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Chemistry, An Asian Journal Nov 2023The properties of electrodes play a crucial role in the processes occurring on them. Therefore, a variety of materials have been tried as electrodes. Carbon composite... (Review)
Review
The properties of electrodes play a crucial role in the processes occurring on them. Therefore, a variety of materials have been tried as electrodes. Carbon composite materials are among the most admired ones. Use of composites as electrode material dates back to the mid of the last century when polymer-carbon composites were tried as general-purpose electrode platforms and epoxy impregnated graphite paste/ solid electrodes were tried in polarography. Later the composite electrodes have seen several phases of development. Plastic Chip Electrode (PCE) is a class of polymer composite electrode developed by our group. This monographic review gives a bird's eye account of polymer composite electrodes and appurtenant work, followed by elaborating on various aspects and state-of-the-art plastic chip electrodes.
PubMed: 37706272
DOI: 10.1002/asia.202300690 -
Cell Biochemistry and Function Jan 2017To examine ryanodine-sensitive Ca channels in mitochondria of rat hepatocytes and their role in energy state of the cells via investigation of the ryanodine effect on...
To examine ryanodine-sensitive Ca channels in mitochondria of rat hepatocytes and their role in energy state of the cells via investigation of the ryanodine effect on mitochondrial membrane potential. Oxygen consumption was measured by polarography using the Clark electrode. The substrates of oxidation such as pyruvate (5mM), α-ketoglutarate (5mM), or succinate (5mM) were used. Oxidative phosphorylation was stimulated by the addition of adenosine diphosphate (200nM). Mitochondrial membrane potential was measured using a voltage-sensitive fluorescent probe tetramethylrhodamine-methyl-ester (0.1μM) and was analyzed by a flow cytometer. To evaluate the intact mitochondria, we used carbonil cyanide m-chlorophenyl hydrazone (CCCP, 10μM). Changes in the ionized calcium concentration in rat liver mitochondria were measured using a fluorescent probe Fluo-4 AM. Effect of ryanodine on oxygen consumption of rat liver mitochondria depends on the oxidation substrate and the incubation time. Oxidation of pyruvate in the presence of ryanodine (0.05μM) decreased the membrane potential of rat liver mitochondria by 38.4%. At higher concentrations, ryanodine (0.1μM or 1μM) led to decrease of membrane potential by 51.7% and 42.8%, respectively. In contrast, oxidation of α-ketoglutarate in the presence of ryanodine (0.05μM) increased mitochondrial membrane potential by 16.8%. However, at higher concentrations, ryanodine (0.1μM or 1μM) triggered a decreasing of membrane potential by 42.5% and 31.0%, respectively. Therefore, ryanodine at various concentrations (0.05μM, 0.1μM, or 1μM) causes differential effects on Ca concentration in the mitochondria matrix under oxidation of pyruvate or α-ketoglutarate. The data suggest the presence of ryanodine receptors in mitochondrial membrane of rat hepatocytes. Their inhibition with higher concentrations of ryanodine leads to decreasing of intra-mitochondrial Ca concentration and affecting the energy state of mictochondria in hepatocytes.
Topics: Animals; Calcium; Calcium Channels; Ketoglutaric Acids; Liver; Male; Membrane Potential, Mitochondrial; Mitochondria, Liver; Oxidation-Reduction; Oxygen Consumption; Pyruvic Acid; Rats; Ryanodine
PubMed: 28052355
DOI: 10.1002/cbf.3243 -
Shock (Augusta, Ga.) Jun 2024Mitochondrial dysfunction is a recognized feature of sepsis, characterized by ultrastructural damage, diminished oxidative phosphorylation, and depletion of...
