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M NaCl (m + nacl)
Terms modified by M NaCl Selected AbstractsVoltammetry as an Alternative Tool for Trace Metal Detection in Peloid Marine SedimentsELECTROANALYSIS, Issue 13 2007Irena Ciglene Abstract Here was demonstrated for the first time a possible application of abrasive stripping voltammetry in the direct measurement of trace metals in anoxic, sulfidic marine sediments (peloid mud) from a small and shallow (0.2,1,m) marine lagoon in Central Dalmatia, Croatia. Trace amounts of sample compounds are transferred to the graphite electrode surface and electrochemical reduction or oxidation processes are followed by the cyclic voltammetry in seawater or 0.55,M NaCl as electrolyte. After a preelectrolysis at potentials ranging from ,1.0 to ,1.5,V (vs. SCE) a well-defined anodic stripping peak corresponding to the oxidation of metal deposits generated at deposition potentials is obtained around ,0.74,V (vs. SCE). The same samples were studied by anodic stripping voltammetry at the Hg electrode and inductively coupled plasma-mass spectrometer (ICP-MS). ICP-MS showed higher concentrations of trace metals such as Al, Fe, Mo, Mn. A relatively high concentration of reduced sulfur species (RSS) (10,3 M) is determined electrochemically in porewater of the peloid mud, indicating that the magnitude of metal enrichment in the sediments is probably controlled by precipitation with sulfide. [source] Simultaneous Determination of Hydroquinone and Catechol at a Glassy Carbon Electrode Modified with Multiwall Carbon NanotubesELECTROANALYSIS, Issue 10 2005Honglan Qi Abstract A simply and high selectively electrochemical method for simultaneous determination of hydroquinone and catechol has been developed at a glassy carbon electrode modified with multiwall carbon nanotubes (MWNT). It was found that the oxidation peak separation of hydroquinone and catechol and the oxidation currents of hydroquinone and catechol greatly increase at MWNT modified electrode in 0.20,M acetate buffer solution (pH,4.5). The oxidation peaks of hydroquinone and catechol merge into a large peak of 302,mV (vs. Ag/AgCl, 3,M NaCl) at bare glassy carbon electrode. The two corresponding well-defined oxidation peaks of hydroquinone in the presence of catechol at MWNT modified electrode occur at 264,mV and 162,mV, respectively. Under the optimized condition, the oxidation peak current of hydroquinone is linear over a range from 1.0×10,6,M to 1.0×10,4,M hydroquinone in the presence of 1.0×10,4,M catechol with the detection limit of 7.5×10,7,M and the oxidation peak current of catechol is linear over a range from 6.0×10,7,M to 1.0×10,4,M catechol in the presence of 1.0×10,4,M hydroquinone with the detection limit of 2.0×10,7 M. The proposed method has been applied to simultaneous determination of hydroquinone and catechol in a water sample with simplicity and high selectivity. [source] Stability Constants and Dissociation Rates of the EDTMP Complexes of Samarium(III) and Yttrium(III)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 30 2008Ferenc Krisztián Kálmán Abstract The stability constants of Sm(EDTMP) (log,KML = 20.71) and Y(EDTMP) (log,KML = 19.19) were determined by a competition reaction between the Ln3+ ion (Ln3+ = Sm3+ or Y3+) and Cu2+ for the EDTMP ligand by spectrophotometry at pH , 10, in the presence of an excess amount of citrate (0.15 M NaCl, 25 °C). For determining the stability constants of Cu(EDTMP) (log,KML = 19.36) and Ca(EDTMP) (log,KML = 8.71) pH,potentiometry was used. In the pH range 4,9 the EDTMP complexes are present in the form of nonprotonated and mono-, di- and triprotonated species. The Ca2+ ion forms a dinuclear complex with Ln(EDTMP). In a simplified blood plasma model consisting of Sm3+, Ca2+ and Zn2+ metal ions, EDTMP, citrate, cysteine and histidine ligands, Sm3+ is practically present in the form of [Sm(HEDTMP)Ca]2,, whereas Zn2+ predominantly forms [Zn(HEDTMP)]5, and [Zn(H2EDTMP)]4, complexes. For studying the dissociation rates of the complexes, the kinetics of the metal exchange (transmetallation) reactions between the Ln(EDTMP) complexes and Cu2+,citrate were investigated in the pH range 7,9 by the stopped-flow method. The rates of the exchange reactions are independent of the Cu2+ concentration and increase with the H+ concentration. The rate constants, characterizing the proton-assisted dissociation of the Ln(EDTMP) complexes, are several orders of magnitude higher than those of the similar Ln(EDTA) complexes, because the protonation constants of Ln(EDTMP) are high and the protonated Ln(HEDTMP) and Ln(H2EDTMP) species are present in higher concentration. The half-times of dissociation of Sm(EDTMP) and Y(EDTMP) at pH = 7.4 and 25 °C are 4.9 and 7.5 s, respectively. These relatively short dissociation half-time values do not predict the deposition of Ln3+ ions in bones in the form of intact Ln(EDTMP) complexes. It is more probable that sorption of the EDTMP ligand and Sm3+ or Y3+ ions occurs independently after the dissociation of complexes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] B,Z DNA Transition Triggered by a Cationic Comb-Type CopolymerADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Naohiko Shimada Abstract The conformational transition from right-handed B,DNA to left-handed Z,DNA,the B,Z transition,has received increased attention recently because of its potential roles in