Kinetics of the oxidation of methyl tert-butyl ether (MTBE) by potassium permanganate

The occurrence of the fuel oxygenate methyl tert-butyl ether (MTBE) in the environment has received considerable scientific attention. The pollutant is frequently found in the groundwater due to leaking of underground storage tanks or pipelines. Concentrations of more than several mg/L MTBE were detected in groundwater at several places in the US and Germany in the last few years. In situ chemical oxidation is a promising treatment method for MTBE-contaminated plumes. This research investigated the reaction kinetics for the oxidation of MTBE by permanganate. Batch tests demonstrated that the oxidation of MTBE by permanganate is second order overall and first order individually with respect to permanganate and MTBE. The second-order rate constant was 1.426 x 10(-6) L/mg/h. The influence of pH on the reaction rate was demonstrated to have no significant effect. However, the rate of MTBE oxidation by potassium permanganate is 2-3 orders of magnitude lower than of other advanced oxidation processes. The slower rates of MTBE oxidation by permanganate limit the applicability of this process for rapid MTBE cleanup strategies. However, permanganate oxidation of MTBE has potential for passive oxidation risk management strategies. (C) 2002 Elsevier Science Ltd. All rights reserved.

OXIDATIVE DISSOLUTION OF RUTHENIUM DIOXIDE HYDRATE BY PERIODATE IONS

The results of a kinetic study of the oxidative dissolution of ruthenium dioxide hydrate to ruthenium tetroxide by periodate ions, IO4-, in acidic solution are described. The kinetics of dissolution give a good fit to a 'soft-centre' model in which the particles of RuO2.xH2O are assumed to be monodispersed, spherical but inhomogeneous in composition, comprising a difficult-to-corrode outer shell and a more easy-to-corrode inner core. In this work metaperiodate appears to act as a two-electron oxidant. The observed kinetics fit a reaction scheme in which the rate-determining step is the reaction between a surface site and an adsorbed IO4 ion and there is competitive adsorption by any IO3- present. In the absence and presence of an excess of IO3- ions, the overall activation energy for the corrosion reaction was determined to be 38 +/- 2 and 54 +/- 4 kJ mol-1, respectively.

Periodate – an alternative oxidant for testing potential water oxidation catalysts

The redox catalyst ruthenium dioxide, prepared via the Adams technique, i.e.Ru(Adams), is used as a water oxidation catalyst using the oxidants (i) Ce(IV) in 0.5M H2SO4 and (ii) periodate in 0.5 M H2SO4, water and 0.1 M KOH. Like Ce(IV),periodate is a very strong oxidant that is able to oxidise water to oxygen and can bereadily monitored spectrophotometrically at 280 nm, compared with 430 nm for Ce(IV).More importantly, unlike Ce(IV), which is unstable towards hydrolysis above pH 1,periodate is stable in acid, water and strong alkali. A spectrophotometric study of thekinetics of periodate reduction, and concomitant oxidation of water to O2, reveals thatin the presence of a suitable redox catalyst, Ru(Adams) in this work, periodate is ableto effect the stoichiometric oxidation of water, with a turnover number > 64. In justwater, the kinetics of the latter reaction appear diffusion-controlled, due to the largethermodynamic driving force, a measure of which is the difference in redox potential,i.e. ∆E = 423 mV. As this difference is decreased, ∆E = 396 mV in acid and 290 mVin strong alkali (0.1 M KOH), the kinetics become increasingly activation-controlledand slower. These findings are discussed briefly with regard to the possible use of (i)periodate as an alternative oxidant in the rapid screening of new potential wateroxidation catalyst material powders that are stable only under near neutral and/oralkaline conditions, and (ii) Ru(Adams) as a benchmark catalyst.

Solid-Phase Synthesis Of Oligonucleotides Containing 3'-Thiothymidine

A 5'-O-monomethoxytritylthymidine-3'-S-thiophosphoramidite (3) has been used to prepare oligodeoxynucleotides containing 3'-thiothymidine on a solid phase support. The intermediate thiophosphites are most efficiently oxidised using tetrabutylammonium periodate.

