Characterisation of a new ceramide EOS species: synthesis and investigation of the thermotropic phase behaviour and influence on the bilayer architecture of stratum corneum lipid model membranes

Abstract

The lipids of the stratum corneum, particularly the ceramides, are known to play a crucial role for the skin barrier properties. Thereby, the unique ω-acyl ceramide EOS is regarded to be a precondition for the formation of a protective envelope. We report on the chemical synthesis of a new ceramide EOS derivative constituting a saturated and branched ω-acyl chain instead of the naturally occurring ω-esterified linoleic acid moiety, therefore showing an improved stability against oxidative influences. In addition, the thermotropic phase behaviour of the new ceramide was studied using differential scanning calorimetry (DSC) and Fourier transform Raman spectroscopy. The results indicate a phase behaviour similar to the one known for the naturally occurring ceramide EOS. Chain packing behaviour as well as phase transition temperatures are found to be comparable for both ceramide species. Furthermore, the present study addresses the issue of characterising oriented quaternary stratum corneum lipid model membranes based on the new ceramide EOS derivative by means of neutron diffraction. The results indicate the formation of a stable bilayer architecture with membrane parameters comparable to the quaternary model systems containing naturally the occurring ceramide EOS species. Additional molecular dynamics simulations corroborated the findings received from neutron diffraction and the proposed lipid bilayer arrangement.