biological systems and its applicability to bionanotechnology. Though the B,Z transition of poly(dG,dC),·,poly(dG,dC) is inducible under high salt concentration conditions (over 4,M NaCl) or by addition of multivalent cations, such as hexaamminecobalt(III), no cationic polymer were known to induce the transition. In this study, it is shown by circular dichroism and UV spectroscopy that the cationic comb-type copolymer, poly(L -lysine)- graft -dextran, but not poly(L -lysine) homopolymer or a basic peptide, induces the B,Z transition of poly(dG,dC),·,poly(dG,dC). At a cationic amino group concentration of 10,4,M the copolymer stabilizes Z,DNA. The transition pathway from the B to the Z form is different to that observed previously. We speculate that the cationic backbone of the copolymer, which reduces electrostatic repulsion among DNA phosphate groups, and the hydrophilic dextran chains, which reduce activity of water, cooperate to induce the B,Z transition. The copolymer specifically modified the micro-environment around DNA molecules to induce Z,DNA formation through stable and spontaneous inter-polyelectrolyte complex formation. [source] The reactivity of Ni(II) toward aspartic and glutamic monohydroxamatesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2006Fawzia Al-Sogair The formation of complexes of Ni(II) with aspartic and glutamic acid hydroxamates was determined by potentiometric methods at I = 0.15 M NaCl and T = 25°C. The equilibrium study of Ni(II) with ASX or GLX revealed that the predominant species formed in solution were (M:L:H+): (1:1:0), (1:1:1), (2:1:0), and (2:1:1) in the whole pH range (,3,11). The formation of polymeric species was not observed. The octahedral structures were predicted in which the ligands act as tridentate ligands. The kinetics of complex formation between Ni(II) with ASX system as well as Ni(II) with GLX were also studied in a wide pH range. The observed rate constants for the Ni(II)-hydroxamates were found to be dependent on the total concentration of hydroxamates at a given pH through the following relations: kobs = Y0 + Z(TASX) and kobs = Y0 + Z(TGLX) + W(TGLX)2. The trans effect of the hydroxyl group present in the reacting species of Ni(OH)+ as well as a ring closure resulted from ligand chelation are introduced as explanations for the rate constants obtained for the reactions of Ni(II) with ASX or GLX. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 540,552, 2006 [source] Effect of salinity on denitrification under limited single carbon source by Marinobacter sp. isolated from marine sedimentJOURNAL OF BASIC MICROBIOLOGY, Issue 3 2010Miyo Nakano Abstract Marinobacter comprises Gram-negative, aerobic, motile, and rod-shaped bacteria within the ,-subclass of the Proteobacteria and is known to be halophilic or halotolerant, heterotrophic neutrophile. Two strains classified as belonging to Marinobacter, named PAD-2 and SeT-1, were isolated from marine sediment. The most closely related species of PAD-2 and SeT-1 are M. alkaliphilus and M. guinea, respectively. The strain PAD-2 exhibited remarkably higher denitrification at concentrations of 0.5 to 1 M NaCl (3,6% w/w) than at other salinities (2 and 3 M NaCl, 12,18% w/w), and optimal denitrification was observed in media with 0.5 M NaCl. The effect of pH on denitrification by strain PAD-2 was also examined, and the optimum denitrification occurred at neutral pH rather than under alkaline conditions. Overall, strain PAD-2 appears to be a novel halotolerant species belonging to the genus Marinobacter that shares many characteristics, such as substrate utilization profile and optimum NaCl concentration for growth with M. alkaliphilus. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] PROTEINASES IN HYBRID CATFISH VISCERA: CHARACTERIZATION AND EFFECT OF EXTRACTION MEDIAJOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2010SAPPASITH KLOMKLAO ABSTRACT Proteolytic activity from viscera extract of hybrid catfish (Clarias macrocephalus × Clarias gariepinus) was investigated. Optimal pH and temperature for casein hydrolysis were 9.0 and 50C, respectively. The enzyme was stable to heat treatment up to 40C and over a pH range of 7,11 for 30,120 min. The proteolytic activity was effectively inhibited by soybean trypsin inhibitor, benzamidine, phenylmethylsulfonyl fluoride and N -p-tosyl-L-lysine chloromethyl ketone. Activities of the viscera extract continuously decreased as NaCl concentration increased, while activities increased as CaCl2 concentration increased. Based on the proteinase activity of zones separated by electrophoresis, the molecular mass of the major proteinases in hybrid catfish viscera was 23 and 20 kDa. The effect of extraction media on recovery of proteinases was also studied. Extraction of the viscera powder with 50 mM Tris-HCl, pH 7.0 containing 0.5 M NaCl and 0.2% (v/v) Brij 35 rendered a higher recovery of proteinase activity than other extractants tested (P < 0.05). The results suggested that major proteinases in hybrid catfish viscera were heat-activated alkaline proteinases, most likely trypsin-like serine proteinases. PRACTICAL APPLICATIONS Hybrid catfish viscera is an abundant and underutilized resource that can be used as a unique proteinase source. Proteinase from various sources catalyzes the hydrolysis of peptide bonds. Thus, it is expected that like other proteinases, hybrid catfish proteinase would be useful in