Sodium chloride is used in a wide variety of biochemical applications, including intravenous fluids (normal saline is 0.9% w/v in water), density gradients, a diluent to increase ionic strength in buffers or culture media and in salt-out procedures in the isolation of DNA. It has also been used in high concentrations for preservation of foods since bacteria cannot grow in high salt conditions. Sodium chloride is widely used in protein crystallization.