Mitochondrial dysfunction is a recognized feature of sepsis, characterized by ultrastructural damage, diminished oxidative phosphorylation, and depletion of mitochondrial antioxidant capacity observed in deceased septic patients. Lipopolysaccharide (LPS) tolerance induces a controlled response to sepsis. This study aimed to evaluate the function of tolerant mitochondria after cecal ligation and puncture (CLP)-induced sepsis. Mytochondrial oxygen consumption was determined using polarography. Extraction and quantification of RNA for the expression of Tfam, Nrf-1 and Ppargc-1α; and Respiratory complex activity were measured. CLP-tolerant animals presented preserved respiratory rates of S3 and S4 and a ratio of respiratory control (RCR) compared to CLP non-tolerant animals with reduced oxidative phosphorylation and increased uncoupled respiration. Complex I Vmax was reduced in septic animals; however, CLP animals sustained normal Vmax. Mitochondrial biogenesis was preserved in CLP-tolerant animals compared to the CLP-nontolerant group, likely due to increased TFAM expression. LPS tolerance protected septic animals from mitochondrial dysfunction, favoring mitochondrial biogenesis and preserving mitochondrial respiration and respiratory complex I activity.
PubMed: 38888558
DOI: 10.1097/SHK.0000000000002399 -
Physiologia Plantarum May 2019High solar flux is known to diminish photosynthetic growth rates, reducing biomass productivity and lowering disease tolerance. Photosystem II (PSII) of plants is...
High solar flux is known to diminish photosynthetic growth rates, reducing biomass productivity and lowering disease tolerance. Photosystem II (PSII) of plants is susceptible to photodamage (also known as photoinactivation) in strong light, resulting in severe loss of water oxidation capacity and destruction of the water-oxidizing complex (WOC). The repair of damaged PSIIs comes at a high energy cost and requires de novo biosynthesis of damaged PSII subunits, reassembly of the WOC inorganic cofactors and membrane remodeling. Employing membrane-inlet mass spectrometry and O -polarography under flashing light conditions, we demonstrate that newly synthesized PSII complexes are far more susceptible to photodamage than are mature PSII complexes. We examined these 'PSII birth defects' in barley seedlings and plastids (etiochloroplasts and chloroplasts) isolated at various times during de-etiolation as chloroplast development begins and matures in synchronization with thylakoid membrane biogenesis and grana membrane formation. We show that the degree of PSII photodamage decreases simultaneously with biogenesis of the PSII turnover efficiency measured by O -polarography, and with grana membrane stacking, as determined by electron microscopy. Our data from fluorescence, Q -inhibitor binding, and thermoluminescence studies indicate that the decline of the high-light susceptibility of PSII to photodamage is coincident with appearance of electron transfer capability Q → Q during de-etiolation. This rate depends in turn on the downstream clearing of electrons upon buildup of the complete linear electron transfer chain and the formation of stacked grana membranes capable of longer-range energy transfer.
Topics: Chloroplasts; Mass Spectrometry; Microscopy, Electron; Organelle Biogenesis; Photosynthesis; Photosystem II Protein Complex
PubMed: 30693529
DOI: 10.1111/ppl.12932 -
Cerebral Cortex (New York, N.Y. : 1991) Jan 2016The human default mode network (DMN) shows decreased blood oxygen level dependent (BOLD) signals in response to a wide range of attention-demanding tasks. Our...
The human default mode network (DMN) shows decreased blood oxygen level dependent (BOLD) signals in response to a wide range of attention-demanding tasks. Our understanding of the specifics regarding the neural activity underlying these "task-negative" BOLD responses remains incomplete. We paired oxygen polarography, an electrode-based oxygen measurement technique, with standard electrophysiological recording to assess the relationship of oxygen and neural activity in task-negative posterior cingulate cortex (PCC), a hub of the DMN, and visually responsive task-positive area V3 in the awake macaque. In response to engaging visual stimulation, oxygen, LFP power, and multi-unit activity in PCC showed transient activation followed by sustained suppression. In V3, oxygen, LFP power, and multi-unit activity showed an initial phasic response to the stimulus followed by sustained activation. Oxygen responses were correlated with LFP power in both areas, although the apparent hemodynamic coupling between oxygen level and electrophysiology differed across areas. Our results suggest that oxygen responses reflect changes in LFP power and multi-unit activity and that either the coupling of neural activity to blood flow and metabolism differs between PCC and V3 or computing a linear transformation from a single LFP band to oxygen level does not capture the true physiological process.