biomedical, food and beverage application. Moreover, the presented extraction media could be adopted to recover the trypsin-like serine proteinase from hybrid catfish viscera, which is currently a solid waste of Pa-duk-ra industry. [source] Fermentation of Cucumbers Brined with Calcium Chloride Instead of Sodium ChlorideJOURNAL OF FOOD SCIENCE, Issue 3 2010Roger F. McFeeters ABSTRACT:, Waste water containing high levels of NaCl from cucumber fermentation tank yards is a continuing problem for the pickled vegetable industry. A major reduction in waste salt could be achieved if NaCl were eliminated from the cucumber fermentation process. The objectives of this project were to ferment cucumbers in brine containing CaCl2 as the only salt, to determine the course of fermentation metabolism in the absence of NaCl, and to compare firmness retention of cucumbers fermented in CaCl2 brine during subsequent storage compared to cucumbers fermented in brines containing both NaCl and CaCl2 at concentrations typically used in commercial fermentations. The major metabolite changes during fermentation without NaCl were conversion of sugars in the fresh cucumbers primarily to lactic acid which caused pH to decrease to less than 3.5. This is the same pattern that occurs when cucumbers are fermented with NaCl as the major brining salt. Lactic acid concentration and pH were stable during storage and there was no detectable production of propionic acid or butyric acid that would indicate growth of spoilage bacteria. Firmness retention in cucumbers fermented with 100 to 300 mM CaCl2 during storage at a high temperature (45 °C) was not significantly different from that obtained in fermented cucumbers with 1.03 M NaCl and 40 mM CaCl2. In closed jars, cucumber fermentations with and without NaCl in the fermentation brine were similar both in the chemical changes caused by the fermentative microorganisms and in the retention of firmness in the fermented cucumbers. [source] Xanthan Enhances Water Binding and Gel Formation of Transglutaminase-Treated Porcine Myofibrillar ProteinsJOURNAL OF FOOD SCIENCE, Issue 3 2010Yongbiao Shang ABSTRACT:, In this study, the effect of xanthan on dynamic rheological properties, textural profile, and water binding of transglutaminase (TG)-treated myofibrillar protein (MP) gels was investigated. In experiment 1, MP suspensions (40 mg/mL protein, 0.6 M NaCl) at pH 6.45 with or without 0.05% xanthan were treated with 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% TG; in experiment 2, MP suspensions (40 mg/mL protein, 0.6 M NaCl) at pHs 6.13, 6.30, 6.45, 6.69 with or without 0.05% xanthan were treated with 0.3% TG. Treated samples were analyzed with differential scanning calorimetry for thermal stability and oscillatory rheometry and Instron penetration tests for gelation properties. The TG treatments lowered the transition temperature (Tm) of MP by as much as 6 °C (P,< 0.05) but increased apparent enthalpy of denaturation. However, there was no detectable thermal stability difference between MP samples with or without xanthan. The shear storage modulus (G,) of MP gels increased markedly upon treatments with ,0.3% TG, and the presence of xanthan further enhanced the gel strength (P,< 0.05). The addition of 0.05% xanthan decreased cooking loss of TG-treated MP gels by 17% to 23% when compared with gels without xanthan at all pH levels evaluated (6.13 to 6.67). Thus, the combination of TG and xanthan offered a feasible means to promote cross-linking and gelation of MP while reducing cooking losses. [source] The effective hard particle model provides a simple, robust, and broadly applicable description of nonideal behavior in concentrated solutions of bovine serum albumin and other nonassociating proteinsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2007Allen P. Minton Abstract Published data on the concentration dependence of osmotic pressure of solutions of bovine serum albumin in 0.15 M NaCl at concentrations up to greater than 400 g/L are shown to be described to within experimental uncertainty by a simple one-parameter model in which protein molecules are represented by effective hard spherical particles. The volume of the effective hard particle reflects both steric and electrostatic repulsion and thus varies with pH and ionic strength. The pH dependence of the effective volume is shown to agree well with that previously obtained from analysis of the concentration dependence of sedimentation equilibrium and static light scattering. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 3466,3469, 2007 [source] Effects of chromium stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypesJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2010Fanrong Zeng Abstract A hydroponic experiment was carried out to study effects of chromium (Cr) stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes differing in Cr accumulation. The results showed that Ca, Mg, Fe, and Zn ions were mainly located in cell walls and vacuoles in roots. However, large amounts of metal ions were transferred from the vacuole to the nucleus and to other functional organelles in shoots. Chromium concentrations in the nutrient solution of 50 ,M and above significantly decreased Ca concentrations in the chloroplast/trophoplast, the nucleus, and in mitochondria. It further increased Mg concentrations in the nucleus and in mitochondria, as well as Zn and Fe