STEADY-STATE FLUORESCENCE STUDIES ON LIPASE-VESICLE INTERACTIONS

The interaction of lipase from Candida cylindracea (CCL) with positive ly charged polymerizable surfactant vesicles was studied by the use of steady-state fluorescence techniques. The phase transition of vesicle s composed of nonpolymerized and polymerized N-allylbis[2-(hexadecanoy loxy)ethyl]methylammonium bromide (ABHEMA Br) was determined in the ab sence of lipase, by measuring the change in fluorescence anisotropy of the membrane probe 1,6-diphenyl-1,3,5-hexatriene (DPH). The phase tra nsition temperature for nonpolymerized vesicles is 49 degrees C and fo r the polymerized analogues 45 degrees C. Fluorescence anisotropy and resonance energy transfer measurements were used to illustrate the inc orporation of the lipase in the vesicle membrane. These studies demons trated that CCL is incorporated into the hydrophobic bilayer of the ve sicle. By using an interfacial membrane probe rimethylammonium)phenyl] -6-phenyl-1,3,5-hexatriene p-toluene sulphonate, TMA-DPH) and an inter nal membrane probe (DPH), it could be determined that the enzyme is in corporated more efficiently into nonpolymerized vesicles, and that the penetration of the enzyme into the bilayer is less deep in the case o f the polymerized vesicles.