scholarly journals Photochromic coenzyme Q derivatives: switching redox potentials with light

2017 ◽  
Vol 8 (9) ◽  
pp. 6474-6483 ◽  
Author(s):  
Nadja A. Simeth ◽  
Andrea C. Kneuttinger ◽  
Reinhard Sterner ◽  
Burkhard König
Keyword(s):  
Redox Reactions ◽  
Coenzyme Q ◽  
Redox Potentials ◽  
Isolated Mitochondria

A photochromic coenzyme Q derivative could be activated through irradiation with orange light and initiate redox reactions with Hantzsch ester and on isolated mitochondria.

scholarly journals Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 437 ◽  
Author(s):  
Peter Cook ◽  
YoungJae Kim ◽  
Ke Yuan ◽  
Maria C. Marcano ◽  
Udo Becker
Keyword(s):  
Photoelectron Spectroscopy ◽  
Redox Reactions ◽  
Redox Potentials ◽  
Free Energies ◽  
Cathodic Peak ◽  
Redox Transformation ◽  
Hydrogen Electrode ◽  
Midpoint Potential ◽  
Ph Conditions ◽  
Cv Measurements

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV.

A Critical Evaluation of the Redox Properties of Uranium, Neptunium and Plutonium Ions in Acidic Aqueous Solutions

1999 ◽  
Vol 71 (9) ◽  
pp. 1771-1807 ◽  
Author(s):  
Sorin Kihara ◽  
Zenko Yoshida ◽  
Hisao Aoyagi ◽  
Kohji Maeda ◽  
Osamu Shirai ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Redox Reactions ◽  
Critical Evaluation ◽  
Redox Properties ◽  
Redox Processes ◽  
Redox Potentials ◽  
Electrode Processes ◽  
Reversible Redox ◽  
Reduction Mechanisms ◽  
Current Potential

Standard redox potentials, E0s, and redox processes of U, Np and Pu ions in acidic aqueous solutions are reviewed and evaluated critically. The E0sof reversible redox processes, MO22+/MO2+ and M4+/M3+ (M: U, Np or Pu) adopted are those proposed mainly by Riglet et al. on the basis of the precise correction of formal potentials, E0's, according to the improved theoretical approach to estimate the activity coefficient. Electrode processes of the U, Np and Pu ions are discussed in terms of current-potential curves, measured so far by polarography, voltammetry or flow coulometry. Special attention is payed to the irreversible MO2+/M4+ reactions. Disproportionation reactions of MO2+ are also discussed. New substances are introduced as intermediates during reductions of MO2+ to M4+ or disproportionations of MO2+.CONTENTSIntroductionStandard redox potentials for uranium, neptunium and plutonium ions in acidic aqueous solutions2.1 Evaluation of E0 from E0' determined by electrochemical measurements2.2 Temperature dependence of E0Redox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by polarography or voltammetry3.1 Uranium3.2 Neptunium3.3 Plutonium3.4 Disproportionation of NpO2+, PuO2+, Np4+ and Pu4+3.5 Reduction of MO2+ and reduction intermediatesRedox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by flow coulometry4.1 Electrode processes of the uranium, neptunium and plutonium ions investigated by flow coulometry at the column electrode at the column electrode4.2 Disproportionation of MO2+ during the electrolysis by flow coulometry4.3 Reduction mechanisms of MO2+ (M = Np or Pu) and reduction intermediates investigated by flow coulometryConclusionsList of abbreviationsAppendixReferences

Darstellung und Charakterisierung der Chloro-Bromo-Iridate(III) und -(IV) einschließlich der Stereoisomeren / Preparation and Characterisation of Chloro-Bromo-Iridates(III) and -(IV) Including Stereoisomers

1985 ◽  
Vol 40 (6) ◽  
pp. 745-754 ◽  
Author(s):  
W. Preetz ◽  
H.-J. Steinebach
Keyword(s):  
Ligand Exchange ◽  
Redox Reactions ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Mixed Ligand ◽  
Redox Potentials ◽  
Exchange Reactions ◽  
Cyclic Voltammetric ◽  
Point Groups ◽  
Voltammetric Measurements

