title: 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.
abstract: 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.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16, Naka-cho, Koganei, Tokyo 184-8588, Japan. ohnoh@cc.tuat.ac.jp.
authors.forename: Yoritsugu
authors.initials: Y
authors.lastname: Ito
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kohno
authors.forename: Nobuhumi
authors.initials: N
authors.lastname: Nakamura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohno
mesh_terms: D045304:Cytochromes c / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D052578:Ionic Liquids; D009943:Organophosphorus Compounds; D011506:Proteins; D014867:Water; D045304:Cytochromes c