceedings of the National Academy of Sciences 116, n. 40 (12 settembre 2019): 19869–74. http://dx.doi.org/10.1073/pnas.1910131116.

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Analyses of thermal diffusivity data on complex insulators and on strongly correlated electron systems hosted in similar complex crystal structures suggest that quantum chaos is a good description for thermalization processes in these systems, particularly in the high-temperature regime where the many phonon bands and their interactions dominate the thermal transport. Here we observe that for these systems diffusive thermal transport is controlled by a universal Planckian timescale τ∼ℏ/kBT and a unique velocity vE. Specifically, vE≈vph for complex insulators, and vph≲vE≪vF in the presence of strongly correlated itinerant electrons (vph and vF are the phonon and electron velocities, respectively). For the complex correlated electron systems we further show that charge diffusivity, while also reaching the Planckian relaxation bound, is largely dominated by the Fermi velocity of the electrons, hence suggesting that it is only the thermal (energy) diffusivity that describes chaos diffusivity.

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Kr�ger, A., J. Paulsen e I. Schr�der. "Phorphorylative electron transport chains lacking a cytochromebc 1 complex". Journal of Bioenergetics and Biomembranes 18, n. 3 (giugno 1986): 225–34. http://dx.doi.org/10.1007/bf00743465.

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Chen, Yongqiang, e Isamu Suzuki. "Effects of electron transport inhibitors and uncouplers on the oxidation of ferrous iron and compounds interacting with ferric iron inAcidithiobacillus ferrooxidans". Canadian Journal of Microbiology 51, n. 8 (1 agosto 2005): 695–703. http://dx.doi.org/10.1139/w05-051.

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Oxidation of Fe2+, ascorbic acid, propyl gallate, tiron, L-cysteine, and glutathione by Acidithiobacillus ferrooxidans was studied with respect to the effect of electron transport inhibitors and uncouplers on the rate of oxidation. All the oxidations were sensitive to inhibitors of cytochrome c oxidase, KCN, and NaN3. They were also partially inhibited by inhibitors of complex I and complex III of the electron transport system. Uncouplers at low concentrations stimulated the oxidation and inhibited it at higher concentrations. The oxidation rates of Fe2+and L-cysteine inhibited by complex I and complex III inhibitors (amytal, rotenone, antimycin A, myxothiazol, and HQNO) were stimulated more extensively by uncouplers than the control rates. Atabrine, a flavin antagonist, was an exception, and atabrine-inhibited oxidation activities of all these compounds were further inhibited by uncouplers. A model for the electron transport pathways of A. ferrooxidans is proposed to account for these results. In the model these organic substrates reduce ferric iron on the surface of cells to ferrous iron, which is oxidized back to ferric iron through the Fe2+oxidation pathway, leading to cytochrome oxidase to O2. Some of electrons enter the uphill (energy-requiring) electron transport pathway to reduce NAD+. Uncouplers at low concentrations stimulate Fe2+oxidation by stimulating cytochrome oxidase by uncoupling. Higher concentrations lower Δp to the level insufficient to overcome the potentially uphill reaction at rusticyanin-cytochrome c4. Inhibition of uphill reactions at complex I and complex III leads to Δp accumulation and inhibition of cytochrome oxidase. Uncouplers remove the inhibition of Δp and stimulate the oxidation. Atabrine inhibition is not released by uncouplers, which implies a possibility of atabrine inhibition at a site other than complex I, but a site somehow involved in the Fe2+oxidation pathway.Key words: Acidithiobacillus ferrooxidans, electron transport, uncouplers, uphill electron transport pathway.

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Onukwufor, John O., Brandon J. Berry e Andrew P. Wojtovich. "Physiologic Implications of Reactive Oxygen Species Production by Mitochondrial Complex I Reverse Electron Transport". Antioxidants 8, n. 8 (6 agosto 2019): 285. http://dx.doi.org/10.3390/antiox8080285.

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Mitochondrial reactive oxygen species (ROS) can be either detrimental or beneficial depending on the amount, duration, and location of their production. Mitochondrial complex I is a component of the electron transport chain and transfers electrons from NADH to ubiquinone. Complex I is also a source of ROS production. Under certain thermodynamic conditions, electron transfer can reverse direction and reduce oxygen at complex I to generate ROS. Conditions that favor this reverse electron transport (RET) include highly reduced ubiquinone pools, high mitochondrial membrane potential, and accumulated metabolic substrates. Historically, complex I RET was associated with pathological conditions, causing oxidative stress. However, recent evidence suggests that ROS generation by complex I RET contributes to signaling events in cells and organisms. Collectively, these studies demonstrate that the impact of complex I RET, either beneficial or detrimental, can be determined by the timing and quantity of ROS production. In this article we review the role of site-specific ROS production at complex I in the contexts of pathology and physiologic signaling.

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Spero, Melanie A., Joshua R. Brickner, Jordan T. Mollet, Tippapha Pisithkul, Daniel Amador-Noguez e Timothy J. Donohue. "Different Functions of Phylogenetically Distinct Bacterial Complex I Isozymes". Journal of Bacteriology 198, n. 8 (1 febbraio 2016): 1268–80. http://dx.doi.org/10.1128/jb.01025-15.

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ABSTRACTNADH:quinone oxidoreductase (complex I) is a bioenergetic enzyme that transfers electrons from NADH to quinone, conserving the energy of this reaction by contributing to the proton motive force. While the importance of NADH oxidation to mitochondrial aerobic respiration is well documented, the contribution of complex I to bacterial electron transport chains has been tested in only a few species. Here, we analyze the function of two phylogenetically distinct complex I isozymes inRhodobacter sphaeroides, an alphaproteobacterium that contains well-characterized electron transport chains. We found thatR. sphaeroidescomplex I activity is important for aerobic respiration and required for anaerobic dimethyl sulfoxide (DMSO) respiration (in the absence of light), photoautotrophic growth, and photoheterotrophic growth (in the absence of an external electron acceptor). Our data also provide insight into the functions of the phylogenetically distinctR. sphaeroidescomplex I enzymes (complex IAand complex IE) in maintaining a cellular redox state during photoheterotrophic growth. We propose that the function of each isozyme during photoheterotrophic growth is either NADH synthesis (complex IA) or NADH oxidation (complex IE). The canonical alphaproteobacterial complex I isozyme (complex IA) was also shown to be important for routing electrons to nitrogenase-mediated H2production, while the horizontally acquired enzyme (complex IE) was dispensable in this process. Unlike the singular role of complex I in mitochondria, we predict that the phylogenetically distinct complex I enzymes found across bacterial species have evolved to enhance the functions of their respective electron transport chains.IMPORTANCECells use a proton motive force (PMF), NADH, and ATP to support numerous processes. In mitochondria, complex I uses NADH oxidation to generate a PMF, which can drive ATP synthesis. This study analyzed the function of complex I in bacteria, which contain more-diverse and more-flexible electron transport chains than mitochondria. We tested complex I function inRhodobacter sphaeroides, a bacterium predicted to encode two phylogenetically distinct complex I isozymes.R. sphaeroidescells lacking both isozymes had growth defects during all tested modes of growth, illustrating the important function of this enzyme under diverse conditions. We conclude that the two isozymes are not functionally redundant and predict that phylogenetically distinct complex I enzymes have evolved to support the diverse lifestyles of bacteria.

