Presence Of Sulfite Research Articles

Fluorometric enzymatic assay of l-arginine

The enzymes of l-arginine (further − Arg) metabolism are promising tools for elaboration of selective methods for quantitative Arg analysis. In our study we propose an enzymatic method for Arg assay based on fluorometric monitoring of ammonia, a final product of Arg splitting by human liver arginase I (further – arginase), isolated from the recombinant yeast strain, and commercial urease. The selective analysis of ammonia (at 415nm under excitation at 360nm) is based on reaction with o-phthalaldehyde (OPA) in the presence of sulfite in alkali medium: these conditions permit to avoid the reaction of OPA with any amino acid. A linearity range of the fluorometric arginase-urease-OPA method is from 100nM to 6μМ with a limit of detection of 34nM Arg. The method was used for the quantitative determination of Arg in the pooled sample of blood serum. The obtained results proved to be in a good correlation with the reference enzymatic method and literature data. The proposed arginase-urease-OPA method being sensitive, economical, selective and suitable for both routine and micro-volume formats, can be used in clinical diagnostics for the simultaneous determination of Arg as well as urea and ammonia in serum samples.

Nanostructured photoelectrochemical solar cell for nitrogen reduction using plasmon-enhanced black silicon.

Ammonia (NH3) is one of the most widely produced chemicals worldwide. It has application in the production of many important chemicals, particularly fertilizers. It is also, potentially, an important energy storage intermediate and clean energy carrier. Ammonia production, however, mostly uses fossil fuels and currently accounts for more than 1.6% of global CO2 emissions (0.57 Gt in 2015). Here we describe a solar-driven nanostructured photoelectrochemical cell based on plasmon-enhanced black silicon for the conversion of atmospheric N2 to ammonia producing yields of 13.3 mg m−2 h−1 under 2 suns illumination. The yield increases with pressure; the highest observed in this work was 60 mg m−2 h−1 at 7 atm. In the presence of sulfite as a reactant, the process also offers a direct solar energy route to ammonium sulfate, a fertilizer of economic importance. Although the yields are currently not sufficient for practical application, there is much scope for improvement in the active materials in this cell.

Comparison of Hydrogen Peroxide to Ammonium Ions and Sulfite as a Free Chlorine Quenching Agent for Disinfection By-Product Measurement

AbstractHydrogen peroxide is a potential dechlorinating agent that can preserve chlorinated drinking water samples for the determination of disinfection by-products (DBPs). The impact of hydrogen peroxide on the storage of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and adsorbable organic halides (AOX) generated by chlorination in a model of natural water was investigated and compared with parallel samples quenched by sodium sulfite and ammonium sulfate. Positive errors of up to 9 μg/L for THMs, 19 μg/L for HAAs, 1 μg/L for HANs, and 22 μg Cl/L for AOX were found after adding ammonium and storing for 9 days at 4°C, primarily due to the continued formation of chloroform, bromodichloromethane, dichloro- and trichloro-acetic acids, and dichloroacetonitrile. Hydrogen peroxide and sulfite led to smaller errors in the determination of THMs, HAAs, and AOX, while HANs degraded in the presence of sulfite. Hydrogen peroxide was the most suitable dechlorinating agent of these three...

Different mechanisms of resistance modulate sulfite tolerance in wine yeasts.

From a technological point of view, yeast resistance to sulfite is of great interest and represents an important technological character for winemaking. Several mechanisms are involved, and strain-dependent strategies to obtain SO2 resistance can deeply influence wine quality, although this choice is less relevant in determining the technological performance of the strain during fermentation. In this study, to better understand the strain-specific mechanisms of resistance, 11 Saccharomyces cerevisiae strains, whose genomes have been previously sequenced, were selected. Their attitude towards sulfites, in terms of resistance and production, was evaluated, and RNA-sequencing of four selected strains was performed during fermentation process in synthetic grape must in the presence of SO2. Results demonstrated that at molecular level, the physical effect of SO2 triggered multiple stress responses in the cell and high tolerance to general enological stressing condition increased SO2 resistance. Adaptation mechanism due to high basal gene expression level rather than specific gene induction in the presence of sulfite seemed to be responsible in modulating strain resistance. This mechanism involved higher basal gene expression level of specific cell wall proteins, enzymes for lipid biosynthesis, and enzymes directly involved in SO2 assimilation pathway and efflux.

Effective Electrochemistry of Human Sulfite Oxidase Immobilized on Quantum-Dots-Modified Indium Tin Oxide Electrode.

