Potentiometry: Solution titration in which the end point is read from the electrode-potential variations with the concentrations of potential determining ions. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Ion-Selective Electrodes: Electrodes which can be used to measure the concentration of particular ions in cells, tissues, or solutions.Methacycline: A broad-spectrum semisynthetic antibiotic related to TETRACYCLINE but excreted more slowly and maintaining effective blood levels for a more extended period.Electrodes: Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.Membranes, Artificial: Artificially produced membranes, such as semipermeable membranes used in artificial kidney dialysis (RENAL DIALYSIS), monomolecular and bimolecular membranes used as models to simulate biological CELL MEMBRANES. These membranes are also used in the process of GUIDED TISSUE REGENERATION.Calibration: Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Spectrophotometry: The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.Microfluidic Analytical Techniques: Methods utilizing the principles of MICROFLUIDICS for sample handling, reagent mixing, and separation and detection of specific components in fluids.Microfluidics: The study of fluid channels and chambers of tiny dimensions of tens to hundreds of micrometers and volumes of nanoliters or picoliters. This is of interest in biological MICROCIRCULATION and used in MICROCHEMISTRY and INVESTIGATIVE TECHNIQUES.Aptamers, Nucleotide: Nucleotide sequences, generated by iterative rounds of SELEX APTAMER TECHNIQUE, that bind to a target molecule specifically and with high affinity.PaperSemiconductors: Materials that have a limited and usually variable electrical conductivity. They are particularly useful for the production of solid-state electronic devices.Oxyphenonium: A quaternary ammonium anticholinergic agent with peripheral side effects similar to those of ATROPINE. It is used as an adjunct in the treatment of gastric and duodenal ulcer, and to relieve visceral spasms. The drug has also been used in the form of eye drops for mydriatic effect.Propantheline: A muscarinic antagonist used as an antispasmodic, in rhinitis, in urinary incontinence, and in the treatment of ulcers. At high doses it has nicotinic effects resulting in neuromuscular blocking.Universities: Educational institutions providing facilities for teaching and research and authorized to grant academic degrees.Fluorides: Inorganic salts of hydrofluoric acid, HF, in which the fluorine atom is in the -1 oxidation state. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Sodium and stannous salts are commonly used in dentifrices.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)Polyvinyl Chloride: A polyvinyl resin used extensively in the manufacture of plastics, including medical devices, tubing, and other packaging. It is also used as a rubber substitute.Electrodes, Implanted: Surgically placed electric conductors through which ELECTRIC STIMULATION is delivered to or electrical activity is recorded from a specific point inside the body.Electrochemistry: The study of chemical changes resulting from electrical action and electrical activity resulting from chemical changes.Electrochemical Techniques: The utilization of an electrical current to measure, analyze, or alter chemicals or chemical reactions in solution, cells, or tissues.Candy: Sweet food products combining cane or beet sugars with other carbohydrates and chocolate, milk, eggs, and various flavorings. In the United States, candy refers to both sugar- and cocoa-based confections and is differentiated from sweetened baked goods; elsewhere the terms sugar confectionary, chocolate confectionary, and flour confectionary (meaning goods such as cakes and pastries) are used.Crystallization: The formation of crystalline substances from solutions or melts. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Lindera: A plant genus in the LAURACEAE family. Lindera benzoin is a source of a balsamic resin called benzoin which is up to 1/3 BENZOIC ACID. This should not be confused with the chemical BENZOIN or the plant STYRAX BENZOIDES.Maple Syrup Urine Disease: An autosomal recessive inherited disorder with multiple forms of phenotypic expression, caused by a defect in the oxidative decarboxylation of branched-chain amino acids (AMINO ACIDS, BRANCHED-CHAIN). These metabolites accumulate in body fluids and render a "maple syrup" odor. The disease is divided into classic, intermediate, intermittent, and thiamine responsive subtypes. The classic form presents in the first week of life with ketoacidosis, hypoglycemia, emesis, neonatal seizures, and hypertonia. The intermediate and intermittent forms present in childhood or later with acute episodes of ataxia and vomiting. (From Adams et al., Principles of Neurology, 6th ed, p936)Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Chlorine Compounds: Inorganic compounds that contain chlorine as an integral part of the molecule.Point-of-Care Systems: Laboratory and other services provided to patients at the bedside. These include diagnostic