Energy-linked transport of permeant ions in Escherichia coli cells: evidence for membrane potential generation by proton-pump.
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Aerobiosis↗
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Results for “BORIC ACID”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
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The excess radioactivity of trypsin mixtures.
The radioactivities of mixtures of trypsin and HB(3)O(3) or LiCl have been measured and compared with the radioactivity of the constituents. No evidence was found for the production of heavy particles, as had been previously reported, neither were the excess counting rates of the mixtures over that of its constituents as large. The residual excess radioactivity was about four orders of magnitude smaller than that published, yet was still statistically significant, consisting mainly of electrons having a maximum energy less than about 400 keV. The excess radioactivity of a mixture of trypsin and LiCl had a probable half-life between 5 and 46 days. Possible mechanisms for these excesses are discussed.
Absorption↗
Mass poisoning in Perak, Malaysia or the Tale of the Nine Emperor Gods and rat tail noodles.
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Adolescent↗
High-performance liquid chromatography of N-terminal tyrosine-containing oligopeptides by pre-column fluorescence derivatization with hydroxylamine, cobalt (II) and borate reagents.
A pre-column fluorescence derivatization method is described for the high-performance liquid chromatographic determination of N-terminal tyrosine-containing oligopeptides involving methionine-enkephalin and leucine-enkephalin. The peptides are converted into fluorescent derivatives by heating in a weakly alkaline medium (pH 8.5) containing hydroxylamine, cobalt(II) ion and borate. The derivatives are separated on a reversed-phase column (TSKgel ODS-120T) by gradient elution of acetonitrile in a mobile phase containing borate buffer (pH 8.5) and tetra-n-butylammonium chloride, and then determined by fluorimetry. The derivatization provides a single fluorescent product for each N-terminal tyrosine-containing oligopeptide, but does not allow the production of fluorescent derivatives for peptides having no tyrosyl residue at the N-terminal. The method is selective and sensitive; the lower limits of detection for the N-terminal tyrosine-containing oligopeptides tested were 140-310 fmol per 100 microliters injected.
Boric Acids↗
Fluorimetric assay of dopamine, norepinephrine and their 3-O-methyl metabolites by using fluorescamine.
Fluorescamine was subjected to reaction with dopamine and norepinephrine (catecholamines) and with 3-methoxytyramine and normetanephrine (3-methyl metabolites of catecholamines) in phosphate or borate buffer. Catecholamines gave the highest fluorescent intensity at pH 8.0 in phosphate buffer but lower fluorescence in borate buffer. The fluorophores produced in phosphate or borate buffer were the same but the fluorescence intensities were suppressed in borate buffer. The dopamine and norepinephrine fluorophores were separated by high-pressure liquid chromatography on Hitachi 3011 gel with methanol-0.10 M Tris buffer of pH 8.0 (7:3). They were measurable at the 100-pmole level. The metabolites were also measurable by the same chromatography. By using methanol-0.15 M borate buffer of pH 8.0, cate-chol-O-methyltransferase activity might be assayed.
Boric Acids↗
Thin-layer chromatography of cyclic 3',5'-guanosine monophosphate on tetraborate-impregnated silica gel layers.
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Animals↗
Separation and simultaneous determination of water-soluble and fat-soluble vitamins by electrokinetic capillary chromatography.
A comparative study of different surfactants, such as sodium dodecyl sulfate and bis(2-ethylhexyl) sodium sulfosuccinate (AOT), as pseudostationary phases was conducted in order to find the best conditions for the separation of the water- and fat-soluble vitamins by electrokinetic capillary chromatography. Separation was accomplished with AOT in a water-acetonitrile solution in the presence of boric acid-sodium borate buffer. A study of different variables was performed in order to obtain the best resolution and quantification of the vitamins: the variables explored were the pH and concentration of the buffer used, the percentage of acetonitrile, the concentration of surfactant and the applied voltage. Calibration curves and precision data were obtained for each analyte. Finally, a method to analyze these substances in pharmaceutical preparations is proposed.
Calibration↗
Analysis of naphthalenesulfonate compounds by cyclodextrin-mediated capillary electrophoresis with sample stacking.
