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PubMed2003

Direct hydroxide attack is a plausible mechanism for amidase antibody 43C9.

Direct hydroxide attack on the scissile carbonyl of the substrate has been suggested as a likely mechanism for esterase antibodies elicited by phosphonate haptens, which mimic the transition states for the alkaline hydrolysis of esters.1 The unique amidase activity of esterase antibody 43C9 has been attributed to nucleophilic attack by an active-site histidine residue.2 Yet, the active site of 43C9 is strikingly similar to those of other esterase antibodies, particularly 17E8. We have carried out quantum mechanical calculations, molecular dynamics simulations, and free energy calculations to assess the mechanism involving direct hydroxide attack for 43C9. Results support this mechanism and suggest that the mechanism is plausible for other antiphosphonate antibodies that catalyze the hydrolysis of (p-nitro)phenyl esters.

Amidohydrolases↗
PubMed1997

Characterization of Silica-Containing Aluminum Hydroxide and Oxide Aerogels

Pure and silica-containing Al hydroxide aerogels were prepared by the supercritical drying method. The samples were later calcined, giving rise to alumina and Si-Al mixed oxides. The materials were characterized from the points of view of their bulk and surface structures. The Si-free material before calcination is well-crystallized boehmite that converts to gamma-alumina by calcination. The silica-containing hydroxides are composed of boehmite layers with silicates in the interlayer region. The resulting mixed oxides present silica essentially in the bulk. The surface structure of alumina seems poorly sensitive to silica addition. Surface silanol groups appear only for SiO2 more than 4%. No Bronsted acidity appears. Silica addition allows mixed oxides with higher surface areas to be obtained.

Journal Article↗
PubMed1999

Study of the Interaction Products of Some N- and O-Containing Compounds with Highly Dispersed Copper(II) Hydroxide.

Composition and structure of the surface compounds formed after interaction between Cu(OH)2 supported on aerosil and bpy, py, PhOH, and H2O2 are studied. The EXAFS and electron spectroscopy methods show the main part of copper ions to remain in a hydroxide surrounding, whose structure does not change practically and does not depend on the nature of the extra ligands used. The colloidal Cu(OH)2 stabilized by starch is found to reveal the same properties as the supported one, but differs by greater sizes of hydroxide particles. Copyright 1999 Academic Press.

Journal Article↗
PubMed2002

Micro volume changes due to Pb(II) and Cu(II) sorption on amorphous Fe(III) hydroxide.

Micro volume changes due to Pb(II) and Cu(II) sorption on amorphous Fe(III) hydroxide (AFH) were determined by a dilatometer at pH 4.50. Volume change is attributed to change in hydration status of dissolved and/or suspended substances. The volume of the system increased due to Pb(II) and Cu(II) sorption, suggesting that water molecules hydrated around Pb(II) or Cu(II) ions and AFH were released during sorption. Volume increases due to Pb(II) and Cu(II) sorption were smaller than those due to bulk precipitation of Pb and Cu hydroxides. Precipitation of Pb(II) and Cu(II) was not likely to occur at pH 4.50 in the presence of AFH. In conclusion, Pb(II) and Cu(II) formed an inner-sphere complex on AFH at pH 4.50, keeping hydrated water on the adsorbed species. Adsorbed Cu(II) kept more hydrated water than adsorbed Pb(II) on AFH.

Journal Article↗
PubMed1995

Prebiotic polymerization: oxidative polymerization of 2,3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide.

The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromoles Fe) for 3 days under anaerobic conditions at 40 degrees C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

Dimercaprol↗
PubMed1996

Application of cobalt ammine complexes for the simultaneous determination of traces of As, Fe, Ti, V and Zr in high-purity cobalt metal by lanthanum hydroxide coprecipitation and inductively coupled plasma-atomic emission spectrometry.

Co is not coprecipitated with lanthanum hydroxide in ammonium hydroxide solution due to the formation of soluble salts of cobalt ammine complexes. This complexation reaction has been applied to the simultaneous determination of five trace impurities (As, Fe, Ti, V and Zr) in high-purity Co metal by inductively coupled plasma-atomic emission spectrometry. Warming the solution and double coprecipitation are effective for separating the trace elements simultaneously from a large amount of cobalt ammine complexes. Matrix-matched solutions are used for calibration. The detection limits of the five elements are in the range of 0.06 and 0.6 microg/g and the recoveries are quantitative.