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Burkhardt, Carolyn, James P. Kelly, Young-Hwa Lim, Christopher M. Filley e W. Davis Parker. "Neuroleptic medications inhibit complex I of the electron transport chain". Annals of Neurology 33, n. 5 (maggio 1993): 512–17. http://dx.doi.org/10.1002/ana.410330516.

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Jackson-Lewis, Vernice, e Serge Przedborski. "Neuroleptic medications inhibit complex I of the electron transport chain". Annals of Neurology 35, n. 2 (febbraio 1994): 244–45. http://dx.doi.org/10.1002/ana.410350221.

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Yan, Liuming, e Jorge M. Seminario. "Electronic Structure and Electron Transport Characteristics of a Cobalt Complex". Journal of Physical Chemistry A 109, n. 30 (agosto 2005): 6628–33. http://dx.doi.org/10.1021/jp052798k.

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Demaurex, Nicolas, e Gábor L. Petheö. "Electron and proton transport by NADPH oxidases". Philosophical Transactions of the Royal Society B: Biological Sciences 360, n. 1464 (4 novembre 2005): 2315–25. http://dx.doi.org/10.1098/rstb.2005.1769.

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The NADPH oxidase is the main weapon of phagocytic white blood cells that are the first line of defence of our body against invading pathogens, and patients lacking a functional oxidase suffer from severe and recurrent infections. The oxidase is a multisubunit enzyme complex that transports electrons from cytoplasmic NADPH to molecular oxygen in order to generate superoxide free radicals. Electron transport across the plasma membrane is electrogenic and is associated with the flux of protons through voltage-activated proton channels. Both proton and electron currents can be recorded with the patch-clamp technique, but whether the oxidase is a proton channel or a proton channel modulator remains controversial. Recently, we have used the inside–out configuration of the patch-clamp technique to record proton and electron currents in excised patches. This approach allows us to measure the oxidase activity under very controlled conditions, and has provided new information about the enzymatic activity of the oxidase and its coupling to proton channels. In this chapter I will discuss how the unique characteristics of the electron and proton currents associated with the redox activity of the NADPH oxidase have extended our knowledge about the thermodynamics and the physiological regulation of this remarkable enzyme.

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Pittman, M. S., e D. J. Kelly. "Electron transport through nitrate and nitrite reductases in Campylobacter jejuni". Biochemical Society Transactions 33, n. 1 (1 febbraio 2005): 190–92. http://dx.doi.org/10.1042/bst0330190.

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Campylobacter jejuni is a small genome pathogen that is incapable of growing strictly anaerobically due to its dependence on an oxygen-requiring ribonucleotide reductase for DNA synthesis. Nevertheless, it has a complex branched respiratory chain, which allows the use of several alternative electron acceptors for growth under oxygen-limited conditions. C. jejuni is equipped with both nitrate reductase (Nap) and nitrite reductase (Nrf) located in the periplasm, each predicted to receive electrons from menaquinol through distinct redox proteins. The pathways of electron transport to nitrate and nitrite are reviewed in this paper. Nitrate is considered as a potential in vivo electron acceptor and a role for nitrite reductase in NO detoxification is suggested.

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Tanaka-Esposito, Christine, Qun Chen, Shadi Moghaddas e Edward J. Lesnefsky. "Ischemic preconditioning does not protect via blockade of electron transport". Journal of Applied Physiology 103, n. 2 (agosto 2007): 623–28. http://dx.doi.org/10.1152/japplphysiol.00943.2006.

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Ischemic preconditioning (IPC) before sustained ischemia decreases myocardial infarct size mediated in part via protection of cardiac mitochondria. Reversible blockade of electron transport at complex I immediately before sustained ischemia also preserves mitochondrial respiration and decreases infarct size. We proposed that IPC would attenuate electron transport from complex I as a potential effector mechanism of cardioprotection. Isolated, Langendorff-perfused rat hearts underwent IPC (3 cycles of 5-min 37°C global ischemia and 5-min reperfusion) or were perfused for 40 min without ischemia as controls. Subsarcolemmal (SSM) and interfibrillar (IFM) populations of mitochondria were isolated. IPC did not decrease ADP-stimulated respiration measured in intact mitochondria using substrates that donate reducing equivalents to complex I. Maximally expressed complex I activity measured as rotenone-sensitive NADH:ubiquinone oxidoreductase in detergent-solubilized mitochondria was also unaffected by IPC. Thus the protection of IPC does not occur as a consequence of a partial decrease in complex I activity leading to a decrease in integrated respiration through complex I. IPC and blockade of electron transport both converge on mitochondria as effectors of cardioprotection; however, each modulates mitochondrial metabolism during ischemia by different mechanisms to achieve cardioprotection.

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Okamoto, Akihiro, Yoshihide Tokunou, Shafeer Kalathil e Kazuhito Hashimoto. "Proton Transport in the Outer-Membrane Flavocytochrome Complex Limits the Rate of Extracellular Electron Transport". Angewandte Chemie International Edition 56, n. 31 (29 giugno 2017): 9082–86. http://dx.doi.org/10.1002/anie.201704241.

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Okamoto, Akihiro, Yoshihide Tokunou, Shafeer Kalathil e Kazuhito Hashimoto. "Proton Transport in the Outer-Membrane Flavocytochrome Complex Limits the Rate of Extracellular Electron Transport". Angewandte Chemie 129, n. 31 (29 giugno 2017): 9210–14. http://dx.doi.org/10.1002/ange.201704241.

