Otherwise hydrophobic room temperature ionic liquids (RTILs), such as 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)-imide can be mixed with water at much higher levels, if a zwitterions is added to the mixture.

Researchers at Tokyo University of Agriculture and Technology have demonstrated that they can increase the water load from less than half a percent by weight to almost 18 % by adding a small amount of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)-imide.

RTILs are non-volatile alternatives to organic solvents, however, they are not necessarily useful media without water for biomolecules, such as enzymes. The Japanese team has shown that a water-loaded RTIL can dissolve horse heart cytochrome c as a test protein without significant damage to its structure.

The approach could enable structural studies for complex biomolecules inaccessible to organic solvents or pure water.

• Addition of suitably-designed zwitterions improves the saturated water content of hydrophobic ionic liquids,
  Yoritsugu Ito, Yuki Kohno, Nobuhumi Nakamura, Hiroyuki Ohno,
  Chem Commun. 2012.
  DOI: 10.1039/C2CC36119A