The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO.

Selection and validation of reference genes for quantitative real-time PCR studies during Saccharomyces cerevisiae alcoholic fermentation in the presence of sulfite

Sulfur dioxide is extensively used during industrial fermentations and contributes to determine the harsh conditions of winemaking together with low pH, high sugar content and increasing ethanol concentration. Therefore the presence of sulfite has to be considered in yeast gene expression studies to properly understand yeast behavior in technological environments such as winemaking. A reliable expression pattern can be obtained only using an appropriate reference gene set that is constitutively expressed regardless of perturbations linked to the experimental conditions.In this work we tested 15 candidate reference genes suitable for analysis of gene expression during must fermentation in the presence of sulfite. New reference genes were selected from a genome-wide expression experiment, obtained by RNA sequencing of four Saccharomyces cerevisiae wine strains grown in enological conditions. Their performance was compared to that of the most common genes used in previous studies. The most popular software based on different statistical approaches (geNorm, NormFinder and BestKeeper) were chosen to evaluate expression stability of the candidate reference genes. Validation was obtained using other wine strains by comparing normalized gene expression data with transcriptome quantification both in the presence and absence of sulfite.Among 15 reference genes tested ALG9, FBA1, UBC6 and PFK1 appeared to be the most reliable while ENO1, PMA1, DED1 and FAS2 were the worst. The most popular reference gene ACT1, widely used for S. cerevisiae gene expression studies, showed a stability level markedly lower than those of our selected reference genes. Finally, as the expression of the new reference gene set remained constant over the entire fermentation process, irrespective of the perturbation due to sulfite addition, our results can be considered also when no sulfite is added to the must.

Modelling and simulation of gold thiosulphate elution in ammoniacal thiosulphate resin solution system

The gold thiosulphate complex and gold thiosulphate–sulphite complex are formed in the adsorption and elution of gold thiosulphate in ammoniacal thiosulphate resin solution (ATRS) systems. This work proposed a mathematical model of gold thiosulphate elution based on mechanistic approach to predict the gold thiosulphate concentration along bed volumes. Adsorption experiment was conducted to highlight the charge distribution for thiosulphate, trithionate and gold thiosulphate adsorbed on resin at equilibrium. The proposed model was simulated to demonstrate the effect of parameter on the GTC and GTSC concentration in elution. Multivariable optimization approach was taken into account to obtain an optimal value of the GTC and GTSC elution parameters. As the results, the optimal anion exchange coefficients of GTC and GTSC elution were worked out becoming approximately 2.4E-04 and 1.5E-04 m2/s, respectively, with the optimal percentile of occupied sites for the GTC and GTSC being approximately 4.06 and 8.15%, respectively, for 0.2 M trithionate with the absence and presence of sulphite, respectively. Overall, the model-based results were in very good agreement with the results based on experimental data referenced with the correlation coefficient (R2 is approximately 0.9 and 0.94 for the GTC and GTSC, respectively).

Experimental and Theoretical Investigation of SO2 Adsorption over the 1,3-Phenylenediamine/SiO2 System

The reversible adsorption of SO2 on 1,3-phenylenediamine was investigated using the step transient response technique coupled with operando infrared spectroscopy, mass spectrometry, UV–vis spectrometry, and density functional theory (DFT). At 50 °C, the reaction of SO2 at the amine site resulted in fixation of sulfur as hydrogen-bonded SO32– (sulfite) and SO42– (sulfate) species. Simulated infrared and UV–vis spectra at the DFT B3LYP/6-31G(d,p) level were compared to the experimental results to help characterize the infrared spectra, molecular interactions, and bonding of the adsorbing species. The theoretically calculated binding energies revealed the sulfite and sulfate species bind stronger at the ammonium sites as compared to the amine site, which agrees with the infrared spectroscopic observations. Temperature-programmed desorption showed a capacity of 1.39 mol SO2/mol sorbent for pure 1,3-phenylenediamine and 2.8 mol SO2/mol sorbent for the SiO2 supported sorbent. The presence of sulfite and sulfate...

Measurement of photosynthesis using PAM technology in a purple sulfur bacterium Thermochromatium tepidum (Chromatiaceae).

We demonstrate that Blue-diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance (P vs E) curves fitted the waiting-in-line model (ETR = (ETRmax × E/Eopt) × exp (1−E/Eopt)). Yield (Y) was only ≈ 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m(−2) s(−1) or ≈15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m(−3)) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m(−3)) but not sulfide and is only marginally increased by the presence of Fe(2+). Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo-organisms or Rhodopseudomonads.