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Fuhrmann, Dominik C., Catherine Olesch, Nina Kurrle, Frank Schnütgen, Sven Zukunft, Ingrid Fleming e Bernhard Brüne. "Chronic Hypoxia Enhances β-Oxidation-Dependent Electron Transport via Electron Transferring Flavoproteins". Cells 8, n. 2 (18 febbraio 2019): 172. http://dx.doi.org/10.3390/cells8020172.

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Hypoxia poses a stress to cells and decreases mitochondrial respiration, in part by electron transport chain (ETC) complex reorganization. While metabolism under acute hypoxia is well characterized, alterations under chronic hypoxia largely remain unexplored. We followed oxygen consumption rates in THP-1 monocytes during acute (16 h) and chronic (72 h) hypoxia, compared to normoxia, to analyze the electron flows associated with glycolysis, glutamine, and fatty acid oxidation. Oxygen consumption under acute hypoxia predominantly demanded pyruvate, while under chronic hypoxia, fatty acid- and glutamine-oxidation dominated. Chronic hypoxia also elevated electron-transferring flavoproteins (ETF), and the knockdown of ETF–ubiquinone oxidoreductase lowered mitochondrial respiration under chronic hypoxia. Metabolomics revealed an increase in citrate under chronic hypoxia, which implied glutamine processing to α-ketoglutarate and citrate. Expression regulation of enzymes involved in this metabolic shunting corroborated this assumption. Moreover, the expression of acetyl-CoA carboxylase 1 increased, thus pointing to fatty acid synthesis under chronic hypoxia. Cells lacking complex I, which experienced a markedly impaired respiration under normoxia, also shifted their metabolism to fatty acid-dependent synthesis and usage. Taken together, we provide evidence that chronic hypoxia fuels the ETC via ETFs, increasing fatty acid production and consumption via the glutamine-citrate-fatty acid axis.

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Yi, John S., Beth C. Holbrook, Ryan D. Michalek, Nathan G. Laniewski e Jason M. Grayson. "Electron Transport Complex I Is Required for CD8+T Cell Function". Journal of Immunology 177, n. 2 (3 luglio 2006): 852–62. http://dx.doi.org/10.4049/jimmunol.177.2.852.

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Kristal, B. S. "Structure-(Dys)function Relationships in Mitochondrial Electron Transport Chain Complex II?" Science of Aging Knowledge Environment 2003, n. 5 (5 febbraio 2003): 3pe—3. http://dx.doi.org/10.1126/sageke.2003.5.pe3.

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Esposti, Mauro Degli, e Anna Ghelli. "The mechanism of proton and electron transport in mitochondrial complex I". Biochimica et Biophysica Acta (BBA) - Bioenergetics 1187, n. 2 (agosto 1994): 116–20. http://dx.doi.org/10.1016/0005-2728(94)90095-7.

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Ogasawara, Hiroshi, Yuji Ishida, Kayoko Yamada, Kaneyoshi Yamamoto e Akira Ishihama. "PdhR (Pyruvate Dehydrogenase Complex Regulator) Controls the Respiratory Electron Transport System in Escherichia coli". Journal of Bacteriology 189, n. 15 (18 maggio 2007): 5534–41. http://dx.doi.org/10.1128/jb.00229-07.

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ABSTRACT The pyruvate dehydrogenase (PDH) multienzyme complex plays a key role in the metabolic interconnection between glycolysis and the citric acid cycle. Transcription of the Escherichia coli genes for all three components of the PDH complex in the pdhR-aceEF-lpdA operon is repressed by the pyruvate-sensing PdhR, a GntR family transcription regulator, and derepressed by pyruvate. After a systematic search for the regulation targets of PdhR using genomic systematic evolution of ligands by exponential enrichment (SELEX), we have identified two novel targets, ndh, encoding NADH dehydrogenase II, and cyoABCDE, encoding the cytochrome bo-type oxidase, both together forming the pathway of respiratory electron transport downstream from the PDH cycle. PDH generates NADH, while Ndh and CyoABCDE together transport electrons from NADH to oxygen. Using gel shift and DNase I footprinting assays, the PdhR-binding site (PdhR box) was defined, which includes a palindromic consensus sequence, ATTGGTNNNACCAAT. The binding in vitro of PdhR to the PdhR box decreased in the presence of pyruvate. Promoter assays in vivo using a two-fluorescent-protein vector also indicated that the newly identified operons are repressed by PdhR and derepressed by the addition of pyruvate. Taken together, we propose that PdhR is a master regulator for controlling the formation of not only the PDH complex but also the respiratory electron transport system.

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Mishra, Sujata R., e Surendra Chandra Sabat. "Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction". Zeitschrift für Naturforschung C 53, n. 9-10 (1 ottobre 1998): 849–56. http://dx.doi.org/10.1515/znc-1998-9-1011.

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Stimulatory effect of divalent cations like calcium (Ca2+) and magnesium (Mg2+) was investigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (NH2OH) - or alkaline Tris - washed thylakoid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimulation of electron transport activity was found. The apparent Km of Ca2+ dependent stimulation of electron flow from H2O (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimulation of electron transport activity in NH2OH - or Tris - washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with NH2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in NH2OH - or Tris - washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Yz and reaction center of photosystem II.

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Matsubayashi, Makoto, Daniel Ken Inaoka, Keisuke Komatsuya, Takeshi Hatta, Fumiya Kawahara, Kimitoshi Sakamoto, Kenji Hikosaka et al. "Novel Characteristics of Mitochondrial Electron Transport Chain from Eimeria tenella". Genes 10, n. 1 (8 gennaio 2019): 29. http://dx.doi.org/10.3390/genes10010029.

