Oxidation of Dimethyl Sulfide to Dimethyl Sulfoxide by Phototrophic Purple Bacteria

Enrichment cultures of phototrophic purple bacteria rapidly oxidized up to 10 mM dimethyl sulfide (DMS) to dimethyl sulfoxide (DMSO). DMSO was qualitatively identified by proton nuclear magnetic resonance. By using a biological assay, DMSO was always quantitatively recovered from the culture media. DMS oxidation was not detected in cultures incubated in the dark, and it was slow in cultures exposed to full daylight. Under optimal conditions, the second-order rate constant for DMS oxidation was 6 day⁻¹ mg of protein⁻¹ ml⁻¹. The rate constant was reduced in the presence of high concentration of sulfide (>1 mM), but was not affected by the addition of acetate. DMS was also oxidized to DMSO by a pure strain (tentatively identified as a Thiocystis sp.) isolated from the enrichment cultures. DMS supported growth of the enrichment cultures and of the pure strain by serving as an electron source for photosynthesis. A determination of the amount of protein produced in the cultures and an estimation of the electron balance suggested that the two electrons liberated during the oxidation of DMS to DMSO were quantitatively used to reduce carbon dioxide to biomass. The oxidation of DMS by phototrophic purple bacteria may be an important source of DMSO detected in anaerobic ponds and marshes.     

二甲基亚砜毒性研究

二甲基亚砜（Dimethyl sulfoxide DMSO）是一种含硫有机化合物,被誉为＂万能溶剂＂,广泛用作溶剂和反应试剂。在医药工业中,DMSO可直接用作某些药物的原料及载体。DMSO本身有消炎止痛,利尿,镇静等作用,亦誉为＂万灵药＂,常作为止痛药物的活性组分添加于药物之中。DMSO也是一种渗透性保护剂,能够降低细胞冰点,减少冰晶的形成,减轻自由基对细胞损害,改变生物膜对电解质、药物、毒物和代谢产物的通透性。DMSO作为组蛋白去乙酰化酶抑制剂（Histone Deacetylases-inhibitor HDACi）的一种,同样具有恢复组蛋白的乙酰化与去乙酰化平衡,抑制细胞程序性死亡,修复DNA双螺旋结构,抗放射性损伤,抗炎症反应及抗癌作用。鉴于其应用广泛,本文就其物理特性及毒性研究做一综述。     

二甲基亚砜毒性研究

二甲基亚砜(Dimethyl sulfoxide DMSO)是一种含硫有机化合物,被誉为"万能溶剂",广泛用作溶剂和反应试剂。在医药工业中,DMSO可直接用作某些药物的原料及载体。DMSO本身有消炎止痛,利尿,镇静等作用,亦誉为"万灵药",常作为止痛药物的活性组分添加于药物之中。DMSO也是一种渗透性保护剂,能够降低细胞冰点,减少冰晶的形成,减轻自由基对细胞损害,改变生物膜对电解质、药物、毒物和代谢产物的通透性。DMSO作为组蛋白去乙酰化酶抑制剂(Histone Deacetylases-inhibitor HDACi)的一种,同样具有恢复组蛋白的乙酰化与去乙酰化平衡,抑制细胞程序性死亡,修复DNA双螺旋结构,抗放射性损伤,抗炎症反应及抗癌作用。鉴于其应用广泛,本文就其物理特性及毒性研究做一综述。     

Study of Liquid Dimethyl Sulfoxide by Computer Simulation

The paper reports Monte Carlo and molecular dynamicsresults for pure liquid dimethyl sulfoxide (DMSO) at298 K and 1 atm. The classical 6–12 Lennard–Jones plusCoulomb pairwise potential was used to calculateintermolecular interaction energy. Potentialparameters for the liquid were optimized in this work.Some thermodynamic and dynamical properties obtained,such as heat of vaporization, density and diffusioncoefficient, are in good agreement with theexperimental values. The present model is comparedwith other models for DMSO reported previously. It isshown to be an improvement over earlier potentials.The structure factors and the radial distributionfunctions (rdf), are compared with experimentalresults for the liquid. The analysis shows that thestructure of DMSO is not completely understood yet anddeserves deeper investigation. The geometry of thedimer that corresponds to the rdf plots obtained, isreported. The results suggest that the dipole momentof this dimer plays an important role in the structureof the liquid.     

