  The Stratum Corneum (SC), the outermost layer of skin, comprises rigid
corneocytes (keratin filled dead cells) in a specialized lipid matrix. The
continuous lipid matrix provides the main barrier against uncontrolled water
loss and invasion of external pathogens. Unlike all other biological lipid
membranes (like intracellular organelles and plasma membranes), molecules in SC
lipid matrix show small hydrophilic group and large variability in the length
of the alkyl tails and in the numbers and positions of groups that are capable
of forming hydrogen bonds. Molecular simulations provide a route for
systematically probing the effects of each of these differences separately. In
this article we present results from atomistic molecular dynamics of selected
lipid bilayers and multilayers to probe the effect of these polydispersities.
We address the nature of the tail packing in the gel-like phase, the hydrogen
bond network among head groups, the bending moduli expected for leaflets
comprising SC lipids, and the conformation of very long ceramide lipids (EOS)
in multibilayer lipid assemblies.
