Highly aligned membrane stacks of either a pure lipid matrix (DLPC/Chol) or differentially composed peptide/ lipid compositions (Fig. 2) were analyzed. The lipid phase of each sample contained 5% cholesterol to enhance the surface mosaicity and reduce bilayer fluctuations allowing for pronounced Bragg reflections and correspondingly higher resolution in the reflectivity experiments (Chen and Rand 1997; Mouritsen and Zuckermann 2004) . The particular sample composition, the variation of parameters, and the obtained data are shown in Table 1 .