Energy Decomposition Analysis Reveals the Nature of Lone Pair-π Interactions with Cationic π Systems in Catalytic Acyl Transfer Reactions.

Lone pair-π (LP-π) interactions between Lewis basic heteroatoms, such as oxygen and sulfur, and electron-deficient π systems are important noncovalent interactions. However, they have seldom been used to control catalyst-substrate interactions in catalysis. We performed density functional theory calculations to investigate the strengths of LP-π interactions between different lone pair donors and cationic π systems, and in different complexation geometries. Energy decomposition analysis calculations indicated that the dominant stabilizing force in LP-π complexes is electrostatic interaction and the electrostatic potential surface of the π system predicts the most favorable site for forming LP-π complexes. Benzotetramisole (BTM) is revealed as a privileged acyl transfer catalyst that promotes LP-π interactions because the positive charge of the acylated BTM is delocalized onto the dihydroimidazole ring, which binds strongly with a variety of oxygen and sulfur lone pair donors.

Sulfur speciation by HPLC-ICPQQQMS in complex human biological samples: taurine and sulfate in human serum and urine.

The advent of the triple quadrupole technology to the inductively coupled plasma mass spectrometry (ICPMS) technique has allowed a strong improvement in the accuracy and detection limits of ICPMS for non-metal elements such as sulfur by removing major polyatomic interferences. Up to now, there has been no report utilizing this development for sulfur speciation in complex human biological matrices. In the present report, we show the success of HPLC-ICPQQQMS for the simultaneous determination of two major sulfur metabolites, taurine and sulfate, in human urine and serum, by direct injection without the need for sample clean-up. The optimized chromatographic method was validated, tested for robustness, and applied for investigating the intra-individual variability in taurine urinary excretion in eight healthy volunteers over a period of 8 weeks. The limit of detection and limit of quantification for taurine determination was found to be 0.2 and 0.7 pmol, respectively. The concentrations found in the analyzed group of urine samples (n = 64) had a range, mean, and SD of 0.6-99, 20.4, and 23.2 µg mL-1 for taurine, and 115-1373, 616, and 259 µg mL-1 for sulfate. Taurine was found to exhibit a much higher intra-individual variability than sulfate. The developed method can be applied in large-scale epidemiological studies and clinical studies in order to establish the potential cardioprotective effects of taurine. Graphical abstract ᅟ.

Classification of benzoyl peroxide as safe and effective and revision of labeling to drug facts format; topical acne drug products for over-the-counter human use; final rule.

We, the Food and Drug Administration (FDA), are issuing this final rule to include benzoyl peroxide as a generally recognized as safe and effective (GRASE) active ingredient in over-the-counter (OTC) topical acne drug products. In addition, this final rule includes new warnings and directions required for OTC acne drug products containing benzoyl peroxide. We are also revising labeling for OTC topical acne drug products containing resorcinol, resorcinol monoacetate, salicylic acid and/or sulfur to meet OTC drug labeling content and format requirements in a certain FDA regulation. This final rule is part of our ongoing review of OTC drug products and represents our conclusions on benzoyl peroxide in OTC acne drug products.

Sulphur isotope compositions of components of coal and S-isotope fractionation during its combustion and flue gas desulphurization.

Sulphur isotope compositions were determined in two different Polish coals (hard coal and lignite) and by-products originating from their combustion. The desulphurization process was also investigated. It was demonstrated that desulphurization changes the isotopic composition of sulphur emitted in the form of SO(2) to the atmosphere even if the process is conducted in a different way (wet lime technology and electron beam method). This fact has to be considered in the studies regarding anthropogenic sulphur genesis and its fate in the environment.

Sulfur speciation by capillary zone electrophoresis. Determination of dithionite and its decomposition products sulfite, sulfate and thiosulfate in commercial bleaching agents.

In this paper, a capillary zone electrophoretic (CZE) method was developed for the separation of the sulfur species dithionite (S2O4(2-)), sulfite (SO3(2-)), sulfate (SO4(2-)) and thiosulfate (S2O3(2-)). A carrier electrolyte (pH 7.0) containing 1.5 mmol L(-1) pyromellitic (PM) acid, 10 mmol L(-1) Tris(hydroxymethyl)-aminomethane (Tris), 0.5 mmol L(-1) diethylenetriamine (DETA) and 0.1% (v/v) formaldehyde (as stabilizer for S2O4(2-) and SO3(2-)) allowed the determination of the sulfur anions after 9 min CZE separation with indirect UV detection at 214 nm. The addition of 0.1% (v/v) formaldehyde to the sample solution stabilizes dithionite and sulfite as HOCH2SO2- and HOCH2SO3- anions. The procedure was applied for the determination of dithionite and its decomposition products sulfite, sulfate and thiosulfate in commercial formulations of bleaching agents. Dithionite was found to be the major component of the commercial formulations in concentrations between 30.80 and 33.30% (w/w). As anticipated, sulfite, sulfate and thiosulfate were found to be present as decomposition or by-products in the commercial formulations at concentrations of 14.30-14.80, 5.20-5.70 and 0.30-0.40% (w/w), respectively. The results were found to be in good agreement with those of polarographic and spectrophotometric determinations.

Evaluación de la actividad desulfurizadora de aislados nativos de Pseudomonas spp. en presencia de hidrocarburo / Desulfurization activity evaluation of native strains of Pseudomonas spp. in the presence of hydrocarbon

El principal inconveniente en la combustión de los hidrocarburos es la conversión del azufre y el nitrógeno a sus respectivos óxidos, los cuales participan en la formación de lluvia acida y deterioran el medio ambiente e infraestructuras. La remoción de azufre a partir de compuestos órgano-azufrados mediante el uso de microorganismos ha surgido como una alternativa frente al proceso catalítico de hidrodesulfurización (HDS). En el presente trabajo se evaluó la actividad desulfurizadora de veintitrés aislados nativos de Pseudomonas spp. sobre dibenzotiofeno (DBT), usando un sistema de fermentación con igual proporción de fase acuosa y orgánica (n-hexano) en presencia de oleato de etanolamina. Los aislados 02,05 y 06 conservaron su viabilidad en este medio y presentaron una remoción de azufre entre 6,0 y 9,4%, generando los metabolitos DBT-sulfona, DBT-sulfóxido, 2-hidroxibifenilo (2-HBP) y sulfato presentes en la ruta metabólica 4S. Con estos aislados se evaluó la actividad desulfurizadora sobre keroseno y se observó una remoción de azufre entre 19,9 y 62,6% y una disminución del poder calorífico entre 0,45 y 5,55%.

The main difficulty with fossil fuel combustión lies in sulphur and nitrogen becoming converted to their respective oxides, forming part of the acid rain which deteriorates the environment and infrastructure. Removing sulphur from organo-sulfur compounds by using micro-organisms has become an alternative to hydrodesulphurisation (HDS). Twenty-three Pseudomonas spp. native strains' desulphurisation activity on dibenzothiophene (DBT) was evaluated by using a fermentation system having equal proportions of aqueous and organic (n-hexane) phases in the presence of ethanolamine oléate. The 02, 05 and 06 strains maintained their viability in this médium, presenting 6,0% to 9,4% sulphur removal, producing DBT-sulphone, DBT-sulphoxide, 2-hydroxybiphenyl (2-HBP) metabolites and sulphate belonging to the 4S pathway. These native strains' desulphurisation activity was evaluated on kerosene, presenting 19,9% to 62,2% sulphur removal having 0,45% to 5,55% calorific power loss.