concentrations in the chloroplast/trophoplast. These Cr-induced changes in ion concentrations were associated with a significant reduction in plant biomass. It is suggested that Cr stress interferes with the functions of mineral nutrients in rice plants, thus causing a serious inhibition of plant growth. The chemical forms of the four nutrients were determined by successive extraction. Except for Ca, which was mainly chelated with insoluble phosphate and oxalic acid, Mg, Zn, and Fe were extractable by 80% ethanol, d-H2O, and 1,M NaCl. The results indicated that these low,molecular weight compounds, such as organic acids and amino acids, may play an important role in deposition and translocation of Mg, Zn, and Fe in the xylem system of rice plants. [source] Starch- graft -(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2007Hank De Bruyn Abstract A method is presented for synthesizing surfactant-free latexes comprising starch- graft -(vinyl polymer) starting with a suspension of amylopectin, either native or modified, then using cerium(IV) with either potassium persulfate or glucose to create grafting sites on the starch. Latex particles comprising polystyrene, poly(styrene- co -(n -butyl acrylate)) and poly(vinyl acetate) grafted onto high molecular weight amylopectin were developed, with up to 80% of the starch effectively grafted to the particles. These latexes were colloidally stable against electrolyte (several months in 4 M NaCl). Reaction rates of Ce4+ with simple sugars and polysaccharides were investigated, as well as the gelation mechanism of the latex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4185,4192, 2007 [source] Evaluation of selective composite cryogel for bromate removal from drinking waterJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2010Solmaz Hajizadeh Abstract Bromate, which is a potential carcinogen, should be removed from drinking water to levels of less than 10,,g/L. A chitosan-based molecularly imprinted polymer (MIP) and a sol,gel ion-exchange double hydrous oxide (Fe2O3·Al2O3·xH2O) adsorbent (inorganic adsorbent) were prepared for this purpose. The sorption behavior of each adsorbent including sorption kinetics, isotherms, effect of pH and selective sorption were investigated in detail. Sorption experimental results showed that the MIP adsorbents had better selectivity for bromate, even in the presence of high concentrations of nitrate, as compared to the inorganic adsorbent. It was found that pH does not affect the adsorption of bromate when using the inorganic adsorbent. Additionally, both adsorbents were immobilized in a polymeric cryogel inside plastic carriers to make them more practical for using in larger scale. Regeneration of the cryogels either containing MIP or inorganic adsorbents were carried out by 0.1,M NaOH and 0.1,M NaCl, respectively. It was found that the regenerated MIP and inorganic adsorbents could be used at least three and five times, respectively, without any loss in their sorption capacity. [source] Chromatographic separation of cytidine triphosphate from fermentation broth of yeast using anion-exchange cryogelJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2008Lianghua Wang Abstract A novel separation method was developed to isolate directly cytidine triphosphate (CTP) from fermentation broth of yeast using anion-exchange supermacroporous cryogel. The anion-exchange cryogel with tertiary amine groups was prepared by graft polymerization. The breakthrough characteristics and elution performance of pure CTP in the cryogel bed were investigated experimentally and the CTP binding capacity was determined. Then the separation experiments of CTP from crude fermentation broth of yeast using the cryogel column were carried out using deionized water and 0.01 M HCl as washing buffer, respectively. The chromatographic behavior was monitored and analyzed. The purity and concentration of the obtained CTP in these processes were determined quantitatively by HPLC. The maximal purity of CTP obtained at the condition of 0.01 M HCl as washing buffer and 0.5 M NaCl in 0.01 M HCl as elution buffer reached 93%. [source] ELECTROSTATIC EFFECTS ON PHYSICAL PROPERTIES OF PARTICULATE WHEY PROTEIN ISOLATE GELSJOURNAL OF TEXTURE STUDIES, Issue 4 2001MATTHEW K. McGUFFEY Physical properties of particulate whey protein isolate gels formed under varying electrostatic conditions were investigated using large strain rheological and microstructural techniques. The two treatment ranges evaluated were adjusting pH (5.2-5.8) with no added NaCl and adjusting the NaCl (0.2-0.6 M) at pH 7. Gels (10% protein w/v) were formed by heating at 80C for 30 min. The large strain properties of fracture strain (,f), fracture stress (,f), and a measure of strain hardening (R0.3) were determined using a torsion method. Gel microstructure was evaluated using scanning electron microscopy (SEM) and gel permeability (Bgel). Overlaying ,f and ,f curves for pH and NaCl treatments demonstrated an overlap where gels of equal ,f and ,f could be formed by adjusting pH or NaCl concentration. The high fracture stress (,f, 23 kPa and ,f, 1.86) pair conditions were pH 5.47 and 0.25 M NaCl, pH 7.0. The low fracture stress (,f, 13 kPa and ,f, 1.90) pair conditions were pH 5.68 and 0.6 M NaCl, pH 7.0. The 0.25 M NaCl, pH 7 treatment demonstrated higher R0.3 values than the pH 5.47 treatment. When the sulfhydryl blocker n-ethylmaleimide