and laboratory testing using automated information entry.Videoconferencing: Communications via an interactive conference between two or more participants at different sites, using computer networks (COMPUTER COMMUNICATION NETWORKS) or other telecommunication links to transmit audio, video, and data.United States Food and Drug Administration: An agency of the PUBLIC HEALTH SERVICE concerned with the overall planning, promoting, and administering of programs pertaining to maintaining standards of quality of foods, drugs, therapeutic devices, etc.Patient Care Team: Care of patients by a multidisciplinary team usually organized under the leadership of a physician; each member of the team has specific responsibilities and the whole team contributes to the care of the patient.Interdisciplinary Communication: Communication, in the sense of cross-fertilization of ideas, involving two or more academic disciplines (such as the disciplines that comprise the cross-disciplinary field of bioethics, including the health and biological sciences, the humanities, and the social sciences and law). Also includes problems in communication stemming from differences in patterns of language usage in different academic or medical disciplines.Device Approval: Process that is gone through in order for a device to receive approval by a government regulatory agency. This includes any required preclinical or clinical testing, review, submission, and evaluation of the applications and test results, and post-marketing surveillance. It is not restricted to FDA.Reagent Kits, Diagnostic: Commercially prepared reagent sets, with accessory devices, containing all of the major components and literature necessary to perform one or more designated diagnostic tests or procedures. They may be for laboratory or personal use.Love: Affection; in psychiatry commonly refers to pleasure, particularly as it applies to gratifying experiences between individuals.Software: Sequential operating programs and data which instruct the functioning of a digital computer.Search Engine: Software used to locate data or information stored in machine-readable form locally or at a distance such as an INTERNET site.Internet: A loose confederation of computer communication networks around the world. The networks that make up the Internet are connected through several backbone networks. The Internet grew out of the US Government ARPAnet project and was designed to facilitate information exchange.Information Storage and Retrieval: Organized activities related to the storage, location, search, and retrieval of information.User-Computer Interface: The portion of an interactive computer program that issues messages to and receives commands from a user.PubMed: A bibliographic database that includes MEDLINE as its primary subset. It is produced by the National Center for Biotechnology Information (NCBI), part of the NATIONAL LIBRARY OF MEDICINE. PubMed, which is searchable through NLM's Web site, also includes access to additional citations to selected life sciences journals not in MEDLINE, and links to other resources such as the full-text of articles at participating publishers' Web sites, NCBI's molecular biology databases, and PubMed Central.Chemistry, Analytic: The branch of chemistry dealing with detection (qualitative) and determination (quantitative) of substances. (Grant & Hackh's Chemical Dictionary, 5th ed)Chemistry Techniques, Analytical: Methodologies used for the isolation, identification, detection, and quantitation of chemical substances.Practice (Psychology): Performance of an act one or more times, with a view to its fixation or improvement; any performance of an act or behavior that leads to learning.Abbreviations as Topic: Shortened forms of written words or phrases used for brevity.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Chemistry, Clinical: The specialty of ANALYTIC CHEMISTRY applied to assays of physiologically important substances found in blood, urine, tissues, and other biological fluids for the purpose of aiding the physician in making a diagnosis or following therapy.Clinical Chemistry Tests: Laboratory tests demonstrating the presence of physiologically significant substances in the blood, urine, tissue, and body fluids with application to the diagnosis or therapy of disease.Blood Chemical Analysis: An examination of chemicals in the blood.Orthopedic Fixation Devices: Devices which are used in the treatment of orthopedic injuries and diseases.Spinal Fusion: Operative immobilization or ankylosis of two or more vertebrae by fusion of the vertebral bodies with a short bone graft or often with diskectomy or laminectomy. (From Blauvelt & Nelson, A Manual of Orthopaedic Terminology, 5th ed, p236; Dorland, 28th ed)Scoliosis: An appreciable lateral deviation in the normally straight vertical line of the spine. (Dorland, 27th ed)Quality Control: A system for verifying and maintaining a desired level of quality in a product or process by careful planning, use of proper equipment, continued inspection, and corrective action as required. (Random House Unabridged Dictionary, 2d ed)

