Scaled particle theory, cavity formation free

An entropic approach to the calculation of the free energy of cavity formation proceeds from the scaled particle theory (SPT). The free energy of the formation of a spherical cavity in a solvent, AGca , can be calculated proceeding within the framework of SPT as follows... 

A hybrid approach of the extended scaled particle theory (SPT) and the Poisson-Boltzmann (PB) equation for the solvation free energy of non-polar and polar solutes has been proposed by us. This new method is applied for the hydration free energy of the protein, avian pancreatic polypeptide (36 residues). The contributions form the cavity formation and the attractive interaction between the solute and the solvent to the solvation free energy compensate each other. The electrostatic conffibution is much larger than other terms in this hyelration free energy, because hydrophilic residues are ionized in water. This work is the first step toward further applications of our new method to free energy difference calculation appeared in the stability analysis of protein. 

The expression for G av, that is the free energy required for the formation of a cavity (first step in Figure 12.2.7), at a temperature T and a pressure P, is taken from the Scaled Particle Theory (SPT) which has been successfully applied in the study of thermodynamic properties of aqueous and non-aqueous solutions ... 

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