scholarly journals Catalytic photoinduced electron transport across a lipid bilayer mediated by a membrane-soluble electron relay

2015 ◽  
Vol 51 (96) ◽  
pp. 17128-17131 ◽  
Author(s):  
B. Limburg ◽  
E. Bouwman ◽  
S. Bonnet
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Lipid Bilayer ◽  
Electron Donor ◽  
Electron Acceptor ◽  
The Other

Unidirectional photocatalytic electron transfer from a hydrophilic electron donor encapsulated in the interior of a liposome, to a hydrophilic electron acceptor on the other side of the membrane, has been achieved using the simple membrane-soluble electron relay 1-methoxy-N-methylphenazinium (MMP+).

Ultrafast IR spectroscopy of photo-induced electron transfer in self-assembled donor–acceptor coordination cages

2017 ◽  
Vol 19 (21) ◽  
pp. 13596-13603 ◽  
Author(s):  
J. Ahrens ◽  
M. Frank ◽  
G. H. Clever ◽  
D. Schwarzer
Keyword(s):  
Electron Transfer ◽  
Ir Spectroscopy ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Donor Acceptor ◽  
Coordination Cages ◽  
Photo Induced Electron Transfer ◽  
Self Assembled

Photo-excitation of self-assembled palladium based coordination cages consisting of phenothiazine electron donor and anthraquinone electron acceptor ligands produce charge separated states with lifetimes of up to 1.5 ns.

scholarly journals 6-Hydroxypseudooxynicotine Dehydrogenase Delivers Electrons to Electron Transfer Flavoprotein during Nicotine Degradation by Agrobacterium tumefaciens S33

2019 ◽  
Vol 85 (11) ◽  
Author(s):  
Rongshui Wang ◽  
Jihong Yi ◽  
Jinmeng Shang ◽  
Wenjun Yu ◽  
Zhifeng Li ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Agrobacterium Tumefaciens ◽  
Electron Transport ◽  
Electron Acceptor ◽  
Aromatic Compounds ◽  
Coenzyme Q ◽  
Content Type ◽  
Electron Transfer Flavoprotein ◽  
Nicotine Degradation

ABSTRACT Agrobacterium tumefaciens S33 degrades nicotine via a novel hybrid of the pyridine and the pyrrolidine pathways. The hybrid pathway consists of at least six steps involved in oxidoreductive reactions before the N-heterocycle can be broken down. Collectively, the six steps allow electron transfer from nicotine and its intermediates to the final acceptor O2 via the electron transport chain (ETC). 6-Hydroxypseudooxynicotine oxidase, renamed 6-hydroxypseudooxynicotine dehydrogenase in this study, has been characterized as catalyzing the fourth step using the artificial electron acceptor 2,6-dichlorophenolindophenol. Here, we used biochemical, genetic, and liquid chromatography-mass spectrometry (LC-MS) analyses to determine that 6-hydroxypseudooxynicotine dehydrogenase utilizes the electron transfer flavoprotein (EtfAB) as the physiological electron acceptor to catalyze the dehydrogenation of pseudooxynicotine, an analogue of the true substrate 6-hydroxypseudooxynicotine, in vivo, into 3-succinoyl-semialdehyde-pyridine. NAD(P)+, O2, and ferredoxin could not function as electron acceptors. The oxygen atom in the aldehyde group of the product 3-succinoyl-semialdehyde-pyridine was verified to be derived from H2O. Disruption of the etfAB genes in the nicotine-degrading gene cluster decreased the growth rate of A. tumefaciens S33 on nicotine but not on 6-hydroxy-3-succinoylpyridine, an intermediate downstream of the hybrid pathway, indicating the requirement of EtfAB for efficient nicotine degradation. The electrons were found to be further transferred from the reduced EtfAB to coenzyme Q by the catalysis of electron transfer flavoprotein:ubiquinone oxidoreductase. These results aid in an in-depth understanding of the electron transfer process and energy metabolism involved in the nicotine oxidation and provide novel insights into nicotine catabolism in bacteria. IMPORTANCE Nicotine has been studied as a model for toxic N-heterocyclic aromatic compounds. Microorganisms can catabolize nicotine via various pathways and conserve energy from its oxidation. Although several oxidoreductases have been characterized to participate in nicotine degradation, the electron transfer involved in these processes is poorly understood. In this study, we found that 6-hydroxypseudooxynicotine dehydrogenase, a key enzyme in the hybrid pyridine and pyrrolidine pathway for nicotine degradation in Agrobacterium tumefaciens S33, utilizes EtfAB as a physiological electron acceptor. Catalyzed by the membrane-associated electron transfer flavoprotein:ubiquinone oxidoreductase, the electrons are transferred from the reduced EtfAB to coenzyme Q, which then could enter into the classic ETC. Thus, the route for electron transport from the substrate to O2 could be constructed, by which ATP can be further sythesized via chemiosmosis to support the baterial growth. These findings provide new knowledge regarding the catabolism of N-heterocyclic aromatic compounds in microorganisms.

scholarly journals Respiration and Growth of Shewanella decolorationis S12 with an Azo Compound as the Sole Electron Acceptor

2006 ◽  
Vol 73 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Yiguo Hong ◽  
Meiying Xu ◽  
Jun Guo ◽  
Zhicheng Xu ◽  
Xingjuan Chen ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Azo Dyes ◽  
Anaerobic Respiration ◽  
Defined Medium ◽  
Whole Cells ◽  
Azo Compound ◽  
Transport Chain ◽  
Dissimilatory Azoreduction