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Eimeria tenella is an intracellular apicomplexan parasite, which infects cecal epithelial cells from chickens and causes hemorrhagic diarrhea and eventual death. We have previously reported the comparative RNA sequence analysis of the E. tenella sporozoite stage between virulent and precocious strains and showed that the expression of several genes involved in mitochondrial electron transport chain (ETC), such as type II NADH dehydrogenase (NDH-2), complex II (succinate:quinone oxidoreductase), malate:quinone oxidoreductase (MQO), and glycerol-3-phosphate dehydrogenase (G3PDH), were upregulated in virulent strain. To study E. tenella mitochondrial ETC in detail, we developed a reproducible method for preparation of mitochondria-rich fraction from sporozoites, which maintained high specific activities of dehydrogenases, such as NDH-2 followed by G3PDH, MQO, complex II, and dihydroorotate dehydrogenase (DHODH). Of particular importance, we showed that E. tenella sporozoite mitochondria possess an intrinsic ability to perform fumarate respiration (via complex II) in addition to the classical oxygen respiration (via complexes III and IV). Further analysis by high-resolution clear native electrophoresis, activity staining, and nano-liquid chromatography tandem-mass spectrometry (nano-LC-MS/MS) provided evidence of a mitochondrial complex II-III-IV supercomplex. Our analysis suggests that complex II from E. tenella has biochemical features distinct to known orthologues and is a potential target for the development of new anticoccidian drugs.

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Lapuente-Brun, Esther, Raquel Moreno-Loshuertos, Rebeca Acín-Pérez, Ana Latorre-Pellicer, Carmen Colás, Eduardo Balsa, Ester Perales-Clemente et al. "Supercomplex Assembly Determines Electron Flux in the Mitochondrial Electron Transport Chain". Science 340, n. 6140 (27 giugno 2013): 1567–70. http://dx.doi.org/10.1126/science.1230381.

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The textbook description of mitochondrial respiratory complexes (RCs) views them as free-moving entities linked by the mobile carriers coenzyme Q (CoQ) and cytochrome c (cyt c). This model (known as the fluid model) is challenged by the proposal that all RCs except complex II can associate in supercomplexes (SCs). The proposed SCs are the respirasome (complexes I, III, and IV), complexes I and III, and complexes III and IV. The role of SCs is unclear, and their existence is debated. By genetic modulation of interactions between complexes I and III and III and IV, we show that these associations define dedicated CoQ and cyt c pools and that SC assembly is dynamic and organizes electron flux to optimize the use of available substrates.

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Tanigawa, Minoru, Tomomitsu Shinohara, Katsushi Nishimura, Kumiko Nagata, Morio Ishizuka e Yoko Nagata. "Purification of Helicobacter pylori NCTC 11637 Cytochrome bc1 and Respiration with d-Proline as a Substrate". Journal of Bacteriology 192, n. 5 (18 dicembre 2009): 1410–15. http://dx.doi.org/10.1128/jb.01111-09.

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ABSTRACT Helicobacter pylori is a microaerophilic bacterium associated with gastric inflammation and peptic ulcers. Knowledge of how pathogenic organisms produce energy is important from a therapeutic point of view. We found d-amino acid dehydrogenase-mediated electron transport from d-proline or d-alanine to oxygen via the respiratory chain in H. pylori. Coupling of the electron transport to ATP synthesis was confirmed by using uncoupler reagents. We reconstituted the electron transport chain to demonstrate the electron flow from the d-amino acids to oxygen using the recombinant cytochrome bc 1 complex, cytochrome c-553, and the terminal oxidase cytochrome cbb 3 complex. Upon addition of the recombinant d-amino acid dehydrogenase and d-proline or d-alanine to the reconstituted electron transport system, reduction of cytochrome cbb 3 and oxygen consumption was revealed spectrophotometrically and polarographically, respectively. Among the constituents of H. pylori's electron transport chain, only the cytochrome bc 1 complex had been remained unpurified. Therefore, we cloned and sequenced the H. pylori NCTC 11637 cytochrome bc 1 gene clusters encoding Rieske Fe-S protein, cytochrome b, and cytochrome c 1, with calculated molecular masses of 18 kDa, 47 kDa, and 32 kDa, respectively, and purified the recombinant monomeric protein complex with a molecular mass of 110 kDa by gel filtration. The absorption spectrum of the recombinant cytochrome bc 1 complex showed an α peak at 561 nm with a shoulder at 552 nm.

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Kruse, Thomas, Bram A. van de Pas, Ariane Atteia, Klaas Krab, Wilfred R. Hagen, Lynne Goodwin, Patrick Chain et al. "Genomic, Proteomic, and Biochemical Analysis of the Organohalide Respiratory Pathway in Desulfitobacterium dehalogenans". Journal of Bacteriology 197, n. 5 (15 dicembre 2014): 893–904. http://dx.doi.org/10.1128/jb.02370-14.

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Desulfitobacterium dehalogenansis able to grow by organohalide respiration using 3-chloro-4-hydroxyphenyl acetate (Cl-OHPA) as an electron acceptor. We used a combination of genome sequencing, biochemical analysis of redox active components, and shotgun proteomics to study elements of the organohalide respiratory electron transport chain. The genome ofDesulfitobacterium dehalogenansJW/IU-DC1Tconsists of a single circular chromosome of 4,321,753 bp with a GC content of 44.97%. The genome contains 4,252 genes, including six rRNA operons and six predicted reductive dehalogenases. One of the reductive dehalogenases, CprA, is encoded by a well-characterizedcprTKZEBACDgene cluster. Redox active components were identified in concentrated suspensions of cells grown on formate and Cl-OHPA or formate and fumarate, using electron paramagnetic resonance (EPR), visible spectroscopy, and high-performance liquid chromatography (HPLC) analysis of membrane extracts. In cell suspensions, these components were reduced upon addition of formate and oxidized after addition of Cl-OHPA, indicating involvement in organohalide respiration. Genome analysis revealed genes that likely encode the identified components of the electron transport chain from formate to fumarate or Cl-OHPA. Data presented here suggest that the first part of the electron transport chain from formate to fumarate or Cl-OHPA is shared. Electrons are channeled from an outward-facing formate dehydrogenase via menaquinones to a fumarate reductase located at the cytoplasmic face of the membrane. When Cl-OHPA is the terminal electron acceptor, electrons are transferred from menaquinones to outward-facing CprA, via an as-yet-unidentified membrane complex, and potentially an extracellular flavoprotein acting as an electron shuttle between the quinol dehydrogenase membrane complex and CprA.

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Guan, T., S. Müller, G. Klier, N. Panté, J. M. Blevitt, M. Haner, B. Paschal, U. Aebi e L. Gerace. "Structural analysis of the p62 complex, an assembly of O-linked glycoproteins that localizes near the central gated channel of the nuclear pore complex." Molecular Biology of the Cell 6, n. 11 (novembre 1995): 1591–603. http://dx.doi.org/10.1091/mbc.6.11.1591.