Anode current on gold in mixed thiosulfate-sulfite electrolytes

The anodic current in individual and mixed thiosulfate-sulfite solutions was studied by means of voltammetry on a fresh gold RDE surface. An unexpected result was obtained: a new additional current maximum appears on the anodic voltammogram in mixed solutions; it is not observed in the individual solutions of sodium thiosulfate and sulfite. The reasons for, and mechanism associated with, this phenomenon require separate and detailed investigation. It is shown that the rate of the anodic process in sulfite solutions is limited by diffusion of discharging particles, while the rate of the anodic process in thiosulfate solutions is limited by slow (in comparison with diffusion) heterogeneous reactions. In mixed solutions, the presence of thiosulfate causes partial passivation of the electrode, while the presence of sulfite causes its partial depassivation. It is stressed that the initial stages of oxygen evolution on gold have opposite effects on anodic currents in sulfite and thiosulfate solutions.

Effect of low- and medium-pressure Hg UV irradiation on bromate removal in advanced reduction process

Advanced Reduction Processes (ARP) have been developed by combining UV irradiation with reducing reagents, which produces reactive reducing free radicals that degrade contaminants (e.g. vinyl chloride, 1,2-dichloroethane, perchlorate, and bromate). This study investigates bromate destruction by ARPs using medium-pressure mercury UV light lamp (UV-M) and low-pressure mercury UV light lamp (UV-L). Effects of experimental parameters including initial bromate concentration, reducing reagent (sulfite) dose, and pH on bromate removal kinetics and quantum yield were evaluated. The pseudo-first-order rate constant (kobs) by UV-M ARP was greater by 3 times than that by UV-L ARP. UV-M and UV-L achieved a complete bromate removal of an initial concentration at 500ppb with fluences of 10.5Jcm−2 and 73.5Jcm−2, respectively. It was found that direct photolysis is a dominant mechanism with the UV-M ARP showing that the effect of sulfite dose had no apparent influence on the bromate removal, whereas kobs was dependent on the sulfite doses in UV-L/sulfite ARP. In the presence of sulfite, kobs was affected by the solution pH in both the UV-M and UV-L ARPs. The pH effect on UV-L ARP or UV-M ARP was explained by the effect of pH on the sulfite species distribution between sulfite and bisulfite or the hydrated electrons concentrations. Also it was found that dominant reaction mechanism of bromate removal was changed by initial bromate concentrations, and its behavior was varied dependent on the UV light sources.

Corrosion behaviour of X52 steel in the presence of sulphite

Purpose– The purpose of this work was to study the corrosion behaviour of X52 steel in the presence of sulphite.Design/methodology/approach– The study was conducted in abiotic solutions containing species typical of sulphate-reducing bacteria (SRB) metabolism. Electrochemical techniques, i.e. linear polarization resistance (LPR), potentiodynamic and electrochemical impedance spectroscopy (EIS), were used to observe the corrosion kinetics and mechanism of X52 steel in the solution containing sulphite. Field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the corrosion products.Findings– LPR and EIS results showed that the addition of sulphite ions to the abiotic solutions increased the rate of X52 steel corrosion. The increase of corrosion rate was due to the increase in the cathodic reaction in the presence of sulphite. It was also observed that sulphite thinned the protective FeS film and caused corrosive species to adsorb on the surface, resulting in an increase in corrosion rate.Originality/value– This paper discusses the effects of sulphite on the corrosion behaviour of X52 steel in abiotic solution containing species typically produced by the SRB-type metabolic process. Irrespective of the presence of sulphide, sulphite is produced by SRB during their metabolic process. However, as far as is known, no published papers are available that discuss the effect of the presence of sulphite as one of the metabolic products of SRB.