was added at 2 mM to the 0.25 M NaCl, pH 7 gel treatment, its rheological behavior was NSD (p>0.05) to the pH 5.47 gel treatment, indicating disulfide bond formation regulated strain hardening. Altering surface charge or counterions, and disulfide bonding, was required to produce gels with similar large strain rheological properties. An increase in gel permeability coincided with an increase in pore size as observed by SEM, independent of rheological properties. This demonstrated that at the length scales investigated, microstructure was not linked to changes in large strain rheological properties. [source] Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2002Suhur Saeed Abstract The effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at ,20 and ,30,°C was studied. Traditional methods including the peroxide value, thiobarbituric acid-reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of ,20,°C compared with samples stored at ,30,°C. Antioxidants had a significant effect (P,<,0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at ,20 than ,30,°C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P,<,0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6,M NaCl) decreased (P,<,0.01) during storage at both ,20 and ,30,°C but was greater at ,20,°C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P,<,0.01) for up to 1 year at ,20,°C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish. © 2002 Society of Chemical Industry [source] Chemical composition of new copper alloys for machining and its effect on their susceptibility to corrosion crackingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2007B. Eremiá Zinc-containing copper alloys, the so-called ,,+,, brasses, are commonly used in contact with potable water. These materials are alloyed with lead to improve machinability. In wrought special brass alloys, reducing the content of this alloying element or replacing it with alternative alloying additions may give rise to a new type of machinable copper alloys which differ from the original alloys by their contents of other modifier elements such as Si (or possibly, Mg, Bi, and P). These alloys have a very low content of lead required for the break-up of chips during machining. Even though these types of brass exhibit a very good machinability, the effects of their chemical composition on the resistance of the alloy to corrosion cracking have not yet been given sufficient attention. This paper aims to present an assessment of three new types of machinable copper alloys regarding their susceptibility to stress corrosion cracking, in comparison to that of the lead-alloyed variety, in 0.05 M NaCl, NaNO2, and Na2SO4 solutions. The slow strain rate test has been used for this purpose, and its results were correlated with metallographic evaluation of the number and depth of the cracks observed on the test specimen surfaces on completion of the test. [source] Production of Reactive Oxygen Species on Photolysis of Dilute Aqueous Quinone SolutionsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Shikha Garg ABSTRACT We have examined the generation of the reactive oxygen species (ROS) superoxide and hydrogen peroxide (H2O2) by irradiation of dilute aqueous solutions of disodium anthraquinone-2-6-disulfonate (AQDS) with simulated sunlight. Irradiating a solution of AQDS in 2 mM NaHCO3 and 0.01 M NaCl produced superoxide and H2O2 at nanomolar concentrations. Experiments in which initial concentrations of dioxygen, H2O2, the superoxide radical trap nitroblue tetrazolium and the electron donor dimethyl sulfoxide were varied suggested that the interaction of solvent water with photo-excited quinone moieties produces dioxygen-reducing radicals, and that these are the primary source of ROS in the system. A kinetic model for ROS production is proposed based on our experimental data. [source] Gene expression profiling of Dunaliella sp. acclimated to different salinitiesPHYCOLOGICAL RESEARCH, Issue 1 2010Minjung Kim SUMMARY To investigate which genes may be important for growth under extreme conditions such as very low or high salinities, a survey of the Dunaliella sp. transcriptome was performed with a cDNA microarray which had been generated previously representing 778 expressed sequence tags. The comparative microarray analysis indicated that 142 genes differed in expression levels by more than twofold in cells grown at extreme salinities (0.08 M and 4.5 M NaCl) when compared with cells grown at intermediate salinity (1.5 M NaCl). Of these genes, 28 had increased expression and 57 were suppressed in cells grown at low salinity. In cells grown at high salinity, 43 genes showed increased expression and 69 genes showed suppressed expression. However, we did observe a large overlap in the expression of extreme salinity-responsive genes based on Venn diagram analysis, which found 55 genes that responded to both of the two extreme salinity conditions. Further, we found that several genes had similar expression levels under low and high salinities, including some general stress response genes that were upregulated in both extreme salinity conditions. For confirmation of the validity of the cDNA microarray analysis, expression of several genes was independently confirmed by the use of gene-specific primers and real-time polymerase chain reaction. The present study is the first large-scale comparative survey of the transcriptome from the microalga