Location of the general anesthetic n-decane in model membranes

Abstract

The location of n-decane molecules within the model biological membrane consisting of dioleoyl-phosphocholine (DOPC) bilayers has been investigated via small angle neutron diffraction (SAND) method and molecular dynamics (MD) simulations. Diffraction patterns of the samples containing varied amounts of labeled and unlabeled n-decane have been obtained at various H2O:D2O scattering contrasts and utilized in the reconstruction of their neutron scattering length density (NSLD) profiles. The experimental data analysis based on mutual comparison of contrast varied NSLD profiles revealed unambiguously the location of n-decane molecules within our complex liquid system. They are distributed mostly in the lipid bilayer center while oriented both perpendicular to the bilayer normal, as well as in orientation parallel to the bilayer normal. In this, the mode of n-decane incorporation differs very little for the different concentrations examined (1:1 and 2:1 n-decane:DOPC molar ratios). The results of MD simulations corroborate experimental observations qualitatively and offer an explanation for the persistence of n-decane incorporation mode.