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Abstract  

To reveal the denaturation mechanism of lysozyme by dimethyl sulfoxide (DMSO), thermal stability of lysozyme and its preferential solvation by DMSO in binary solutions of water and DMSO was studied by differential scanning calorimetry (DSC) and using densities of ternary solutions of water (1), DMSO (2) and lysozyme (3) at 298.15 K. A significant endothermic peak was observed in binary solutions of water and DMSO except for a solution with a mole fraction of DMSO (x 2) of 0.4. As x 2 was increased, the thermal denaturation temperature T m decreased, but significant increases in changes in enthalpy and heat capacity for denaturation, ΔH cal and ΔC p, were observed at low x 2 before decreasing. The obtained amount of preferential solvation of lysozyme by DMSO (∂g 2/∂g 3) was about 0.09 g g−1 at low x 2, indicating that DMSO molecules preferentially solvate lysozyme at low x 2. In solutions with high x 2, the amount of preferential solvation (∂g 2/∂g 3) decreased to negative values when lysozyme was denatured. These results indicated that DMSO molecules do not interact directly with lysozyme as denaturants such as guanidine hydrochloride and urea do. The DMSO molecules interact indirectly with lysozyme leading to denaturation, probably due to a strong interaction between water and DMSO molecules.

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dissolved in dimethyl sulfoxide (DMSO) were studied at different amount by a RD496-2000 calorimeter at 298.15 K. In addition, the kinetic formula and the half-life were calculated. This will be useful to provide a potential reference for the clinical

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Abstract  

Excess enthalpies of sixteen binary mixtures between one each of methyl methylthiomethyl sulfoxide (MMTSO) and dimethyl sulfoxide (DMSO) and one of ketone {CH3CO(CH2)nCH3, n=0 to 6 and CH3COC6H5} have been determined at 298.15 K. All the mixtures showed positive excess enthalpies over the whole range of mole fractions. Excess enthalpies of ketone+MMTSO or DMSO increased with increasing the number of methylene radicals in the methyl alkyl ketone molecules. Excess enthalpies of MMTSO+ketone are smaller than those of DMSO+ketone for the same ketone mixtures. The limiting excess partial molar enthalpies of the ketone, H 1 E,∞, in all the mixtures with MMTSO were smaller than those of DMSO. Linear relationships were obtained between limiting excess partial molar enthalpies and the number of methylene groups except 2-propanone.

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Journal of Thermal Analysis and Calorimetry
Authors: Li Bai Xiao, Xiao Ling Xing, Xue Zhong Fan, Feng Qi Zhao, Zhi Ming Zhou, Hai Feng Huang, Ting An, Hai Xia Hao, and Qing Pei

have never been reported so far. Dimethyl sulfoxide (DMSO) and N -methyl pyrrolidone (NMP) as solvents have been used extensively in our production and application, so thermochemical properties of its solution have been studied first by means of a RD

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Abstract  

Extensive thermal analysis has shown that DMSO-containing reaction mixtures can be more energetic and decompose at lower temperatures than pure DMSO. Several processes at Merck using DMSO as a solvent were found to have the onset temperatures of decompositions reduced to the point where it became a thermal and operational hazard. The onset temperature depended on the reagents in the reaction mixture and the thermal history of the mixture. The case studies presented in this paper will include discussion on what process hazards were identified, how the process hazards differ from the pure DMSO hazards, and how to scale up these processes safely.

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Excess enthalpies of ten binary mixtures of each of methyl methylthiomethyl sulfoxide (MMTSO) and dimethyl sulfoxide (DMSO) with one of the cycloethers (oxane, 1,3- and 1,4-dioxanes, oxolane and 1,3-dioxolane) have been determined at 298.15 K. All the mixtures show positive excess enthalpies over the whole composition range. Excess enthalpies of the cycloether + MMTSO or DMSO decrease with increasing number of oxygen atoms in the cycloether molecules, except for oxolane + MMTSO. Excess enthalpies of MMTSO + cycloethers are smaller than those of DMSO + cycloethers for the same cycloether except for the 1,3-dioxolane mixtures.