Journal Article↗
PubMed1999

Fungal biosolubilization of rhenish brown coal monitored by Curie-point pyrolysis/gas chromatography/mass spectrometry using tetraethylammonium hydroxide

Residues and coal fractions that remained after the biosolubilization of Rhenish brown coal by strains of Lentinula edodes and Trametes versicolor have been studied by Curie-point pyrolysis/gas chromatography/mass spectrometry using tetraethylammonium hydroxide (NEt4OH) at 610 degrees C. To differentiate methyl derivatives of esters and ethers from free or bound hydroxyl and carboxyl groups NEt4OH was used in the thermochemolysis experiments instead the commonly used tetramethylammonium hydroxide. A comparison of humic acid fractions before and after fungal attack shows considerable alteration of the soluble macromolecules of coal. Depending on the coal fraction studied and the fungi used, the assortment of fatty acid esters released during the pyrolysis varies significantly. Furthermore, dicarbonic acid ethyl diesters as well as ethyl derivatives of aromatic ethers and acids yield information about humic acid structure and the biosolubilization of brown coal. Variations in the mixture produced are possibly caused by differences in the pattern of extracellular enzymes secreted that attack the macromolecular structural elements of brown coal. Therefore pyrolysis of native and microbiologically altered geomacromolecules using NEt4OH allows one to differentiate between free hydroxyl groups as well as substances that are attached to humic substances via ester or ether bridges, and their methylated counterparts.

Journal Article↗
PubMed1984

Hybridization of DNA to RNA in methylmercuric hydroxide agarose gels.

We describe a method for hybridization of cDNA probes to RNA directly in agarose gels which provides a practical alternative to methods involving transfer of the RNA out of the gel. Total cellular RNA is subjected to electrophoresis in agarose gels containing methylmercuric hydroxide as the denaturing agent. After removal of the methylmercuric hydroxide, the gel is dried and 32P-labeled DNA probes are hybridized to the immobilized RNA. This method is more economical in time and expense than methods involving transfer of the RNA out of the gel, while maintaining a level of sensitivity comparable to other procedures.

Animals↗
PubMed1989

Acute toxicity of triphenyltin hydroxide to three cladoceran species.

The toxicity of an organotin pesticide, triphenyltin hydroxide, was assessed with several freshwater cladoceran species. Daphnia pulex, Daphnia magna, and Ceriodaphnia dubia were exposed for 48 h to triphenyltin hydroxide in static acute toxicity tests. Values of the 48-h trimmed Spearman-Karber EC(50)s for the three species were found to be 14.5, 16.5, and 11.3 microg litre(-1), respectively. Analysis of variance performed on EC(50) values of replicates revealed no significant differences between the three species. Methods were employed which decrease animal handling stress and increase the accuracy and precision of the concentrations.

Journal Article↗
PubMed1989

Testicular cell population dynamics following palmitine hydroxide treatment in male dogs.

Palmitine hydroxide isolated from the roots of Berberis chitria administered orally to dogs 30 mg/kg per day for 60 days brings about a consistent impairment of primary and secondary spermatocytes and elongated spermatids (Stages IV-VIII). The primary and secondary spermatocytes were reduced by 60 and 68%, respectively, and the elongated spermatids were decreased by 58%. The number of spermatogonia and Sertoli cells remained unaltered. The production of immature and mature Leydig cells decreased by 66% and 27%, respectively. Protein, sialic acid and glycogen content and acid phosphatase activity of testes and epididymides were lowered to varying extents. Testicular cholesterol was elevated significantly. Weights of the testes and epididymides were significantly reduced. The antispermatogenic action of palmitine hydroxide may be mediated by disturbances in Leydig cell function.

Animals↗
PubMed1995

Structural identification of valine hydroperoxides and hydroxides on radical-damaged amino acid, peptide, and protein molecules.

We have previously demonstrated the formation of two reactive moieties on proteins during free radical attack: hydroperoxides, and 3,4-dihydroxyphenylalanine (DOPA). Here we have undertaken the structural elucidation of the hydroperoxides of valine, the amino acid which is most susceptible to peroxidation. Exposure of L-valine to free radicals generated by radiolysis in an oxygen-saturated system produced three valine hydroperoxides. Upon treatment with sodium borohydride these were reduced to their corresponding hydroxides, which can be separated and purified by high performance liquid chromatography (HPLC). Based on spectroscopic data from high resolution chemical ionization (CI) mass spectrometry (MS), electrospray (ES) MS, electron impact (EI) MS, proton (1H) nuclear magnetic resonance (NMR) and carbon-13 (13C) NMR studies, the three valine hydroxides have been identified as beta-hydroxyvaline [(2S)-2-amino-3-hydroxy-3-methyl-butanoic acid], (2S,3S)-gamma-hydroxyvaline [(2S,3S)-2-amino-3-hydroxymethyl-butanoic acid], and (2S,3R)-gamma-hydroxyvaline [(2S,3R)-2-amino-3-hydroxymethyl-butanoic acid]. HPLC analysis of O-phthaldialdehyde (OPA) derivatives of the hydroxyvalines provides a sensitive and accurate method for quantitative measurement. This method enabled hydroxyvalines to be detected in the hydrolysates of a tripeptide (glutamyl-valinyl-phenylalanine) and a protein (bovine serum albumin) that had been gamma-radiolysed and treated with sodium borohydride. Hydroxyvaline may be useful as a marker in studying protein oxidation in some biological systems under oxidative stress.

