Crystallization in the presence of glycerol displaces water molecules in the structure of thaumatin

The intensely sweet protein thaumatin has been crystallized at 293 K in the presence of sodium tartrate and 25%(v/v) glycerol for X-ray diffraction data collection at 100 K. A comparison of the three-dimensional structure model derived from a crystal grown in the presence of glycerol with that of a control deprived of this additive reveals only minor changes in the overall structure but a ∼20% reduction in the number of water molecules. X-ray topography analyses show that the overall quality of the crystals prepared in the presence of this cryoprotectant is enhanced.