Topics: Action Potentials; Animals; Attention; Brain Mapping; Evoked Potentials, Visual; Image Processing, Computer-Assisted; Macaca; Magnetic Resonance Imaging; Neurons; Oxygen; Photic Stimulation; Visual Cortex; Visual Perception
PubMed: 25385710
DOI: 10.1093/cercor/bhu260 -
Methods in Molecular Biology (Clifton,... 2022The Seahorse Extracellular Flux Analyzer enables the high-throughput characterization of oxidative phosphorylation capacity based on the electron transport chain...
The Seahorse Extracellular Flux Analyzer enables the high-throughput characterization of oxidative phosphorylation capacity based on the electron transport chain organization and regulation with relatively small amount of material. This development over the traditional polarographic Clark-type electrode approaches make it possible to analyze the respiratory features of mitochondria isolated from tissue samples of particular animal models. Here we provide a description of an optimized approach to carry out multi-well measurement of O consumption, with the Agilent Seahorse XFe96 analyzer on mouse brain and muscles to determine the tissue-specific oxidative phosphorylation properties. Protocols include the preparation of the tissue samples, isolation of mitochondria, and analysis of their function; in particular, the preparation and optimization of the reagents and samples.
Topics: Animals; Electron Transport; Mice; Mitochondria; Oxidative Phosphorylation; Oxygen Consumption; Polarography; Smegmamorpha
PubMed: 35771439
DOI: 10.1007/978-1-0716-2309-1_8 -
Food Chemistry Nov 2022In this study, enhancement of electrochemical performance of electrochemically reduced graphene oxide (ERGO) on a screen-printed carbon electrode (SPCE) (ERGO/SPCE)...
In this study, enhancement of electrochemical performance of electrochemically reduced graphene oxide (ERGO) on a screen-printed carbon electrode (SPCE) (ERGO/SPCE) coupled with ion-pairing (cetyltrimethylammonium bromide, CTAB) for the determination of iodide in table salt has been described. The electrode modification of ERGO/SPCE was conducted using cyclic voltammetric (CV) scanning in the potential range of 1.3-0.4 V for 50 cycles after the drop-casting of graphene oxide (GO) suspension on the SPCE. It was found that the electro-active surface area of ERGO/SPCE was increased by 1.5-fold compared to the bare SPCE. ERGO/SPCE sensor displays linearity towards iodide in the concentration range from 0.020 to 1.0 mg/L (sensitivity = 5.40 µA(mg/L), R = 0.9906) with the limit of detection (LOD) and limit of quantitation (LOQ) of 0.070 mg/L and 0.21 mg/L, respectively. The comparison between polarography and ERGO/SPCE sensor was in good agreement.
Topics: Carbon; Electrochemical Techniques; Electrodes; Graphite; Iodides; Salts; Sodium Chloride, Dietary
PubMed: 35667176
DOI: 10.1016/j.foodchem.2022.133382 -
Journal of the Science of Food and... Sep 2021Lead (Pb ) is one of the most toxic heavy metals and can be found in various quantities in the environment. The five native probiotic bacteria and inulin were used to...
BACKGROUND
Lead (Pb ) is one of the most toxic heavy metals and can be found in various quantities in the environment. The five native probiotic bacteria and inulin were used to assess in vitro lead nitrate and lead acetate binding capacities, as well as removal potentials.
RESULTS
The highest decrease in media pH was seen for samples containing a combination of Lactobacillus paracasei IRBC-M 10784, lead nitrate and inulin (5.30 ± 0.012). The presence of inulin in the environment accelerated decreases in the pH of all samples with no significance. In all groups, lead nitrate-containing samples included maximum pH decreases. From the highest to the lowest, the ability of lead removal was linked to Lactobacillus acidophilus PTCC-1932 (88.48%), Bifidobacterium bifidum BIA-7 (85.32%), Bifidobacterium lactis BIA-6 (85.24%), Lactobacillus rhamnosus IBRC-M 10782 (83.18%) and L. paracasei IRBC-M 10784 (80.66%). Most species included the highest decrease in lead nitrate. Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated that various functional groups (hydroxyl, carboxylic, carbonyl, amino and amide binds) on the bacterial cell wall were involved in lead ion binding during incubation. Principal component analysis of the FTIR results showed differences with respect to treated groups and control groups.
