For analysis of the resulting reflectivities, a self-written MATLAB software tool was applied ). The reflectivity data were plotted as a function of the vertical momentum transfer q z after subtraction of the diffuse scattering (offset scan) and illumination correction. The electron density profiles were calculated by applying an empirical Fourier Synthesis (FS) scheme, exploiting the area under Bragg peak intensities I n , as it is used for such multilamellar lipid membranes (Münster et al. 2000; Spaar et al. 2004; Wu et al. 1995) . In simple terms the onedimensional electron density profile q(z) was obtained via Fourier synthesis method from the integrated peak intensities via Gaussian fitting, applying the Lorentz correction factor 1/q z 2 and phases -, -, ?, -, -, -, -in accordance with the number of observed Bragg reflexes. The phases t n are reduced to positive/negative signs due to the point symmetry and were reconstructed in accordance with the 1D swelling method approach using Eq. 3 to obtain the continuous form factor F(q z ) with its relative amplitude |F(q z,n )| and phase t n : Eur Biophys J (2011) 40:417-436 423