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The p62 complex is an oligomeric assembly of O-linked glycoproteins of the nuclear pore complex that interacts with cytosolic transport factors and is part of the machinery for nuclear protein import. In this study we have purified the p62 complex from rat liver nuclear envelopes and analyzed its structure and composition. The p62 complex consists of four distinct polypeptides (p62, p58, p54, and p45) and has a mass of approximately 234 kDa, calculated from its hydrodynamic properties and supported by chemical cross-linking and scanning transmission electron microscopy. These data suggest that the p62 complex contains one copy of each constituent polypeptide. Analysis of preparations of the p62 complex by electron microscopy using rotary metal shadowing and negative staining revealed donut-shaped particles with a diameter of approximately 15 nm. Immunogold electron microscopy of isolated rat liver nuclear envelopes demonstrated that p62 occurs on both the nucleoplasmic and cytoplasmic sides of the pore complex near the central gated channel involved in active transport of proteins and RNAs. The properties and localization of the p62 complex suggest that it may be involved in binding transport ligands near the center of the nuclear pore complex and in subsequently transferring them to the gated transport channel.

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Parrish, Jonathan C., J. Guy Guillemette e Carmichael JA Wallace. "Contribution of leucine 85 to the structure and function of Saccharomyces cerevisiae iso-1 cytochrome c". Biochemistry and Cell Biology 79, n. 4 (1 agosto 2001): 517–24. http://dx.doi.org/10.1139/o01-077.

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Cytochrome c is a small electron-transport protein whose major role is to transfer electrons between complex III (cytochrome reductase) and complex IV (cytochrome c oxidase) in the inner mitochondrial membrane of eukaryotes. Cytochrome c is used as a model for the examination of protein folding and structure and for the study of biological electron-transport processes. Amongst 96 cytochrome c sequences, residue 85 is generally conserved as either isoleucine or leucine. Spatially, the side chain is associated closely with that of the invariant residue Phe82, and this interaction may be important for optimal cytochrome c activity. The functional role of residue 85 has been examined using six site-directed mutants of Saccharomyces cerevisiae iso-1 cytochrome c, including, for the first time, kinetic data for electron transfer with the principle physiological partners. Results indicate two likely roles for the residue: first, heme crevice resistance to ligand exchange, sensitive to both the hydrophobicity and volume of the side chain; second, modulation of electron-transport activity through maintenance of the hydrophobic character of the protein in the vicinity of Phe82 and the exposed heme edge, and possibly of the ability of this region to facilitate redox-linked conformational change.Key words: protein engineering, cytochrome c, structure-function relations, electron transfer, hydrophobic packing.

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Harrison, Elizabeth. "Role-Playing Activity to Demonstrate the Electron Transport Chain". American Biology Teacher 82, n. 5 (1 maggio 2020): 338–40. http://dx.doi.org/10.1525/abt.2020.82.5.338.

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The role of the electron transport chain, its associated proteins, and carrier molecules can be difficult for introductory biology students to understand. Role-playing activities provide a simple, active, cost-effective method for demonstrating and comprehending complex biological processes. This role-playing activity was designed to help introductory biology students learn the role of the electron transport chain in the synthesis of ATP. The activity can be completed within a single class period and, when combined with a post-activity writing assignment, can enhance student understanding of how the electron transport chain functions.

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Storti, Mattia, Maria Paola Puggioni, Anna Segalla, Tomas Morosinotto e Alessandro Alboresi. "The chloroplast NADH dehydrogenase-like complex influences the photosynthetic activity of the moss Physcomitrella patens". Journal of Experimental Botany 71, n. 18 (4 giugno 2020): 5538–48. http://dx.doi.org/10.1093/jxb/eraa274.

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Abstract Alternative electron pathways contribute to regulation of photosynthetic light reactions to adjust to metabolic demands in dynamic environments. The chloroplast NADH dehydrogenase-like (NDH) complex mediates the cyclic electron transport pathway around PSI in different cyanobacteria, algae, and plant species, but it is not fully conserved in all photosynthetic organisms. In order to assess how the physiological role of this complex changed during plant evolution, we isolated Physcomitrella patens lines knocked out for the NDHM gene that encodes a subunit fundamental for the activity of the complex. ndhm knockout mosses indicated high PSI acceptor side limitation upon abrupt changes in illumination. In P. patens, pseudo-cyclic electron transport mediated by flavodiiron proteins (FLVs) was also shown to prevent PSI over-reduction in plants exposed to light fluctuations. flva ndhm double knockout mosses had altered photosynthetic performance and growth defects under fluctuating light compared with the wild type and single knockout mutants. The results showed that while the contribution of NDH to electron transport is minor compared with FLV, NDH still participates in modulating photosynthetic activity, and it is critical to avoid PSI photoinhibition, especially when FLVs are inactive. The functional overlap between NDH- and FLV-dependent electron transport supports PSI activity and prevents its photoinhibition under light variations.

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29

White, Gaye F., Zhi Shi, Liang Shi, Alice C. Dohnalkova, James K. Fredrickson, John M. Zachara, Julea N. Butt, David J. Richardson e Thomas A. Clarke. "Development of a proteoliposome model to probe transmembrane electron-transfer reactions". Biochemical Society Transactions 40, n. 6 (21 novembre 2012): 1257–60. http://dx.doi.org/10.1042/bst20120116.

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The mineral-respiring bacterium Shewanella oneidensis uses a protein complex, MtrCAB, composed of two decahaem cytochromes brought together inside a transmembrane porin to transport electrons across the outer membrane to a variety of mineral-based electron acceptors. A proteoliposome system has been developed that contains Methyl Viologen as an internalized electron carrier and valinomycin as a membrane-associated cation exchanger. These proteoliposomes can be used as a model system to investigate MtrCAB function.

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30

Kocherga, Margaret, Jose Castaneda, Michael G. Walter, Yong Zhang, Nemah-Allah Saleh, Le Wang, Daniel S. Jones et al. "Si(bzimpy)2 – a hexacoordinate silicon pincer complex for electron transport and electroluminescence". Chemical Communications 54, n. 100 (2018): 14073–76. http://dx.doi.org/10.1039/c8cc07681b.