AbstractThe mixed chloro-bromo complexes [IrClnBr6-n]2- and [IrClnBr6-n]3-, n = 1 - 5. were separated by ion exchange chromatography on diethylaminoethylcellulose. Due to the stronger trans-effect of Br compared with Cl, on treatment of [IrBr6]2- 3- with Cl- nearly pure cis/fac-isomers and by reaction of [IrCl6]2,3- with Br- trans/mer-isomers for n = 2,3,4 were formed. The stereoselectivi­ty of successive ligand exchange reactions is better for the Ir(III) than for the Ir(IV) system. The diamagnetic Ir(III) and the paramagnetic Ir(IV) complexes can be interconverted reversibly by redox reactions at low temperature. As shown by cyclic voltammetric measurements, the redox potentials within the series [IrClnBr6-n]2- 3- are linearly dependent on n. In aqueous solution the normal potentials are in the range of Eo = 0.838 V ([IrBr6]2-,3-) to Eo = 0.908 V ([IrCl6]2-,3-). The vibrational spectra of the mixed ligand complexes are assigned according to point groups D4h, C4v, C3v and C2v. They are similar for corresponding chloro-bromo-iridates, but distinguished by a shift of 10-25 cm-1 to higher wave numbers for most of the stretching vibrations going from Ir(III) to Ir(IV).

Redox Reactions of Bio Molecule for Nano-bio Battery

2006 ◽  
Vol 915 ◽  
Author(s):  
Kwang Min Shin ◽  
Sang Jun Park ◽  
Seong Gil Yoon ◽  
Chang Kee Lee ◽  
Su Ryon Shin ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Energy Storage ◽  
Metal Oxide ◽  
Redox Reactions ◽  
Methyl Viologen ◽  
Metal Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Redox Potentials ◽  
Inorganic Elements ◽  
Reduction And Oxidation

AbstractMetal oxide nanoparticles within the protein ferritin can act as an energy storage source in nano-bio batteries containing ferrous ferritin and a reconstituted ferritin cage containing different inorganic elements, such as Co, Mn, Ni, and Pt. These components were introduced as two ferritin half-cells with different redox potentials existing between the ferrous ferritin and the reconstituted ferritin. The reduction of ferritin was analyzed in a solution containing 3-[N-morpholino] propanesulfonic acid buffer and oxidized methyl viologen using cyclic voltammetry. The reduction and oxidation peaks of the methyl viologen occurred at potentials of −300 and −100 mV, respectively, and the reduction and the oxidation peaks of the released Fe occurred at potentials of −300 and −100 mV, respectively. The reduction of ferritin was influenced by the pH of the ferritin solution.

scholarly journals Quantum chemistry reveals the thermodynamic principles of redox biochemistry

2018 ◽  
Author(s):  
Adrian Jinich ◽  
Avi Flamholz ◽  
Haniu Ren ◽  
Sung-Jin Kim ◽  
Benjamin Sanchez-Lengeling ◽  
...  
Keyword(s):  
Quantum Chemistry ◽  
Material Flow ◽  
Redox Reactions ◽  
Redox Potentials ◽  
Accurate Calculation ◽  
Cellular Redox ◽  
Cellular Energy ◽  
Reduction Potentials ◽  
And Function ◽  
Electron Carriers

AbstractThermodynamics dictates the structure and function of metabolism. Redox reactions drive cellular energy and material flow. Hence, accurately quantifying the thermodynamics of redox reactions should reveal key design principles that shape cellular metabolism. However, only a limited number of redox potentials have been measured experimentally, and mostly with inconsistent, poorly-reported experimental setups. Here, we develop a quantum chemistry approach for the calculation of redox potentials of biochemical reactions. We demonstrate that our method predicts experimentally measured potentials with unparalleled accuracy. We calculate the reduction potentials of all redox pairs that can be generated from biochemically relevant compounds and highlight fundamental thermodynamic trends that define cellular redox biochemistry. We further use the calculated potentials to address the question of why NAD/NADP are used as the primary cellular electron carriers, demonstrating how their physiological redox range specifically fits the reactions of central metabolism and minimizes the concentration of reactive carbonyls. The use of quantum chemistry tools, as demonstrated in this study, can revolutionize our understanding of key biochemical phenomena by enabling fast and accurate calculation of large datasets of thermodynamic values.

