Abstract  The conditional stability constant at pH 7.4 for Cu(II) binding at the N-terminal site (NTS) of human serum albumin (HSA) was determined directly by competitive UV-vis spectroscopy titrations using nitrilotriacetic acid (NTA) as the competitor in 100 mM NaCl and 100 mM N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (Hepes). The log Kc (NTS) value of 12.0 +/- 0.1 was determined for HSA dissolved in 100 mM NaCl. A false log log Kc (NTS) (c) value of 11.4 +/- 0.1 was obtained in the 100 mM Hepes buffer, owing to the formation of a ternary Cu(NTA)(Hepes) complex. The impact of the picomolar affinity of HSA for Cu(II) on the availability of these ions in neurodegenerative disorders is briefly discussed.

Abstract  The present study was conducted to assess in rats the comparative effects of a number of chelating agents on the urinary excretion and tissue distribution of A1. Adult male Sprague-Dawley rats received a single intraperitoneal dose of aluminium (A1) nitrate nonahydrate (0.24 mmol/kg). Ten min. after A1 injection 1,2-dimethyl-3-hydroxypyrid-4-one, 2,3-dihydroxybenzoic acid, picolinic acid, methylmalonic acid, ethylenediamine-di(o-hydroxyphenylacetic) acid, 1-benzyl-2-methyl-3-hydroxypyrid-4-one, 1-(p-methylbenzyl)-2-methyl-3-hydroxypyrid-4-one, 1-(p-methoxy-benzyl)-2-methyl-3-hydroxypyrid-4-one, 1-(p-chlorobenzyl)-2-methyl-3-hydroxypyrid-4-one, 1-benzyl-2-ethyl-3-hydroxypyrid-4-one, 1-(p-methyl-benzyl)-2-ethyl-3-hydroxypyrid-4-one, 1-[3-hydroxy-2-methyl-4-oxopyridyl]-2-ethanesulfonic acid and 1-benzyl-(4-carboxylic acid)-3-hydroxy-2-methyl-4-oxopyridine were given by gavage at 1.79 mmol/kg. A control group received similar volumes of distilled water. An additional group of rats received a subcutaneous injection of desferrioxamine at 1.79 mmol/ kg. Urine samples were collected daily for three consecutive days and the animals were killed after this period. Samples of brain, bone, liver, kidney and spleen were collected. Although desferrioxamine, 1,2-dimethyl-3-hydroxypirid-4-one, 1-(p-methylbenzyl)-2-methyl-3-hydroxypyrid-4-one, 1-(p-methoxybenzyl)-2-methyl-3- hydroxypyrid-4-one, 1-(p-methylbenzyl)-2-ethyl-3-hydroxypyrid-4-one, 1-[3-hydroxy-2-methyl-4-oxopyridyl]-2-ethanesulfonic acid and 1-benzyl-(4-carboxylic acid)-3-hydroxy-2-methyl-4-osopyridine significantly enhanced the total excretion of A1 into urine, only treatment with 1-(p-chlorobenzyl)-2-methyl-3-hydroxypyrid-4-one and 1-benzyl-2-ethyl-3-hydroxypyrid-4-one significantly reduced A1 concentrations in all analyzed tissues. No beneficial effects of the remaining chelators on Al mobilization were observed. Further studies on the effects of some 3-hydoxrypyrid-4-ones on A1 removal can be of interest for the treatment of A1 accumulation and toxicity.