Molecular Weight Determination of Sendai RNA by Dimethyl Sulfoxide Gradient Sedimentation

The molecular weight of the large RNA of Sendai virus has been determined by sedimentation analysis in sucrose gradients containing 99% dimethyl sulfoxide (DMSO) to be 2.3 × 10⁶. Sendai RNA recovered from 99% DMSO was found to cosediment with nondenatured Sendai RNA at 46 to 48s in ordinary sucrose gradients. The molecular weight value of 2.3 × 10⁶ is considerably smaller than the estimates of 6 × 10⁶ to 7 × 10⁶ determined under nondenaturing conditions, suggesting a unique structure for Sendai RNA.     

Host-controlled Restriction of T-even Bacteriophages: Relation of Four Bacterial Deoxyribonucleases to Restriction

Escherichia coli strains B and K-12, which restrict growth of nonglucosylated T- even phage (T(*) phage), and nonrestricting strains (Shigella sonnei and mutants of E. coli B) were tested for levels of endonuclease I and exonucleases I, II, and III, by means of in vitro assyas. Cell-free extracts freed from deoxyribonucleic acid (DNA) were examined with three substrates: E. coli DNA, T(*)2 DNA, and T2 DNA. Both restricting and nonrestricting strains had comparable levels of the four nuclease activities and had similar patterns of preference for the three substrates. In addition, mutants of E. coli B and K-12 that lack endonuclease I were as effective as their respective wild types in restricting T(*) phage.     

Dimethyl Sulfoxide and Ebselen Prevent Convulsions Induced by 5-Aminolevulinic Acid

We investigated whether intrastriatal (i.s.) administration of 5-aminolevulinic acid (ALA) induces oxidative damage and whether behavioral alterations induced by i.s. administration of ALA could be affected by antioxidants. Unilateral injection of ALA (6 micromol/striatum) increased (approximately 30%) thiobarbituric acid-reactive substances (TBARS), but did not affect striatal content of total thiol groups. ALA-induced body asymmetry was not prevented by pretreatment with ascorbic acid (100 mg/kg, s.c.), dimethyl sulfoxide (DMSO, 0.5 microl/striatum, i.s.) or ebselen (10 nmol/striatum, i.s.). ALA-induced convulsions were not prevented by ascorbic acid, but were partially prevented by DMSO and completely prevented by ebselen. Ebselen completely prevented the increase of striatal TBARS induced by ALA. Results obtained suggest the involvement of reactive species in ALA-induced convulsions and may be of value in understanding the physiopathology of neurological dysfunctions associated to ALA overload.     

Plaque Formation with Simian Virus 40: Enhancement by Dimethyl Sulfoxide

Dimethyl sulfoxide (DMSO) added to agar overlays during plaque assays of simian virus 40 (SV40) in CV1 monkey cells increases the plaque size and number and enables plaques to be read several days earlier than usual. DMSO appears to act during development of plaques, perhaps by causing cell lysis at smaller burst sizes in the presence of near-lethal DMSO concentrations. It does not act synergistically in determining virus inactivation with UV light and is equally effective on wild type and a late mutant of SV40.     

Isomerization of 1,3,4,5,6-Pentachlorocyclohexene-1 Isomers in Dimethyl Sulfoxide

In dimethyl sulfoxide, isomerization of 1,3,4,5,6-pentachlorocyclohexene-1 isomers was studied. Exchange of the allylic chlorine was indicated by the experiments with ³⁶Cl-labeled compounds. Isomerization at the position-3 proceeded faster than at the position-6. Initial reaction rates for the isomers decreased in the order: 34/56 > 35/46 (δ) > 346/5> 356/4 ? 36/45 (γ)^??. The specific rates at the initial stages increased by increasing the initial concentration of the substrates. After a prolonged reaction, the γ-isomer (36/45) was the most abundant component.

The isomers of the configuration: (34/56), (346/5), and (356/4) were isolated for the first time, on which PMR studies were performed.     

Inactivation of MXR1 Abolishes Formation of Dimethyl Sulfide from Dimethyl Sulfoxide in Saccharomyces cerevisiae

Dimethyl sulfide (DMS) is a sulfur compound of importance for the organoleptic properties of beer, especially some lager beers. Synthesis of DMS during beer production occurs partly during wort production and partly during fermentation. Methionine sulfoxide reductases are the enzymes responsible for reduction of oxidized cellular methionines. These enzymes have been suggested to be able to reduce dimethyl sulfoxide (DMSO) as well, with DMS as the product. A gene for an enzymatic activity leading to methionine sulfoxide reduction in Saccharomyces yeast was recently identified. We confirmed that the Saccharomyces cerevisiae open reading frame YER042w appears to encode a methionine sulfoxide reductase, and propose the name MXR1 for the gene. We found that Mxr1p catalyzes reduction of DMSO to DMS and that an mxr1 disruption mutant cannot reduce DMSO to DMS. Mutant strains appear to have unchanged fitness under several laboratory conditions, and in this paper I hypothesize that disruption of MXR1 in brewing yeasts would neutralize the contribution of the yeast to the DMS content in beer.     

