title: The effect of pressure and the volume of activation on the monovalent cation and glucose permeabilities of liposomes of varying composition.
abstract: Measurement of the cation permeability of phospholipid microvesicles as a function of pressure confirmed that a single rate-determining step occurred in each case. The volume of activation was 20 ml-mole minus 1 for Na+ and K+, and about 40 ml-mole minus 1 for valinomycin-mediated K+ permeability. It was virtually independent of membrane composition. The results were explained in terms of Träuble's theory of kink-substrate dissociation at the membrane interface involving possible 2gl and 2g2 kink isomers. The volume of activation for D-glucose was 37 ml-mole minus 1, which was not significantly different from that for any of the valinomycin-mediated K+ permeabilities. However, other data suggest that the rate-limiting steps for the sugar and cation permeabilities are not the same.
mesh_terms: D001665:Binding Sites; D002784:Cholesterol; D005947:Glucose; D007700:Kinetics; D008081:Liposomes; D008433:Mathematics; D008958:Models, Molecular; D008968:Molecular Conformation; D010539:Permeability; D010743:Phospholipids; D011188:Potassium; D011312:Pressure; D012964:Sodium; D013816:Thermodynamics; D014634:Valinomycin
chemical_list: D008081:Liposomes; D010743:Phospholipids; D014634:Valinomycin; D002784:Cholesterol; D012964:Sodium; D005947:Glucose; D011188:Potassium