Abstract  1-Anilinonaphthalene-8-sulfonic acid (1,8-ANS), 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) and 2-(p-toluidino)naphthalene-6-sulfonic acid (2,6-TNS) were evaluated as additives in different buffers for the detection of bovine whey proteins using laser-induced fluorescence (LIF) monitoring in capillary electrophoresis (CE). These N-arylaminonaphthalene sulfonates furnish a large fluorescence emission when associated to some proteins whereas their emission in aqueous buffers, such as those used in CE separations, is very small. To select the best detection conditions, the fluorescence of these probes was first compared using experiments carried out in a fluorescence spectrophotometer. Using bovine serum albumin (BSA) as a model protein, it was demonstrated that 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer (pH 8 and pH 10.2) and the fluorescent probe 2,6-TNS gave rise to the highest increase in fluorescence for BSA. When the composition of these separation buffers was optimized for the electrophoretic separations, CHES buffer, pH 10.2 was chosen as the most suitable buffer to detect bovine whey proteins. The limit of detection obtained for some whey proteins in CE separations was about 6.10(-8) M for BSA, 3.10(-7) M for beta-lactoglobulin A (beta-LGA), 3.10(-7) M for beta-lactoglobulin B (beta-LGB), and 3.10(-6) M for alpha-lactalbumin (alpha-LA). These detection limits were compared to those achieved using UV detection under the same separation conditions. The results showed that the detection limits of BSA, beta-LGA and beta-LGB were twice as good using LIF than with UV detection. However, the limit of detection for alpha-LA was better when UV was used. The applicability of LIF detection to CE separation of whey proteins in bovine milk samples was also demonstrated. (C) 1999 Elsevier Science B.V. All rights reserved.

Abstract  NO and its derivative ONOO- are potent free radicals that can cause cell damage, especially in the presence of O2. To determine the potential pulmonary toxicities of nitric oxide (NO) and peroxynitrite (ONOO-) in vitro, Survanta (2.5 mg/ml) was exposed to ONOO- (0.3-8 mM) in the presence of two different buffering systems (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid and phosphate buffer) and minimum surface tension (MST) was determined with an oscillating bubble surfactometer. Significant increases in MST were seen only with exposure to 8 mM ONOO-, indicating that in vitro, high concentrations of ONOO- can inhibit natural surfactant function. The in vivo effects of NO and hyperoxia were then studied in four groups of newborn piglets ventilated for 48 h with 21% O2, 100% O2, 21% O2 and 100 ppm NO, or with 90% O2 and 100 ppm NO. Five animals served as an untreated control group. Bronchoalveolar lavage fluid (BAL) obtained at 48 h was subjected to centrifugation and the surfactant pellet was reconstituted to 5 mg phospholipid/ml. Significant increases in MST were seen in surfactant from piglets ventilated with NO and 90% O2, compared with either untreated controls or piglets ventilated with 21% O2 for 48 h (P < 0.05, analysis of variance). Significant increases in neutrophil chemotactic activity (NCA) of BAL were also found in the NO and O2 group (P < 0.05), with significant positive interaction between NO and O2 found (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract  In a study screening anaerobic microbes utilizing D: -galactitol as a fermentable carbon source, four bacterial strains were isolated from an enrichment culture producing H₂, ethanol, butanol, acetic acid, butyric acid, and hexanoic acid. Among these isolates, strain BS-1 produced hexanoic acid as a major metabolic product of anaerobic fermentation with D: -galactitol. Strain BS-1 belonged to the genus Clostridium based on phylogenetic analysis using 16S rRNA gene sequences, and the most closely related strain was Clostridium sporosphaeroides DSM 1294(T), with 94.4% 16S rRNA gene similarity. In batch cultures, Clostridium sp. BS-1 produced 550 ± 31 mL L⁻¹ of H₂, 0.36 ± 0.01 g L⁻¹ of acetic acid, 0.44 ± 0.01 g L⁻¹ of butyric acid, and 0.98 ± 0.03 g L⁻¹ of hexanoic acid in a 4-day cultivation. The production of hexanoic acid increased to 1.22 and 1.73 g L⁻¹ with the addition of 1.5 g L⁻¹ of sodium acetate and 100 mM 2-(N-morpholino)ethanesulfonic acid (MES), respectively. Especially when 1.5 g L⁻¹ of sodium acetate and 100 mM MES were added simultaneously, the production of hexanoic acid increased up to 2.99 g L⁻¹. Without adding sodium acetate, 2.75 g L⁻¹ of hexanoic acid production from D-galactitol was achieved using a coculture of Clostridium sp. BS-1 and one of the isolates, Clostridium sp. BS-7, in the presence of 100 mM MES. In addition, volatile fatty acid (VFA) production by Clostridium sp. BS-1 from D-galactitol and D: -glucose was enhanced when a more reduced culture redox potential (CRP) was applied via addition of Na₂S·9H₂O.

