Reductive Lithiation in the Absence of Aromatic Electron Carriers. A Steric Effect Manifested on the Surface of Lithium Metal Leads to a Difference in Relative Reactivity Depending on Whether the Aromatic Electron Carrier Is Present or Absent

2015 ◽  
Vol 80 (17) ◽  
pp. 8571-8582 ◽  
Author(s):  
Nicole Kennedy ◽  
Gang Lu ◽  
Peng Liu ◽  
Theodore Cohen
Keyword(s):  
Steric Effect ◽  
Relative Reactivity ◽  
Lithium Metal ◽  
Electron Carrier ◽  
Reductive Lithiation ◽  
Electron Carriers

scholarly journals Plastocyanin is the long-range electron carrier between photosystem II and photosystem I in plants

2020 ◽  
Vol 117 (26) ◽  
pp. 15354-15362 ◽  
Author(s):  
Ricarda Höhner ◽  
Mathias Pribil ◽  
Miroslava Herbstová ◽  
Laura Susanna Lopez ◽  
Hans-Henning Kunz ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Long Range ◽  
Narrow Range ◽  
Higher Plants ◽  
Regulatory Element ◽  
Photosynthetic Electron Transport ◽  
Electron Carrier ◽  
Mobile Electron ◽  
Electron Carriers

In photosynthetic electron transport, large multiprotein complexes are connected by small diffusible electron carriers, the mobility of which is challenged by macromolecular crowding. For thylakoid membranes of higher plants, a long-standing question has been which of the two mobile electron carriers, plastoquinone or plastocyanin, mediates electron transport from stacked grana thylakoids where photosystem II (PSII) is localized to distant unstacked regions of the thylakoids that harbor PSI. Here, we confirm that plastocyanin is the long-range electron carrier by employing mutants with different grana diameters. Furthermore, our results explain why higher plants have a narrow range of grana diameters since a larger diffusion distance for plastocyanin would jeopardize the efficiency of electron transport. In the light of recent findings that the lumen of thylakoids, which forms the diffusion space of plastocyanin, undergoes dynamic swelling/shrinkage, this study demonstrates that plastocyanin diffusion is a crucial regulatory element of plant photosynthetic electron transport.

Electron Transport to Assimilatory Nitrate Reductase in A zotobacter vinelandii

1981 ◽  
Vol 36 (11-12) ◽  
pp. 1030-1035 ◽  
Author(s):  
Hermann Bothe ◽  
Klaus-Peter Häger
Keyword(s):  
Electron Transport ◽  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Azotobacter Vinelandii ◽  
Additive Effects ◽  
Electron Carrier ◽  
Transport Chain ◽  
Solubilized Enzyme ◽  
Electron Carriers ◽  
Bound Electron

Abstract Assimilatory nitrate reductase was particle-bound in extracts from Azotobacter vinelandii. Nitrate reduction by particle fractions was dependent on NADPH and a particle-bound electron carrier. When the enzyme was solubilized from the particles by treatment with detergents, the particle-bound electron carrier could be substituted by ferredoxin or flavodoxin. Flavodoxin reduced at the expense of photoreduced deazaflavin was much more efficient than ferredoxin in transferring electrons to nitrate reductase. The addition of both ferredoxin and flavodoxin to the assays with photoreduced deazaflavin gave additive effects. With the solubilized enzyme, NADPH only poorly supported nitrate reduction even after the addition of electron carriers. The experiments indicate that A. vinelandii utilizes an electron transport chain between NADPH and nitrate reductase with some properties similar to those described for the generation of reductants to nitrogenase.

Reductive Functionalization of Single-Walled Carbon Nanotubes with Lithium Metal Catalyzed by Electron Carrier Additives

2008 ◽  
Vol 20 (13) ◽  
pp. 4433-4438 ◽  
Author(s):  
Ainara García-Gallastegui ◽  
Isabel Obieta ◽  
Izaskun Bustero ◽  
Gorka Imbuluzqueta ◽  
Jordi Arbiol ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Single Walled Carbon Nanotubes ◽  
Lithium Metal ◽  
Electron Carrier ◽  
Single Walled Carbon ◽  
Metal Catalyzed ◽  
Walled Carbon Nanotubes

scholarly journals The role of exogenous electron carriers in NAD(P)-dependent dehydrogenase cytochemistry studied in vitro and with a model system of polyacrylamide films.