Amino Acids↗
PubMed2004

Relative fibrolytic activities of anaerobic rumen fungi on untreated and sodium hydroxide treated barley straw in in vitro culture.

The fibrolytic activities of rumen fungi were studied in terms of dry matter loss, plant cell wall degradation and enzyme (cellulase and xylanase) activities, when grown in vitro on either untreated or sodium hydroxide treated stems of barley straw over a 12 day period. Changes in fungal growth, development and overall biomass were followed using chitin assay and scanning electron microscopy. Treatment with sodium hydroxide resulted in a decrease in the NDF content together with the disruption of cuticle and the loosening and separation of the plant cells within the straw fragments. The enzyme activities of the anaerobic fungi have a high positive correlation (R(2)=0.99) with their biomass concentration assessed by chitin assay indicating that chitin is a valuable index for the estimation of the fungal biomass in vitro. The anaerobic fungi produced very extensive rhizoidal systems in these in vitro cultures. After incubation with rumen fungi, dry matter losses were, respectively, 35% and 38% for the untreated and treated straw samples and the overall fungal biomass, determined by chitin assay, was significantly higher in the treated samples. In vitro degradation of cellulose and hemicellulose was also higher in the treated than that of untreated cultures. Although, comparatively, xylanase activity was higher than that of cellulase, the cellulose fraction of the straw was degraded more than hemicellulose in both treated and untreated straw.

Journal Article↗
PubMed2004

In situ Fourier-transform infrared spectroscopy studies of inorganic ions adsorption on metal oxides and hydroxides.

In this work, the studies describing the use of attenuated total reflection-infrared spectroscopy to obtain information on the sorption mechanism of inorganic ions on metal oxy-hydroxides are reviewed. ATR-IR is amongst the rare techniques which allow to analyze the sorption phenomena in situ and led to several results about the speciation of sorbed anions (sulfate, carbonate, phosphate, perchlorate, ...) or ternary inorganic complexes since it is able to distinguish outer-sphere and inner-sphere complexes. The principles of this method are summarized, and the experimental protocols, the results and the limitations are elaborated. The sample deposition method, initially based on a paste or a concentrated suspension, has evolved towards the coating of the ATR crystal by a colloid layer, increasing the sensibility and the reproducibility of the measurements. Observed absorption frequencies of ions sorbed on metal oxy-hydroxides (goethite, hematite, alumina, silica, TiO2, ...) are reported to help the identification of peaks in new experimental works. This method, characterized by an in situ analysis performed with a special cell used in a widespread instrumentation (IR spectrometer), is very recent but its advantages suitable for the current problems in the sorption field should help its rapid development for the next years.

Journal Article↗
PubMed2004

Intrinsic hydration of monopositive uranyl hydroxide, nitrate, and acetate cations.

The intrinsic hydration of three monopositive uranyl-anion complexes (UO(2)A)(+) (where A = acetate, nitrate, or hydroxide) was investigated using ion-trap mass spectrometry (IT-MS). The relative rates for the formation of the monohydrates [(UO(2)A)(H(2)O)](+), with respect to the anion, followed the trend: Acetate > or = nitrate >> hydroxide. This finding was rationalized in terms of the donation of electron density by the strongly basic OH(-) to the uranyl metal center, thereby reducing the Lewis acidity of U and its propensity to react with incoming nucleophiles, viz., H(2)O. An alternative explanation is that the more complex acetate and nitrate anions provide increased degrees of freedom that could accommodate excess energy from the hydration reaction. The monohydrates also reacted with water, forming dihydrates and then trihydrates. The rates for formation of the nitrate and acetate dihydrates [(UO(2)A)(H(2)O)(2)](+) were very similar to the rates for formation of the monohydrates; the presence of the first H(2)O ligand had no influence on the addition of the second. In contrast, formation of the [(UO(2)OH)(H(2)O)(2)](+) was nearly three times faster than the formation of the monohydrate.

