Fig. 5. Effects of HFE and halothane on the lipid head group orientation. Shown is the average DMPC Phosphatidylcholine (P-N) dipole orientational distribution, where, θ is the angle between the P–N dipole and the normal to the lipid bilayer plane (see inset). The solid (A ), dotted and long-dashed lines correspond to the pure lipid, the low and the high HFE concentrations, respectively. Differences between the curves are not statistically significant. Analogous results (B ) for the DPPC/halothane system. 15,16The plots show that in contrast to HFE, halothane has an effect on the lipid head group dipole orientation, particularly at small angles.