Solvation and solubility of globular proteins

We end this long chapter with a brief discussion of a very important subject of intensive research. We present here only a few aspects of protein solvation. Since proteins do not have any measurable vapor pressure, their solvation Gibbs energy cannot be measured. It is also extremely difficult to compute it either theoretically or by simulation methods. However, owing to the utmost 

Clearly, the solvation Gibbs energy of proteins cannot be studied experimentally. This would require measurable vapor of the protein. Therefore, the only option of studying the solvation of proteins is by theoretical means. As we shall see below, in spite of the enormous complexity of the problem, theory does suggest some guidance as to how to dissect the problem into relatively small and manageable problems. 

But what makes this special class of protein soluble As we shall see, the answer is not fully known. However, some indications as to the molecular reasons for the solubility were recently revealed (Wang and Ben-Naim 1996, 1997). 

The solubility is determined relative to the solid phase. At saturation we have the equilibrium condition  

Since pss, the chemical potential of the pure solid, is constant we can estimate the relative solubilities of s in two liquids, say and lt and l2 by 

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