Protein crystallization with and without precipitants

Crystals for X-ray structure analysis can be obtained from supersaturated protein solutions using the vapour-diffusion technique. Added electrolytes can act as competitors for water in the droplets as well as to reduce the activity of water and decrease the water vaporization rate. The water vaporization rate is critical for the protein crystallization process. It is a function of the type of electrolyte used and can be altered when testing the influence of various electrolytes on protein crystallization. Here we present a new approach to controlling the water vaporization rate using a vacuum pump to lower the pressure during the crystallization process. The successful application of the method for crystallization of adrenodoxin is described.