This study systematically investigates the optimal conditions for analyzing the positional isomers of multi-charged naphthalenesulfonate compounds by cyclodextrin-mediated capillary electrophoresis (CE). Specifically, this work employs large-volume sample injection with the electrode polarity switching technique. The most effective separation and sample stacking conditions were 15 mM borate buffer with a mixture of beta- and gamma-cyclodextrin (concentration ratio 3:7 mM) at pH 9.2, and the sample hydrodynamic injection of up to 60 s at 3 p.s.i. (around 1.8 microl, and 1 p.s.i. = 6.9 kPa). Significantly selective and sensitive improvements were observed and a more than 100-fold enrichment was achieved (based on peak area). The reproducibility of migration time and quantitative results of stacking CE can be improved by using an internal standard. The quantitation limits of these naphthalenesulfonate isomers, based on a signal-to-noise ratio above 10, can be about 4 microg/l with UV detection. This method was successfully applied to determine the trace amount of naphthalenesulfonate isomers in a spiked drinking water sample.
Boric Acids↗
Separation of pd(GC)12 from pd(AT)12 by free solution capillary electrophoresis.
The two synthetic self complementary oligonucleotides pd(AT)12 and pd(GC)12 were separated by free solution capillary electrophoresis (CZE) using simple borate buffers. The effects of pH (7.5-9) and the concentration of the buffer (0.03-0.35 M) were investigated. Higher pH values and buffer concentrations led to better resolution and longer migration times, the pH having a more pronounced effect on the separation than the concentration of the buffer. It is proposed that the conformation and effective length of the oligonucleotides may have a role in their separation in free solution capillary electrophoresis.
Boric Acids↗
Capillary electrophoresis of some tetracycline antibiotics coupled with reductive fast cyclic voltammetric detection.
The separation and quantitative performance parameters for tetracycline, chlortetracycline and oxytetracycline antibiotics were investigated by capillary zone electrophoresis coupled with fast cyclic voltammetric detection. Optimization of pH and complexation with a boric acid-sodium tetraborate buffer provided good resolution of all compounds. Detection by electrochemical reduction using fast on-line cyclic voltammetric detection with a Hg-film-microm electrode gave detection limits (2 x peak-to-peak baseline noise) of 7 x 10(-7) mol/l for tetracycline and chlortetracycline, and 1.5 x 10(-6) mol/l for oxytetracycline. The influence of electrode material, potential range and scan rate was examined and discussed. Optimal electrochemical detection was obtained at a Hg-film electrode with a waveform that consisted of an initial constant potential of -0.6 V for 200 ms followed by a cyclic voltammetry (CV) scan at 300 V/s from - 0.6 V to a vertex potential of 1.7 V. The analytical signal was obtained by plotting the integrated values of the CV current from each applied waveform as a function of time. The calibration plot (peak areas) for each separated peak was found to be linear over three-orders of magnitude.
Anti-Bacterial Agents↗
Serum calcium and magnesium concentrations and the use of a calcium-magnesium-borogluconate solution in the treatment of Friesian mares with retained placenta.
The purpose of the present study was to compare serum calcium and magnesium concentrations in mares with or without a retained placenta (RP) and to evaluate treatment of mares with RP with oxytocin versus oxytocin combined with Ca-Mg-borogluconate solution. Blood samples were obtained within 12 h of foaling from Friesian mares with and without an RP (n = 90 and 65, respectively). Serum Ca and Mg concentrations were analyzed by atomic absorption spectrophotometry. In total, we treated 112 cases of RP in 101 Friesian mares by infusion of either oxytocin dissolved in saline solution or oxytocin dissolved in Ca-Mg-borogluconate solution. We defined RP as the failure to expel all or a part of the fetal membranes up to 3 h after delivery of the foal. We defined a positive response to the treatment as the passage of the entire placenta within 2 h after the infusion. Mares with RP had significantly lower serum calcium levels within 12 h of foaling than mares without RP. Serum magnesium levels showed no difference. Sixty-four percent of the mares treated with oxytocin in Ca-Mg-borogluconate solution responded positively to the treatment, compared to 44% of the mares treated with oxytocin in saline solution (P < 0.05).
Animals↗
Chemical synthesis of polysaccharides.
