The enzymatic sphingomyelin to ceramide conversion increases the shear membrane viscosity at the air-water interface

- The rheological information obtained by compression and shear surface rheology of premixed SM/Cer monolayers is reviewed.
- The shear flowing properties of SM monolayers upon SMase-driven conversion to ceramide is reported.
- The mechanical perturbations associated to SM to ceramide conversion correlate with the topographical phase behavior.

Whereas most of lipids have viscous properties and they do not have significant elastic features, ceramides behave as very rigid solid assemblies, displaying viscoelastic behaviour at physiological temperatures. The present review addresses the surface rheology of lipid binary mixtures made of sphingomyelin and ceramide. However, ceramide is formed by the enzymatic cleavage of sphingomyelin in cell plasma membranes. The consequences of the enzymatically-driven ceramide formation involve mechanical alterations of the embedding membrane. Here, an increase on surface shear viscosity was evidenced upon enzymatic incubation of sphingomyelin monolayers. The overall rheological data are discussed in terms of the current knowledge of the thermotropic behaviour of ceramide-containing model membranes.

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