Denaturation, volume change

Results from thermal denaturation and heat capacity studies have shown that the proteins are not necessarily completely unfolded in this process. The volume observations also suggest that the denatured state is not one in which all hydrophobic groups are exposed to water. But the results can also be understood from the effect of close polar and electrostatic groups interacting with the water structure surrounding the hydrophobic groups. The volume change is heavily... 

Knowledge of the partial specific volume of a protein in the denaturant, t>2,03, which is essential for determining its molecular weight by small-angle x-ray scattering, permits also the calculation of the volume change upon denaturation since... 

Fig. 31. Denaturation pressure ( p ), volume change of pressure-induced unfolding (A T°), and standard Gibbs free energy change (AG ), extrapolated to 1 bar, for the pressure-induced tmfolding of SNase at different molar concentrations (c) of cosolvents.

The picture arrived at after exhaustive research with luminous bacteria, and eventually discussed at length with reference to many other types of biological processes, involved molecular volume changes of activation in the enzyme reaction and volume changes of reaction in the reversible denaturation of the protein moiety. Continued research concerning the... 

At T = 300K, A ° = lOkcalmol. Applying about 10,000 atm of pressure can denature a protein at T = 300K. What is the volume change Av for the unfolding process ... 

The fact that the pressure effect on the alcohol inhibition tends to disappear at the higher temperatures indicates that the volume change in the equilibrium combination between the alcohol and the enzyme protein is very small, the pressure effects at lower temperatures being mediated through the ordinary temperature- and pressure-sensitive denaturation equilibrium. 

An illustrative example of this kind is shown in Fig. 5, where the denaturation of serum albumin was followed upon addition of increasing concentrations of the denaturant GdmCl [83D1], The volume changes observed in densimetric studies were found to parallel changes of the extinction coefficient and intrinsic viscosity. 

Fig. 5a - c. Molecular properties of bovine serum albumin as a function of the molar concentration, C3, of the denaturant guanidinium chloride (from [83D1]). a apparent isopotential specific volume (in cm g ) b extinction coefficient c intrinsic viscosity (in cm g ). For experimental details see the original reference. Reprinted from International Journal of Biological Macromolecules, Vol. 5, H. Durchschlag and R. Jaenicke, Partial specific volume changes of proteins ultracentrifugal and viscometric studies, pp. 143-148, 1983, with permission from Elsevier Science. 

Denaturation is a change in which the natural protein becomes insoluble in solutions in which it was previously soluble. It is brought about by physical means such as heat, pressure, and surface force, or by chemical means, although very few chemical agents are used in this connection in the food field. Gel-type solutions are usually beaten before they become too thick or firmly set. As air is incorporated, the volume increases and the firmness of the gel stabilizer sets the foam. 

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