title: Phospholipid-protein coatings for chiral capillary electrochromatography.
abstract: A phospholipid-bovine serum albumin (BSA) coating was developed for chiral capillary electrochromatographic separation of d- and l-tryptophan. Temperature, liposome composition, and liposome-BSA mixing and extrusion were found to have critical effects on the chiral separation of d- and l-tryptophan in terms of resolution, separation efficiency, and migration times. A solution of 0.5mM phosphatidylcholine (PC)-1 mg/ml BSA performed better than a solution of 0.5mM PC/phosphatidylserine (PS) (80:20, mol%)-1 mg/ml BSA as capillary coating; baseline separation of the enantiomers with satisfactory resolution was then achieved. Temperature played a crucial role in the chiral separation, as demonstrated for phospholipid-coated capillaries immobilized with BSA and lysozyme. The d- and l-tryptophans showed a marked difference in separation efficiency on the PC-BSA-coated capillary; the theoretical plate number of l-tryptophan was above 500,000 m(-1), whereas that of d-tryptophan was only about 22,000 m(-1). Immobilized BSA (pI 4.7) showed better chiral separation selectivity for the enantiomers than did immobilized lysozyme (pI 10.5), alpha-chymotrypsin (pI 8.1-8.3), or avidin (pI 10.0-10.5); also resolution was better and analysis time was faster. Hydrophobic interactions played an important role in the BSA-immobilized phospholipid-coated capillaries. The importance of protein net charge and molar mass for its immobilization in phospholipid-coated capillaries is discussed.
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, University of Helsinki, PO Box 55, FIN-00014, Helsinki, Finland.
authors.forename: Susanne K
authors.initials: SK
authors.lastname: Wiedmer
authors.forename: Tao
authors.initials: T
authors.lastname: Bo
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Riekkola
mesh_terms: D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D010743:Phospholipids / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D010743:Phospholipids; D011506:Proteins