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2-chloroethanol Densities and volumetric properties

Time:2015/11/30 6:22:37

Structure of Muramidase (Lysozyme):III. Effect of 2-Chloroethanol, Ethanol and Dioxane on the Stability of Muramidase

In order to elucidate the structure of muramidase, the effects of 2-chloroethanol, ethanol and dioxane were studied by following changes in optical rotation, viscosity and ultraviolet difference spectrum. The following observations have been made: 1. The values of reduced viscosity and Δε at 292 mμ changed at 16% (v/v) 2-chloro-ethanol, whereas the values of bo and [M]436 changed at 32%. This observation suggests that the change in the muramidase molecule from native to a highly helical structure in the presence of 2-chloroethanol occurs through an intermediate in which internal hydro-phobic region is disrupted. The presence of such an intermediate can be demonstrated directly by a large spectral change. 2. The value of b0 of muramidase is constant up to 80% (v/v) ethanol while the levorotation increases and the value of Δε at 292mμ changes above 60%. This suggests. that only the internal hydrophobic region is. disrupted while the helical portions remain-unchanged. 3. The results described above present. a possibility that internal hydrophobic region of the muramidase molecule is not made of helix. 4. The decrease in the magnitude of b0 of muramidase in the presence of dioxane accompanies the decrease in levorotation. This is contrary to usual protein denaturation. The possible conformations of muramidase in the presence of dioxane are discussed. The authors are indebted to Prof. T. Isemura. for his encouragement in the course of this research. They also wish to thank Prof. M. Funatsu, Drs. K. Hayashi and T. Takagi for numerous helpful discussions.

Densities and volumetric properties of 2-chloroethanol with N,N-dimethylformamide and water at different temperatures

Densities of binary mixtures of 2-chloroethanol with N,N-dimethylformamide (DMF) and water have been measured over the full range of compositions at various temperatures. From these results, excess molar volumes, V-E and excess partial molar volumes at infinite dilution, (V) over bar (E,0)(i) have been calculated. V-E for (DMF + 2-chloroethanol) mixture are positive over the whole mole fraction range and negative values are obtained for (water+ 2-chloroethanol) mixture. (C) 2005 Elsevier B.V. All rights reserved