Do Trehalose and Dimethyl Sulfoxide Affect Intermembrane Forces?

The sugar trehalose is produced in some organisms that survive dehydration and desiccation, and it preserves the integrity of membranes in model systems exposed to dehydration and freezing. Dimethyl sulfoxide, a solute which permeates membranes, is added to cell suspensions in many protocols for cryopreservation. Using a surface forces apparatus, we measured the very large, short-range repulsion between phosphatidylcholine bilayers in water and in solutions of trehalose, sorbitol, and dimethyl-sulfoxide. To the resolution of the technique, the force-distance curves between bilayers are unchanged by the addition of trehalose or sorbitol in concentrations exceeding 1 kmol · m^-3. A relatively small increase in adhesion in the presence of trehalose and sorbitol solutions may be explained by their osmotic effects. The partitioning of trehalose between aqueous solutions and lamellar phases of dioleylphosphatidylcholine was measured gravimetrically. The amount of trehalose that preferentially adsorbs near membrane surfaces is at most small. The presence of dimethyl sulfoxide in water ( 1:2 by volume) makes very little difference to the short-range interaction between deposited bilayers, but it sometimes perturbs them in ways that vary among experiments: free bilayers and/or fusion of the deposited bilayers were each observed in about one-third of the experiments.     

二甲基亚砜对生物膜的作用机理

二甲基亚砜被广泛应用于生物、化学和药学领域,这些应用大多与其增加生物膜的通透性、促进活性分子跨膜传输的作用密切相关。本文对二甲基亚砜增加生物膜通透性的理论及实验研究做简要综述,主要强调二甲基亚砜在生物膜中诱导水性孔道形成的分子动力学模拟及其相关的实验研究。     

Preservation of Primary Bovine Embryonic Kidney Cells with Dimethyl Sulfoxide

Primary bovine embryonic kidney cells frozen with dimethyl sulfoxide can be recultured with satisfactory results.     

Host-controlled Restriction of T-even Bacteriophages: Relation of Endonuclease I and T-even-induced Nucleases to Restriction

Restriction of nonglucosylated T2 phage (T(*)2) as a function of bacterial growth state was the same for endonuclease I-containing and endonuclease I-deficient strains of Escherichia coli B. Furthermore, E. coli strains with various levels of restriction for T2 had comparable endonuclease I activities. It was also found that a T4 mutant temperature-sensitive for gene 46 and 47 functions was fully restricted at 42 C. It therefore appears that neither endonuclease I nor the phage-induced nucleases whose activities are blocked by mutations in genes 46 and 47 catalyze the initial event in restriction of nonglucosylated T-even phages.     

二甲基亚砜对离体猪皮肤组织的拉曼光谱的影响

拉曼光谱技术作为鉴定生物分子种类最有力的分析工具之一,具有快速、简单、无损、准确等优点.目前,拉曼光谱已被国内外学者广泛开展了在人体组织的应用研究,但由于生物组织具有高散射性,因此限制了拉曼光谱对其的检测深度.本文主要采用光透明剂--二甲基亚砜对组织拉曼光谱的影响进行研究,对离体猪皮组织的不同深度（100 μm,200 μm,300 μm,400 μm）拉曼光谱强度随处理前、后不同时间（0 min,10 min,20 min,30 min,60 min）的变化进行对比.结果发现,不管是经二甲基亚砜处理前还是后,都出现随着距猪皮组织表面的深度加深,其拉曼光谱强度都不断减少;同时发现各层猪皮组织随着处理后时间的加长,其特征峰的强度不断加强,信噪比逐渐提高,在处理后的60 min效果最好;而且出现了在经二甲亚砜处理前看不见的峰（1 126 cm-1和1 426 cm-1）.结果表明：5%DMSO对组织的处理能增强其拉曼光谱的强度,同时也能使拉曼光谱仪的信噪比提高,并且使组织谱图中特征峰也得到相应的增加.     

