二甲基亚砜和四氢呋喃对胃蛋白酶催化动力学和分子光谱的影响

为了研究二甲基亚砜(DMSO)和四氢呋喃(THF)对胃蛋白酶(Pepsin, PP)催化活性的影响及其作用本质, 测定了在这两种有机溶剂的作用下胃蛋白酶的催化活性、 动力学参数、 紫外吸收光谱、 紫外差示光谱和荧光发射光谱的变化. 结果表明, 体积分数为9%的DMSO使PP活性提高83.4%; 而体积分数为1%的THF只能使PP活性提高3.59%. 在盐酸溶液中, PP的动力学参数K_m=2.22 mg/mL, v_max=1.1×10⁶ U/mg Pro; 在9%DMSO中, 其K_m=1.50 mg/mL, v_max=0.5×10⁶ U/mg Pro; 在1%THF中的K_m=1.91 mg/mL, v_max=0.51×10⁶ U/mg Pro. 9%DMSO强烈抑制PP分子肽键的紫外吸收, 而对芳香族氨基酸无影响; 1%THF则对PP的紫外吸收光谱影响不大. 9%DMSO和1%THF都使PP的紫外差示光谱出现明显的负吸收峰和正吸收峰. 9%DMSO使酶分子的荧光发射峰向短波方向移动1 nm; 而1%THF则对其无影响. 实验结果表明, 在9%DMSO和1%THF中, PP分子的立体构象发生了变化, 使酶分子的K_m下降, 酶分子对底物的亲和力有所升高, 从而导致酶分子的催化活性有不同程度的提高.     

活化二甲亚砜选择性氧化醇的反应

介绍活化二甲亚砜在醇类选择性氧化方面的反应及机理     

Photopolymerization of Methyl Acrylate in Dimethyl Sulfoxide

Abstract

Methyl acrylate in dimethyl sulfoxide was polymerized by 2537 A ultraviolet light. The photo reaction exhibited zero-order kinetics for a given initial concentration and produced short chain polymers (M[Mbar]_W ～ 20,000). Low sulfur values of isolated polymers indicated no appreciable solvent incorporation during the polymerization.     

FT IR ATR Study of Molecular Interactions in the Urea/Dimethyl Sulfoxide and Urea/Diethyl Sulfoxide Binary Systems

FT IR ATR spectra of urea/dimethyl sulfoxide and urea/diethyl sulfoxide mixtures in the S=O and N—H stretching vibration regions at different molar ratios have been measured. On the basis of the band deconvolution data, various types of intermolecular associated forms, including dimers and hydrogen-bonded urea–sulfoxide complexes, have been revealed. The latter has been confirmed also by ab initio calculations.     

Raman and Infrared Spectra for All-trans-astaxanthin in Dimethyl Sulfoxide Solvent

The Raman and infrared spectra of all-trans-astaxanthin (AXT) in dimethyl sulfoxide (DMSO) solvent were investigated experimentally and theoretically. Density functional cal-culations of the Raman spectra predict the splitting of the υ₁ band into υ_1-1 and υ_1-2 compo-nents. The absence of splitting in Raman experimental spectra is ascribed to the competition between the two symmetric C=C stretching vibrations of the backbone chain. The υ₁ band is very sensitive to the excitation wavelength: resonance excitation stimulates the higher-frequency υ_1-2 mode, and off-resonance excitation corresponds to the lower-frequency υ_1-1 mode. Analyses of the intramolecular hydrogen bonding between C=O and O-H in the AXT/DMSO system reveal that the C4=O1...H1-O3 and C4'=O2...H2-O4 bonds are strengthened and weakened, respectively, in the electronically excited state compared with those in the ground state. This result reveals significant variations of the AXT molecular structure in different electronic states.     

