The lipid matrix of the skin contains cholesterol (CHOL), free fatty acids (FFAs) and ceramides (CERs), arranged as lamellar phases with d-spacings of ~5.4 nm (SPP) and ~12.5 nm (LPP). In previous studies at ILL, we successfully resolved the scattering length density profiles of the SPP and LPP, and determined the positions within the LPP of the FFAs, CER-2 acyl chain, CHOL, and CER-1 linoleate. The LPP system studied previously involved an 8-component mixture, and was found to have a complex structure involving three lipid layers, with water at the boundaries and interior of the unit cell. We have now established through X-ray studies that the LPP can be prepared using just CER-1, CER-2, CHOL, and FFAs. However, the repeat distance in this system is not the same as in the 8-component LPP system, and so it is not known if these two systems are structurally equivalent. Moreover, we still do not know whether the CER-2 adopts a hairpin or fully extended conformation. Here, we aim to use CER-2 with a d7-sphingosine tail, to allow unambiguous determination of CER-2 conformation, and also to determine if the arrangement of CER-2 differs between the complex and simple LPP model systems.