title: Extraction and separation of a lysine-rich protein by formation of supramolecule between crown ether and protein in aqueous two-phase system.
abstract: The macrocyclic calixarenes and crown ethers have recently been found to form hydrophobic complexes with the cationic protein cytochrome c (Cyt-c), by recognizing lysine residues on the protein surface. In the present study, it was found that the distribution of cytochrome c in Li(2)SO(4)/PEG aqueous two-phase system (ATPS) can be controlled by complexation with the crown ether dicyclohexano-18-crown-6 (DCH18C6). The protein was quantitatively extracted into the PEG-rich phase in the presence of DCH18C6 and perchlorate ion. Of various crown ethers and their analogues that were investigated, only DCH18C6 was able to extract cytochrome c into the PEG-rich phase. Extraction of cytochrome c in the ATPS using DCH18C6 is complete within 5 min. Cytochrome c complexed with DCH18C6 in the PEG-rich phase was quantitatively recovered into a salt-rich phase using K(2)SO(4) by ion exchange of potassium ion and cationic protein in the cationic protein complex with DCH18C6. Selective extraction of cationic proteins was demonstrated in the ATPS. Under optimum conditions, the lysine-rich protein cytochrome c was selectively extracted over other cationic proteins using DCH18C6.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, University of Miyazaki, 1-1, Gakuen Kibanadai Nishi, Miyazaki, 889-2192, Japan. oshimat@cc.miyazaki-u.ac.jp
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Oshima
authors.forename: Akinori
authors.initials: A
authors.lastname: Suetsugu
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Baba
mesh_terms: D000818:Animals; D005591:Chemical Fractionation / Q000379:methods*; D043844:Crown Ethers / Q000737:chemistry*; D045304:Cytochromes c / Q000737:chemistry / Q000302:isolation & purification*; D006736:Horses; D018020:Lithium Compounds / Q000737:chemistry; D008239:Lysine / Q000737:chemistry / Q000302:isolation & purification; D011092:Polyethylene Glycols / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D043844:Crown Ethers; D018020:Lithium Compounds; D013431:Sulfates; D014867:Water; C002570:dicyclohexyl-18-crown-6; D011092:Polyethylene Glycols; D045304:Cytochromes c; C054097:lithium sulfate; D008239:Lysine