The precise molecular mechanism of general anesthetics remains unknown. It is therefore important to understand where molecules with anesthetic properties locali e within biological membranes. e ha e determined the free energy pro le of a ben ocaine molecule B C across a biological membrane using molecular dynamics simulation. e use an asymmetric phospholipid bilayer with DPPS in one lea et of a DPPC bilayer Lope Cascales et al. J. Phys. Chem. B 2006, 110, 2358-2363) to model a biological bilayer. From the free energy pro le, we predict the one of actuation of a ben ocaine is located in the hydrocarbon region or at the end of the lipid head, depending of the presence of charged lipids DPPS in the lea et. e obser e a moderate increase in the disorder of the membrane and in particular an increase in the disorder of DPPS. Statistic and dynamic physicochemical properties of the ben ocaine, such as its dipole orientation, translational diffusion coefficient, and rotational relation time were measured.