The Effect of Temperature on Protein Solubility

Proteins have been documented to crystallize at a wide variety of temperatures, yet most proteins are crystallized at room temperature (25 °C) or in a refrigerator (4 °C), This observation is a reflection of experimental tradition in the protein crystallography field. Accessibility to cold rooms operating at 4 °C and fear of protein losses due to microbial attack prompts crystallographers to inves- 

For example, lysozyme is documented to undergo a crystalline phase transition from tetragonal (low temperature form) to orthorhombic (high temperature form) at approximately 25 °C (Pusey and Gernert 1988). Protein solubility can increase, decrease or remain constant as the temperature of the system increases. All three effects have been observed on real protein systems. 

Classical thermodynamics describes the effect of temperature on the solubility of a molecule in solution. If the heat of crystallization, AHcry, and solubility, C, at one temperature (T ) are known, the solubility as a function of temperature can be determined via the van t Hoff equation  

---