Protein Solubility and Crystallization

In addition to the fairly specific interactions we have considered so far, there are numerous non-specific interactions that make proteins and polypeptides quite sticky , with a tendency to adhere both to each other and to other surfaces. As a consequence, proteins and polypeptides usually have quite low solubilities that are sensitive to changes in pH, ionic strength and other solutes. This is important in both experimental and practical applications, since most proteins are only properly active in solution. Some general guidelines are as follows. 

The solubility of any component is the concentration of solule (mol dm ) in the solution phase at equilibrtum and in contact with the X)lid phase. 

In thermodynamics, this can be related to the standard free energy of transfer from the solid to solution (AG iuiion)  

Anything that increases this free energy will reduce the solubility, and vice versa. 

Electrostatic interactions between charged groups on proteins appear to be one of the main factors controlling their solubility in aqueous systems. 

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Describe the thermodynamic basis for protein solubility and crystallization... 

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