Synthesis of specifically deuterated ceramide [AP]-C18 and its biophysical characterization using neutron diffraction

The very heterogeneous group of ceramides is known to be mandatory for proper barrier functions of the outermost layer of mammalian skin, referred to as stratum corneum (SC). The synthesis of a specifically deuterated ceramide [AP]-C18 variant is described. The synthesized ceramide contains the racemic forms of the α hydroxy fatty acid. For the biophysical implementation, the received diastereomeric ceramide was applied in a neutron diffraction experiment. Therefore, a SC lipid model membrane was prepared containing the described ceramide (CER), cholesterol (CHOL), stearic acid (SA), and cholesterol sulfate (ChS) in a ratio of 55/25/15/5 wt%. Thus, we were able to localize the deuterated molecule part within the bilayers. In the process, a short-periodicity phase (SPP) was observed with a unit cell scale of about 44 Å. For the first time, we were able to confirm former ideas concerning the arrangement of the CER within this quaternary lipid model membrane.