Unusual Reaction of Trifluorophenylsilane with Dimethyl Sulfoxide

Russian Journal of General Chemistry -     

Reaction of Dimethyl Sulfoxide with 4-Acyloxycoumarins

Dimethyl sulfoxide converts 4-acetoxycoumarin (1) exclusively to 2-(2-hydroxybenzoyl)-2-[(methylthio)methyl]-2,3-dihydro-4 H-furo[3,2-c]chromen-4-one (3) at 180°C under a nitrogen atmosphere, but in the absence of nitrogen, the products obtained are dicoumarol and its dehydrative cyclization products 7 H-bis[1]benzopyrano[4,3-b: 3′,4′-c]pyran-6,8-dione (9) and (3). Under similar conditions, 4-benzoyloxycoumarin (1a) affords benzoic acid, 4-hydroxy-3-({2-[(methylthio)methyl]-3-oxo-2,3-dihydro-1-benzofuran-2-yl}methyl)-2H-chromen-2-one (7), and 3-(2-hydroxybenzoyl)-3,4-dihydro-2H,5H-pyrano[2,3-b] chromen-5-one (8).     

Mixing Schemes for Aqueous Dimethyl Sulfoxide: Support by X-ray Diffraction Data

Aqueous dimethyl sulfoxide (DMSO) was studied by X-ray diffraction at room temperature. The results indicated that there are three distinct composition regions. In the DMSO-rich region, DMSO molecules retain the same molecular arrangement as in the pure state, while H₂O does not show any structural feature. These findings are in the complete agreement with the suggestion by our earlier thermodynamic study on aqueous DMSO.⁽¹⁾ In the H₂O-rich region, there is an indication that DMSO molecules exist as small clusters bound mainly by S=O dipole attraction. Hence, hydrophobic CH₃ groups point outward from such a cluster and DMSO acts in effect as a hydrophobic solute. This is also consistent with the findings of our earlier thermodynamic study. In the intermediate region, a gradual change in the radial distribution function with composition was observed.     

The Reaction of Ethyl Bromoacetate with Dimethyl Sulfoxide

The reaction of excess dimethyl sulfoxide with ethyl bromoacetate has been shown to produce ethyl glyoxylate, hydrogen bromide, and dimethyl sulfide. The yield of glyoxylate at first was reduced because the dimethyl sulfide reacted with bromoacetate to form trimethylsulfonium bromide and ethyl (methylmercapto) acetate, presumably via carbethoxymethyldimethylsulfonium bromide. These side reactions were diminished in a thin-film reactor, but the result was not satisfiable, the yield was 51%, and the side reactions were prevented by addition of methyl bromide, which rapidly consumed the dimethyl sulfide with formation of trimethylsulfonium bromide. Addition of 1, 2-epoxy-3-phenoxypropane removed the hydrogen bromide, thereby preventing the deleterious effects casued by its reduction of dimethyl sulfoxide to dimethyl sulfide. In this way has been developed a convenient preparation of ethyl glyoxylate in yields averaging about 70%. Identification and stoichiometry of the reaction products are presented.     

Dimethyl Sulfoxide Pivaloyl Chloride: A New Reagent for Oxidation of Alcohols to Carbonyls

An efficient procedure for conversion of alcohols to the corresponding carbonyl compounds, an alternative to the classical Swern oxidation, is described. Pivaloyl chloride is employed as a mild and inexpensive electrophile. A possible reaction mechanism is proposed.     

Effects of Acetone,Ethanol, Isopropanol,and Dimethyl Sulfoxide on Amylose-Iodine Complex

ABSTRACT

The amylose-iodine (AI) complex formation was studied by absorption spectra in water and water containing varying proportions of ethanol, acetone, isopropanol and dimethyl sulfoxide (DMSO). Complex formation is most favored in pure water and decreases as the proportion of nonaqueous solvent is increased. A decrease in the absorbance intensity at around 615 nm (for AI complex) is accompanied by a peak shift towards 550 nm and an increased absorbance at around 350 nm (for unbound iodine). The amount of the nonaqueous solvent added, as well as the order in which it is added relative to amylose and iodine solution, change remarkably the extent of the AI complex formation. A mechanism of the complex formation is proposed.     

Sensing Mechanism of Excited-State Intermolecular Hydrogen Bond for Phthalimide:Indispensable Role of Dimethyl Sulfoxide

Main observation and conclusion Excited-state hydrogen bond strongly affects the intramolecular charge conversion process,which is very suitable for the design ...     