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31

Miller, Kenneth R., e Jules S. Jacob. "Surface structure of the photosystem II complex". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 196–97. http://dx.doi.org/10.1017/s0424820100085289.

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The Photosystem II (PS-II) complex is organized around a photosynthetic reaction center (RC) embedded in the photosynthetic membrane. PS-II traps the energy of sunlight and uses it drive highenergy electron transport across the photosynthetic membrane. PS-II is closely associated with a group of proteins known as the oxygen-evolving complex (OEC), which are bound to the inner surface of the photosynthetic membrane. This complex splits water to yield electrons that are passed to the RC, releasing molecular oxygen. We have used freeze-etch electron microscopy to study 2-dimensional crystals of the PS-II complex obtained from a photosynthetic mutant of barley (viridiszb63) kindly provided by Dr. David Simpson of the Carlsberg Institute of Copenhagen (Simpson & von Wettstein, 1980). The photosynthetic membranes of these mutant plants lack photosystem I, and consequently contain extensive crystalline membrane regions enriched in PS-II. These plants are an excellent source of PS-II sheetlike crystals, obtainable without the use of detergents or chemical modification: Figure 1, prepared by quick-freezing, deep-etching, and rotary shadowing, illustrates the appearance of these sheetlike crystals.

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32

Liang, C. J., Z. R. Hong, X. Y. Liu, D. X. Zhao, D. Zhao, W. L. Li, J. B. Peng, J. Q. Yu, C. S. Lee e S. T. Lee. "Organic electroluminescent devices using europium complex as an electron-transport emitting layer". Thin Solid Films 359, n. 1 (gennaio 2000): 14–16. http://dx.doi.org/10.1016/s0040-6090(99)00713-0.

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33

Tikhonov, Alexander N. "The cytochrome b6f complex at the crossroad of photosynthetic electron transport pathways". Plant Physiology and Biochemistry 81 (agosto 2014): 163–83. http://dx.doi.org/10.1016/j.plaphy.2013.12.011.

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34

Schlegel, Katharina, Cornelia Welte, Uwe Deppenmeier e Volker Müller. "Electron transport during aceticlastic methanogenesis byMethanosarcina acetivoransinvolves a sodium-translocating Rnf complex". FEBS Journal 279, n. 24 (8 novembre 2012): 4444–52. http://dx.doi.org/10.1111/febs.12031.

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35

Robb, Ellen L., Andrew R. Hall, Tracy A. Prime, Simon Eaton, Marten Szibor, Carlo Viscomi, Andrew M. James e Michael P. Murphy. "Control of mitochondrial superoxide production by reverse electron transport at complex I". Journal of Biological Chemistry 293, n. 25 (9 maggio 2018): 9869–79. http://dx.doi.org/10.1074/jbc.ra118.003647.

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36

Jones, T. W., I. L. Tregillis e D. Ryu. "Computation of relativistic electron acceleration, transport and emissions in complex astrophysical flows". Computer Physics Communications 147, n. 1-2 (agosto 2002): 476–79. http://dx.doi.org/10.1016/s0010-4655(02)00335-1.

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37

Lee, Seonmin, Eunyoung Tak, Jisun Lee, MA Rashid, Michael P. Murphy, Joohun Ha e Sung Soo Kim. "Mitochondrial H2O2 generated from electron transport chain complex I stimulates muscle differentiation". Cell Research 21, n. 5 (29 marzo 2011): 817–34. http://dx.doi.org/10.1038/cr.2011.55.

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38

JÜNEMANN, SUSANNE, e JOHN M. WRIGGLESWORTH. "Inhibitors of electron transport in the cytochrome bd complex of Azotobacter vinelandii". Biochemical Society Transactions 22, n. 3 (1 agosto 1994): 287S. http://dx.doi.org/10.1042/bst022287s.

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39

Maeda, H., R. Sakamoto e H. Nishihara. "Electron Transport Behavior Analysis of Bis(terpyridine) Metal Complex Wires on Electrodes". ECS Transactions 75, n. 11 (23 settembre 2016): 17–24. http://dx.doi.org/10.1149/07511.0017ecst.

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40

Herter, Stefan Michael, Christiane Maria Kortlüke e G. Drews. "Complex I of Rhodobacter capsulatus and its role in reverted electron transport". Archives of Microbiology 169, n. 2 (5 febbraio 1998): 98–105. http://dx.doi.org/10.1007/s002030050548.

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41

Sirey, Tamara M., e Chris P. Ponting. "Insights into the post-transcriptional regulation of the mitochondrial electron transport chain". Biochemical Society Transactions 44, n. 5 (15 ottobre 2016): 1491–98. http://dx.doi.org/10.1042/bst20160100.

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Abstract (sommario):

The regulation of the mitochondrial electron transport chain is central to the control of cellular homeostasis. There are significant gaps in our understanding of how the expression of the mitochondrial and nuclear genome-encoded components of the electron transport chain are co-ordinated, and how the assembly of the protein complexes that constitute the electron transport chain are regulated. Furthermore, the role post-transcriptional gene regulation may play in modulating these processes needs to be clarified. This review summarizes the current knowledge regarding the post-transcriptional gene regulation of the electron transport chain and highlights how noncoding RNAs may contribute significantly both to complex electron transport chain regulatory networks and to mitochondrial dysfunction.

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42

Panagaki, Theodora, Elisa B. Randi, Fiona Augsburger e Csaba Szabo. "Overproduction of H2S, generated by CBS, inhibits mitochondrial Complex IV and suppresses oxidative phosphorylation in Down syndrome". Proceedings of the National Academy of Sciences 116, n. 38 (3 settembre 2019): 18769–71. http://dx.doi.org/10.1073/pnas.1911895116.

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Down syndrome (DS) is associated with significant perturbances in mitochondrial function. Here we tested the hypothesis that the suppression of mitochondrial electron transport in DS cells is due to high expression of cystathionine-β-synthase (CBS) and subsequent overproduction of the gaseous transmitter hydrogen sulfide (H2S). Fibroblasts from DS individuals showed higher CBS expression than control cells; CBS localization was both cytosolic and mitochondrial. DS cells produced significantly more H2S and polysulfide and exhibited a profound suppression of mitochondrial electron transport, oxygen consumption, and ATP generation. DS cells also exhibited slower proliferation rates. In DS cells, pharmacological inhibition of CBS activity with aminooxyacetate or siRNA-mediated silencing of CBS normalized cellular H2S levels, restored Complex IV activity, improved mitochondrial electron transport and ATP synthesis, and restored cell proliferation. Thus, CBS-derived H2S is responsible for the suppression of mitochondrial function in DS cells. When H2S overproduction is corrected, the tonic suppression of Complex IV is lifted, and mitochondrial electron transport is restored. CBS inhibition offers a potential approach for the pharmacological correction of DS-associated mitochondrial dysfunction.