Abstract  This study describes the activity of Pt40%/Vulcan XC-72 carbon catalyst modified with Rb2.5H0.5PW12O40 zeolite-type matrix prepared by a mixing method. The catalyst is used to induce the anodic oxidation of ethanol in an acidic medium as well as to investigate its suitability for use in direct ethanol fuel cells (DEFCs). Under the same Pt-loading, mass, and experimental conditions for ethanol oxidation, the catalysts containing the above mentioned zeolite-type supports display significantly enhanced electrocatalytic activity in comparison to unmodified Pt40%/Vulcan XC-72 carbon. Our new system containing the Nafion-treated rubidium salt of Keggin-type heteropolyacid as a matrix and the Pt40%/Vulcan XC-72 carbon catalyst was characterized with respect to its electrochemical properties and its electrocatalytic activity towards the ethanol oxidation. Results clearly indicate that proposed catalyst containing Rb2.5H0.5PW12O40 (RbPW) matrix is of potential utility to direct ethanol fuel cell.

Abstract  A new portable instrument has been developed that offers rapid detection of ozone at the parts per billion (ppb) level for personal exposure monitoring. The personal ozone monitor is based on the EPA Federal Reference Method of UV absorbance and has the advantage of being small (10 cm x 7.6 cm x 3.8 cm), lightweight (0.3 kg), low power (2.9 W), and battery-operated. The instrument can be worn by an individual during normal daily activities because it is unaffected by humidity, physical orientation, temperature, and vibration. In order to eliminate any significant interference from water vapor, Nafion tubing was installed before the detection cell, and the optical path was lined with quartz. A precision of 1.5 parts per billion by volume (ppbv) and limit of detection of 4.5 ppbv (S/N = 3) was demonstrated with the instrument making measurements every 10 s.

Abstract  Patients with human African trypanosomiasis present a major dysruption of the circadian rhythmicity of the sleep-wake cycle, which was also found in rats infected with Trypanosoma brucei brucei (T.b.b.). The alterations in the immune function and nervous system in African trypsanosomiasis led us to investigate the involvement of nitric oxide (NO), a key molecule in immune and neurophysiological mechanisms, in experimental trypanosomiasis. NO was measured in 35 Sprague Dawley rats using differential impulsional voltammetry with a carbon fiber coated with porphyrin-nickel and nafion, ex vivo in the blood and in vivo in the brain. The rats were anaesthetized with sodium chlorate. Infection was performed intraperitoneally (i.p.) with 0.2 ml of a T.b.b. cryostabilate (clone AnTat 1.1E). Blood was collected by an intracardiac puncture with immediate replacement of blood volume (1 ml) in 7 control rats and 8 rats infected since 15 days, before and after i.p. administration of L-ANA (L-arginine-p-nitro-anilide, 100 mg.kg-1, an inhibitor of NO synthase). Brain measures were done in 20 rats (8 controls, and 12 rats infected since 15 or 21 days), in the cortex (H, -0.5 mm; AP, -0.8 mm; L, 1.2 mm) and the lateral ventricle (H,-3.2 mm). In infected rats, blood NO was at 70% of control values (p < 0.001), and L-ANA suppressed the NO signal in all animals (p < 0.0001), demonstrating that the signal originated from NO. Cortical NO was higher than in the ventricle in both control (p < 0.0001) and infected rats (p < 0.001). NO was more elevated in both structures in 15-day-infected rats than in control rats (p < 0.0001), the difference being enhanced in 21-day-infected rats (p < 0.001). L-ANA suppressed the NO signal in 30 to 60 min. These data suggest that NO intervenes in the development of trypanosomiasis in different manners. It is increased in the brain, which remains unexplained, where it may be involved in blood-brain barrier permeation. Conversely, it is decreased in the blood, may be because of macrophage function impairment, which would explain why trypanosomes can multiply in the host.

