title: Protein refolding by N-alkylpyridinium and N-alkyl-N-methylpyrrolidinium ionic liquids.
abstract: An important property of ionic liquids consisting of cations and anions is that the chemical structures can be easily tuned. To expand the repertoire of effective ionic liquid-based refolding additives, we focused on this tunable property and investigated the effects of new candidates such as N-alkylpyridinium chlorides and N-alkyl-N-methylpyrrolidinium chlorides on protein refolding. Denatured lysozyme (30 mg/mL) was used as a model protein and refolded by 30-fold dilution with various refolding buffers containing different ionic liquids consisting of a systematic variety of alkyl chains. Compared with the refolding yield without additives (lower than 10%), less hydrophobic ionic liquids such as N-ethyl, N-butyl and N-hexylpyridinium chlorides, and N-butyl-N-methylpyrrolidinium chloride were effective in enhancing the refolding yields (46-69%), because they primarily suppressed aggregation because of their chaotropic properties. N-alkylpyridinium cations were more hydrophobic than N-alkyl-N-methylpyrrolidinium cations according to the calculated log P values and prevented aggregation at lower concentrations because of their hydrophobicity. The results provide a range of new effective ionic liquid-based additives for higher protein refolding yields and the knowledge of the effect of chemical structures of additives on protein refolding.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
authors.forename: Etsushi
authors.initials: E
authors.lastname: Yamamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Nagamune
mesh_terms: D000818:Animals; D002645:Chickens; D052578:Ionic Liquids / Q000737:chemistry*; D009113:Muramidase / Q000737:chemistry*; D058849:Protein Refolding; D011726:Pyridinium Compounds / Q000737:chemistry*; D011759:Pyrrolidines / Q000737:chemistry*
chemical_list: D052578:Ionic Liquids; D011726:Pyridinium Compounds; D011759:Pyrrolidines; D009113:Muramidase