1982 ◽  
Vol 30 (1) ◽  
pp. 12-20 ◽  
Author(s):  
C J Van Noorden ◽  
J Tas
Keyword(s):  
Dehydrogenase Activity ◽  
Nicotinamide Adenine Dinucleotide ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Model System ◽  
Tetrazolium Salt ◽  
Phenazine Methosulfate ◽  
Electron Carrier ◽  
Electron Carriers ◽  
Meldola Blue

The applicability of phenazine methosulfate, 1-methoxyphenazine methosulfate, menadione, and meldola blue as exogenous electron carriers for the cytochemical staining of nicotinamide adenine dinucleotide (phosphate) (NAD(P))-dependent dehydrogenases has been studied quantitatively with tetranitro BT in vitro and with a model system of polyacrylamide films incorporating either purified glucose-6-phosphate dehydrogenase or intact rat liver parenchymal cells. It was found that every assay in which a tetrazolium salt is used, whether or not an electron carrier is present, has to be carried out in darkness. Menadione did not appear to be useful, because electrons were not found to be transferred directly from reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) to this compound. Phenazine methosulfate at higher concentrations and meldola blue at concentrations optimal for carrying electrons to tetrazolium salts yielded a high level of "nothing dehydrogenase" activity in cell-containing films, but no inhibition of enzymatic activity was found. Factors involved in the interference of oxygen with tetrazolium salt reduction are discussed. 1-Methoxyphenazine methosulfate did not stain cellular compounds and caused only a very low nothing dehydrogenase activity. The cytochemical demonstration of dehydrogenase activity was shown to be independent on the concentration of 1-methoxyphenazine methosulfate used (50-1000 microM). It is concluded that 1-methoxyphenazine methosulfate is the exogenous electron carrier of choice.

Steric Effect Tuned Ion Solvation Enabling Stable Cycling of High-Voltage Lithium Metal Battery

2021 ◽  
Author(s):  
Yuelang Chen ◽  
Zhiao Yu ◽  
Paul Rudnicki ◽  
Huaxin Gong ◽  
Zhuojun Huang ◽  
...  
Keyword(s):  
High Voltage ◽  
Steric Effect ◽  
Ion Solvation ◽  
Lithium Metal ◽  
Lithium Metal Battery

scholarly journals Characterization of the Cofactors Involved in Non-Enzymatic Metmyoglobin Reduction In Vitro

2019 ◽  
Vol 3 (2) ◽  
Author(s):  
M. Denzer ◽  
H. Comstock ◽  
C. Mowery ◽  
N. Maheswarappa ◽  
G. Mafi ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Cytochrome C ◽  
Electron Donors ◽  
Meat Color ◽  
Electron Carrier ◽  
Enzymatic Reduction ◽  
Muscle Ph ◽  
Lower Temperature ◽  
Electron Carriers

