Abstract
Lipid bilayer permeability coefficient of benzoil-tyrosin-p-nitroanilide (Bz-Tyr-pNA) was evaluated using large unilamellar vesicles prepared from POPC (1-palmitoyl-2-oleoyl-sn-glycero- 3-phosphocholine) and cholesterol containing the entrapped α-chymotrypsin. Alpha-chymotrypsin-catalyzed reactions occurred inside the vesicles after external addition of Bz-Tyr-pNA as a bilayer permeable substrate. From such kinetic measurements, the permeability coefficient could directly be determined by dynamic modeling. Using this method, the permeability coefficient can be determined accurately within 9% deviation. The effects of temperature and cholesterol content on the permeability were examined quantitatively. The permeability increased with temperature in the absence or presence of cholesterol. In the presence of cholesterol, the permeability was highest at 10 mol%. These changes of the permeability coefficient were discussed in relation to the lipid bilayer fluidity measured by steady-state fluorescent anisotropy.
