Fig. 3. Changes in the structural characteristics of the lipid bilayer as a function of mole fraction of agent. (A ) Averaged area per lipid molecule (open symbols) and bilayer thickness, d-spacing, (closed symbols) for the DMPC/HFE system. The error bars are standard deviations. Similar plots (B ) are shown for the DPPC/Halothane system. 21,22Note the opposite effects as the concentration of agent increases.