Cryosolvents useful for protein and enzyme studies below -100 degrees C

For the study of protein structure, dynamics, and function, at very low temperatures it is desirable to use cryosolvents that resist phase separation and crystallisation. We have examined these properties in a variety of cryosolvents. Using visual and X-ray diffraction criteria, methanol:ethanediol (70%:10%), methanol:glycerol (70%:10%), acetone:methoxy-ethanol:ethanediol (35%:35%:10%), dimethylformamide:ethanediol (70%:10%), dimethylformamide (80%), methoxyethanol (80%), and methoxyethanol:ethanediol (70%:10%) were all found to be free of phase-changes down to at least -160 degrees C. The least viscous of these, methanol:ethanediol (70%:10%), was miscible down to -125 degrees C and showed no exo or endothermic transitions when examined using DSC. It is therefore potentially particularly suitable for very low temperature cryoenzymology.