Influence of a new antiulcer agent, ammonium 7-oxobicyclo (2, 2, 1) hept-5-ene-3-carbamoyl-2-carboxylate (KF-392) on gastric lesions and gastric mucosal barrier in rats. (1/661)

Antiulcer effects of KF-392 were studied in several experimental gastric ulcer models in rats. It was found that KF-392 given orally at 1.0 to 5.0 mg/kg had a marked suppression on the developments of Shay ulcer as well as the aspirin-, stress-, and reserpine-induced gastric lesions. The influence of KF-392 on gastric mucosal barrier was also studied. A back diffusion of H+ into the gastric mucosa and a fall of transmucosal potential difference were induced with KF-392 given orally at the above mentioned doses. KF-392 given s.c. at 5.0 mg/kg showed no inhibition of Shay ulcer and no induction of back diffusion of H+ into the gastric mucosa.  (+info)

Potential difference across the normal and the abnormal gastric mucosa in man. (2/661)

The mucosal potential difference in the body of the stomach was measured in 18 patients with gastric ulcers, five with gastritis, and three with pernicious anaemia. The results were compared with those of 12 normal volunteers. Significantly lower than normal levels were found in the groups of patients with gastric ulcers and gastritis. The patients with pernicious anaemia had even lower potential differences. In an additional 25 subjects, measurements were made in the duodenal bulb and at five sites in the stomach under direct vision at endoscopy. Biopsies were taken from each site for histology. Subjects with gastritis at the high lesser curve had a significantly lower potential difference at that site than those without gastritis. In the latter group, the potential difference at the high lesser curve was as low as in the antrum, and invariably lower than at the high greater curve.  (+info)

Characterization of DorC from Rhodobacter capsulatus, a c-type cytochrome involved in electron transfer to dimethyl sulfoxide reductase. (3/661)

The dorC gene of the dimethyl sulfoxide respiratory (dor) operon of Rhodobacter capsulatus encodes a pentaheme c-type cytochrome that is involved in electron transfer from ubiquinol to periplasmic dimethyl sulfoxide reductase. DorC was expressed as a C-terminal fusion to an 8-amino acid FLAG epitope and was purified from detergent-solubilized membranes by ion exchange chromatography and immunoaffinity chromatography. The DorC protein had a subunit Mr = 46,000, and pyridine hemochrome analysis indicated that it contained 5 mol heme c/mol DorC polypeptide, as predicted from the derived amino acid sequence of the dorC gene. The reduced form of DorC exhibited visible absorption maxima at 551.5 nm (alpha-band), 522 nm (beta-band), and 419 nm (Soret band). Redox potentiometry of the heme centers of DorC identified five components (n = 1) with midpoint potentials of -34, -128, -184, -185, and -276 mV. Despite the low redox potentials of the heme centers, DorC was reduced by duroquinol and was oxidized by dimethyl sulfoxide reductase.  (+info)

Redox components of cytochrome bc-type enzymes in acidophilic prokaryotes. I. Characterization of the cytochrome bc1-type complex of the acidophilic ferrous ion-oxidizing bacterium Thiobacillus ferrooxidans. (4/661)

