Tailoring an HSO4- anion hybrid receptor based on a phenazine derivative.

A catechol-functionalized phenazine imidazole (PD) was tailored with 2,3-diaminophenazine and 3,4-dihydroxy benzaldehyde, and it served as a hybrid acceptor for capturing HSO4- anions. The selectivity and sensitivity of the PD receptor for anion sensing were studied. It was found that the PD receptor could not only display a preferable sensitivity to HSO4- ions with a "turn-off" fluorescence response, but also have a strong anti-interference ability toward other common anions, especially basic anions such as CH3COO-, HPO42-, and H2PO4-. The anion recognition mechanism of PD towards HSO4- is based on multiple hydrogen bond interactions. Finally, the strips for anion detection were prepared, which were verified to be a convenient and high-efficiency test kit for detecting HSO4- ions with the naked eye.

Synthesis of Cyclic Sulfite Diesters and their Evaluation as Sulfur Dioxide (SO2 ) Donors.

Although sulfur dioxide (SO2 ) finds widespread use in the food industry as its hydrated sulfite form, a number of aspects of SO2 biology remain to be completely understood. Of the tools available for intracellular enhancement of SO2 levels, most suffer from poor cell permeability and a lack of control over SO2 release. We report 1,2-cyclic sulfite diesters as a new class of reliable SO2 donors that dissociate in buffer through nucleophilic displacement to produce SO2 with tunable release profiles. We provide data in support of the suitability of these SO2 donors to enhance intracellular SO2 levels more efficiently than sodium bisulfite, the most commonly used SO2 donor for cellular studies.

Exploring the catalytic mechanism of alkanesulfonate monooxygenase using molecular dynamics.

The complex mechanistic properties of alkanesulfonate monooxygenase (SsuD) provide a particular challenge for identifying catalytically relevant amino acids. In response, a joint computational and experimental study was conducted to further elucidate the SsuD mechanism. Extensive unbiased molecular dynamics (MD) simulations were performed for six SsuD systems: (1) substrate-free, (2) bound with FMNH2, (3) bound with a C4a-peroxyflavin intermediate (FMNOO(-)), (4) bound with octanesulfonate (OCS), (5) co-bound with FMNH2 and OCS, and (6) co-bound with FMNOO(-) and OCS. A previous theoretical study suggested that salt bridges between Arg297 and Glu20 or Asp111 initiated conformational changes critical for catalysis. However, our MD simulations and steady-state kinetic experiments did not corroborate this result. Similar kcat/Km values for both the E20A and D111A SsuD variants to wild-type SsuD suggest that the salt bridges are not critical to the desulfonation mechanism. Instead, the predicted role of Arg297 is to favorably interact with the phosphate group of the reduced flavin. Concomitantly, Arg226 functioned as a "protection" group shielding FMNOO(-) from bulk solvent and was more pronounced when both FMNOO(-) and OCS were bound. The stabilization of FMNOO(-) through electrostatic interactions with Arg226 would properly position the C4a peroxy group for the proposed nucleophilic attack on the sulfur of octanesulfonate.

Inhibition of norovirus 3CL protease by bisulfite adducts of transition state inhibitors.

Noroviruses are the most common cause of acute viral gastroenteritis, accounting for >21 million cases annually in the US alone. Norovirus infections constitute an important health problem for which there are no specific antiviral therapeutics or vaccines. In this study, a series of bisulfite adducts derived from representative transition state inhibitors (dipeptidyl aldehydes and α-ketoamides) was synthesized and shown to exhibit anti-norovirus activity in a cell-based replicon system. The ED(50) of the most effective inhibitor was 60 nM. This study demonstrates for the first time the utilization of bisulfite adducts of transition state inhibitors in the inhibition of norovirus 3C-like protease in vitro and in a cell-based replicon system. The approach described herein can be extended to the synthesis of the bisulfite adducts of other classes of transition state inhibitors of serine and cysteine proteases, such as α-ketoheterocycles and α-ketoesters.

