Design of phosphonium-type zwitterion as an additive to improve saturated water content of phase-separated ionic liquid from aqueous phase toward reversible extraction of proteins.

International journal of molecular sciences

PubMedID: 24013379

Ito Y, Kohno Y, Nakamura N, Ohno H. Design of phosphonium-type zwitterion as an additive to improve saturated water content of phase-separated ionic liquid from aqueous phase toward reversible extraction of proteins. Int J Mol Sci. 2013;14(9):18350-61.
We designed phosphonium-type zwitterion (ZI) to control the saturated water content of separated ionic liquid (IL) phase in the hydrophobic IL/water biphasic systems. The saturated water content of separated IL phase, 1-butyl-3-methyimidazolium bis(trifluoromethanesulfonyl)imide, was considerably improved from 0. 4 wt% to 62. 8 wt% by adding N,N,N-tripentyl-4-sulfonyl-1-butanephosphonium-type ZI (P555C4S). In addition, the maximum water content decreased from 62. 8 wt% to 34. 1 wt% by increasing KH2PO4/K2HPO4 salt content in upper aqueous phosphate buffer phase. Horse heart cytochrome c (cyt. c) was dissolved selectively in IL phase by improving the water content of IL phase, and spectroscopic analysis revealed that the dissolved cyt. c retained its higher ordered structure. Furthermore, cyt. c dissolved in IL phase was re-extracted again from IL phase to aqueous phase by increasing the concentration of inorganic salts of the buffer solution.