The redox components of the cytochrome bc1 complex from the acidophilic chemolithotrophic organism Thiobacillus ferrooxidans were investigated by potentiometric and spectroscopic techniques. Optical redox titrations demonstrated the presence of two b-type hemes with differing redox midpoint potentials at pH 7.4 (-169 and + 20 mV for bL and bH, respectively). At pH 3.5, by contrast, both hemes appeared to titrate at about +20 mV. Antimycin A, 2-heptyl-4-hydroxyquinoline N-oxide, and stigmatellin induced distinguishable shifts of the b hemes' alpha-bands, providing evidence for the binding of antimycin A and 2-heptyl-4-hydroxyquinoline N-oxide near heme bH (located on the cytosolic side of the membrane) and of stigmatellin near heme bL (located on the periplasmic side of the membrane). The inhibitors stigmatellin, 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole, and 2, 5-dibromo-3-methyl-6-isopropyl-p-benzoquinone affected the EPR spectrum of the Rieske iron-sulfur center in a way that differs from what has been observed for cytochrome bc1 or b6f complexes. The results obtained demonstrate that the T. ferrooxidans complex, although showing most of the features characteristic for bc1 complexes, contains unique properties that are most probably related to the chemolithotrophicity and/or acidophilicity of its parent organism. A speculative model for reverse electron transfer through the T. ferrooxidans complex is proposed.  (+info)

Redox components of cytochrome bc-type enzymes in acidophilic prokaryotes. II. The Rieske protein of phylogenetically distant acidophilic organisms. (5/661)

The Rieske proteins of two phylogenetically distant acidophilic organisms, i.e. the proteobacterium Thiobacillus ferrooxidans and the crenarchaeon Sulfolobus acidocaldarius, were studied by EPR. Redox titrations at a range of pH values showed that the Rieske centers of both organisms are characterized by redox midpoint potential-versus-pH curves featuring a common pK value of 6.2. This pK value is significantly more acidic (by almost 2 pH units) than that of Rieske proteins in neutrophilic species. The orientations of the Rieske center's g tensors with respect to the plane of the membrane were studied between pH 4 and 8 using partially ordered samples. At pH 4, the Sulfolobus Rieske cluster was found in the "typical" orientation of chemically reduced Rieske centers, whereas this orientation changed significantly on going toward high pH values. The Thiobacillus protein, by contrast, appeared to be in the "standard" orientation at both low and high pH values. The results are discussed with respect to the molecular parameters conveying acid resistance and in light of the recently demonstrated long-range conformational movement of the Rieske protein during enzyme turnover in cytochrome bc1 complexes.  (+info)

Extinction coefficients and midpoint potentials of cytochrome c(6) from the cyanobacteria Arthrospira maxima, Microcystis aeruginosa, and Synechocystis 6803. (6/661)

Cytochrome c(6) is a soluble heme protein that serves as a photosynthetic electron transport component in cyanobacteria and algae, carrying electrons from the cytochrome bf complex to photosystem I. The rapid accumulation of cytochrome c(6) sequence data from a wide range of species, combined with significant advances in determining high resolution three-dimensional structures, provides a powerful database for investigating the relationship between structure and function. The fact that the gene encoding cytochrome c(6) can be readily modified in a number of species adds to the usefulness of cytochrome c(6) as a tool for comparative analysis. Efforts to relate cytochrome c(6) sequence information to structure, and structural information to function depend on knowledge of the physical and thermodynamic properties of the cytochrome from different species. To this end we have determined the optical extinction coefficient, the oxidation/reduction midpoint potential, and the pH dependence of the midpoint potential of cytochrome c(6) isolated from three cyanobacteria, Arthrospira maxima, Microcystis aeruginosa, and Synechocystis 6803.  (+info)

Donnan potential of rabbit skeletal muscle myofibrils I: electrofluorochromometric detection of potential. (7/661)

The fluorescence of the dye CC-6 [(3-hexyl-2-(3-hexyl-2-benzoxazolinylidene)-1-propenyl)-benzoxazolium iodide] has been shown to indicate Donnan potentials in rabbit skeletal muscle myofibrils. These results are in agreement with previously published work in which the potentials were measured with microelectrodes on glycerol-extraced muscle fibers. The magnitude of the Donnan potential of the myofibrils has been shown to be dependent on the state (rigor or relaxed) of the system.  (+info)

