  The structure of membrane-active peptides and their interaction with lipid
bilayers can be studied in oriented lipid membranes deposited on solid
substrates. Such systems are desirable for a number of surface-sensitive
techniques. Here we focus on structural characterization by x-ray and neutron
reflectivity and give an account of recent progress in sample preparation and
measurements. We show that the degree of mesoscopic disorder in the films can
significantly influence the scattering curves. Static defects should be
minimized by optimization of the preparation techniques and their presence must
be taken into account in the modelling. Examples are given for alamethicin and
magainin in bilayers of different phosphocholines.
