Sphingomyelin is found in the outerleaflet of the mammalian plasma membrane, where, in concert with cholesterol, it is thought to play a crucial role in the lateral organization of membrane proteins. Published NMR data reveals average chain structure in mixtures containing sphingomyelin and cholesterol; phase diagrams and lateral organization on 100 nm lengthscales based on fluorescence microscopy have also been published. Here we present detailed results on the nanoscale organization of sphingomyelin and cholesterol with either POPC or DOPC as the unsaturated lipid. As in our previously published work on mixtures of DPPC/DOPC/CHOL, we observe hexagonally ordered substructure within the liquid-ordered phase. Differences are observed, however, including tighter packing and persistent hydrogen bonds, which likely have significance for partitioning of membrane proteins in sphingomyelin liquid-ordered phases.

Nanoscale structure of sphingolipid containing liquid-ordered phases

249th National Meeting (2015)

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