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Boric Acids↗
Generation and biomimetic chemistry of tungsten-dithiolene complexes containing the hydrotris(3,5-dimethylpyrazol-1-yl)borate ligand.
Reactions of bis(thio)-W(VI) complexes, LWS2X (L = hydrotris (3,5-dimethylpyrazol-1-yl)borate, X = monoanion), with alkynes produce dithiolene complexes, LWX(dithiolene). The synthesis and characterization of orange LW(OPh){S2C2(CO2Me)2} (1) and burgundyred LW(SePh) {S2C2(Ph)(2-quinoxalinyl)} (2) and the X-ray crystal structure of 1.0.5CH2Cl2, are described in detail. Crystals of 1.0.5CH2Cl2 are orthorhombic, space group Pbcn, with a = 29.826(6), b = 13.291(4), c = 16.078(4) A, V = 6373(5) A3, and Z = 8. The six-coordinate, distorted-octahedral complex features a tridentate L ligand, a monodentate phenoxide ligand, and a bidentate dithiolene ligand. The short W-S bonds (2.267(4) and 2.279(4) A) and the parameters associated with the phenoxide ligand (W-O = 1.850(8) A, W-O-C = 146(1) degree), point to a considerable degree of W-ligand multiple bonding in the [W(OPh)(dithiolene)]+ unit. For 2, W-Se and average W-S distances of 2.49(2) A and 2.30(2) A, respectively, have been obtained from EXAFS studies. The formation of yellow 3,3'-dithiobis[2-(phenyl)thieno[2,3-b]quinoxaline] (3) upon oxidation of 2 supports the likely generation of urothione upon oxidative degradation of molybdopterin-containing tungsten enzymes from hyperthermophilic organisms.
Boric Acids↗
Physico-chemical characterization of proteins by capillary electrophoresis.
The electrophoretic mobility of proteins was successfully determined by means of capillary electrophoresis (CE) with various background electrolytes (BGEs). The objective was focused on the variation in BGE physico-chemical composition and the consequential impact on the observed protein charge. Experimental and calculated mobilities, according to Henry's equation, versus ionic strength have been compared. For positively-charged lysozyme, a good agreement between observed and calculated mobilities was observed using triethanolamine chloride at pH 7.0 as the BGE. Mobility close to zero was shown using borate (pH 8.0) and phosphate (pH 7.0) at a low ionic strength of about 20 mmol l(-1), and as a consequence, specific adsorption of oxyanions was evidenced. Lysozyme retention in the case of reversed-phase high-performance liquid chromatography (RP-HPLC) was decreased by the presence of phosphate ions. CE and HPLC are complementary tools for characterizing the behaviour of lysozyme. On the other hand, the mobility of the negatively-charged alpha-lactalbumin remained constant as regards phosphate at pH 7.0 in the 20-200 mmol l(-1) range, contrary to the decrease that had been expected with the increasing ionic strength. beta-Lactoglobulin exhibited increasingly lower mobilities than those expected of boric acid/borate at pH 7.0 and 8.0 (I=20 mmol l(-1)).
Boric Acids↗
Determination of bisnafide, a novel bis-naphthalimide anticancer agent, in human plasma by high-performance liquid chromatography with UV detection.
A simple, specific, and sensitive high-performance liquid chromatographic (HPLC) assay utilizing ultraviolet (UV) detection for the determination of bisnafide in human plasma was developed, validated, and applied to plasma samples from patients undergoing cancer therapy. Plasma samples, containing an internal standard, XE842, were first deproteinized with 2.0 ml acetonitrile, and subsequently, 1.0 ml and pH 9 boric acid-potassium chloride-sodium hydroxide buffer (0.1 M) was added. To this mixture, 9.0 ml of ethyl ether was added then vortex mixed. Following centrifugation, the ether layer was back-extracted into 250 microliters of 0.1 M phosphoric acid, then removed by vacuum aspiration. A portion of the remaining acid layer was directly injected onto the HPLC. Bisnafide was quantified using a Shiseido Capcell Pak C8 HPLC column and ultraviolet detection (274 nm). The lower limit of quantification was 10 ng ml-1 using 1.0 ml plasma. The intraday precision (RSD) ranged from 2.7 to 8.6% over a concentration range of 10-1000 ng ml-1. The interday precision (RSD) ranged from 5.6 to 11.5%. Overall mean accuracy was +/- 5.2%. The drug was stable in frozen heparinized human plasma stored at -20 degrees C for at least 1 year and stable throughout at least two freeze-thaw cycles. This method was successfully utilized for quantifying plasma concentrations needed to study the clinical pharmacokinetics of bisnafide in patients undergoing cancer therapy.
