Denaturation of protein

Measurements were carried out using a Privalov-type calorimeter (see Section 2.2.2) which has sufficiently high resolution and stability to measure the partial heat capacity of the protein in a dilute 

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Ice formation is both beneficial and detrimental. Benefits, which include the strengthening of food stmctures and the removal of free moisture, are often outweighed by deleterious effects that ice crystal formation may have on plant cell walls in fmits and vegetable products preserved by freezing. Ice crystal formation can result in partial dehydration of the tissue surrounding the ice crystal and the freeze concentration of potential reactants. Ice crystals mechanically dismpt cell stmctures and increase the concentration of cell electrolytes which can result in the chemical denaturation of proteins. Other quaHty losses can also occur (12). 

Here,. Ai(X) is the partial SASA of atom i (which depends on the solute configuration X), and Yi is an atomic free energy per unit area associated with atom i. We refer to those models as full SASA. Because it is so simple, this approach is widely used in computations on biomolecules [96-98]. Variations of the solvent-exposed area models are the shell model of Scheraga [99,100], the excluded-volume model of Colonna-Cesari and Sander [101,102], and the Gaussian model of Lazaridis and Karplus [103]. Full SASA models have been used for investigating the thermal denaturation of proteins [103] and to examine protein-protein association [104]. 

Like most chemical reactions, the rates of enzyme-catalyzed reactions generally increase with increasing temperature. However, at temperatures above 50° to 60°C, enzymes typically show a decline in activity (Figure 14.12). Two effects are operating here (a) the characteristic increase in reaction rate with temperature, and (b) thermal denaturation of protein structure at higher tem-... 

Human skin compatibility has a high priority in manual dishwashing detergents. Recently, it was shown that there are some new possibilities to lower the Zein number by intelligent formulations. The Zein number is a common measure of the denaturation of protein under controlled conditions [84], A better... 

In addition to chemical reactions, the isokinetic relationship can be applied to various physical processes accompanied by enthalpy change. Correlations of this kind were found between enthalpies and entropies of solution (20, 83-92), vaporization (86, 91), sublimation (93, 94), desorption (95), and diffusion (96, 97) and between the two parameters characterizing the temperature dependence of thermochromic transitions (98). A kind of isokinetic relationship was claimed even for enthalpy and entropy of pure substances when relative values referred to those at 298° K are used (99). Enthalpies and entropies of intermolecular interaction were correlated for solutions, pure liquids, and crystals (6). Quite generally, for any temperature-dependent physical quantity, the activation parameters can be computed in a formal way, and correlations between them have been observed for dielectric absorption (100) and resistance of semiconductors (101-105) or fluidity (40, 106). On the other hand, the isokinetic relationship seems to hold in reactions of widely different kinds, starting from elementary processes in the gas phase (107) and including recombination reactions in the solid phase (108), polymerization reactions (109), and inorganic complex formation (110-112), up to such biochemical reactions as denaturation of proteins (113) and even such biological processes as hemolysis of erythrocytes (114). 

Purely thermal denaturation of proteins requires much longer times collagen in moist heat below 120 °C needs 30 min to denature (Meyer et ah, 2005), wheat glutens must be subjected to 200-215 °C of dry heat for 72 min (Friedman et ah, 1987), and as mentioned above, whey proteins require at least 50 °C and 30 min for texturization without the use of extrusion processing. 

Korhonen, H., Pihlanto-Leppala, A., Rantamaki, P., and Tupasela, T. (1998). Impact of processing on bioactive proteins and peptides. Trends Food Sci. Technol. 9,307-319. Kunugi, S. and Tanaka, N. (2002). Cold denaturation of proteins under high pressure. Biochim. Biophys. Acta 1595, 329-344. 

Observing and Inferring What type of pH change results in the denaturation of protein ... 

Although ionic surfactants are often associated with denaturation of proteins [104], the nonionic surfactant polysorbate 80 has been included in several marketed formulations and serves to inhibit protein aggregation. The mechanism may be the greater tendency of the surfactant molecules to align themselves at the liquid/ air interface, excluding the protein from the interface and inhibiting surface denaturation. 

Wu, H. (1931). Studies on denaturation of proteins. Chinese Journal of Physiology V, 321-344. 

The denaturation of proteins generally involves at least partial unfolding, with the loss of secondary and tertiary structure. In the present context, we are interested in the end point of this process — proteins that are unfolded to the maximal extent by various agents heat, cold, acid, urea, Gdm-HCl.1 Three major questions concerning unfolded proteins are of interest in the present chapter. Do different unfolding agents... 

The simplicity and accuracy of such models for the hydration of small molecule solutes has been surprising, as well as extensively scrutinized (Pratt, 2002). In the context of biophysical applications, these models can be viewed as providing a basis for considering specific physical mechanisms that contribute to hydrophobicity in more complex systems. For example, a natural explanation of entropy convergence in the temperature dependence of hydrophobic hydration and the heat denaturation of proteins emerges from this model (Garde et al., 1996), as well as a mechanistic description of the pressure dependence of hydrophobic... 

Hummer, G., Garde, S., Garcia, A. E., Paulaitis, M. E., and Pratt, L. R. (1998b). The pressure dependence of hydrophobic interactions is consistent with the observed pressure denaturation of proteins. Proc. Natl. Acad. Sci. USA 95, 1552-1555. Hummer, G., Garde, S., Garcia, A. E., Pohorille, A., and Pratt, L. R. (1996). An information theory model of hydrophobic interactions. Proc. Natl. Acad. Sci. USA 93, 8951-8955. 

Denaturation of proteins by irradiation can occur in small amounts at moderate or high doses. Some reduction in the availability of certain amino acids (lysine, methionine, etc.) has been reported in the proteins of irradiated foods. However, these effects are rather small, even at high radiation doses. 

Herskovits TT, Jaullet H. On the structural stability and solvent denaturation of proteins. J. Biol. Chem. 1970 245 2588-2598. 

Frying an egg is another familiar example of a one-way chemical reaction. As the egg is cooked, chemical changes, involving the denaturation of proteins, occur. These processes cannot be reversed. 

Heat-denatured Gl exhibited a surface hydrophobicity greater than that of native Gl. The increase was not unexpected since hydrophobic groups are commonly oriented towards the center of proteins in aqueous solvents. Heat denaturation of protein exposes hydrophobic groups to the solvent. Binding of denatured Gl to bean procyanidin oligomer was predominantly hydrophobic. 

The denaturation of protein was caused by the ECT haemoglobin is converted to acid haemin around the anode and alkaline haemin around the cathode. 

The van t Hoff plots for thermal denaturation of proteins are linear in the transition region, thus allowing the enthalpy change (AHm) of unfolding at the transition temperature (Tm) to be estimated. Because of the change in free energy in (AG) = 0 at Tm (reversible process), the entropy of unfolding (ASm) at the transition midpoint can be calculated from ... 

Joly, M. 1965. A Physico-Chemical Approach to the Denaturation of Proteins. Academic Press, London. 

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