CONCLUSION
The results obtained in the present study reveal that the simultaneous use of native probiotics and inulin can be an effective and safe approach for removing various toxic substances, especially Pb. © 2021 Society of Chemical Industry.
Topics: Adsorption; Bifidobacterium; Biodegradation, Environmental; Cell Wall; Hydrogen-Ion Concentration; Inulin; Lactobacillus; Lead; Nitrates; Organometallic Compounds; Probiotics
PubMed: 33608880
DOI: 10.1002/jsfa.11160 -
Physiologia Plantarum Feb 2021The Mn CaO cluster of photosystem II (PSII) advances sequentially through five oxidation states (S to S ). Under the enzyme cycle, two water molecules are oxidized, O is...
The Mn CaO cluster of photosystem II (PSII) advances sequentially through five oxidation states (S to S ). Under the enzyme cycle, two water molecules are oxidized, O is generated and four protons are released into the lumen. Umena et al. (2011) have proposed that, with other charged amino acids, the R323 residue of the D1 protein could contribute to regulate a proton egress pathway from the Mn CaO cluster and Tyr via a proton channel identified from the 3D structure. To test this suggestion, a PsbA3/R323E site-directed mutant has been constructed and the properties of its PSII have been compared to those of the PsbA3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV-visible absorption spectroscopy. Neither the oscillations with a period four nor the kinetics and S-state-dependent stoichiometry of the proton release were affected. However, several differences have been found: (1) the P decay in the hundreds of ns time domain was much slower in the mutant, (2) the S Q /DCMU and S Q /DCMU radiative charge recombination occurred at higher temperatures and (3) the S Tyr , S Tyr , S Tyr split EPR signals induced at 4.2 K by visible light from the S Tyr , S Tyr , S Tyr , respectively, and the (S Tyr )' induced by NIR illumination at 4.2 K of the S Tyr state differed. It is proposed that the R323 residue of the D1 protein interacts with Tyr likely via the H-bond network previously proposed to be a proton channel. Therefore, rather than participating in the egress of protons to the lumen, this channel could be involved in the relaxations of the H-bonds around Tyr by interacting with the bulk, thus tuning the driving force required for Tyr oxidation.
Topics: Arginine; Electron Spin Resonance Spectroscopy; Oxidation-Reduction; Photosystem II Protein Complex; Protons
PubMed: 32359083
DOI: 10.1111/ppl.13115 -
Research in Microbiology 2016(51)V NMR spectroscopy was used for detection and identification of cell-associated vanadate (V(5+)) species after exposure of Phycomyces blakesleeanus mycelium, in...
(51)V NMR spectroscopy was used for detection and identification of cell-associated vanadate (V(5+)) species after exposure of Phycomyces blakesleeanus mycelium, in exponential phase of growth, to sodium orthovanadate. Complete disappearance of monomer and dimer signals and decreased intensity of the tetramer signal were observed about 40 min after treatment. Simultaneously, a signal at -532 ppm, with increasing intensity, was detected in spectra. The time-dependent rise in this signal was connected to a decrease in the extracellular monomer signal, indicating its transport into the cell. The signal at -532 ppm did not belong to any known simple oxido-vanadate species, nor to a complex with any of the components of experimental medium. This signal was the only one present in spectrum of the mycelium washed 35 min after treatment, and the only one observed in mycelium cultivated on vanadate-contained medium. Therefore, its appearance can be attributed to intracellular complexation, and may represent an important detoxification mechanism of the cell exposed to a physiologically relevant concentration of vanadate. Experiments ((51)V NMR and polarography) performed with Cd-pretreated mycelium (inhibitor of an enzyme responsible for V(5+) reduction) and ferricyanide-preincubated mycelium excluded the possibility of V(5+) tetramer's entry into the cell.
Topics: Inactivation, Metabolic; Magnetic Resonance Spectroscopy; Mycelium; Phycomyces; Vanadates
PubMed: 27164550
DOI: 10.1016/j.resmic.2016.04.012