PROPERTIES OF MODEL MEMBRANES CONTAINING GLYCOLIPDS

Biological membranes are essential for life and are mainly composed of lipids and proteins. Plasma membranes have additionally a rich glycocalyx that is important for all cell signaling. In neuronal cells, a significant portion of lipids is composed of glycolipids. From this, the aim of our work is to study the properties of liposomes (both large and giant unilamellar vesicles - LUVs and GUVs, respectively, and multilamellar vesicles - MLVs) composed of phosphatidylcholine (PC) and three classes of glycolipids, namely cerebrosides, sulfatides and gangliosides. Cerebrosides are neutral lipids consisting of a ceramide attached to a galactose. On the other hand, sulfatides have an anionic sulfate group. Gangliosides have a bulky headgroup consisting of a polysaccharide that also has a negative charge. The focus of our work is to investigate the impact of glycolipids on membrane packing, stability and liquid ordered/liquid disordered phase separation. For that, different techniques were used, such as differential scanning calorimetry (DSC) and fluorescence anisotropy to probe the gel-fluid transition of LUVs composed of dipalmitoyl phosphatidylcholine (DPPC) with up to 20 mol% glycolipids, and optical microscopy of GUVs, to assess membrane stability, most specifically pore edge tension, and macroscopic phase separation of (GUVs) composed of palmitoyl oleoyl phosphatidylcholine (POPC) with up to 20 mol% glycolipids or raft-like mixtures containing glycolipids. Initially, DSC and fluorescence anisotropy measurements of DPPC with 0-20 mol% cerebroside were performed. DSC traces of pure DPPC and cerebroside liposomes exhibit peaks at 41 and 65 ^oC, respectively. We found that the presence of cerebroside caused mainly a broadening of the main transition, which remained at 41 ^oC and with enthalpy variation around 9 kcal/mol.

This work was supported by The São Paulo Research Foundation FAPESP (# 2024/00974-0).