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The effect of a cosolvent on the structure and stability of a protein depends upon the nature of preferential protein- water, protein-cosolvent or cosolvent-water interactions. The preferential interaction parameters of glycerol, sorbitol and sucrose with β-globulin (from Sesamum indicum L. seeds) were evaluated and the results showed the exclusion of cosolvents and preferential hydration of the protein. Data from fluorescence, circular dichroism (CD) and thermal stability measurements inferred that the preferential hydration had a considerable effect on the structure of protein under native conditions. Such cosolvent-protein interactions bring out a previously unnoticed, but outstanding phenomenon of cosolvent induced structural effects on the protein. This study reveals that these cosolvents interact with β-globulin in such a way that they induce a structural reshuffling to enhance the protein stability, mostly by intensifying intra-molecular hydrophobic interactions.

Alpha-lactalbumin constitutes about 3% of bovine milk proteins. The preferential solvent interactions between selected cosolvents (sorbitol, sucrose and glycerol) and alpha-lactalbumin at pH 7.5 was determined using precision densitimetry. The preferential interaction parameter (xi(3)) and other thermodynamic parameters were calculated at different solvent concentrations. The xi(3) parameter was maximum at 30%, 45% and 40% (w/v) concentrations with the values of -0.282g/g, -0.171g/g and -0.299g/g for sorbitol, sucrose and glycerol, respectively. Thus the principal driving energy in the system being preferential hydration and mutual exclusion of bulk solvent. There was only a marginal change in the CD spectra of the protein with these cosolvents indicating the integrity of secondary structures. The results of thermal denaturation measurements indicated an increase in thermal stability of alpha-lactalbumin with these cosolvents. In the presence of 30% sorbitol there was an increase in the apparent thermal transition temperature (apparent T(m)) from 65 to 71 degrees C. These results indicate that the selected cosolvents in this study stabilizes alpha-lactalbumin without altering the structure of the protein.

We report a case of arterio-venous malformation (AYM) of the external ear with hypertrophy in a 25 years old male which had been stable for many years, only to expand following trauma, with occasional bleeding episodes. Surgical correction and plastic reconstruction without proximal ligation of the feeding arterial system was contemplated.