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43

Lesnefsky, Edward J., Tatyana I. Gudz, Catharina T. Migita, Masao Ikeda-Saito, Medhat O. Hassan, Peter J. Turkaly e Charles L. Hoppel. "Ischemic Injury to Mitochondrial Electron Transport in the Aging Heart: Damage to the Iron–Sulfur Protein Subunit of Electron Transport Complex III". Archives of Biochemistry and Biophysics 385, n. 1 (gennaio 2001): 117–28. http://dx.doi.org/10.1006/abbi.2000.2066.

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44

Sakamoto, Ryota, Kuo-Hui Wu, Ryota Matsuoka, Hiroaki Maeda e Hiroshi Nishihara. "π-Conjugated bis(terpyridine)metal complex molecular wires". Chemical Society Reviews 44, n. 21 (2015): 7698–714. http://dx.doi.org/10.1039/c5cs00081e.

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Abstract (sommario):

This review focuses on the bottom-up fabrication of linear and branched bis(terpyridine)metal complex wires on electrode surfaces, which feature distinct and characteristic electronic functionalities such as intra-wire redox conduction and excellent long-range electron transport ability.

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45

Ricci, Jean-Ehrland, Roberta A. Gottlieb e Douglas R. Green. "Caspase-mediated loss of mitochondrial function and generation of reactive oxygen species during apoptosis". Journal of Cell Biology 160, n. 1 (6 gennaio 2003): 65–75. http://dx.doi.org/10.1083/jcb.200208089.

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Abstract (sommario):

During apoptosis, the permeabilization of the mitochondrial outer membrane allows the release of cytochrome c, which induces caspase activation to orchestrate the death of the cell. Mitochondria rapidly lose their transmembrane potential (ΔΨm) and generate reactive oxygen species (ROS), both of which are likely to contribute to the dismantling of the cell. Here we show that both the rapid loss of ΔΨm and the generation of ROS are due to the effects of activated caspases on mitochondrial electron transport complexes I and II. Caspase-3 disrupts oxygen consumption induced by complex I and II substrates but not that induced by electron transfer to complex IV. Similarly, ΔΨm generated in the presence of complex I or II substrates is disrupted by caspase-3, and ROS are produced. Complex III activity measured by cytochrome c reduction remains intact after caspase-3 treatment. In apoptotic cells, electron transport and oxygen consumption that depends on complex I or II was disrupted in a caspase-dependent manner. Our results indicate that after cytochrome c release the activation of caspases feeds back on the permeabilized mitochondria to damage mitochondrial function (loss of ΔΨm) and generate ROS through effects of caspases on complex I and II in the electron transport chain.

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46

Otten, Marijke F., John van der Oost, Willem N. M. Reijnders, Hans V. Westerhoff, Bernd Ludwig e Rob J. M. Van Spanning. "Cytochromes c550,c552, and c1 in the Electron Transport Network of Paracoccus denitrificans: Redundant or Subtly Different in Function?" Journal of Bacteriology 183, n. 24 (15 dicembre 2001): 7017–26. http://dx.doi.org/10.1128/jb.183.24.7017-7026.2001.

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ABSTRACT Paracoccus denitrificans strains with mutations in the genes encoding the cytochrome c 550,c 552, or c 1 and in combinations of these genes were constructed, and their growth characteristics were determined. Each mutant was able to grow heterotrophically with succinate as the carbon and free-energy source, although their specific growth rates and maximum cell numbers fell variably behind those of the wild type. Maximum cell numbers and rates of growth were also reduced when these strains were grown with methylamine as the sole free-energy source, with the triple cytochromec mutant failing to grow on this substrate. Under anaerobic conditions in the presence of nitrate, none of the mutant strains lacking the cytochrome bc 1 complex reduced nitrite, which is cytotoxic and accumulated in the medium. The cytochrome c 550-deficient mutant did denitrify provided copper was present. The cytochromec 552 mutation had no apparent effect on the denitrifying potential of the mutant cells. The studies show that the cytochromes c have multiple tasks in electron transfer. The cytochrome bc 1 complex is the electron acceptor of the Q-pool and of amicyanin. It is also the electron donor to cytochromes c 550 andc 552 and to thecbb 3-type oxidase. Cytochromec 552 is an electron acceptor both of the cytochrome bc 1 complex and of amicyanin, as well as a dedicated electron donor to theaa 3-type oxidase. Cytochromec 550 can accept electrons from the cytochrome bc 1 complex and from amicyanin, whereas it is also the electron donor to both cytochromec oxidases and to at least the nitrite reductase during denitrification. Deletion of the c-type cytochromes also affected the concentrations of remaining cytochromes c, suggesting that the organism is plastic in that it adjusts its infrastructure in response to signals derived from changed electron transfer routes.

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47

Eguchi, Reo, Yuya Takekuma, Tsuyoshi Ochiai e Morio Nagata. "Improving Interfacial Charge-Transfer Transitions in Nb-Doped TiO2 Electrodes with 7,7,8,8-Tetracyanoquinodimethane". Catalysts 8, n. 9 (30 agosto 2018): 367. http://dx.doi.org/10.3390/catal8090367.

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Abstract (sommario):

Interfacial charge-transfer (ICT) transitions involved in charge-separation mechanisms are expected to enable efficient photovoltaic conversions through one-step charge-separation processes. With this in mind, the charge-transfer complex fabricated from TiO2 nanoparticles and 7,7,8,8-tetracyanoquinodimethane (TCNQ) has been applied to dye-sensitized solar cells. However, rapid carrier recombination from the conduction band of TiO2 to the highest occupied molecular orbital (HOMO) of TCNQ remains a major issue for this complex. In this study, to inhibit surface-complex recombinations, we prepared Nb-doped TiO2 nanoparticles with different atomic ratios for enhanced electron transport. To investigate the effects of doping on electron injection through ICT transitions, these materials were examined as photoelectrodes. When TiO2 was doped with 1.5 mol % Nb, the Fermi level of the TiO2 electrode shifted toward the conduction band minimum, which improved electron back-contact toward the HOMO of TCNQ. The enhancement in electron transport led to increases in both short circuit current and open circuit voltage, resulting in a slight (1.1% to 1.3%) improvement in photovoltaic conversion efficiency compared to undoped TiO2. Such control of electron transport within the photoelectrode is attributed to improvements in electron injection through ICT transitions.

