Herwig Peterlik

When the ancestors of men moved from aquatic habitats to the drylands, their evolutionary strategy to restrict water loss is to seal the skin surface with lipids. It is unknown how these rigid ceramide‐dominated lipids with densely packed chains squeeze through narrow extracellular spaces and how they assemble into their complex multilamellar architecture. Here it is shown that the human corneocyte lipid envelope, a monolayer of ultralong covalently bound lipids on the cell surface protein, templates the functional barrier assembly by partly fluidizing and rearranging the free extracellular lipids in its vicinity during the sculpting of a functional skin lipid barrier. The lipid envelope also maintains the fluidity of the extracellular lipids during mechanical stress. This local lipid fluidization does not compromise the permeability barrier. The results provide new testable hypotheses about epidermal homeostasis and the pathophysiology underlying diseases with impaired lipid binding to corneocytes, such as congenital ichthyosis. In a broader sense, this lipoprotein‐mediated fluidization of rigid (sphingo)lipid patches may also be relevant to lipid rafts and cellular signaling events and inspire new functional materials.

Polymer‐derived ceramics (PDCs) are a class of advanced materials obtained by pyrolysis in a controlled atmosphere of an organosilicon polymer. Their functional as well as mechanical properties originate from the peculiar nanostructures developed during the pyrolysis. Herein, we investigate the formation of transient microporosity in a model PDC (methyl‐silsesquioxane) obtained in Ar, Ar–5%H 2 , CO 2 , and air. It is shown that a common evolution can be detected up to 700°C. At this temperature, the structure of the material in terms of chemical bonds is marginally changed (only redistribution reactions take place), but the medium‐range order is clearly modified moving the system to a more disordered state (detected by small angle x‐ray scattering [SAXS]) and causing the formation of a large amount of open micropores sized at about 1.2–1.7 nm. In the 700–800°C range, the proper ceramization starts causing the formation of a new class of small (around 1 nm) open micropores. These partially annihilate at 900°C in Ar and Ar–H 2 (i.e., in the second part of the ceramization process), whereas they totally collapse in CO 2 due to the formation of a more silica‐like SiOC (less polymerized and viscous). Finally, SAXS points out the persistence of relatively large closed nanovoids of about 1 nm at 1250°C for the samples treated in Ar and Ar–H 2 . These might explain anomalies in terms of density, elastic modulus, and thermal conductivity of this class of ceramics as reported in the literature.