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Electrochemical Potential (electrochemical + potential)
Selected AbstractsDual-Gate Organic Field-Effect Transistors as Potentiometric Sensors in Aqueous SolutionADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Mark-Jan Spijkman Abstract Buried electrodes and protection of the semiconductor with a thin passivation layer are used to yield dual-gate organic transducers. The process technology is scaled up to 150-mm wafers. The transducers are potentiometric sensors where the detection relies on measuring a shift in the threshold voltage caused by changes in the electrochemical potential at the second gate dielectric. Analytes can only be detected within the Debye screening length. The mechanism is assessed by pH measurements. The threshold voltage shift depends on pH as ,Vth,=,(Ctop/Cbottom),×,58,mV per pH unit, indicating that the sensitivity can be enhanced with respect to conventional ion-sensitive field-effect transistors (ISFETs) by adjusting the ratio of the top and bottom gate capacitances. Remaining challenges and opportunities are discussed. [source] Nitrosative stress induced cytotoxicity in Giardia intestinalisJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2003D. Lloyd Abstract Aims: To investigate the antigiardial properties of the nitrosating agents: sodium nitrite, sodium nitroprusside and Roussin's black salt. Methods and Results: Use of confocal laser scanning microscopy and flow cytometry indicated permeabilization of the plasma membrane to the anionic fluorophore, DiBAC4(3) [bis(1,3-dibutylbarbituric acid) trimethine oxonol]. Loss of plasma membrane electrochemical potential was accompanied by loss of regulated cellular volume control. Changes in ultrastructure revealed by electron microscopy and capacity for oxygen consumption, were also consequences of nitrosative stress. Roussin's black salt (RBS), active at micromolar concentrations was the most potent of the three agents tested. Conclusions: These multitargeted cytotoxic agents affected plasma membrane functions, inhibited cellular functions in Giardia intestinalis and led to loss of viability. Significance and Impact of the Study: Nitrosative damage, as an antigiardial strategy, may have implications for development of chemotherapy along with suggesting natural host defence mechanisms. [source] Functional role of Coenzyme Q in the energy coupling of NADH-CoQ oxidoreductase (Complex I): Stabilization of the semiquinone state with the application of inside-positive membrane potential to proteoliposomesBIOFACTORS, Issue 1-4 2008Tomoko Ohnishi Ph.D. Abstract Coenzyme Q10 (which is also designated as CoQ10, ubiquinone-10, UQ10, CoQ, UQ or simply as Q) plays an important role in energy metabolism. For NADH-Q oxidoreductase (complex I), Ohnishi and Salerno proposed a hypothesis that the proton pump is operated by the redox-driven conformational change of a Q-binding protein, and that the bound form of semiquinone (SQ) serves as its gate [FEBS Letters 579 (2005) 45,55]. This was based on the following experimental results: (i) EPR signals of the fast-relaxing SQ anion (designated as Q) are observable only in the presence of the proton electrochemical potential (,,); (ii) iron-sulfur cluster N2 and Q are directly spin-coupled; and (iii) their center-to-center distance was calculated as 12Å, but Q is only 5Å deeper than N2 perpendicularly to the membrane. After the priming reduction of Q to Nf, the proton pump operates only in the steps between the semiquinone anion (Q) and fully reduced quinone (QH2). Thus, by cycling twice for one NADH molecule, the pump transports 4H+ per 2e,. This hypothesis predicts the following phenomena: (a) Coupled with the piericidin A sensitive NADH-DBQ or Q1 reductase reaction, ,, would be established; (b) ,, would enhance the SQ EPR signals; and (c) the dissipation of ,, with the addition of an uncoupler would increase the rate of NADH oxidation and decrease the SQ signals. We reconstituted bovine heart complex I, which was prepared at Yoshikawa's laboratory, into proteoliposomes. Using this system, we succeeded in demonstrating that all of these phenomena actually took place. We believe that these results strongly support our hypothesis. [source] Application of the self-potential method to archaeological prospection: some case historiesARCHAEOLOGICAL PROSPECTION, Issue 2 2004M. G. DrahorArticle first published online: 12 MAY 200 Abstract The self-potential (SP) method is very rarely used in archaeological prospection because related phenomena are not very well known. The aim of this study is to discuss the different SP phenomena that might be observed at archaeological sites, and therefore the SP method was applied at different archaeological sites in Anatolia (Turkey), such as Acemhöyük, Amorium, Burgaz and Ulucakhöyük archaeological areas and the Sinop amphorae workshop site. These studies indicated that SP anomalies existed over both burned or unburned materials at archaeological sites, such as walls, pits, kilns, etc. Furthermore, SP anomalies were also found over areas of complex soil distribution and visible physical changes on the surface. Other kinds of SP anomalies were also observed in those archaeological structures located very close to the coastline. These results were confirmed by archaeological excavations, which were carried out after geophysical surveys in the areas studied. All the studies supported that electrokinetic and electrochemical potentials might be the main cause of SP anomalies in the buried archaeological structures. The SP data collected with the gradient and total measurement techniques were processed by forward and inversion methods, and the main SP parameters (h, Q and x0) were determined. In addition, the SP results were compared with other applied geophysical methods such as resistivity and magnetic. Copyright © 2004 John Wiley & Sons, Ltd. [source] Ionic Liquid for in situ Vis/NIR and Raman Spectroelectrochemistry: Doping of Carbon NanostructuresCHEMPHYSCHEM, Issue 9 2003Ladislav Kavan Prof. Dr. Abstract 1-butyl-3-methylimidazolium tetrafluoroborate (an ionic liquid) is an advantageous electrolyte for the study of charge-transfer reactions at single-walled carbon nanotubes (SWCNTs) and fullerene peapods (C60@SWCNT). Compared to traditional electrolyte solutions, this medium offers a broader window of electrochemical potentials to be applied, and favorable optical properties for in situ Vis/NIR and Raman spectroelectrochemistry of nano-carbon species. The electrochemistry of both nanotubes and peapods is dominated by their capacitive double-layer charging. Vis/NIR spectroelectrochemistry confirms the charging-induced bleaching of transitions between Van Hove singularities. At high positive potentials, new optical transitions were activated in partly filled valence band. The bleaching of optical transitions is mirrored by the quenching of resonance Raman scattering in the region of tube-related modes. The Raman frequency of the tangential displacement mode of SWCNT shifts to blue upon both anodic and cathodic charging in the ionic liquid. The Raman modes of intratubular C60 exhibit a considerable intensity increase upon anodic doping of peapods. [source] | ||||||||||