Thermal denaturation of proteins

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-... 

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. 

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 ... 

Water activity influences the rate of thermal denaturation of proteins, including enzymes. Generally, the denaturation temperature increases with decreasing aw. The rate of nearly all enzyme-catalyzed reactions increases with increasing aw, as a consequence of increased molecular mobility. 

The use of differential scanning microcalorimetry for measuring the thermal denaturation of proteins is described in Chapter 17, section Ale. Typically, 0.5-1 mg of protein in 1 mL of buffer, or 0.1-0.2 mg in 0.5 mL with the most sensitive apparatus, is required for an accurate determination of the enthalpy of denaturation. The thermodynamics of dissociation of a reversibly bound ligand may be calculated from its effects on the denaturation curve of a protein.14 The binding of ligands always raises the apparent Tm (temperature at 50% denaturation) of a protein because of the law of mass action the ligand does not bind to the denatured state of the protein, and so binding displaces the denaturation equilibrium toward the native state. 

Hofmann, G.E., and G.N. Somero (1996b). Interspecific variation in thermal denaturation of proteins in the congeneric mussels Mytilus trossulus and M. galloprovincialis evidence from the... 

Commonly, the thermal denaturation of proteins is often discussed in terms of the Lumry-Eyring model, which involves two steps reversible unfolding and irreversible alteration of the unfolded state to produce the final denatured state, which is unable to fold back to the native protein. 

With the availability of new non-steroidal agents as reference compounds, the development of new in vitro assays as potential primary screens has been much facilitated. According to Mizushima 4 the thermal denaturation of protein can be inhibited by a number of antiinflammatory compounds with an order of activity roughly in agreement with their in vivo potency. As a simple model to study the stabilization of lysosomal membrauie, Brown J has described a new... 

The stabilizing (destabilizing) effect of pressure on the thermal denaturation of proteins has been associated with the presence (absence) of aggregation of the unfolded protein [79]. Intermolecular aggregation is indeed one of the most commonly observed effects of thermal denaturation. The temperature of unfolding may however be lowered considerably by a... 

Ibanoglu, E. Effect of hydrocolloids on the thermal denaturation of proteins. Food Chemistry, 2005, 90(4), 621-626. 

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What remains to be done is to elucidate directly the mechanism upon which cosolvents work to alter the thermal denaturation of proteins, rather than to rely indirectly on the correlation with the chemical denaturation. Here, I apply FST to show that it is the binding or exclusion of the cosolvents that modulates thermal denaturation (Shimizu 2011). 

Heat treatment is one of the most commonly used techniques in food processing, and is frequently responsible for the transition of proteins from the native folded state to the denatured unfolded state. Thermal denaturation of proteins involves a structural change which affects the nutritional quality of foods (Plum, 2009). 

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Huttmann, G. and Bimgmber, R. (1999) On the possibility of high-predsion photothermal microeifects and the measurement of fast thermal denaturation of proteins. Journal of Selected Topics in Quantum Electronics, 5, 954-62. 

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