响应面法降低肝细胞冷冻保护液中的二甲基亚砜浓度

为有效降低干细胞冷冻保护液中的二甲基亚砜(Me2SO,DMSO)浓度,减少其作为冷冻保护剂对细胞低温保存时产生的毒性,提高细胞存活率,以肝细胞为目标,采取响应面法对冷冻保护剂配方进行了优化。结果表明：冷冻保护剂的最佳配比为DMSO浓度3%、甘油浓度6%、海藻糖浓度0.1%,在此条件下肝细胞复温存活率可达到84.35%,研究结果有效地降低了DMSO的浓度,减少了由此带来的对肝细胞造成的毒性损害,为后续的研究奠定了基础。     

Dimethyl Sulfoxide Damages Mitochondrial Integrity and Membrane Potential in Cultured Astrocytes

Dimethyl sulfoxide (DMSO) is a polar organic solvent that is used to dissolve neuroprotective or neurotoxic agents in neuroscience research. However, DMSO itself also has pharmacological and pathological effects on the nervous system. Astrocytes play a central role in maintaining brain homeostasis, but the effect and mechanism of DMSO on astrocytes has not been studied. The present study showed that exposure of astrocyte cultures to 1% DMSO for 24 h did not significantly affect cell survival, but decreased cell viability and glial glutamate transporter expression, and caused mitochondrial swelling, membrane potential impairment and reactive oxygen species production, and subsequent cytochrome c release and caspase-3 activation. DMSO at concentrations of 5% significantly inhibited cell variability and promoted apoptosis of astrocytes, accompanied with more severe mitochondrial damage. These results suggest that mitochondrial impairment is a primary event in DMSO-induced astrocyte toxicity. The potential cytotoxic effects on astrocytes need to be carefully considered during investigating neuroprotective or neurotoxic effects of hydrophobic agents dissolved by DMSO.     

Use of Dimethyl Sulfoxide to Detect Hydroxyl Radical during Bacteria-Induced Hypersensitive Reaction

Excess active oxygen is generated during the hypersensitive reaction (HR), an incompatible reaction of plants to bacterial pathogens. During HR, lipid peroxidation correlates chronologically with production of the oxygen species, superoxide (O₂^.−). However, O₂^.− may not be the active oxygen species that initiates lipid peroxidation. Evidence from other systems suggest that O₂^.− is converted to the hydroxyl radical (HO^.) before lipid peroxidation is initiated. Until recently, HO^. could not be detected directly in vivo. This study utilizes a newly reported method to directly detect and quantify the formation of HO^. in vivo. Dimethyl sulfoxide (DMSO), used as a molecular probe, is oxidized by HO^., forming the stable compound methanesulfinic acid. The methanesulfinic acid can be easily extracted from plant tissues and measured with a colorimetric assay. This study demonstrates significant increases in HO^. concentration after simultaneous infiltration of cucumber (Cucumis sativa L.) plants with paraquat and DMSO. The concentration of HO^. did not increase significantly when cucumber plants were infiltrated simultaneously with the HR-inducing bacteria, Pseudomonas syringae pv. pisi, and with DMSO. Lipid peroxidation, however, could be measured at times when HO^. was not detectable. It appears that HO^. is not generated during bacteria-induced HR; therefore, HO^. is not responsible for the initiation of lipid peroxidation.     

Microbial Activity in Aquatic Environments Measured by Dimethyl Sulfoxide Reduction and Intercomparison with Commonly Used Methods

A new method to determine microbial (bacterial and fungal) activity in various freshwater habitats is described. Based on microbial reduction of dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS), our DMSO reduction method allows measurement of the respiratory activity in interstitial water, as well as in the water column. DMSO is added to water samples at a concentration (0.75% [vol/vol] or 106 mM) high enough to compete with other naturally occurring electron acceptors, as determined with oxygen and nitrate, without stimulating or inhibiting microbial activity. Addition of NaN₃, KCN, and formaldehyde, as well as autoclaving, inhibited the production of DMS, which proves that the reduction of DMSO is a biotic process. DMSO reduction is readily detectable via the formation of DMS even at low microbial activities. All water samples showed significant DMSO reduction over several hours. Microbially reduced DMSO is recovered in the form of DMS from water samples by a purge and trap system and is quantified by gas chromatography and detection with a flame photometric detector. The DMSO reduction method was compared with other methods commonly used for assessment of microbial activity. DMSO reduction activity correlated well with bacterial production in predator-free batch cultures. Cell-production-specific DMSO reduction rates did not differ significantly in batch cultures with different nutrient regimes but were different in different growth phases. Overall, a cell-production-specific DMSO reduction rate of 1.26 × 10⁻¹⁷ ± 0.12 × 10⁻¹⁷ mol of DMS per produced cell (mean ± standard error; R² = 0.78) was calculated. We suggest that the relationship of DMSO reduction rates to thymidine and leucine incorporation is linear (the R² values ranged from 0.783 to 0.944), whereas there is an exponential relationship between DMSO reduction rates and glucose uptake, as well as incorporation (the R² values ranged from 0.821 to 0.931). Based on our results, we conclude that the DMSO reduction method is a nonradioactive alternative to other methods commonly used to assess microbial activity.