Dunaliella sp. acclimated to extreme salinities, thus providing a platform for further functional investigation of differentially expressed genes in Dunaliella. [source] The Effect of Irradiance on Carboxylating/Decarboxylating Enzymes and Fumarase Activities in Mesembryanthemum crystallinum L. Exposed to Salinity StressPLANT BIOLOGY, Issue 1 2001Z. Miszalski Abstract: In Mesembryanthemum crystallinum plants, treated for 9 days with 0.4 M NaCl at low light intensities (80 - 90 or 95 - 100 ,E m -2 s -1; , = 400 - 700 nm), no day/night malate level differences (,malate) were detected. At high light (385 - 400 ,E m -2 s -1) strong stimulation of PEPC activity, accompanied by a ,malate of 11.3 mM, demonstrated the presence of CAM metabolism. This indicates that, to evolve day/night differences in malate concentration, high light is required. Salt treatment at low light induces and increases the activity of NAD- and NADP-malic enzymes by as much as 3.7- and 3.9-fold, while at high light these values reach 6.4- and 17.7-fold, respectively. The induction of activity of both malic enzymes and PEPC (phospoenolpyruvate carboxylase) take place before ,malate is detectable. An increase in SOD (superoxide dismutase) was observed in plants cultivated at high light in both control and salt-treated plants. However, in salt-treated plants this effect was more pronounced. Carboxylating and decarboxylating enzymes seem to be induced by a combination of different signals, i.e., salt and light intensity. Plants performing CAM, after the decrease of activity of both the decarboxylating enzymes at the beginning of the light period, showed an increase in these enzymes in darkness when the malate pool reaches higher levels. In CAM plants the activity of fumarase (Krebs cycle) is much lower than that in C3 plants. The role of mitochondria in CAM plants is discussed. [source] Protein self-association in solution: The bovine , -lactoglobulin dimer and octamerPROTEIN SCIENCE, Issue 11 2003Michael Gottschalk Abstract We have used proton magnetic relaxation dispersion (MRD) to study the self-association of bovine , -lactoglobulin variant A (BLG-A) as a function of temperature at pH 4.7 (dimer,octamer equilibrium) and as a function of NaCl concentration at pH 2.5 (monomer,dimer equilibrium). The MRD method identifies coexisting oligomers from their rotational correlation times and determines their relative populations from the associated dispersion amplitudes. From MRD-derived correlation times and hydrodynamic model calculations, we confirm that BLG-A dimers associate to octamers below room temperature. The tendency for BLG-A dimers to assemble into octamers is found to be considerably weaker than in previous light scattering studies in the presence of buffer salt. At pH 2.5, the MRD data are consistent with an essentially complete transition from monomers in the absence of salt to dimers in 1 M NaCl. Because of an interfering relaxation dispersion from nanosecond water exchange, we cannot determine the oligomer populations at intermediate salt concentrations. This nanosecond dispersion may reflect intersite exchange of water molecules trapped inside the large binding cavity of BLG-A. [source] Optical recordings of taste responses from fungiform papillae of mouse in situTHE JOURNAL OF PHYSIOLOGY, Issue 2 2001Yoshitaka Ohtubo 1Single taste buds in mouse fungiform papillae consist of ,50 elongated cells (TBCs), where fewer than three TBCs have synaptic contacts with taste nerves. We investigated whether the non-innervated TBCs were chemosensitive using a voltage-sensitive dye, tetramethylrhodamine methyl ester (TMRM), under in situ optical recording conditions. 2Prior to the optical recordings, we investigated the magnitude and polarity of receptor potentials under in situ whole-cell clamp conditions. In response to 10 mM HCl, several TBCs were depolarized by ,25 mV and elicited action potentials, while other TBCs were hyperpolarized by ,12 mV. The TBCs eliciting hyperpolarizing receptor potentials also generated action potentials on electrical stimulation. 3A mixture of 100 mM NaCl, 10 mM HCl and 500 mM sucrose depolarized six TBCs and hyperpolarized another three TBCs out of 13 identified TBCs in a taste bud viewed by optical section. In an optical section of another taste bud, 1 M NaCl depolarized five TBCs and hyperpolarized another two TBCs out of 11 identified TBCs. 4The number of chemosensitive TBCs was much larger than the number of innervated TBCs in a taste bud, indicating the existence of chemosensitivity in non-innervated TBCs. There was a tendency for TBCs eliciting the same polarity of receptor potential to occur together in taste buds. We discuss the role of non-innervated TBCs in taste information processing. [source] Regulation of restitution after superficial injury in isolated guinea pig gastric mucosaAPMIS, Issue 4-5 2004ARUN BHOWMIK The immediate response of the gastrointestinal epithelium to superficial (i.e. microscopic) injury is primarily directed towards restoring the disturbed epithelial continuity. Both structural (i.e. cytoskeleton) and humoral (i.e. growth factors and cytokines) involvement in the process has recently been documented. Yet it is unclear whether humoral signaling regulating mucosal recovery after superficial injury is associated with tyrosine phosphorylation, and whether there are other signs of downstream activation of the signaling