The stimulation of photophosphorylation and ATPase by artificial redox mediators in chromatophores ofRhodopseudomonas capsulata at different redox potentials

1979 ◽  
Vol 11 (1-2) ◽  
pp. 1-16 ◽  
Author(s):  
Assunta Baccarini-Melandri ◽  
B. Andrea Melandri ◽  
G�nter Hauska
Keyword(s):  
Redox Potentials ◽  
Redox Mediators ◽  
Stimulation Of

scholarly journals Laccases: Versatile Biocatalysts for the Synthesis of Heterocyclic Cores

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3719
Author(s):  
Ana Catarina Sousa ◽  
Lígia O. Martins ◽  
M. Paula Robalo
Keyword(s):  
Membered Ring ◽  
Low Molecular Weight ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Multicopper Oxidases ◽  
Phenothiazine Derivatives ◽  
Ph Values ◽  
Electron Shuttles ◽  
Specific Oxidation ◽  
Optimal Ph

Laccases are multicopper oxidases that have shown a great potential in various biotechnological and green chemistry processes mainly due to their high relative non-specific oxidation of phenols, arylamines and some inorganic metals, and their high redox potentials that can span from 500 to 800 mV vs. SHE. Other advantages of laccases include the use of readily available oxygen as a second substrate, the formation of water as a side-product and no requirement for cofactors. Importantly, addition of low-molecular-weight redox mediators that act as electron shuttles, promoting the oxidation of complex bulky substrates and/or of higher redox potential than the enzymes themselves, can further expand their substrate scope, in the so-called laccase-mediated systems (LMS). Laccase bioprocesses can be designed for efficiency at both acidic and basic conditions since it is known that fungal and bacterial laccases exhibit distinct optimal pH values for the similar phenolic and aromatic amines. This review covers studies on the synthesis of five- and six-membered ring heterocyclic cores, such as benzimidazoles, benzofurans, benzothiazoles, quinazoline and quinazolinone, phenazine, phenoxazine, phenoxazinone and phenothiazine derivatives. The enzymes used and the reaction protocols are briefly outlined, and the mechanistic pathways described.

scholarly journals Electrolyte Composition in Li/O2 Batteries with LiI Redox Mediators: Solvation Effects on Redox Potentials and Implications for Redox Shuttling

2018 ◽  
Vol 122 (3) ◽  
pp. 1522-1534 ◽  
Author(s):  
Azusa Nakanishi ◽  
Morgan L. Thomas ◽  
Hoi-Min Kwon ◽  
Yuki Kobayashi ◽  
Ryoichi Tatara ◽  
...  
Keyword(s):  
Electrolyte Composition ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Solvation Effects

scholarly journals Sharp kinetic acceleration potentials during mediated redox catalysis of insulators

2021 ◽  
Author(s):  
Deqing Cao ◽  
Xiaoxiao Shen ◽  
Aiping Wang ◽  
Fengjiao Yu ◽  
Yuping Wu ◽  
...  
Keyword(s):  
Redox Potentials ◽  
Redox Catalysis ◽  
Redox Mediators ◽  
Fast Kinetics ◽  
Surface Conditions ◽  
Storage Materials ◽  
Surface Facets

Abstract Redox mediators could catalyse otherwise slow and energy-inefficient cycling of Li-S and Li-O2 batteries by shuttling electrons/holes between the electrode and the solid insulating storage materials. For mediators to work efficiently they need to oxidize the solid with fast kinetics yet the lowest possible overpotential. Here, we found that when the redox potentials of mediators are tuned via, e.g., Li+ concentration in the electrolyte, they exhibit distinct threshold potentials, where the kinetics accelerate several-fold within a range as small as 10 mV. This phenomenon is independent of types of mediators and electrolyte. The acceleration originates from the overpotentials required to activate fast Li+/e– extraction and the following chemical step at specific abundant surface facets. Efficient redox catalysis at insulating solids requires therefore carefully considering the surface conditions of the storage materials and electrolyte-dependent redox potentials, which may be tuned by salt concentrations or solvents.

Catalytic effects of different redox mediators on the reductive decolorization of azo dyes

2006 ◽  
Vol 54 (2) ◽  
pp. 165-170 ◽  
Author(s):  
A.A. Encinas-Yocupicio ◽  
E. Razo-Flores ◽  
F. Sánchez-Díaz ◽  
A.B. dos Santos ◽  
J.A. Field ◽  
...  
Keyword(s):  
Azo Dyes ◽  
Granular Sludge ◽  
Order Rate Constant ◽  
Anaerobic Treatment ◽  
Redox Mediator ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Direct Blue ◽  
Reactive Orange ◽  
Catalytic Effects

The catalytic effects of redox mediators, with distinct standard redox potentials (E′0), were evaluated on the first-order rate constant of decolorization (Kd) of recalcitrant azo dyes by an anaerobic granular sludge. The dyes studied included mono-azo (Reactive Orange 14, RO14), di-azo (Direct Blue 53, DB53), and tri-azo (Direct Blue 71, DB71) compounds. Toxicity and auto-catalytic aspects seemed to play a role in determining the rate of decolorization. Addition of riboflavin, anthraquinone-2,6-disulphonate (AQDS) or lawsone as a redox mediator, increased the Kd value for all dyes studied, although their impact varied in every case. Kd values were increased from 1.1-fold up to 3.8-fold depending on the redox mediator applied. Moreover, catalysts with moderately similar E′0 value caused distinct stimulation on the rate of decolorization. These results should be considered for selecting the proper redox mediator to be applied during the anaerobic treatment of textile wastewaters and effluents containing electron-withdrawing pollutants, such as nitro-aromatic and polychlorinated compounds.