ObjectivesConsumers’ meat purchasing decisions are strongly influenced by color. Myoglobin is the primary meat pigment that contributes to meat color. Myoglobin consists of an iron-containing heme ring and amino acids in the form of globin chains. Both the state of the heme iron and the type of ligand affects meat color. The consumer-preferred bright cherry-red color oxymyoglobin is formed when the iron is in the ferrous state and oxygen bind to the heme. The oxidation of oxymyoglobin or deoxymyoglobin results in the formation of the brown color, ferric metmyoglobin. Predominant metmyoglobin accumulation negatively impacts consumer purchasing choices. Although muscle type and pre- and post-harvest factors can influence meat discoloration, meat has an inherent ability to reduce metmyoglobin through enzymatic pathways, mitochondria-mediated pathways, and non-enzymatic mechanisms. In the enzymatic pathway, an electron from NADH is transferred to metmyoglobin by an enzyme and an electron carrier; while in mitochondria-mediated pathway, an electron from the electron-transport chain is transferred via cytochromes. Previous research speculated the role of non-enzymatic pathway in meat color; however, limited studies have characterized the cofactors present in a meat system. The objectives of this study were to characterize cofactors in non-enzymatic metmyoglobin reduction and determine the effect of storage temperature and postmortem muscle pH in-vitro.Materials and MethodsPurified equine metmyoglobin was reduced in the presence of combinations of electron carriers and donors. Methylene blue and cytochrome c were evaluated as the electron carriers, and NADH and ascorbate were considered as the electron donors. The cofactors were held at 4 and 25°C to determine temperature effects on the reduction of metmyoglobin, and the same cofactor combinations were evaluated at pH of 5.2, 5.6, 6.0, and 6.4 to reflect postmortem muscle pH. Spectrophotometry was utilized to monitor the rates of metmyoglobin reduction. The experiments were replicated five times, and the data were analyzed using the Mixed Procedure of SAS.ResultsThe results indicated that methylene blue was a significantly more effective electron carrier than cytochrome c with both electron donors, ascorbate and NADH. EDTA had no impact on the non-enzymatic metmyoglobin reducing the ability of methylene blue (P = 0.91). Temperature and pH had cofactor specific effects on the non-enzymatic reduction of metmyoglobin. Lower temperature resulted in an increased non-enzymatic metmyoglobin reduction for methylene blue regardless of electron donor (ascorbate, P = 0.03, NADH, P = 0.04). As pH increased, the non-enzymatic metmyoglobin reducing activity reduced significantly in the presence of NADH and methylene blue.ConclusionIn conclusion, the characteristics of the cofactors at specific temperatures and pH impacted the non-enzymatic reduction of metmyoglobin. Further, current in vitro research indicated that non-enzymatic metmyoglobin reduction is possible at lower temperature and meat pH.

scholarly journals Purification of the membrane-bound hydrogenase of Escherichia coli

1979 ◽  
Vol 183 (1) ◽  
pp. 11-22 ◽  
Author(s):  
M W W Adams ◽  
D O Hall
Keyword(s):  
Escherichia Coli ◽  
Methyl Viologen ◽  
Hydrophobic Interaction Chromatography ◽  
H2 Evolution ◽  
Ph Optimum ◽  
Benzyl Viologen ◽  
Electron Carrier ◽  
Membrane Bound ◽  
High Concentrations ◽  
Electron Carriers

The membrane-bound hydrogenase (EC class 1.12) of aerobically grown Escherichia coli cells was solubilized by treatment with deoxycholate and pancreatin. The enzyme was further purified to electrophoretic homogeneity by chromoatographic methods, including hydrophobic-interaction chromatography, with a yield of 10% as judged by activity and an overall purification of 2140-fold. The hydrogenase was a dimer of identical subunits with a mol.wt. of 113,000 and contained 12 iron and 12 acid-labile sulphur atoms per molecule. The epsilon 400 was 49,000M-1 . cm-1. The hydrogenase catalysed both H2 evolution and H2 uptake with a variety of artificial electron carriers, but would not interact with flavodoxin, ferredoxin or nicotinamide and flavin nucleotides. We were unable to identify any physiological electron carrier for the hydrogenase. With Methyl Viologen as the electron carrier, the pH optimum for H2 evolution and H2 uptake was 6.5 and 8.5 respectively. The enzyme was stable for long periods at neutral pH, low temperatures and under anaerobic conditions. The half-life of the hydrogenase under air at room temperature was about 12 h, but it could be stabilized by Methyl Viologen and Benzyl Viologen, both of which are electron carriers for the enzyme, and by bovine serum albumin. The hydrogenase was strongly inhibited by carbon monoxide (Ki = 1870Pa), heavy-metal salts and high concentrations of buffers, but was resistant to inhibition by thiol-blocking and metal-complexing reagents. These aerobically grown E. coli cells lacked formate hydrogenlyase activity and cytochrome c552.