Antineoplastic Agents↗
Advances in understanding mechanisms of toxicity and implications for risk assessment.
Knowledge of mechanism of action of a toxicant can greatly improve the accuracy of risk estimation by replacing with data the many default assumptions of risk assessment. Results from studies on comparative pharmacokinetics, metabolism, cell biology, and molecular biology have been successfully applied to problems of interspecies extrapolation, interindividual differences in susceptibility, and the relevance of high-dose findings for low-dose risk estimation. Examples are provided. Extremely rapid progress in understanding the molecular control of embryonic pattern formation and organogenesis has the potential to significantly improve the accuracy of risk assessment, especially by providing a sounder basis for characterizing interspecies differences, individual susceptibility, and multifactorial (gene-environment) etiologies of abnormal development. However, it will be necessary to quantitate toxicant-induced changes at the molecular level and to determine the level of change needed to perturb higher levels of biological organization at which adverse effects are manifested. It will also be important for risk assessment methodology to evolve so that it can better and more routinely accommodate mechanistic information. There is great potential for the recent and coming advances in knowledge of the molecular and cellular basis of abnormal development to be applied to risk assessment. Consideration should be given to shifting some of the resources now allocated to hazard screening to investigating the mechanisms of chemically induced abnormal development.
Abnormalities, Drug-Induced↗
Mechanism of microbial aggregation during capillary electrophoresis.
We studied the aggregation of a rod-shaped bacteria, Bifidobacterium infantis, during capillary electrophoresis (CE). A microscope with an intensified CCD camera was employed to monitor the migration and aggregation of bacteria, which are labeled with fluorescent dye Syto 9 and excited with a 488-nm argon ion laser. A collision-based aggregation mechanism is proposed, in which collisions between microbes result from different mobilities and migration directions in the electric field. Individual microbes are aligned differently with respect to the direction of the electric field and exhibit different drag coefficients. The long-range forces include van der Waals attraction and electrostatic repulsion as qualitatively described by DLVO theory. Collisions in CE produce sufficient energy to overcome electrostatic repulsion, thus improving the efficiency of aggregation. This is supported by the fact that higher electric fields always resulted in faster aggregation. Also, when sodium phosphate buffer was used, increasing the ionic strength resulted in faster aggregation. However, when Tris-boric acid-EDTA (TBE, pH 9.1) buffer was used, the aggregation speed decreased when the ionic strength increased. We attribute this to the change of the surface of the bacteria at high borate and EDTA concentration, such as the loss of polysaccharides or the presence of complexation. This reduces the hydrophobicity of the surface and, thus, the short-range attractive forces. The addition of 0.05% poly(ethylene oxide) (PEO) into high ionic strength TBE buffer increased the aggregation rate. This can be attributed to the bridging effect of PEO between microbes. Further increase in the concentration of polymer reduced the aggregation rate, especially when the electric field was low, due in part to the increase in viscosity. The decrease in migration velocity produced lower collision energies and lower aggregation efficiencies as well.
Bifidobacterium↗
[eta 5-Cyclopentadienyl]metal tricarbonyl pyrylium salts: novel reagents for the specific conjugation of proteins with transition organometallic labels.
New specific reagents for the conjugation of organo transition metal species to proteins are described. These reagents are pyrylium salts bearing a (eta 5-C5H4)M(CO)3 (M = Mn and Re) at position 4. They couple with simple amines (n-butylamine and tert-butylamine) and to lysine side chains of proteins (bovine serum albumin and lysozyme) with varying yields. In almost all cases, the final conjugated species is a pyridinium salt, with the exception of lysozyme, for which the reaction ends at the divinylogous amide form. Differences in reactivity for bovine serum albumin and lysozyme can be explained in terms of differences of isoelectric point and steric local environment around the reactive lysine residue.
Acetonitriles↗