The Role of Ubiquinone-10 in Cyclic Electron Transport in Rhodopsendomonas capsulata Ala pho+: Effects of Lyophilization and Extraction

1978 ◽  
Vol 33 (9-10) ◽  
pp. 704-711 ◽  
Author(s):  
John R. Bowyer ◽  
Assunta Baccarini-Melandri ◽  
B. Andrea Melandri ◽  
Antony R. Crofts
Keyword(s):  
Electron Transport ◽  
Reaction Center ◽  
Cytochrome B ◽  
Rhodopseudomonas Capsulata ◽  
Redox Mediators ◽  
Ferrocytochrome C ◽  
Ubiquinone 10 ◽  
Kinetics Of ◽  
Stimulation Of

Abstract 1. The effects of lyophilization and the extraction of ubiquinone-10 on the kinetics of electron transport in Rhodopseudomonas capsulata Ala pho+ have been investigated.2. Lyophilization reduced the amount of ferrocytochrome c2 photo-oxidized on a microsecond time scale following a single excitation.3. Lyophilization increased the reactivity of the electron transfer components with redox mediators, particularly N-methyl phenazonium methosulphate (PMS). At a concentration of 1 µᴍ , PMS accelerated reaction center re-reduction, ferricytochrome c2 re-reduction and ferrocytochrome b50 oxidation. The cytochrome c2 re-reduction stimulated by PMS was antimycin A insensitive but the cytochrome b50 oxidation was partially antim ycin sensitive.4. Removal of 25- 30 molecules of ubiquinone 10 per reaction center removed a secondary acceptor pool, had very little effect on the kinetics of ferricytochrome b50 reduction and ferricyto­ chrome c2 re-reduction, but markedly inhibited ferrocytochrome b50 oxidation. Ubiquinone extraction also caused an increased stimulation of ferrocytochrome b50 oxidation by PMS.5. The involvement of tightly bound ubiquinone in cytochrome b reduction and in the cytochrome b-c2 oxido-reductase, and the role of semiquinone species is discussed.

Investigation of cobalt redox mediators and effects of TiO2 film topology in dye-sensitized solar cells

RSC Advances ◽  
2016 ◽  
Vol 6 (61) ◽  
pp. 56580-56588 ◽  
Author(s):  
Majid Safdari ◽  
Peter W. Lohse ◽  
Leif Häggman ◽  
Sara Frykstrand ◽  
Daniel Högberg ◽  
...  
Keyword(s):  
Solar Cells ◽  
Light Absorption ◽  
Dye Sensitized Solar Cells ◽  
Cobalt Complexes ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Visible Light Absorption ◽  
Dye Sensitized ◽  
Sensitized Solar Cells ◽  
Interesting Alternative

Cobalt complexes represent interesting alternative redox mediators in dye-sensitized solar cells, with weak visible light absorption and a wide variety in redox potentials. Its diffusion in mesoporous TiO2 may, however, limit its performance.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Gap junctions in the prothoracic glands of the tobacco hornworm, Manduca sexta

1992 ◽  
Vol 50 (1) ◽  
pp. 706-707
Author(s):  
Ji-da Dai ◽  
M. Joseph Costello ◽  
Lawrence I. Gilbert
Keyword(s):  
Gap Junctions ◽  
Small Molecules ◽  
Manduca Sexta ◽  
Freeze Fracture ◽  
Cell Communication ◽  
Cellular Level ◽  
Thin Sections ◽  
Prothoracic Glands ◽  
Polyhydroxylated Steroids ◽  
Stimulation Of

Insect molting and metamorphosis are elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands (PGs). Prothoracicotropic hormone stimulation of steroidogenesis by the PGs at the cellular level involves both calcium and cAMP. Cell-to-cell communication mediated by gap junctions may play a key role in regulating signal transduction by controlling the transmission of small molecules and ions between adjacent cells. This is the first report of gap junctions in the PGs, the evidence obtained by means of SEM, thin sections and freeze-fracture replicas.

Activator protein-1 is necessary for angiotensin-II stimulation of human adrenocorticotropin receptor gene transcription

2001 ◽  
Vol 268 (6) ◽  
pp. 1802-1810
Author(s):  
Danielle Naville ◽  
Estelle Bordet ◽  
Marie-Claude Berthelon ◽  
Philippe Durand ◽  
Martine Begeot
Keyword(s):  
Angiotensin Ii ◽  
Gene Transcription ◽  
Receptor Gene ◽  
Activator Protein 1 ◽  
Activator Protein ◽  
Stimulation Of
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