Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “OXIDATION REDUCTION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed1982

Studies on reduced and oxidized coenzyme Q (ubiquinones). II. The determination of oxidation-reduction levels of coenzyme Q in mitochondria, microsomes and plasma by high-performance liquid chromatography.

Reduced and oxidized coenzyme Q10 (Q10H2 and Q10) in guinea-pig liver mitochondria were rapidly extracted and determined by high-performance liquid chromatography (HPLC). The percentages of Q10H2 as compared to the total (sum of Q10 and Q10H2) were increased by the addition of respiratory substrates such as succinate, malate and beta-hydroxybutyrate (State 4). The levels of Q10H2 in State 4 were increased more extensively with electron-transport inhibitors such as KCN, NaN3 and antimycin A. These results indicate that the method for determining Q10H2 and Q10 by HPLC is quite useful for investigation of the physiological function of coenzyme Q in mitochondria and other organelles. The reduced and oxidized coenzyme Q levels of rat liver mitochondria, which contain both coenzyme Q9 and coenzyme Q10, were measured simultaneously. The results suggest that coenzymes Q9 and Q10 play a similar role as an electron carriers. The liver microsomes of guinea-pig contained approx. 133 nmol total coenzyme Q10 per g protein. The Q10H2 levels of microsomes were increased from 46.5 to 67.5 and 64.8% with NADH and NADPH, respectively. The plasma levels of total coenzyme Q were 0.92 microgram/ml for man, 0.35 microgram/ml for guinea-pig and 0.27 microgram/ml for rat. The reduced coenzyme Q were also present in those plasma samples. The levels of reduced coenzyme Q were 51.1, 48.9 and 65.3%, respectively.

Animals↗
PubMed1986

Reduction-oxidation state and protein degradation in skeletal muscle of fasted and refed rats.

Redox state and protein degradation were measured in isolated muscles of fasted (up to 10 d) and refed (up to 4 d) 7- to 14-wk-old rats. Protein degradation in the extensor digitorum longus muscle, but not in the soleus muscle, was greater in the fasted rats than in weight-matched muscle from fed rats. The NAD couple was more oxidized in incubated and fresh extensor digitorum longus muscles and in some incubated soleus muscles of fasted rats than in weight-matched muscle from fed rats. In the extensor digitorum longus muscle of refed or prolonged fasted rats, protein degradation was slower and the NAD couple was more reduced than in the fed state. Therefore, oxidation of the NAD couple was associated with increased muscle breakdown during fasting, whereas reduction of the NAD couple was associated with muscle conservation and deposition.

Animals↗
PubMed2002

Complex I-mediated reactive oxygen species generation: modulation by cytochrome c and NAD(P)+ oxidation-reduction state.

Several lines of evidence indicate that mitochondrial reactive oxygen species (ROS) generation is the major source of oxidative stress in the cell. It has been shown that ROS production accompanies cytochrome c release in different apoptotic paradigms, but the site(s) of ROS production remain obscure. In the current study, we demonstrate that loss of cytochrome c by mitochondria oxidizing NAD(+)-linked substrates results in a dramatic increase of ROS production and respiratory inhibition. This increased ROS production can be mimicked by rotenone, a complex I inhibitor, as well as other chemical inhibitors of electron flow that act further downstream in the electron transport chain. The effects of cytochrome c depletion from mitoplasts on ROS production and respiration are reversible upon addition of exogenous cytochrome c. Thus in these models of mitochondrial injury, a primary site of ROS generation in both brain and heart mitochondria is proximal to the rotenone inhibitory site, rather than in complex III. ROS production at complex I is critically dependent upon a highly reduced state of the mitochondrial NAD(P)(+) pool and is achieved upon nearly complete inhibition of the respiratory chain. Redox clamp experiments using the acetoacetate/L-beta-hydroxybutyrate couple in the presence of a maximally inhibitory rotenone concentration suggest that the site is approx. 50 mV more electronegative than the NADH/NAD(+) couple. In the absence of inhibitors, this highly reduced state of mitochondria can be induced by reverse electron flow from succinate to NAD(+), accounting for profound ROS production in the presence of succinate. These results lead us to propose a model of thermodynamic control of mitochondrial ROS production which suggests that the ROS-generating site of complex I is the Fe-S centre N-1a.