Highly efficient SO2 absorption/activation and subsequent utilization by polyethylene glycol-functionalized Lewis basic ionic liquids.

Up to now, flue-gas desulfurization (FGD) is one of the most effective techniques to control SO(2) emission from the combustion of fossil fuels. The conventional technology for FGD poses serious inherent drawbacks such as formation of byproducts and volatilization of solvents. In this work, polyethylene glycol (PEG)-functionalized Lewis basic ionic liquids (ILs) derived from DABCO were proved to be highly efficient absorbents for FGD due to its specific features such as high thermal stability, negligible vapor pressure, high loading capacity. Notably, PEG(150)MeDABCONTf(2) gave an extremely high SO(2) capacity (4.38 mol mol(-1) IL), even under 0.1 bar SO(2) partial pressure (1.01 mol mol(-1) IL), presumably owing to the strong SO(2)-philic characterization of the PEG chain. Furthermore, the absorbed SO(2) could be easy to release by just bubbling N(2) at room temperature, greatly reducing energy requirement for SO(2) desorption. In addition, SO(2)/CO(2) selectivity (110) of PEG(150)MeDABCONTf(2) is two times larger than the non-functionalized imidazolium IL (45). On the other hand, through activation of SO(2) with the tertiary nitrogen in the cation, Lewis basic ILs such as PEG(150)MeDABCOBr proved to be efficient catalysts for the conversion of SO(2) to some value-added chemicals such as cyclic sulfites without utilization of any organic solvent or additive. Thus, this protocol would pave the way for the development of technological innovation towards efficient and low energy demanded practical process for SO(2) absorption and subsequent transformation.

Synthesis of cyclic sulfites from epoxides and sulfur dioxide with silica-immobilized homogeneous catalysts.

Quaternary ammonium- and amino-functionalized silica catalysts have been prepared for the selective synthesis of cyclic sulfites from epoxides and sulfur dioxide, demonstrating the effects of immobilizing the homogeneous catalysts on silica. The cycloaddition of sulfur dioxide to various epoxides was conducted under solvent-free conditions at 100 °C. The quaternary ammonium- and amino-functionalized silica catalysts produced cyclic sulfites in high yields (79-96 %) that are comparable to those produced by the homogeneous catalysts. The functionalized silica catalysts could be separated from the product solution by filtration, thereby avoiding the catalytic decomposition of the cyclic sulfite products upon distillation of the product solution. Heterogenization of a homogeneous catalyst by immobilization can, therefore, improve the efficiency of the purification of crude reaction products. Despite a decrease in catalytic activity after each recycling step, the heterogeneous pyridine-functionalized silica catalyst provided high yields after as many as five recycling processes.

Access to antigens related to anthrose using pivotal cyclic sulfite/sulfate intermediates.

Anthrose is the upstream terminal unit of the tetrasaccharide side chain from a major glycoprotein of Bacillus anthracis exosporium and is part of important antigenic determinants. A novel entry to anthrose-containing antigens and precursors is described. The synthetic route, starting from D(+)-fucose, makes use of intermediates featuring a cyclic sulfite or sulfate function which serves successively as a protecting and a leaving group.

From sulfur-amine solutions to metal sulfide nanocrystals: peering into the oleylamine-sulfur black box.

In this Article, we present our findings on the formation of metal sulfide nanocrystals from sulfur-alkylamine solutions. By pulsed field gradient diffusion NMR along with the standard toolbox of 1D and 2D NMR, we determined that sulfur-amine solutions used as a sulfur precursor exist as alkylammonium polysulfides at low temperatures. Upon heating to temperatures used in nanocrystal synthesis, the polysulfide ions react with excess amine to generate H(2)S, which combines with the metal precursor to form metal sulfide. Four different reaction pathways were found, each of which produced H(2)S and the byproducts identified in this Article. Thioamides were identified as an intermediate and were shown to exhibit much more rapid kinetics than sulfur-alkylamine solutions at low temperatures in the synthesis of metal sulfide nanocrystals.