Solubility and redox reactions of Pu(IV) hydrous oxide: Evidence for the formation of PuO2+x(s, hyd)

2007 ◽  
Vol 95 (4) ◽  
Author(s):  
Volker Neck ◽  
M. Altmaier ◽  
A. Seibert ◽  
J. I. Yun ◽  
Christian M. Marquardt ◽  
...  
Keyword(s):  
Oxidation State ◽  
Redox Reactions ◽  
Redox Potentials ◽  
Hydrous Oxide ◽  
Solubility Studies

The solubility and redox reactions of Pu(IV) hydrous oxide were analyzed by comparing total Pu concentrations, oxidation state distributions and simultaneously measured redox potentials under air and under Ar containing only traces of oxygen. At pH>3 the aqueous Pu concentration is dominated by Pu(V) for both solubility studies under air and argon. Combining all information strongly indicates that PuO

Synthesis and electrochemical properties of bis(octacyanophthalocyaninato)neodymium(III) complex

2005 ◽  
Vol 09 (01) ◽  
pp. 54-58 ◽  
Author(s):  
Tatsuya Yonekura ◽  
Takeo Ohsaka ◽  
Fusao Kitamura ◽  
Koichi Tokuda
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Properties ◽  
Electrochemical Behavior ◽  
Redox Reactions ◽  
Square Wave Voltammetry ◽  
Cyano Group ◽  
Cyclic Voltammogram ◽  
Redox Potentials ◽  
Strong Electron ◽  
Wave Voltammetry

The bis(octacyanophthalocyaninato)neodymium(III) was synthesized and its electrochemical behavior in N,N-dimethylformamide ( DMF ) was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). Multiple redox reactions were observed on the cyclic voltammogram, although the voltammetric feature was complicated due to aggregation. With the aid of SWV, it was concluded that the redox potentials of the complex positively shifted by about 700 mV compared with potentials of the unsubstituted complex, which was ascribed to the strong electron-withdrawn effect of the substituted cyano group.

Redox potentials and redox reactions in deep groundwater systems

1992 ◽  
Vol 98 (1-2) ◽  
pp. 131-150 ◽  
Author(s):  
I. Grenthe ◽  
W. Stumm ◽  
M. Laaksuharju ◽  
A.C. Nilsson ◽  
P. Wikberg
Keyword(s):  
Redox Reactions ◽  
Redox Potentials ◽  
Deep Groundwater ◽  
Groundwater Systems

scholarly journals Effects of Endurance Training on the Coenzyme Q Redox State in Rat Heart, Liver and Brain at the Tissue and Mitochondrial Levels: Implications for Reactive Oxygen Species Formation and Respiratory Chain Remodeling

2022 ◽  
Vol 23 (2) ◽  
pp. 896
Author(s):  
Karolina Dominiak ◽  
Lukasz Galganski ◽  
Adrianna Budzinska ◽  
Andrzej Woyda-Ploszczyca ◽  
Jerzy A. Zoladz ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Endurance Training ◽  
Respiratory Chain ◽  
Rat Heart ◽  
Redox State ◽  
Coenzyme Q ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Isolated Mitochondria ◽  
Ros Formation

Sixteen adult, 4-month-old male Wistar rats were randomly assigned to the training group (n = 8) or the control group (n = 8). We elucidated the effects of 8 weeks of endurance training on coenzyme Q (Q) content and the formation of reactive oxygen species (ROS) at the tissue level and in isolated mitochondria of the rat heart, liver and brain. We demonstrated that endurance training enhanced mitochondrial biogenesis in all tested organs, while a significant increase in the Q redox state was observed in the heart and brain, indicating an elevated level of QH2 as an antioxidant. Moreover, endurance training increased the mQH2 antioxidant pool in the mitochondria of the heart and liver, but not in the brain. At the tissue and isolated mitochondria level, an increase in ROS formation was only observed in the heart. ROS formation observed in the mitochondria of individual rat tissues after training may be associated with changes in the activity/amount of individual components of the oxidative phosphorylation system and its molecular organization, as well as with the size of the oxidized pool of mitochondrial Q acting as an electron carrier in the respiratory chain. Our results indicate that tissue-dependent changes induced by endurance training in the cellular and mitochondrial QH2 pool acting as an antioxidant and in the mitochondrial Q pool serving the respiratory chain may serve important roles in energy metabolism, redox homeostasis and the level of oxidative stress.

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