3-Hydroxybutyric Acid↗
PubMed1974

Terminal oxidation-reduction of N-acetyl-phenylalanyl-tRNA blocks initiation complex formation with Escherichia coli 30S ribosomal subunits.

Terminally oxidized-reduced tRNA(Phe) of yeast, exclusively acylated at the 2'-hydroxyl of the 3'-terminal ribose of the tRNA, is a useful model for investigating the stereospecificity of AA-tRNA in protein synthesis. In this work, the ability of N-acetyl-Phe-tRNA(ox-red) to form an initiation complex with Escherichiacoli 30S ribosomal subunits was investigated. Thirty per cent of added control N-acetyl-Phe-tRNA was bound in a reaction dependent on initiation factors, GTP, and poly U, but no binding of the oxidized-reduced analog could be detected. These results imply that initiation complex formation may be specific for the 3'-ester of initiator tRNA.

Binding Sites↗
PubMed1998

Denitrification and nitric oxide reduction in an aerobic toluene-treating biofilter.

The presence of significant denitrification activity in an aerobic toluene-treating biofilter was demonstrated under batch and flow-through conditions. N2O concentrations of 9.2 ppmv were produced by denitrifying bacteria in the presence of 15% acetylene, in a flow-through system with a bulk gas phase O2 concentration of >17%. The carbon source for denitrification was not toluene but a byproduct or metabolite of toluene catabolism. Denitrification conditions were successfully used for the reduction of 60 ppmv nitric oxide to 15 ppmv at a flow rate of 3 L min-1 (EBRT of 3 min) in a fully aerated, 17% v/v O2 (superficially aerobic) biofilter. Higher NO removal efficiency (97%) was obtained by increasing the toluene supply to the biofilter.

Aerobiosis↗
PubMed2000

Reduction-oxidation control of beta-sheet assembly in genetically engineered silk.

Genetically engineered spider dragline silk protein was modified to incorporate methionines flanking the beta-sheet forming polyalanine regions. The methionines could be selectively chemically oxidized and reduced. This chemical change altered the bulkiness and charge of the sulfhydryl groups, and in turn, the beta-sheet forming tendencies of the polyalanine domains and solubility of the protein. The genes encoding these redesigned proteins were constructed, cloned and expressed in Escherichia coli. In the reduced state (beta-mercaptoethanol) the approximately 25 kDa protein behaved similarly to native spider dragline silk, crystallizing into beta-sheets based on diffraction analysis and appearing fibrous by TEM. The addition of the methionines into the consensus dragline silk sequence did not disrupt the normal macromolecular assembly behavior of the protein. In the oxidized state (phenacyl bromide) the protein did not form beta-sheet crystals and appeared morphologically featureless based on TEM. A reduction in beta-strand content was also observed upon oxidation based on FTIR and TEM analysis and confirmed by X-ray diffraction analysis. To further confirm changes in assembly behavior observed for the recombinant protein containing the methionines, a model peptide with the same repeat amino acid sequence was synthesized and characterized. Shifts in molecular weight, observed by MALDI, along with corresponding changes in crystallinity, by electron diffraction, agreed with the changes expected on activation and deactivation of the redox trigger. These results support the use of a redox trigger as a useful feature with which to control the assembly of beta-sheet forming proteins.

Amino Acid Sequence↗
PubMed1977

Oxidation-reduction coupled phosphorylation in the dark with isolated spinach chloroplasts.

1. Spinach chloroplasts, pre-incubated with ferricyanide, acquire the ability to make ATP in the dark provided they are supplied with a reductant and a lipophilic mediator that can penetrate the membrane. The mediator must be of the type that, upon oxidation, releases protons into the surrounding medium such as 2,3,5,6-tetramethyl-p-phenylenediamine (DAD). 2. Dark phosphorylation is not affected by the electron transport inhibitor, 3(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) or 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), but is inhibited by uncouplers of photophosphorylation (e.g. NH4Cl and carbonylcyanide-m-chlorophenylhydrazone (CCCP)) and high concentrations of the energy transfer inhibitor, Dio-9. 3. Because only catalytic amounts of the mediator DAD are required to saturate dark phosphorylation, it is concluded that DAD shuttles reducing equivalents across the membrane from the reductant, ascorbate, on the outside to ferricyanide, the oxidant, trapped on the inside. 4. The results are interpreted within the framework of the chemiosmotic hypothesis for the coupling of electron transport to phosphorylation.

Adenosine Triphosphate↗