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The chromatographic behavior of twenty-four amino acids has been studied on untreated and on triaryl phosphate (TAP)-impregnated adsorbent layers with 1 + 1 dimethyl sulfoxide-1 m HCl as mobile phase. The unconventional adsorbent talc, and alumina, starch, and silica gel GF 254 have been used to study the retention behavior of the amino acids. The effect of amino acid pI (isoelectric point) in Ri ( R F on unimpregnated layers minus R F on impregnated layers) is discussed. The effect of the molar refractive index ( Rm ) of the amino acids on their R F values on mixed layers containing talc has also been investigated. The talc-alumina mixture was used to effect several binary separations of amino acids. The mechanism of migration is explained in terms of adsorption by, and the polarity of, the stationary phases used.

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Abstract  

The stability constants , of monochloride complex of Eu(III) in the tracer concentrations have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of decrease up to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase. Calculation of Eu3+−Cl distance using a Born-type equation of the Gibbs' free energy derived from the revealed that the estimated distance between Eu3+ and Cl (d Eu−Cl) increases linearly withX s in 0≤X s<0.043 and 0.043<X s<0.172, but their slopes are different. The line in the first region means a linear enlargement of the thickness of the primary solvation sphere of Eu3+ with increasingX s. The larger slope againstX s in 0.043<X s<0.172 is attributable to lowering of , based on the increase in the solvation number of the primary solvation sphere of Eu3+. The considerably large value ofd Eu−Cl atX s=0.202 might result from lowering of by a coordination of ClO 4 into the secondary solvation sphere of Eu3+ and the extremely drop ofd Eu−Cl atX s=0.276 might reflect on a conversion of the ion-pair type, i.e., the coexistence of two kinds of a solvent-shared ion-pair and a contact one by the appearance of the contact one.

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Abstract  

The stability constants, β1, of each monochloride complex of Ln(III) (Ln=Nd or Tm) have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Ln(III) decrease to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase withX s (>about 0.2). However, the variation mode of β1 of Nd(III) withX s somewhat differs from that of Tm(III). Calculation of Ln3+−Cl distance using a Born-type equation of the Gibbs' free energy derived from the β1 evealed the followings: (1) For Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl (d Tm-Cl) increases linearly withX s in 0.00≤X s≤0.17. This means an enlargement of the primary solvation sphere size of Tm3+ withX s. On the other hand, thed Tm-Cl shows a decrease withX s in 0.17<X s<0.28. (2) The estimatedd Nd-Cl increases linearly withX s in 0.00≤X s<0.06 and 0.06<X s≤0.17, but their slopes are different. The larger slope againstX s in 0.06<X s≤0.17 is attributable to a lowering of the β1 by a coordination of ClO4 into the secondary solvation sphere of Nd3+ and/or by an increase in the solvation number of the primary solvation sphere of Nd3+.

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Abstract  

The stability constants, β1, of monochloride complex of Am(III) have been determined in a mixed system of dimethyl sulfoxide (DMSO) and water at 1.00 mol·dm−3 ionic strength using solvent extraction. The values of β1 in mixed DMSO+H2O solutions decrease rapidly with an increase in the mole fraction of DMSO (X s) in mixed solvents and become negative ones, which is not in a definition of stability constant, inX s>0.04. The variation of β1 inX s≦0.02 was accounted for by the size-variation of the primary solvation sphere around Am(III), which was present as a solventshared ion-pair, and by a little effect due to an invasion (coordination) of ClO4 into the secondary solvation sphere of Am3+. On the other hand, it was concluded that the β1 obtained by solvent extraction inX s>0.02 was an apparent value, because of a large effect due to an invasion (coordination) of ClO4 into the secondary solvation sphere of Am(III).

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