pathway. To evaluate the effects of exogenous genistein and phorbol-myristate acetate in the assessment of the role of tyrosine receptor-mediated signaling in the immediate repair of gastric mucosa after superficial injury. Guinea pig gastric mucosa was mounted in a Ussing chamber, injured with 1.25 M NaCl, and perfused for 4 h. Simultaneously, potential difference and tissue resistance were recorded. In some sets of experiments the tissue was exposed bilaterally either to genistein in order to inhibit tyrosine receptor-mediated signaling or to 4-phorbol-myristate 13-acetate (PMA) in order to enhance PKC signaling during the 4 h recovery. Phosphotyrosine (PTYR) and protein kinase C (PKC) immunoreactivity were assessed by immunoblotting and by immunohistochemistry. Proliferative activity was determined morphometrically after staining of the tissue for Ki-67 nuclear antigen and expressed as proliferative index (PI). The inhibition of tyrosine kinases with exogenous genistein resulted in a significant decrease of the PTYR and the stimulation of PKC with PMA increased the PTYR. Nevertheless, no change in the PTYR was observed by immunoblotting after superficial injury alone. Several PKC isoenzymes were found in the guinea pig gastric mucosa, including PKC-,, -,, -, and -,. They were unaffected either by the injury or the PMA treatment. The mean PI of tissues subjected to NaCl-injury was higher than that of uninjured control tissues (p<0.05) (n=7). Exposure of tissue to genistein during recovery decreased the PI, while stimulation with PMA increased it (p<0.05 for both) (n=6). Both electrophysiologic and morphologic restitution were sensitive to genistein, but not to PMA. Superficial injury alone does not influence tyrosine phosphorylation to a degree which could be assessed by immunoblotting. Nevertheless, exogenous modulation of tyrosine receptor-mediated signaling results in downstream signaling effects. The injury-associated induction of proliferation is sensitive to modulation of tyrosine phosphorylation and PKC, suggesting that superficial epithelial injury results in endogenous activation of the epithelium, presumably after paracrine stimulation of the neighboring cells. [source] Purification, crystallization and preliminary X-ray analysis of Caenorhabditis elegans ubiquitin-conjugation enzyme M7.1ACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2003José A. Gavira M7.1 is a class IV ubiquitin-conjugation enzyme (UBC) that belongs to the ubiquitination cascade in Caenorhabditis elegans. The clone for this UBC has been overexpressed in Escherichia coli and the 16.7,kDa protein was purified from the soluble fraction. M7.1 was crystallized by sitting-drop vapor diffusion in 10% ethanol, 1.5,M NaCl at 277.5,K. Crystals diffracted to 1.75,Å and belong to the orthorhombic space group P212121, with unit-cell parameters a = 44.3, b = 54.3, c = 60.2,Å. The asymmetric unit contains a single monomer. A molecular-replacement model has been determined and refinement is in progress. [source] Crystallization and preliminary X-ray analysis of the major peanut allergen Ara,h,1 core regionACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 9 2010Cerrone Cabanos Peanuts contain some of the most potent food allergens known to date. Ara,h,1 is one of the three major peanut allergens. As a first step towards three-dimensional structure elucidation, recombinant Ara,h,1 core region was cloned, expressed in Escherichia coli and purified to homogeneity. Crystals were obtained using 0.1,M sodium citrate pH 5.6, 0.1,M NaCl, 15% PEG 400 as precipitant. The crystals diffracted to 2.25,Å resolution using synchrotron radiation and belonged to the monoclinic space group C2, with unit-cell parameters a = 156.521, b = 88.991, c = 158.971,Å, , = 107.144°. Data were collected at the BL-38B1 station of SPring-8 (Hyogo, Japan). [source] Expression, purification and preliminary crystallization of amaranth 11S proglobulin seed storage protein from Amaranthus hypochondriacus L.ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2010Mary Rose Tandang-Silvas 11S globulin is one of the major seed storage proteins in amaranth. Recombinant protein was produced as up to ,80% of the total bacterial protein using Escherichia coli Rosetta-gami (DE3) containing pET21d with amaranth 11S globulin cDNA. The best expression condition was at 302,K for 20,h using LB medium containing 0.5,M NaCl. The recombinant protein was easily separated from most of the Escherichia coli proteins by precipitation with 0,40% ammonium sulfate solution. It formed aggregates at low temperature and at low salt concentrations. This behaviour may imply that it has a more hydrophobic nature than other 11S seed globulins. The crystals diffracted to 6,Å resolution and belonged to space group P63, with unit-cell parameters a = b = 97.6, c = 74.8,Å, , = 120.0°. One subunit of a trimer was estimated to be present in the asymmetric unit, assuming a Vsol of 41%. To obtain the complete structure solution, experiments to improve crystallization and flash-cooling conditions are in progress. [source] Expression, purification, crystallization and preliminary X-ray analysis of rice (Oryza sativa L.) Os4BGlu12 ,-glucosidaseACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010Sompong Sansenya Rice (Oryza sativa L.) Os4BGlu12, a glycoside hydrolase family 1 ,-glucosidase (EC 3.2.1.21), was expressed as a fusion protein with