Journal Article↗
PubMed2006

Screening and optimization of the derivatization of polar herbicides with trimethylanilinium hydroxide for GC-MS analysis.

In the present study, a derivatization method for the determination of acidic herbicides has been investigated. This procedure involves the methylation with the quaternary ammonium salt trimethylanilinium hydroxide (TMAH) directly in the gas chromatographic auto-sampler vial for analysis by gas chromatography combined with mass spectrometry. The derivatization reaction has been screened for influential factors and statistically significant parameters. The identified factors, reaction time, temperature and hold-up time were optimized by a complete factorial response surface design and optimal reaction conditions were generated. Finally, the optimized methylation procedure was compared to different alkylation methods and obtained results demonstrated the applicability of derivatization with trimethylanilinium hydroxide. Acidic herbicides used in the study consist of several families of compounds like derivatives of acetic acid (2,4-D and 2,4,5-T), butanoic acid (MCPB), benzoic acid (chloramben, dicamba), phenol (dinoseb and dinoterb), propanoic acid (mecoprop) and other miscellaneous acids such as pyridinecarboxlyic acid (picloram). A reliably working, rapid method for the preparation of methyl compounds is generated with respect to automation for routine analysis.

Diazomethane↗
PubMed2004

Formation of particles of metal hydroxides in water solution of polymer.

The stages of the formation of metal hydroxide particles in water medium were described. The first stage is the formation of complexes between the stabilizer and metal ion or of metal polyions containing a few metal ions. Dependence between the number of metal ions in polyion and its charge on the pH is described. The second stage is the formation of the metal hydroxide particles by the aggregation of polyions or their adsorption on/in the stabilizer. The distribution of the polyion number in the particles in polyion aggregation is described by the equation p(k) = k(ks-1)(k-1)/ksk and in polyion adsorption on/in the stabilizer particles is more narrow and is described by the equation p(k) = exp(-ks)/ks(-k)/k!, where k and ks are the number and the average number of polyions in the particle.

Journal Article↗
PubMed2005

Effects of the molar ratio of hydroxide and fluoride to Al(III) on fluoride removal by coagulation and electrocoagulation.

The effect of the molar ratio of hydroxide and fluoride ions to Al(III) ions (gamma(OH) and gamma(F)) on coagulation and electrocoagulation (EC) was studied to solve the problem of the over addition of acid or base. The efficiency of defluoridation was approximately 100% when the sum of gamma(OH) and gamma(F) (gamma(OH+F)) was close to 3. This finding reveals that the fluoride ions and the hydroxide ions can co-precipitate with Al(III) ions and the formula of the precipitate is Al(n)F(m)(OH)(3n-m). However, when gamma(OH) was less than 2.4, the defluoridation efficiency, given that gamma(OH+F)=3, dropped as gamma(OH) fell, because the amount of aluminum polymer formed dropped. The efficiency of defluoridation of EC exceeded that of coagulation for equal gamma(OH) and gamma(OH+F), when gamma(OH+F)>3, proving the existence of an electrocondensation effect.

Journal Article↗
PubMed2006

Compositional and structural control on anion sorption capability of layered double hydroxides (LDHs).

Layered double hydroxides (LDHs) have shown great promise as anion getters. In this paper, we demonstrate that the sorption capability of a LDH for a specific oxyanion can be greatly increased by appropriately manipulating material composition and structure. We have synthesized a large set of LDH materials with various combinations of metal cations, interlayer anions, and molar ratios of divalent cation M(II) to trivalent cation M(III). The synthesized materials have then been tested systematically for their sorption capabilities for pertechnetate (TcO(-)(4)). It is discovered that for a given interlayer anion (either CO(2-)(3) or NO(-)(3)) the Ni-Al LDH with a Ni/Al ratio of 3:1 exhibits the highest sorption capability among all the materials tested. The sorption of TcO(-)(4) on M(II)-M(III)-CO(3) LDHs may be dominated by the edge sites of LDH layers and correlated with the basal spacing d(003) of the materials, which increases with the decreasing radii of both divalent and trivalent cations. The sorption reaches its maximum when the layer spacing is just large enough for a pertechnetate anion to fit into a cage space among three adjacent octahedra of metal hydroxides at the edge. Furthermore, the sorption is found to increase with the crystallinity of the materials. For a given combination of metal cations and an interlayer anion, the best crystalline LDH material is obtained generally with a M(II)/M(III) ratio of 3:1. Synthesis with readily exchangeable nitrate as an interlayer anion greatly increases the sorption capability of a LDH material for pertechnetate. The work reported here will help to establish a general structure-property relationship for the related layered materials.

Journal Article↗