A group of thermodynamic potentials applicable to ligand binding by a polyfunctional macromolecule. (8/661)

The binding of ligands by a macromolecule can be well described by a group of potentials derivable from the energy and of which the original binding potential is one. The group is Abelian and is isomorphic with a group of symmetries. Each member corresponds to a particular set of experimental conditions--system open to some, closed to others, of the ligand-and the group as a whole is an immediate source of all possible linkage relations applicable to the macromolecule. Seen in terms of information theory it can be interpreted as a program for the response of the macromolecule to its ligands according to the conditions with which it is faced. The group provides a ready formulation of the effect of a ligand on the equilibrium constant for a reaction involving a set of macromolecules, and it leads to a clear-cut distinction between true and pseudolinkage.  (+info)

  • In contrast to normal potentiometry where the potential is measured in a steady-state, PPD involves the application of one or more independent pre-pulses to the detection electrode prior to the measurement period. (edu.au)
  • Key Words: Titrations, Potentiometry, Biochemistry. (edaq.com)
  • This second part Potentiometry brings, firstly a sufficient information of experimental technique recommended for potentiornetric (equilibria) titrimetry, secondly, an introduction to analytical aspects of potentiometric titrations, thirdly, an account of frequently used programs in potentiometric equilibria study. (upce.cz)
  • Besold J, Reiss G, Hoffmann H. Scanning tunneling potentiometry (STP) studies of gold islands on a thin carbon film. (uni-bielefeld.de)
  • J. Besold, G. Reiss, and H. Hoffmann, "Scanning tunneling potentiometry (STP) studies of gold islands on a thin carbon film", Applied surface science , vol. 65-66, 1993, pp. 23-27. (uni-bielefeld.de)
  • This site contains materials from a lecture course in Biophysics, covering activity, free energy, equilibrium constants, and effect of pH on redox potentials, potentiometry, and reaction rates. (nottingham.ac.uk)
  • Borras, M. Potentiometry, Nanostructured Materials and the Emergence of Paradigm-Shifting Analytical Platforms. (mdpi.com)
  • Highlighted are some case studies of analytical problems which have been solved using potentiometry. (abebooks.com)
  • The copper(ii) ion binding of the Ac-KGHGNG-NH2 and Ac-PTVHNE-NH2 fragments of FomA adhesin from Fusobacterium nucleatum was studied using potentiometry, UV-Vis, CD, EPR and DFT techniques. (wroc.pl)
  • Other articles where Potentiometry is discussed: chemical analysis: Potentiometry: This is the method in which the potential between two electrodes is measured while the electric current (usually nearly zero) between the electrodes is controlled. (besatwise.com)
  • Although coulometric titration and potentiometric electrode analysis yielded results that had a strong linear relationship, the results of potentiometry were consistently and significantly higher, by about 20 mEq/L. This difference was investigated further by analyzing a series of fluids containing different concentrations of sodium acetate. (oregonstate.edu)
  • In this study, a detailed multilevel systems approach combining microscopy, respirometry, potentiometry, and extracellular flux analysis (EFA) was utilized to examine metabolic adaptations that occur under aglycemic growth media conditions in HCC-derived (HEPG2) cells. (biomed.news)
  • The methods used in the study: titration with visual indication of the equivalence point, potentiometry, computer processing the results of the titration method fragmented linearization. (elsevier.com)
  • The in-solution behavior of the systems containing iba and the selected 3d metal ions was studied by potentiometry. (fq.edu.uy)
  • In agreement with previous reports, the -log*β values obtained by NMR and potentiometry, at 0.020 M ≤ [Al(III)] total ≤ 0.500 M are 12.96 ± 0.02 for Al(OH) 3 , 13.50±0.02 for Al 3 (OH) 4 5+ , and 109.70±0.09 for Al 13 (OH) 32 7+ , by assuming that Al(OH) 2 + has a value of 5.29. (scielo.org.mx)