Reaction of Organylchlorosilanes with Dimethyl Sulfoxide in the Presence of Octamethyltrisiloxane

Dichloro(methyl)(vinyl)silane reacts with DMSO in the presence of octamethyltrisiloxane to form cyclooligomethyl(vinyl)siloxanes(MeViSiO) _n (n = 3-6). The reaction involves disproportionation of octamethyltrisiloxane into hexamethyldisiloxane and decamethyltetrasiloxane. Along with the latter two products, insertion products of methyl vinyl silanone into both permethyloligosiloxanes were identified. Alkyltrichlorosilanes RSiCl₃ (R = Me, Et) react with DMSO in the presence of octamethyltrisiloxane to form cyclic oligoalkyltrichlorosiloxanes (RClSiO) _m (m = 3-6).     

Graft Photopolymerization of Styrene to Wheat Gluten Protein in Dimethyl Sulfoxide

To determine the suitability of dimethyl sulfoxide (DMSO) as a solvent for photo polymerization, solutions of wheat gluten protein (0.28-0.93% by weight) and styrene (4.13-12.65% by weight) in DMSO were irradiated by a 200.W high-pressure mercury arc lamp from 3 min up to 1 hr. Graft copolymers of gluten styrene resulted that contained styrene residues ranging from 2 to 23% by weight. When gluten protein was photolyzed in DMSO alone, a significant amount of sulfur from the solvent was incorporated; however, styrene successfully competed with the solvent for free radical sites. The rate of grafting was directly related to both the concentration of gluten and of styrene. Also, the ratio of grafted polystyrene to gluten in the graft polymer indicated that the grafts were composed of small units of polystyrene.     

Anthraquinone Electroreduction Mechanism in 0.1 M Tetrabutylammonium Bromide in Dimethyl Sulfoxide

Electroreduction of anthraquinone in 0.1 M tetrabutylammonium bromide in dimethyl sulfoxide is studied by cyclic voltammetry in an argon atmosphere at 373–423 K. According to steady- and non-steady-state measurements, the process involves two one-electron stages at potentials of –0.6 to –0.7 and –1.5 to –1.6 V vs. a quasi-reversible platinum electrode. The electrode material (platinum, silver, glassy carbon) barely affects the electroreduction mechanism. The process is controlled by the mass transfer rate. Anthraquinone can be reduced to mono- and diphenoxide anions. Optimum conditions for obtaining the latter are found.     

二甲基亚砜防冻机理的拉曼光谱分析

采用拉曼光谱对不同体积比的二甲基亚砜(DMSO)水溶液进行测量, 并利用Origin 7.5对水的光谱带进行分峰, 求得拉曼光谱峰面积比值. 应用混合模型对实验结果进行了分析, 分析结果表明, 防冻剂二甲基亚砜与水混合时, 其SO基团与水分子的OH基团形成氢键(SO…H—O), 有效地阻止了四面体结构冰的生成, 并证实了二甲基亚砜与水的体积比为1∶1时, 防冻效果最佳.     

Affinity of Tripodal and Linear Tetraamines for Silver(I) in Dimethyl Sulfoxide

The thermodynamic functions of the complexation of Ag(I) by the tripodal ligands, tris(2-(methylamino)ethyl)amine (Me₃tren) and tris(2-(dimethylamino)ethyl)amine (Me₆tren) (L), are determined in dimethyl sulfoxide (DMSO) by potentiometric and calorimetric techniques at 298.0 K and 0.1 mol⋅dm⁻³ ionic strength (Et₄NClO₄). A comparison is made between previous data concerning Ag(I) complex formation with the non-alkylated tripodal 2,2′,2″-triaminotriethylamine (tren), in order to analyze the influence of N-methylation on this type of branched donor, and with those relative to the linear triethylenetetramine (trien) and 1,1,4,7,10,10-hexamethyltriethylenetetramine (Me₆trien). The results are discussed taking into account different σ-donating properties, geometric arrangement of the ligands, steric repulsions and solvation effects.