Synthesis and antiviral evaluation of bisnoradamantane sulfites and related compounds.

The reaction of a series of 1,2-diols with thionyl chloride led to bisnoradamantane sulfites in very good yields. The reaction has also been applied to related polycyclic scaffolds. The compounds have been tested for antiviral activity but none of them showed to be active. Several attempts to generate and trap SO from these polycyclic sulfites have been unsuccessful.

Seven-membered cyclic sulfite eudesmane derivatives: partial synthesis, structural determination, and enzymatic resolution.

Two chromatographically inseparable, diastereomeric eudesmane cyclic sulfites have been semisynthesized from alpha-santonin. This diastereomeric mixture was resolved by enzymatic acetylation with CCL. Each cyclic sulfite derivative was individually characterized on the basis of its spectroscopic and crystallographic properties.

Antitumor agents. Part 232: Synthesis of cyclosulfite podophyllotoxin analogues as novel prototype antitumor agents.

An 11,13-O,O'-cyclosulfite GL-331 analogue (7) was synthesized in six steps from podophyllotoxin and evaluated as a potential antitumor agent. Compound 7 was significantly cytotoxic against human tumor cell lines, but showed no inhibition against human DNA topoisomerase II in vitro. This compound represents a novel prototype of antitumor podophyllotoxin analogues.

Determination of organic anions in waste liquid of sodium hydrosulfite production by ion chromatography.

An ion chromatographic method for simultaneous determination of formate, hydroxyethyl sulfonate (HES), hydroxyethyl thiosulfate (HET), and coexisting anions in the industrial waste liquid of sodium hydrosulfite production was developed. The mixture of 1.6 mmol/l of phthalic acid and 1.2 mmol/l tri-(hydroxyethyl) aminomethane was used as eluent. The interference of coexisting sulfite anion with HES was avoided by selective oxidation with hydrogen peroxide as oxidizer. The other coexisting inorganic anions, Cl-, SO4(2-) and S2O3(2-) can be determined simultaneously. The linear range of the peak area calibration curves for all analytes was up to two or three orders of magnitude. The detection limits (S/N = 3) for formate, HES and HET were 2.4, 1.0 and 0.5 mg/l, respectively. The recoveries for all analytes were 91.61-100.6%.

Immobilization of phospholipid vesicles and protein-lipid vesicles containing red cell membrane proteins on octyl derivatives of large-pore gels.

