Small-angle X-ray Scattering Studies on the Structure of Disc-shaped Bicelles Incorporated with Neutral PEGylated lipids

In this study, small-angle X-ray scattering (SAXS) is successfully employed to investigate the structure of the DPPC/diC7PC disc shaped bicelles incorporated with different amounts of C16-PEG2000-Ceramide lipids. The incorporation of the C16-PEG2000-Ceramide lipids could provide antifouling capability to the bicelle for biomedical applications. However, traditionally it is believed that most of the incorporated PEGlylated lipids should lie in the rim of the disc shaped bicelle. In this study, high sensitivity SAXS　reveals the distribution of the added C16-PEG2000-Ceramide lipids in both the planar region and in the rim of the bicelle. The PEG brushes of C16-PEG2000-Ceramide lipids form a second shell outside the lipid head group shell of the bicelle. A double shell disc bicelle model is used in analyzing the SAXS data. The lipid density of C16-PEG2000-Ceramide in the rim is found to be about 1.7 times of the C16-PEG2000-Ceramide lipid density in the planar region for all the three C16-PEG2000-Ceramide con...