Preserving Proteins Under High Pressure and Low Temperature

Our group has a continuing interest in devising new freezing-protection agents. To this end, we have systematically investigated the structure of aqueous electrolyte salt solutions and room-temperature ionic liquids (RTILs), which consist of the cations and anions. We found that such water-mixed solutions remain liquid even at 1.0 GPa and 77 K (achieved by rapid cooling at 500 K/min) (Imai et al., 2010; Takekiyo et al., 2006a, 2006b; Yoshimura et al., 2009, 2011) and that water-soluble RTILs such as 1-butyl-3-methylimidazolium tetrafluoroborate remain liquid even at 2.0 GPa (Imai et al., 2011, Takekiyo et al., 2011). These results suggest that high pressure and low temperature by the use of RTILs-water mixtures might be useful for the freezing preservation of aqueous protein solutions.