For improved immobilization of phospholipid vesicles and protein-lipid vesicles (cf. Sandberg, M., Lundahl, P., Greijer, E. and Belew, M. (1987) Biochim. Biophys. Acta 924, 185-192) and for chromatographic experiments with vesicles containing membrane protein, we have prepared octyl sulfide derivatives of the large-pore gels Sephacryl S-1000 and Sepharose 2B with ligand concentrations up to 14 and 5 mumol/ml gel, respectively. The Sephacryl derivatives allowed higher flow rates, gave higher rates of adsorption and showed equally high or higher capacities than the Sepharose adsorbents. 'Small', 'medium' and 'large' vesicles of radii approx. 20, 50 and 100 nm showed distribution coefficients on Sephacryl S-1000 of 0.7, 0.5 and 0.05, respectively and could be immobilized on octyl sulfide-Sephacryl S-1000 in amounts corresponding to 110, 40 and 20 mumol of phospholipids per ml gel, respectively. 'Small' vesicles became absorbed onto this gel at a rate of 1.5 mumol of phospholipids per min per ml gel until 60 mumol of phospholipids had become immobilized, whereas the initial adsorption rate was about 0.4 mumol.min-1.ml-1 on octyl sulfide-Sepharose 4B (see reference above) and on octyl sulfide-Sepharose 2B. Lower ligand concentrations gave lower capacities for 'small' vesicles. When vesicles entrapping calcein were immobilized on octyl sulfide-Sephacryl S-1000 some calcein was released during the adsorption process. For 'small' and 'medium' vesicles, respectively, the leakage was 75 and 25% at a ligand concentration of 14 mumol/ml but only 3 and 2% at 5 mumol/ml. The internal volumes of immobilized 'small' and 'medium' vesicles were estimated at 0.97 and 2.9 microliters per mumol of phospholipid by determination of entrapped calcein, which could indicate vesicle radii 20 and 50 nm, respectively. The total volumes of immobilized 'medium' lipid vesicles and 'medium' protein-lipid vesicles containing integral membrane proteins from human red cells, were estimated at 2.9 and 2.0 microliters/mumol, respectively, by chromatography of D- and L-[14C]glucose and calcein on the octyl sulfide-Sephacryl S-1000 column before and after immobilization. These volumes are roughly consistent with the internal volume of the vesicles. A zone of D-glucose eluted 90 microliters later than a zone of L-glucose on a 4- or 5-ml column of octyl sulfide-Sephacryl S-1000 with immobilized 'medium' protein-lipid vesicles containing the glucose transporter from human red cells, probably since part of the internal vesicle volume was accessible to the D-glucose but not to the L-glucose. This indicates that the glucose transporter was active in the immobilized vesicles.(ABSTRACT TRUNCATED AT 400 WORDS)

Generatation and characterization of sodium sulfite aerosols for applications in inhalation toxicologic research.

A method has been developed for generation of submicrometer aerosols of sodium sulfite suitable for use in inhalation toxicologic research. Concentrations ranging up to about 30 mg/m3 Na2SO3 were achieved in a 0.44 m3 exposure chamber with an air flow rate of 0.20 m3/min for periods up to 16 days. The coefficient of variation of the sulfite aerosol mass concentration was about 4% during a typical exposure period. The measured mass median aerodynamic diameters (MMADar) of the generated aerosols were 1.2 (+/- 0.2SD) microns with a geometric standard deviation (sigma g) of 1.9 (+/- 0.3SD). The chamber was sampled for gas phase SO2 concentration, and aerosol samples were analyzed for particulate sulfite and sulfate. The fraction of sulfur qas sulfite in the aerosol was usually 95% and was always greater than 90%. Gas phase SO2 amounted to less than 2% of the total S(IV) present in the chamber.

Study of bisulfite and metabisulfite aerosol generation systems.

Sulfur (IV) aerosols may be generated only as the fully neutralized sulfite by nebulization techniques. Attempts to generate bisulfite and metabisulfite aerosols result in the production of sulfite aerosols and large amounts of SO2. Previous toxicologic studies on metabisulfite and bisulfite aerosols apparently documented the effects of high concentrations of gaseous SO2.

Nucleophilic addition of bisulfite ion to prostaglandins E2 and A2: implication in aqueous stability.

Evidence is presented to indicate that the bisulfite ion (HSO3-) adds across the C-9 carbonyl group of dinoprostone (prostaglandin E2) and across the delta 10,11- bond of prostaglandin A2. At room temperature, the apparent equilibrium constant, determined by phase solubility analysis, circular dichroism, UV spectroscopy, and partitioning, for the formation of the bisulfite adduct of dinoprostone is about 7.5 M-1 at neutral pH. From this result and a free energy relationship reported in the literature for the thermodynamics of nucleophilic addition to carbonyl groups, it is concluded that the chemical reactivity of the C-9 carbonyl group of dinoprostone is not high enough to improve aqueous stability through reversible one-step nucleophilic reactions. However, from a series of kinetic experiments, it is concluded that the equilibrium is extremely favorable for the formation of the bisulfite adduct of prostaglandin A2 over pH 4-8 at room temperature. The second-order rate constant for the attack of sulfite ion (SO3 2-) to prostaglandin A2 is 1.75 sec-1 M-1.