Thermal unfolding thermodynamic parameters

The thermal stability of metmyoglobin and apomyoglobin has been extensively studied under different solvent conditions (Privalov et al., 1986). In particular, it was shown that at low pH values both the heat and cold denaturation peaks are clearly visible in the calorimetric scans. Figure 10 shows the excess heat capacity function for apomyoglobin predicted by the hierarchical partition function and the thermodynamic parameters described above. In order to simulate the experimental curve obtained at pH 3.83 (Privalov et al., 1986), the protonation of five specific histidine residues on unfolding was... 

An interesting aspect of the photoreaction of PYP is the similarity to the protein folding/unfolding reaction. Hellingwerf and his coworkers applied the transition state theory to the photoreaction of PYP and estimated the thermodynamic parameters, the entropy, enthalpy, and heat capacity changes of activation [29]. They also carried out thermodynamic analysis on the thermal denaturation of PYP. Consequently, they found that the heat capacity changes in the photoreaction are comparable to those in the unfolding... 

The studies discussed above gives an idea of conformational stability of proteins in ILs as inferred from the t measurement and melting temperature determination followed by various spectroscopic methods. However, stability of a protein/enzyme has contributions from both thermodynamic and kinetic parameters [55]. While thermal unfolding studies help to extract important thermodynamic parameters, stability of the proteins could also arise from the kinetic barrier to the conformational changes in the protein scaffold [55]. However, except for monellin [48], the thermodynamic stability in other cases has not been examined. Thus, in context of stability of proteins/enzymes in ILs, it is important and imperative to study and probe thermal unfolding as well as the thermodynamics and kinetics of the conformational change of the proteins in ILs. 

Thermodynamic parameters can be defined only for a reversible process. The midpoint corresponding to a thermally reversible folding-unfolding transition of a protein is defined by the temperature of transition, (i.e., the temperature at which the apparent transition constant K is equal to 1, and AG, the variation of free energy, is nul under conditions where a two-state approximation is valuable). Under these conditions is equal to AH/AS and AG is equal to AH(1 — T/T ). The different parameters are defined in Chapter 6 however, it is noted here that Privalov and Khechinaschvili (1974) have shown that AH is a linear function of temperature for a number... 

---