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The biochemical pathway through which sulfur may be assimilated from dimethylsulfide (DMS) is proposed to proceed via oxidation of DMS to dimethylsulfoxide (DMSO) and subsequent conversion of DMSO to dimethylsulfone (DMSO2). Analogous chemical oxidation processes involving biogenic DMS in the atmosphere result in the deposition of DMSO2 into the terrestrial environment. Elucidating the enzymatic pathways that involve DMSO2 contribute to our understanding of the global sulfur cycle. Dimethylsulfone monooxygenase SfnG and flavin mononucleotide (FMN) reductase MsuE from the genome of the aerobic soil bacterium Pseudomonas fluorescens Pf0-1 were produced in Escherichia coli, purified, and biochemically characterized. The enzyme MsuE functions as a reduced nicotinamide adenine dinucleotide (NADH)-dependent FMN reductase with apparent steady state kinetic parameters of Km = 69 μM and kcat/Km = 9 min(-1) μM (-1) using NADH as the variable substrate, and Km = 8 μM and kcat/Km = 105 min(-1) μM (-1) using FMN as the variable substrate. The enzyme SfnG functions as a flavoprotein monooxygenase and converts DMSO2 to methanesulfinate in the presence of FMN, NADH, and MsuE, as evidenced by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The results suggest that methanesulfinate is a biochemical intermediate in sulfur assimilation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Electrochemical study of the mechanism of dimethylsulfoxide electrooxidation on a platinum electrode in acidic and alkaline solutions is carried out. On the stationary anodic polarization curves taken in acidic and alkaline dimethylsulfoxide solutions, the oxidation currents preceded those measured in the supporting electrolyte. By the analyzing of linear segments of anodic voltammograms, the coefficients of the Tafel equation are determined. This allowed choosing the current density range and conditions for the dimethylsulfoxide electrooxidation on the platinum electrode. The electrolysis was carried out at controlled current density in electrolyzers both with unseparated compartments and the anodic and cathodic compartments separated with MK-40, MA-40 membranes and a MF-4SK fluoropolymer sulfocationite membrane. The high electrical conductivity and selectivity of the membranes provided good performance of the electrolysis process and obtaining of high-purity final product. Raman spectroscopy and gas chromatography–mass spectrometry confirmed that the products of dimethylsulfoxide electrooxidation in the acidic solution are dimethylsulfone and dimethylsulfoxide; in alkaline solution, the dimethyl sulfone and sodium methanesulfonate. The method of quantum-chemical calculations showed good adsorption of dimethylsulfoxide molecules at platinum within the frames of the cluster model. It is shown that the dimethylsulfoxide formation at the platinum electrode surface at high current densities occurs by the radical-ion mechanism, involving breaking of the C–S bond. Based on the experimental results obtained, a scheme for the dimethylsulfoxide electrochemical oxidation at platinum is proposed. [ABSTRACT FROM AUTHOR]

a comparative assessment of dimethylsulfoxide and dimethylsulfone adsorption on a smooth platinum electrode in acidic medium in the region of anode potentials is presented. The adsorption isotherms in the "hydrogen" potential range, depending on the dimethylsulfoxide and dimethylsulfone concentration, are S-shaped. At the adsorbate concentrations in the solution exceeding 0.1 M, the surface coverage with dimethylsulfoxide and dimethylsulfone is nearly the same and changes but slightly. A significant difference in the adsorption characteristics of dimethylsulfoxide and dimethylsulfone in the potential region of oxygen adsorption is found. According to the Pt-electrode surface coverage with oxygen in the presence of the test substances, it was concluded that the value of the dimethylsulfoxide and dimethylsulfone adsorption is maximal only when their bulk concentration is higher than 0.1 M, here the oxygen surface coverage in the presence of dimethylsulfone exceeds that in the background solution. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we provide a dielectric study on dimethylsulfone (DMSO2) solutions in water and dimethylsulfoxide (DMSO) in the frequency range from 100MHz to 50GHz and for temperatures from 298.15 to 318.15K. The dielectric data are parametrized utilizing a Cole–Davidson spectral function, which presumes an unsymmetrical relaxation time distribution. The conductivity contribution to the total relaxation must be taken into account only in an aqueous solution of DMSO2. The concentration dependent static dielectric constant (εS), relaxation time (τ) and relaxation strength (Δε) of these solutions have been determined. [Copyright &y& Elsevier]

Abstract: In this paper the densities and enthalpies of solution of dimethylsulfone (DMSO2) in dimethylsulfoxide (DMSO) and DMSO/water equimolar mixture have been measured over available concentration range (up to about 1molkg−1). Densities of solutions and apparent molar volumes were determined over the 293.15–323.15K temperature range. In DMSO2–DMSO–water system the strongest interaction between DMSO and water molecules leads to the increase of partial molar volumes for DMSO2. It was shown that the competitive intermolecular interactions are responsible for the observed phenomena. Solution enthalpies of DMSO2 in the above mentioned solvents and the enthalpies of transfer of DMSO2 from water to DMSO and DMSO/water mixture have been calculated. The obtained results confirm that the endothermal process of sulfone crystalline lattice decomposition predominates during the dissolution of sulfones. With the transfer of DMSO2 from water to DMSO and mixed solvent the endothermic increase of transfer enthalpies takes place. [Copyright &y& Elsevier]

Abstract: The mild catalytic oxidation of dimethylsulfoxide (DMSO) into biodegradable dimethylsulfone is proposed as an efficient pretreatment of wastewaters subjected to biological treatment processes. A SiO2–TiO2 mesoporous xerogel prepared by a non-hydrolytic route, as well as titanium silicalite TS-1 showed very good activity and stability in the catalytic oxidation of DMSO with H2O2 in dilute aqueous solution, at room temperature. [Copyright &y& Elsevier]