Figure 2.

Effect of rigidifying a single leaflet on formamide permeability. (A) Effect of extravesicular Pr³⁺ on bilayer fluidity at different temperatures. DPPC liposomes were incubated in 1 mM DPH-HPC, and then loaded with 200 mM formamide before performing anisotropy measurements at different temperatures. (•) Control liposomes, (○) liposomes treated with 10 mM Pr³⁺. (B) Stopped-flow experiments on control and Pr³⁺-treated vesicles showing formamide flux through liposomes at 43°C. Averaged time courses and fitted single exponential curves are shown. (C) Effect of extravesicular Pr³⁺ on formamide permeability at different temperatures. Results shown are from four separate liposome preparations (mean ± SEM). Where error bars are not visible, the symbol is wider than the error. (•) Control DPPC liposomes, (○) the Pr³⁺-treated liposomes. *P < 0.05 by t test.