Enhanced Ion Transport in an Ether Aided Super Concentrated Ionic Liquid Electrolyte for Long-Life Practical Lithium Metal Battery Applications

2020 ◽  
Author(s):  
Urbi Pal ◽  
Fangfang Chen ◽  
Derick Gyabang ◽  
Thushan Pathirana ◽  
Binayak Roy ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Ion Transport ◽  
Current Density ◽  
Coulombic Efficiency ◽  
High Energy ◽  
Liquid Electrolyte ◽  
High Mass ◽  
Lithium Metal ◽  
Ionic Liquid Electrolyte ◽  
Lithium Metal Battery

We explore a novel ether aided superconcentrated ionic liquid electrolyte; a combination of ionic liquid, <i>N</i>-propyl-<i>N</i>-methylpyrrolidinium bis(fluorosulfonyl)imide (C<sub>3</sub>mpyrFSI) and ether solvent, <i>1,2</i> dimethoxy ethane (DME) with 3.2 mol/kg LiFSI salt, which offers an alternative ion-transport mechanism and improves the overall fluidity of the electrolyte. The molecular dynamics (MD) study reveals that the coordination environment of lithium in the ether aided ionic liquid system offers a coexistence of both the ether DME and FSI anion simultaneously and the absence of ‘free’, uncoordinated DME solvent. These structures lead to very fast kinetics and improved current density for lithium deposition-dissolution processes. Hence the electrolyte is used in a lithium metal battery against a high mass loading (~12 mg/cm<sup>2</sup>) LFP cathode which was cycled at a relatively high current rate of 1mA/cm<sup>2</sup> for 350 cycles without capacity fading and offered an overall coulombic efficiency of >99.8 %. Additionally, the rate performance demonstrated that this electrolyte is capable of passing current density as high as 7mA/cm<sup>2</sup> without any electrolytic decomposition and offers a superior capacity retention. We have also demonstrated an ‘anode free’ LFP-Cu cell which was cycled over 50 cycles and achieved an average coulombic efficiency of 98.74%. The coordination chemistry and (electro)chemical understanding as well as the excellent cycling stability collectively leads toward a breakthrough in realizing the practical applicability of this ether aided ionic liquid electrolytes in lithium metal battery applications, while delivering high energy density in a prototype cell.

Participation by some oxygen containing groups in hypobromous acid addition to double bond

1983 ◽  
Vol 48 (12) ◽  
pp. 3660-3673 ◽  
Author(s):  
Pavel Kočovský
Keyword(s):  
Double Bond ◽  
Functional Groups ◽  
Relative Reactivity ◽  
Product Analysis ◽  
Acid Addition ◽  
Hypobromous Acid ◽  
Electron Withdrawing Substituents

5(O)n and 6(O)π,n participations by some oxygen containing functional groups in the course of reaction with hypobromous acid have been studied on olefinic models of steroid type (I and II). The ability of these groups to participate has been compared on the basis of their relative reactivity with water (as externally attacking nucleophile) competing with participation. The results of the product analysis show that the ability to react with 5(O)n participation decreases in the order HO > CH3O ≃ CH3OCH2O > CH3CO2 > HCO2 > CH3SO3 ≥ (C2H5O)2PO2 > C6H5CO2 > O2NO ≫ CF3CO2, C2H5OCO2; in the last two functional groups is this ability completely suppressed. The 6(O)π,n participation comes in consideration only for compounds of the type II bearing the groups with the -X=O moiety which are ordered in the following sequence: C2H5OCO2 ≃ CH3CO2 ≥ (C2H5O)2PO2 > HCO2 > C6H5CO2. The remaining functional groups (CF3CO2, O2NO and CH3SO3do not undergo this process. Generally, it is valid that introduction of electron-withdrawing substituents into a participating group impedes or completely suppresses its ability to participate.

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