Abstract  A dynamic supported liquid membrane tip extraction (SLMTE) procedure for the effective extraction and preconcentration of glyphosate (GLYP) and its metabolite aminomethylphosphonic acid (AMPA) in water has been investigated. The SLMTE procedure was performed in a semi-automated dynamic mode and demonstrated a greater performance against a static extraction. Several important extraction parameters such as donor phase pH, cationic carrier concentration, type of membrane solvent, type of acceptor stripping phase, agitation and extraction time were comprehensively optimized. A solution of Aliquat-336, a cationic carrier, in dihexyl ether was selected as the supported liquid incorporated into the membrane phase. Quantification of GLYP and AMPA was carried out using capillary electrophoresis with contactless conductivity detection. An electrolyte solution consisting of 12 mM histidine (His), 8 mM 2-(N-morpholino)ethanesulfonic acid (MES), 75 microM cetyltrimethylammonium bromide (CTAB), 3% methanol, pH 6.3, was used as running buffer. Under the optimum extraction conditions, the method showed good linearity in the range of 0.01-200 microg/L (GLYP) and 0.1-400 microg/L (AMPA), acceptable reproducibility (RSD 5-7%, n=5), low limits of detection of 0.005 microg/L for GLYP and 0.06 microg/L for AMPA, and satisfactory relative recoveries (90-94%). Due to the low cost, the SLMTE device was disposed after each run which additionally eliminated the possibility of carry-over between runs. The validated method was tested for the analysis of both analytes in spiked tap water and river water with good success.

Abstract  One acetamide and 5 acetanilide herbicides are currently registered for use in the United States. Over the past several years, ethanesulfonic acid (ESA) and oxanilic acid (OA) degradation products of these acetanilide/acetamide herbicides have been found in U.S. ground waters and surface waters. Alachlor ESA and other acetanilide degradation products are listed on the U.S. Environmental Protection Agency's (EPA) 1998 Drinking Water Contaminant Candidate List. Consequently, EPA is interested in obtaining national occurrence data for these contaminants in drinking water. EPA currently does not have a method for determining these acetanilide degradation products in drinking water; therefore, a research method is being developed using liquid chromatography/negative ion electrospray/mass spectrometry with solid-phase extraction (SPE). A novel chromatographic separation of the acetochlor/alachlor ESA and OA structural isomers was developed which uses an ammonium acetate-methanol gradient combined with heating the analytical column to 70 degrees C. Twelve acetanilide degradates were extracted by SPE from 100 mL water samples using carbon cartridges with mean recoveries >90% and relative standard deviations < or =16%.

Abstract  This review paper describes recent developments in both the fundamental and technological aspects of direct methanol fuel cells (DMFCs). Most previous studies in this field have dealt with fundamental aspects, whereas in recent years, the technology of these devices has become the object of significant interest. This is mainly due to the fact that a probable application of DMFCs in portable power sources and in hybrid electrical vehicles has only recently been envisaged. The section on fundamentals is particularly focused on the electrocatalysis of the methanol oxidation reaction and oxygen electroreduction. In this regard, particular relevance is given to the interpretation of the promoting effect on Pt of additional elements and some aspects of the electrocatalysis of oxygen reduction in the presence of methanol crossover have been treated. The technology section deals with the development of both components and devices. Particular emphasis is given to the development of high surface area electrocatalysts and alternative electrolyte membranes to Nafion, also the fabrication methodologies for the M&E assembly have been discussed. The last part of the paper describes the recent efforts in developing DMFC stacks for both portable and electro-traction applications. The current status of the technology in this field is presented and some important technical and economical challenges are been discussed.