an N-terminal thioredoxin/His6 tag in Escherichia coli strain Origami B (DE3) and purified with subsequent removal of the N-terminal tag. Native Os4BGlu12 and its complex with 2,4-dinitrophenyl-2-deoxy-2-fluoro-,- d -glucopyranoside (DNP2FG) were crystallized using 19% polyethylene glycol (3350 or 2000, respectively) in 0.1,M Tris,HCl pH 8.5, 0.16,M NaCl at 288,K. Diffraction data sets for the apo and inhibitor-bound forms were collected to 2.50 and 2.45,Å resolution, respectively. The space group and the unit-cell parameters of the crystal indicated the presence of two molecules per asymmetric unit, with a solvent content of 50%. The structure of Os4BGlu12 was successfully solved in space group P43212 by molecular replacement using the white clover cyanogenic ,-glucosidase structure (PDB code 1cbg) as a search model. [source] Expression, purification and preliminary X-ray diffraction studies of VERNALIZATION1208,341 from Arabidopsis thalianaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009Gordon King VERNALIZATION1 (VRN1) is required in the model plant Arabidopsis thaliana for the epigenetic suppression of the floral repressor FLC by prolonged cold treatment. Stable suppression of FLC accelerates flowering, a physiological process known as vernalization. VRN1 is a 341-residue DNA-binding protein that contains two plant-specific B3 domains (B3a and B3b), a putative nuclear localization sequence (NLS) and two putative PEST domains. VRN1208,341 includes the second B3 domain and a region upstream that is highly conserved in the VRN1 orthologues of other dicotyledonous plants. VRN1208,341 was crystallized by the hanging-drop method in 0.05,M sodium acetate pH 6.0 containing 1.0,M NaCl and 18%(w/v) PEG 3350. Preliminary X-ray diffraction data analysis revealed that the VRN1208,341 crystal diffracted to 2.1,Å and belonged to space group C2, with unit-cell parameters a = 105.2, b = 47.9, c = 61.2,Å, , = 90.0, , = 115.4, , = 90.0°. Assuming that two molecules occupy the asymmetric unit, a Matthews coefficient of 2.05,Å3,Da,1 and a solvent content of 40.1% were calculated. [source] Purification, crystallization and preliminary X-ray diffraction studies on avian haemoglobin from pigeon (Columba livia)ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Pon. Sathya Moorthy Haemoglobin is a physiologically significant metalloprotein that is involved in the exchange of gases for sustaining life. The respiratory system of birds is unique and complex compared with that of mammals. Many investigations of avian haemoglobins have revealed the presence of inositol pentaphosphate (IP5), a principal allosteric effector that is involved in regulation of their function. Structural investigations of avian haemoglobins are presently not adequate to explain their function. Efforts have been made in this direction in order to understand the oxygen-binding affinity involved in adapting to hypoxia in avian haemoglobins. Fresh whole blood was collected from pigeon (Columba livia) and purified using a DEAE cellulose anion-exchange chromatographic column. Crystallization of pigeon haemoglobin was accomplished using the hanging-drop vapour-diffusion method using PEG 3350 as a precipitant in 50,mM sodium acetate buffer pH 5.5 with 1,M NaCl. Data collection was carried out using a MAR345 image-plate detector system. The crystals diffracted to 2,Å resolution. Pigeon haemoglobin crystallizes in a triclinic space group, with two whole biological molecules in the asymmetric unit and with unit-cell parameters a = 55.005, b = 65.528, c = 104.370,Å, , = 78.742, , = 89.819, , = 65.320°. [source] Electronic Speckle Pattern Interferometry: A Tool for Determining Diffusion and Partition Coefficients for Proteins in GelsBIOTECHNOLOGY PROGRESS, Issue 6 2002David Karlsson The aim of this study was to demonstrate electronic speckle pattern interferometry (ESPI) as a powerful tool in determining diffusion coefficients and partition coefficients for proteins in gels. ESPI employs a CCD camera instead of a holographic plate as in conventional holographic interferometry. This gives the advantage of being able to choose the reference state freely. If a hologram at the reference state is taken and compared to a hologram during the diffusion process, an interferometric picture can be generated that describes the refraction index gradients and thus the concentration gradients in the gel as well as in the liquid. MATLAB is then used to fit Fick's law to the experimental data to obtain the diffusion coefficients in gel and liquid. The partition coefficient is obtained from the same experiment from the flux condition at the interface between gel and liquid. This makes the comparison between the different diffusants more reliable than when the measurements are performed in separate experiments. The diffusion and partitioning coefficients of lysozyme, BSA, and IgG in 4% agarose gel at pH 5.6 and in 0.1 M NaCl have been determined. In the gel the diffusion coefficients were 11.2 ± 1.6, 4.8 ± 0.6, and 3.0 ± 0.3 m2/s for lysozyme, BSA, and IgG, respectively. The partition coefficients were determined to be 0.65 ± 0.04, 0.44 ± 0.06, and 0.51 ± 0.04 for lysozyme, BSA, and IgG, respectively. The current study shows that ESPI is easy to use and gives diffusion coefficients and partition coefficients for proteins with sufficient accuracy from the same experiment. [source] | |||||||||||||||||||||||||||||||