title: Immobilization of phospholipid vesicles and protein-lipid vesicles containing red cell membrane proteins on octyl derivatives of large-pore gels.
abstract: For improved immobilization of phospholipid vesicles and protein-lipid vesicles (cf. Sandberg, M., Lundahl, P., Greijer, E. and Belew, M. (1987) Biochim. Biophys. Acta 924, 185-192) and for chromatographic experiments with vesicles containing membrane protein, we have prepared octyl sulfide derivatives of the large-pore gels Sephacryl S-1000 and Sepharose 2B with ligand concentrations up to 14 and 5 mumol/ml gel, respectively. The Sephacryl derivatives allowed higher flow rates, gave higher rates of adsorption and showed equally high or higher capacities than the Sepharose adsorbents. 'Small', 'medium' and 'large' vesicles of radii approx. 20, 50 and 100 nm showed distribution coefficients on Sephacryl S-1000 of 0.7, 0.5 and 0.05, respectively and could be immobilized on octyl sulfide-Sephacryl S-1000 in amounts corresponding to 110, 40 and 20 mumol of phospholipids per ml gel, respectively. 'Small' vesicles became absorbed onto this gel at a rate of 1.5 mumol of phospholipids per min per ml gel until 60 mumol of phospholipids had become immobilized, whereas the initial adsorption rate was about 0.4 mumol.min-1.ml-1 on octyl sulfide-Sepharose 4B (see reference above) and on octyl sulfide-Sepharose 2B. Lower ligand concentrations gave lower capacities for 'small' vesicles. When vesicles entrapping calcein were immobilized on octyl sulfide-Sephacryl S-1000 some calcein was released during the adsorption process. For 'small' and 'medium' vesicles, respectively, the leakage was 75 and 25% at a ligand concentration of 14 mumol/ml but only 3 and 2% at 5 mumol/ml. The internal volumes of immobilized 'small' and 'medium' vesicles were estimated at 0.97 and 2.9 microliters per mumol of phospholipid by determination of entrapped calcein, which could indicate vesicle radii 20 and 50 nm, respectively. The total volumes of immobilized 'medium' lipid vesicles and 'medium' protein-lipid vesicles containing integral membrane proteins from human red cells, were estimated at 2.9 and 2.0 microliters/mumol, respectively, by chromatography of D- and L-[14C]glucose and calcein on the octyl sulfide-Sephacryl S-1000 column before and after immobilization. These volumes are roughly consistent with the internal volume of the vesicles. A zone of D-glucose eluted 90 microliters later than a zone of L-glucose on a 4- or 5-ml column of octyl sulfide-Sephacryl S-1000 with immobilized 'medium' protein-lipid vesicles containing the glucose transporter from human red cells, probably since part of the internal vesicle volume was accessible to the D-glucose but not to the L-glucose. This indicates that the glucose transporter was active in the immobilized vesicles.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Institute of Biochemistry, University of Uppsala, Sweden.
authors.forename: Q
authors.initials: Q
authors.lastname: Yang
authors.forename: M
authors.initials: M
authors.lastname: Wallstén
authors.forename: P
authors.initials: P
authors.lastname: Lundahl
mesh_terms: D001786:Blood Glucose / Q000378:metabolism; D005452:Fluoresceins; D006801:Humans; D007202:Indicators and Reagents; D007700:Kinetics; D008024:Ligands; D008081:Liposomes; D008565:Membrane Proteins / Q000097:blood / Q000302:isolation & purification*; D009004:Monosaccharide Transport Proteins / Q000097:blood / Q000302:isolation & purification; D010743:Phospholipids / Q000302:isolation & purification*; D012685:Sepharose / Q000031:analogs & derivatives / Q000138:chemical synthesis; D013447:Sulfites / Q000138:chemical synthesis
chemical_list: D001786:Blood Glucose; D005452:Fluoresceins; D007202:Indicators and Reagents; D008024:Ligands; D008081:Liposomes; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D010743:Phospholipids; D013447:Sulfites; D012685:Sepharose; C007740:fluorexon