The yeastWickerhamomyces anomalusAS1 secretes a multifunctional exo-β-1,3-glucanase with implications for winemaking

A multifunctional exo-β-1,3-glucanase (WaExg2) was purified from the culture supernatant of the yeast Wickerhamomyces anomalus AS1. The enzyme was identified by mass spectroscopic analysis of tryptic peptide fragments and the encoding gene WaEXG2 was sequenced. The latter codes for a protein of 427 amino acids, beginning with a probable signal peptide (17 aa) for secretion. The mature protein has a molecular mass of 47 456 Da with a calculated pI of 4.84. The somewhat higher mass of the protein in SDS-PAGE might be due to bound carbohydrates. Presumptive disulphide bridges confer a high compactness to the molecule. This explains the apparent smaller molecular mass (35 kDa) of the native enzyme determined by electrophoresis, whereas the unfolded form is consistent with the theoretical mass. Enzymatic hydrolysis of selected glycosides and glycans by WaExg2 was proved by TLC analysis of cleavage products. Glucose was detected as the sole hydrolysis product from laminarin, underlining that the enzyme acts as an exoglucanase. In addition, the enzyme efficiently hydrolysed small β-linked glycosides (arbutin, esculin, polydatin, salicin) and disaccharides (cellobiose, gentiobiose). WaExg2 was active under typical wine-related conditions, such as low pH (3.5-4.0), high sugar concentrations (up to 20% w/v), high ethanol concentrations (10-15% v/v), presence of sulphites (up to 2 mm) and various cations. Therefore, the characterized enzyme might have multiple uses in winemaking, to increase concentrations of sensory and bioactive compounds by splitting glycosylated precursors or to reduce viscosity by hydrolysis of glycan slimes.

The Escherichia coli CysZ is a pH dependent sulfate transporter that can be inhibited by sulfite

The Escherichia coli inner membrane protein CysZ mediates the sulfate uptake subsequently utilized for the synthesis of sulfur-containing compounds in cells. Here we report the purification and functional characterization of CysZ. Using Isothermal Titration Calorimetry, we have observed interactions between CysZ and its putative substrate sulfate. Additional sulfur-containing compounds from the cysteine synthesis pathway have also been analyzed for their abilities to interact with CysZ. Our results suggest that CysZ is dedicated to a specific pathway that assimilates sulfate for the synthesis of cysteine. Sulfate uptake via CysZ into E. coli whole cells and proteoliposome offers direct evidence of CysZ being able to mediate sulfate uptake. In addition, the cysteine synthesis pathway intermediate sulfite can interact directly with CysZ with higher affinity than sulfate. The sulfate transport activity is inhibited in the presence of sulfite, suggesting the existence of a feedback inhibition mechanism in which sulfite regulates sulfate uptake by CysZ. Sulfate uptake assays performed at different extracellular pH and in the presence of a proton uncoupler indicate that this uptake is driven by the proton gradient.

Vallitalea pronyensis sp. nov., isolated from a marine alkaline hydrothermal chimney

A novel thermotolerant, anaerobic, Gram-stain-positive, spore-forming bacterium was isolated from a hydrothermal chimney in Prony Bay, New Caledonia. This strain, designated FatNI3(T), grew at 15-55 °C (optimum 30 °C) and at pH 5.8-8.9 (optimum 7.7). It was slightly halophilic, requiring at least 0.5 % NaCl for growth (optimum 2.5-3.0 %), and was able to grow at up to 6 % NaCl. Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Growth of strain FatNI3(T) was inhibited in the presence of sulfite (2 mM) or nitrite (2 mM). Strain FatNI3(T) fermented cellobiose, glucose, mannose, maltose, sucrose, galactose, lactose, ribose, fructose, rhamnose, raffinose, xylose, yeast extract, peptone and biotrypticase. The main fermentation products from glucose metabolism were acetate, ethanol, H2 and CO2. The predominant cellular fatty acids were iso-C15 : 0 and anteiso-C15 : 0. The main polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, and unknown glycolipids and phospholipids. The G+C content of the genomic DNA was 36.6 mol%. On the basis of phylogenetic and physiological properties, strain FatNI3(T) ( = DSM 25904 = JCM 18391) belonging to the phylum Firmicutes, class Clostridia, order Clostridiales, is proposed as the type strain of a novel species of the genus Vallitalea, for which the name Vallitalea pronyensis sp. nov. is proposed.

Inhibition of phloem loading by sulfite affects sugar distribution in pea leaves

Under the influence of sulfite, changes in the rate of <sup>14</sup>CO<sub>2</sub> fixation, <sup>14</sup>C-sucrose uptake and sugar content of the apoplastic and intracellular spaces of pea leaves varied according to the time of treatment and the anion concentration used. The greatest decrease of the rate of <sup>14</sup>CO<sub>2</sub> and <sup>14</sup>C-sucrose uptake in the presence of sulfite at concentrations from 0.1 to 5.0 mM was detected immediately (i.e. 5 min.) after supplying sulfite to the medium. Two hours later, a significant inhibition of photosynthesis and sucrose uptake was observed only with 5.0 and 2.5 and 5.0 mM concentrations of sulfite, respectively. The effect of sulfite (0.1-5.0 mM) on the apoplastic and intracellular sugar content for the first 30 min of treatment was negligible. However, after longer periods under sulfite treatment at concentrations ≥ 1.0 mM, significant increases in the apoplastic sucrose content were observed. An increase in the accumulation of starch was also noted. In light of our observations it suggested that the inhibition of phloem loading by sulfite induces disturbances in sugar distribution.