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48

Daldal, Fevzi, Sevnur Mandaci, Christine Winterstein, Hannu Myllykallio, Kristen Duyck e Davide Zannoni. "Mobile Cytochrome c2 and Membrane-Anchored Cytochrome cy Are Both Efficient Electron Donors to the cbb3- andaa3-Type Cytochrome cOxidases during Respiratory Growth of Rhodobacter sphaeroides". Journal of Bacteriology 183, n. 6 (15 marzo 2001): 2013–24. http://dx.doi.org/10.1128/jb.183.6.2013-2024.2001.

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ABSTRACT We have recently established that the facultative phototrophic bacterium Rhodobacter sphaeroides, like the closely relatedRhodobacter capsulatus species, contains both the previously characterized mobile electron carrier cytochromec 2 (cyt c 2) and the more recently discovered membrane-anchored cytc y. However, R. sphaeroides cytc y, unlike that of R. capsulatus, is unable to function as an efficient electron carrier between the photochemical reaction center and the cyt bc 1complex during photosynthetic growth. Nonetheless, R. sphaeroides cyt c y can act at least in R. capsulatus as an electron carrier between the cytbc 1 complex and thecbb 3-type cyt c oxidase (cbb 3-Cox) to support respiratory growth. Since R. sphaeroides harbors both acbb 3-Cox and anaa 3-type cyt c oxidase (aa 3-Cox), we examined whetherR. sphaeroides cyt c y can act as an electron carrier to either or both of these respiratory terminal oxidases. R. sphaeroides mutants which lacked either cyt c 2 or cyt c y and either the aa 3-Cox or thecbb 3-Cox were obtained. These double mutants contained linear respiratory electron transport pathways between the cyt bc 1 complex and the cytc oxidases. They were characterized with respect to growth phenotypes, contents of a-, b-, andc-type cytochromes, cyt c oxidase activities, and kinetics of electron transfer mediated by cytc 2 or cyt c y. The findings demonstrated that both cyt c 2 and cytc y are able to carry electrons efficiently from the cyt bc 1 complex to either thecbb 3-Cox or theaa 3-Cox. Thus, no dedicated electron carrier for either of the cyt c oxidases is present in R. sphaeroides. However, under semiaerobic growth conditions, a larger portion of the electron flow out of the cytbc 1 complex appears to be mediated via the cytc 2-to-cbb 3-Coxand cytcy -to-cbb 3-Coxsubbranches. The presence of multiple electron carriers and cytc oxidases with different properties that can operate concurrently reveals that the respiratory electron transport pathways of R. sphaeroides are more complex than those ofR. capsulatus.

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ESPOSTI DEGLI, Mauro, Anna NGO, Gabrielle L. McMULLEN, Anna GHELLI, Francesca SPARLA, Bruna BENELLI, Marina RATTA e Anthony W. LINNANE. "The specificity of mitochondrial complex I for ubiquinones". Biochemical Journal 313, n. 1 (1 gennaio 1996): 327–34. http://dx.doi.org/10.1042/bj3130327.

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Abstract (sommario):

We report the first detailed study on the ubiquinone (coenzyme Q; abbreviated to Q) analogue specificity of mitochondrial complex I, NADH:Q reductase, in intact submitochondrial particles. The enzymic function of complex I has been investigated using a series of analogues of Q as electron acceptor substrates for both electron transport activity and the associated generation of membrane potential. Q analogues with a saturated substituent of one to three carbons at position 6 of the 2,3-dimethoxy-5-methyl-1,4-benzoquinone ring have the fastest rates of electron transport activity, and analogues with a substituent of seven to nine carbon atoms have the highest values of association constant derived from NADH:Q reductase activity. The rate of NADH:Q reductase activity is potently but incompletely inhibited by rotenone, and the residual rotenone-insensitive rate is stimulated by Q analogues in different ways depending on the hydrophobicity of their substituent. Membrane potential measurements have been undertaken to evaluate the energetic efficiency of complex I with various Q analogues. Only hydrophobic analogues such as nonyl-Q or undecyl-Q show an efficiency of membrane potential generation equivalent to that of endogenous Q. The less hydrophobic analogues as well as the isoprenoid analogue Q-2 are more efficient as substrates for the redox activity of complex I than for membrane potential generation. Thus the hydrophilic Q analogues act also as electron sinks and interact incompletely with the physiological Q site in complex I that pumps protons and generates membrane potential.

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50

KRUNGKRAI, J. "The multiple roles of the mitochondrion of the malarial parasite". Parasitology 129, n. 5 (5 ottobre 2004): 511–24. http://dx.doi.org/10.1017/s0031182004005888.

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Abstract (sommario):

Mitochondria of the malaria parasitePlasmodium falciparumare morphologically different between the asexual and sexual blood stages (gametocytes). In this paper recent findings of mitochondrial heterogeneity are reviewed based on their ultrastructural characteristics, metabolic activities and the differential expression of their genes in these 2 blood stages of the parasite. The existence of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II), cytochrome c reductase (complex III) and cytochrome c oxidase (complex IV) suggests that the biochemically active electron transport system operates in this parasite. There is also an alternative electron transport branch pathway, including an anaerobic function of complex II. One of the functional roles of the mitochondrion in the parasite is the coordination of pyrimidine biosynthesis, the electron transport system and oxygen utilization via dihydroorotate dehydrogenase and coenzyme Q. Complete sets of genes encoding enzymes of the tricarboxylic acid cycle and the ATP synthase complex are predicted fromP. falciparumgenomics information. Other metabolic roles of this organelle include membrane potential maintenance, haem and coenzyme Q biosynthesis, and oxidative phosphorylation. Furthermore, the mitochondrion may be a chemotherapeutic target for antimalarial drug development. The antimalarial drug atovaquone targets the mitochondrion.

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