Abstract  We report the development and application of a capillary hollow fibre membrane interface using methanol as an acceptor phase to deliver target analytes to an electrospray ionization source and a triple quadrupole mass spectrometer. Superior fluid handling systems lead to greater signal stability and membrane integrity for the continuous on-line monitoring of polar and charged analytes in complex aqueous samples with detection limits in the parts-per-trillion to parts-per-billion range. The system can be operated in either a continuous flow or a stopped acceptor flow mode - the latter giving rise to greater sensitivity. We report detection limits, enrichment factors and signal response times for selected analytes with polydimethylsiloxane and Nafion® polymer membrane interfaces. In addition, we demonstrate the use of this interface to detect pharmaceuticals and other contaminants in natural water and artificial urine. The improved sensitivity and analytical response times of our CP-MIMS system make it possible to continuously monitor dynamic chemical systems with temporal resolutions on the order of minutes. Presented is a comparison of the performance of CP-MIMS versus direct infusion electrospray ionization, demonstrating the potential advantages over direct infusion for trace analyte measurements in complex, high ionic strength samples. Furthermore, by continuously flowing a reaction mixture in a closed loop over the interface, we demonstrate the use of the system as an in situ reaction-monitoring platform for the chlorination of a model organic compound in aqueous solution.

Abstract  Methanol crossover from the anode side to the cathode site across the membrane in direct methanol fuel cells causes loss of fuel and catalyst poisoning. Many reports deal with the modification of the commonly used Nafion(R) membrane or the development of new polymer membranes exhibiting reduced methanol permeability. The present study reports on the use of tetra(orthoaminophenyl)porphyrin ((o-NH2)TPP) as the methanol barrier when electropolymerized on a direct methanol fuel cell cathode. Using the electrochemical quartz crystal microbalance and atomic force microscopy techniques, the (poly(o-NH2)TPP) films which efficiently reduced methanol permeability were shown to be non-porous, 0.55 mum thick and characterized by a high density (0.94 g/cm(3)) and high porphyrin site concentration (1.4 M). For a glassy carbon electrode electrodeposited with Pt (Pt/GC), the oxygen reduction current density in 1 M H2SO4 at +0.1 V decreases from 0.42 to 0.23 mA/cm(2) in the presence of 0.5 M methanol while a similar electrode coated with the electropolymerized porphyrin shows almost no decrease after methanol addition (0.58 and 0.56 mA/cm(2), respectively). For Pt/C electrodes with a surface morphology coarser than that of Pt/GC, the surface was first coated with electropolymerized aniline-2-sulfonic acid (PAS) and then with the electropolymerized porphyrin. The ratio of oxygen reduction currents after and before adding 0.25 M methanol was approximately 90% in this case. Experiments in a two-electrode configuration showed that it is possible to operate a DMFC with low current output without using an electrolytic membrane separating the anode from the cathode, provided that the cathode is coated with a bilayer of PAS/poly(o-NH2)TPP. (C) 2004 Elsevier B.V. All rights reserved.

Abstract  A novel flow injection analysis (FIA) system suitable for measurement of S-nitrosothiols (RSNOs) in blood plasma is described. In the proposed (FIA) system, samples and standards containing RSNO species are injected into a buffer carrier stream that is mixed with the reagent stream containing 3,3'-dipropionicdiselenide (SeDPA) and glutathione (GSH). SeDPA has been shown previously to catalytically decompose RSNOs in the presence of a reducing agent, such as GSH, to produce nitric oxide (NO). The liberated NO is then detected downstream by an amperometric NO sensor. This sensor is prepared using an electropolymerized m-phenylenediamine (m-PD)/resorcinol and Nafion composite films at the surface of a platinum electrode. Using optimized flow rates and reagent concentrations, detection of various RSNOs at levels in the range of 0.25-20 μM is possible. For plasma samples, detection of background sensor interference levels within the samples must first be carried out using an identical FIA arrangement, but without the added SeDPA and GSH reagents. Subtraction of this background sensor current response allows good analytical recovery of RSNOs spiked into animal plasma samples, with recoveries in the range of 90.4-101.0%.