Effects of Reduced Sulfur Compounds on Pd-Catalytic Hydrodechlorination of Trichloroethylene in Groundwater by Cathodic H2under Electrochemically Induced Oxidizing Conditions

Reduced sulfur compounds (RSCs) poison Pd catalysts for catalytic hydrodechlorination of contaminants in anoxic groundwater. This study investigates the effects of RSCs on Pd-catalytic hydrodechlorination of trichloroethylene (TCE) in oxic groundwater. Water electrolysis in an undivided electrolytic cell is used to produce H2 for TCE hydrodechlorination under oxidizing conditions. TCE is efficiently hydrodechlorinated to ethane, with significant accumulation of H2O2 under acidic conditions. The presence of sulfide at concentrations less than 93.8 μM moderately inhibits TCE hydrodechlorination and H2O2 production. The presence of sulfite at low concentrations (≤1 mM) significantly enhances TCE decay, while at high concentration (3 mM) inhibits initially and enhances afterward when sulfite concentration declines to less than 1 mM. Using radical scavenging experiments and an electron spin resonance assay, SO3(•-), which is generated from sulfite under oxidizing conditions, is validated as the new reactive species contributing to the enhancement. This study reveals a distinct mechanism of effect of sulfite on TCE hydrodechlorination by Pd and H2 in oxic groundwater and presents an alternative approach to increasing resistance of Pd to RSCs poisoning.

Indirect Spectrophotometric Determination of Thiamine Hydrochloride in Presence of Sulphite Via Chromium-1,5-Diphenylcarbazide Complex

A simple, rapid, accurate and precise spectrophotometric method is proposed for the determination of thiamine hydrochloride (Vitamin B1) in both pure form and in its pharmaceutical formulations. The method is based on the oxidation-reduction reaction between vitamin B1 and known amount of chromate CrO4-2 in acidic medium of 2N H2SO4. Then, the excess of chromate is measured via 1,5-diphenylcarbazide which gives a pinkish-violet, water soluble and stable complex and exhibits maximum absorption at 543 nm, with a molar absorptivity of 1.5×104 l. mol-1. cm-1, Sandell's sensitivity index of 0.02248 μg.cm-2 and a relative standard deviation of ±0.31 to ± 0.57%, depending on the concentration level. Beer's law is obeyed in the concentration range from 0.4 to 40 µg. ml-1 of thiamine hydrochloride. The present method has been developed for the determination of thiamine hydrochloride in the presence of sulphite. The proposed method has been applied successfully to the determination of vitamin B1 in pharmaceutical preparations.

Voltammetric trace level determination of sulfide in presence of sulfite and thiosulfate

Voltammetric trace level determination of sulfide in presence of sulfite and thiosulfate

Development and validation of a spectrofluorimetric method for the quantification of ceftriaxone in pharmaceutical formulations and plasma

We describe the development and validation of a new, simple, sensitive and cost-effective method for the determination of ceftriaxone in commercial formulations and spiked human plasma. The method proposes the conversion of ceftriaxone into a fluorescent product by reacting with ortho-phthalaldehyde (OPA) in the presence of sulfite at room temperature. The reaction medium is buffered to pH 10 using borate buffer. The derivatized reaction product is highly fluorescent and exhibits maximum fluorescence intensity at λ(em) = 386 nm after excitation at λ(ex) = 324 nm. The experimental parameters affecting progress of the derivatization reaction were carefully studied and optimized. Under optimum experimental conditions, the method has an excellent correlation coefficient of 0.9984 with a broad linear range of 0.4-20 µg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 1.30 × 10(-3) and 3.90 × 10(-3) µg/mL, respectively. The interference effects of common excipients on the quantification of drug were investigated and no interference effect was observed. The proposed method has been successfully applied to the determination of ceftriaxone in pharmaceutical formulations and spiked human plasma samples. The method has been validated statistically through percent recovery studies using standard addition and by comparison with a reference HPLC method. The developed method exhibits excellent inter- and intraday precision.