OXIDATIVE DISSOLUTION OF CHROMIUM(III) OXIDES BY METAPERIODATE IONS IN PERCHLORIC-ACID

The kinetics of oxidative dissolution of a number of different samples of chromium(III) oxide by periodate ions in 1 mol dm-3 HClO4 solution have been studied and the results interpreted using the inverse-cubic rate law. The metaperiodate acts as a two-electron oxidant and the overall reaction stoichiometry involves the reaction of 3 mol of periodate with 1 mol of Cr(III) oxide. From a detailed study of the kinetics of dissolution the rate-determining step appears to be the reaction between an adsorbed periodate ion and its associated Cr(III) oxide surface site, with inhibition by one of the reaction products, iodate, through competitive adsorption. Analysis of the kinetic data generates values for the Langmuir adsorption coefficients for periodate and iodate ions on highly hydrated Cr(III) oxide of 84 +/- 8 and 2600 +/- 370 dm3 mol-1, respectively. The Cr(III) oxide-periodate reaction has a high overall activation energy, 82 +/- 6 kJ mol-1. The kinetics of dissolution of highly hydrated Cr(III) oxide under conditions in which the simple inverse-cubic rate law function does not apply can be successfully predicted using a simple kinetic model.

MarA-mediated transcriptional repression of the rob promoter

The Escherichia coli transcriptional regulator MarA affects functions that include antibiotic resistance, persistence, and survival. MarA functions as an activator or repressor of transcription utilizing similar degenerate DNA sequences (marboxes) with three different binding site configurations with respect to the RNA polymerase-binding sites. We demonstrate that MarA down-regulates rob transcripts both in vivo and in vitro via a MarA-binding site within the rob promoter that is positioned between the -10 and -35 hexamers. As for the hdeA and purA promoters, which are repressed by MarA, the rob marbox is also in the "backward" orientation. Protein-DNA interactions show that SoxS and Rob, like MarA, bind the same marbox in the rob promoter. Electrophoretic mobility shift analyses with a MarA-specific antibody demonstrate that MarA and RNA polymerase form a ternary complex with the rob promoter DNA. Transcription experiments in vitro and potassium permanganate footprinting analysis show that MarA affects the RNA polymerase-mediated closed to open complex formation at the rob promoter.

Immunochemical characterization of a polysaccharide antigen of Bacteroides fragilis with an IgM monoclonal antibody

An IgM mouse monoclonal antibody (McAb) Bf4 was produced to a surface polysaccharide of Bacteroides fragilis NCTC 9343. Immunoblotting showed that McAb Bf4 reacted strongly with a high molecular mass structure which was sensitive to oxidation with periodate but resisted protease treatment. An inhibition enzyme-linked immunosorbent assay (ELISA) indicated that McAb Bf4 did not cross react with the sixteen Bacteroides species and strains tested. Cells of B. fragilis NCTC 9343 recovered from the various interfaces of a Percoll discontinuous density gradient were tested in the inhibition ELISA. Bacteria from the 0-20%, 20-40% and 40-60% interfaces inhibited the ELISA; however, cells from the 60-80% interface did not. Electron microscopy with immunogold labelling showed that McAb Bf4 did not react with the extracellular fibrous network on bacteria recovered from the 0-20% interface, or the extracellular electron dense layer on cells from the 60-80% interface; however, it was associated with a surface structure on cells from the 20-40% interface. Growth in vivo did not enrich for bacteria with this structure.