ABSTRACT The ability of Shewanella decolorationis S12 to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory azoreduction was investigated. This microorganism can reduce a variety of azo dyes by use of formate, lactate, pyruvate, or H2 as the electron donor. Furthermore, strain S12 grew to a maximal density of 3.0 × 107 cells per ml after compete reduction of 2.0 mM amaranth in a defined medium. This was accompanied by a stoichiometric consumption of 4.0 mM formate over time when amaranth and formate were supplied as the sole electron acceptor and donor, respectively, suggesting that microbial azoreduction is an electron transport process and that this electron transport can yield energy to support growth. Purified membranous, periplasmic, and cytoplasmic fractions from S12 were analyzed, but only the membranous fraction was capable of reducing azo dyes with formate, lactate, pyruvate, or H2 as the electron donor. The presence of 5 μM Cu2+ ions, 200 μM dicumarol, 100 μM stigmatellin, and 100 μM metyrapone inhibited anaerobic azoreduction activity by both whole cells and the purified membrane fraction, showing that dehydrogenases, cytochromes, and menaquinone are essential electron transfer components for azoreduction. These results provide evidence that the microbial anaerobic azoreduction is linked to the electron transport chain and suggest that the dissimilatory azoreduction is a form of microbial anaerobic respiration. These findings not only expand the number of potential electron acceptors known for microbial energy conservation but also elucidate the mechanisms of microbial anaerobic azoreduction.

THE INFLUENCE OF SUBSTITUENTS ON THE EASE AND DIRECTION OF RING OPENING IN THE LiAlH4–AlCl3 REDUCTIVE CLEAVAGE OF SUBSTITUTED 1,3-DIOXOLANES

1964 ◽  
Vol 42 (5) ◽  
pp. 990-1004 ◽  
Author(s):  
B. E. Leggetter ◽  
R. K. Brown
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Ring Opening ◽  
Room Temperature ◽  
Reductive Cleavage ◽  
The Other ◽  
Ring Cleavage ◽  
Other Hand ◽  
Influence Of Substituents

The room temperature hydrogenolysis by LiAlH4–AlCl3 of ether solutions of a number of 1,3-dioxolanes has been studied.Electron donor substituents on the C2 atom of the ring accelerate while electron acceptor substituents on C2 retard the reductive ring cleavage. The same effect but to a lesser extent is observed when these substituents are attached to the C4 or C5 atom of the ring.When electron donor substituents are attached to C4, ring cleavage occurs predominantly at the C2—O bond remote from the C4 position. On the other hand, electron-withdrawing groups attached to C4 give predominantly scission of the C2—O bond closer to the C4-substituted position. In contrast to this marked control over the direction of ring cleavage exhibited by substituents on C4, those on C2 generally have little or no effect on the direction of ring opening.A mechanistic interpretation of the results is presented.

scholarly journals Cytochromes c550,c552, and c1 in the Electron Transport Network of Paracoccus denitrificans: Redundant or Subtly Different in Function?

2001 ◽  
Vol 183 (24) ◽  
pp. 7017-7026 ◽  
Author(s):  
Marijke F. Otten ◽  
John van der Oost ◽  
Willem N. M. Reijnders ◽  
Hans V. Westerhoff ◽  
Bernd Ludwig ◽  
...  
Keyword(s):  
Energy Source ◽  
Electron Transfer ◽  
Free Energy ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Paracoccus Denitrificans ◽  
Cell Numbers ◽  
Genes Encoding ◽  
Maximum Cell ◽  
Specific Growth Rates

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.

Effect of proteolytic and lipolytic enzymes on the electron transport particle fraction of rhodospirillum rubrum

1970 ◽  
Vol 25 (12) ◽  
pp. 1448-1450 ◽  
Author(s):  
M. Boll
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Total Protein ◽  
Rhodospirillum Rubrum ◽  
The Other ◽  
Proteolytic Digestion ◽  
Particle Fraction ◽  
Lipolytic Enzymes ◽  
Transport Particle

Digestion of the electron transport particle fraction of Rhodospirillum rubrum with the proteases chymotrypsin, trypsin, subtilisin and pronase resulted in a release of protein from the membranal system. The solubilization was, however, limited to only 15 - 18 percent of the total protein, being the same with each of the four proteases. The enzymes catalyzing electron transfer which are located on these particles were not solubilized by the proteolytic digestion but were found to become differently inactivated already with low protease concentrations. The proteolytic attack revealed differences in the specificity of proteolysis between chymotrypsin and the other proteases

scholarly journals Electricity Production by Geobacter sulfurreducens Attached to Electrodes

2003 ◽  
Vol 69 (3) ◽  
pp. 1548-1555 ◽  
Author(s):  
Daniel R. Bond ◽  
Derek R. Lovley
Keyword(s):  
Electron Transfer ◽  
Fuel Cells ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Microbial Fuel Cells ◽  
Electrical Current ◽  
Geobacter Sulfurreducens ◽  
Electricity Production ◽  
Organic Substrates ◽  
Current Production

ABSTRACT Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 μM), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 μmol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (Eo′ =+0.37 V). The production of current in microbial fuel cell (65 mA/m2 of electrode surface) or poised-potential (163 to 1,143 mA/m2) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.

Fixed distance photoinduced electron transfer between Fe and Zn porphyrins encapsulated within the Zn HKUST-1 metal organic framework

2015 ◽  
Vol 44 (7) ◽  
pp. 2959-2963 ◽  
Author(s):  
Randy W. Larsen ◽  
Lukasz Wojtas
Keyword(s):  
Electron Transfer ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Photoinduced Electron Transfer ◽  
Metal Organic Framework ◽  
Fixed Distance ◽  
Metal Organic ◽  
Organic Framework

An attractive strategy for the development of photocatalytic metal organic framework (MOF) materials is to co-encapsulate a photoactive electron donor with a catalytic electron acceptor within the MOF.

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