A comparison of the haemagglutinating and enzymic activities of Bacteroides fragilis whole cells and outer membrane vesicles

The haemagglutinating and enzymic activities of the obligately anaerobic pathogenic bacterium Bacteroides fragilis were examined. Outer membrane vesicles are released from the surface of B. fragilis. They can be detected by electron microscopy in ultrathin sections and bacterial suspensions after negative staining. Electron microscopy and immunogold labelling with a MAb specific for surface polysaccharide of B. fragilis confirmed that the vesicles carried outer membrane associated epitopes. The haemagglutinating activity of whole cells from populations of B. fragilis strains NCTC9343, BE3 and LS66 enriched by Percoll density gradient centrifugation for a large capsule (LC), electron dense layer (EDL); non-capsulate by light microscopy) and outer membrane vesicles (OMV) which had been purified by centrifugation from EDL-enriched populations were compared using human and horse erythrocytes. The enzymic activity of OMV, LC- and EDL-enriched populations, as detected by the API ZYM kit, was compared for strains NCTC 9343 and BE3. Purified OMV from the strains examined exhibited both haemagglutinating and enzymatic activity. Haemagglutination by the EDL-enriched population was sensitive to treatment with sodium periodate. The LC-enriched population haemagglutinated only after ultrasonic removal of the capsule. This indicates that the LC masks a haemagglutinin. The results suggest a potential role for OMV in the virulence of B. fragilis.

Identification of the lipopolysaccharide core of Yersinia pestis and Yersinia pseudotuberculosis as the receptor for bacteriophage φA1122

fA1122 is a T7-related bacteriophage infecting most isolates of Yersinia pestis, the etiologic agent of plague, and used by the CDC in the identification of Y. pestis. fA1122 infects Y. pestis grown both at 20 °C and at 37 °C. Wild-type Yersinia pseudotuberculosis strains are also infected but only when grown at 37 °C. Since Y. pestis expresses rough lipopolysaccharide (LPS) missing the O-polysaccharide (O-PS) and expression of Y. pseudotuberculosis O-PS is largely suppressed at temperatures above 30 °C, it has been assumed that the phage receptor is rough LPS. We present here several lines of evidence to support this. First, a rough derivative of Y. pseudotuberculosis was also fA1122 sensitive when grown at 22 °C. Second, periodate treatment of bacteria, but not proteinase K treatment, inhibited the phage binding. Third, spontaneous fA1122 receptor mutants of Y. pestis and rough Y. pseudotuberculosis could not be isolated, indicating that the receptor was essential for bacterial growth under the applied experimental conditions. Fourth, heterologous expression of the Yersinia enterocolitica O:3 LPS outer core hexasaccharide in both Y. pestis and rough Y. pseudotuberculosis effectively blocked the phage adsorption. Fifth, a gradual truncation of the core oligosaccharide into the Hep/Glc (L-glycero-D-manno-heptose/D-glucopyranose)-Kdo/Ko (3-deoxy-D-manno-oct-2-ulopyranosonic acid/D-glycero-D-talo-oct-2-ulopyranosonic acid) region in a series of LPS mutants was accompanied by a decrease in phage adsorption, and finally, a waaA mutant expressing only lipid A, i.e., also missing the Kdo/Ko region, was fully fA1122 resistant. Our data thus conclusively demonstrated that the fA1122 receptor is the Hep/Glc-Kdo/Ko region of the LPS core, a common structure in Y. pestis and Y. pseudotuberculosis.

Detection and partial characterization of human B cell colony stimulating activity in synovial fluids of patients with rheumatoid arthritis

The joint fluids of 37 patients with rheumatoid arthritis, eight patients with traumatic injuries to their joints, two patients with Reiter's syndrome and three patients with psoriatic arthritis were tested for the presence of B cell colony stimulating activity (B cell CSA). B cell CSA was found in all of the joint fluids from the patients with rheumatoid arthritis but in none of the joint fluids from patients with traumatic injuries to their joints or in the joint fluids from the patients with Reiter's syndrome. A trace of B cell CSA was found in the joint fluid of one of the three patients with psoriatic arthritis. There was a positive correlation (r = 0.796) between the amount of rheumatoid factor present in the joint fluids and the titre of B cell CSA. This correlation was highly significant (P less than 0.001). The B cell CSA was localized to component(s) with molecular weight ranges 115-129 kD and 64-72 kD and an isoelectric point of 6.8. Its activity was sensitive to reduction with 2-mercaptoethanol and to the oxidising action of potassium periodate.