PROPERTIES OF MODEL MEMBRANES CONTAINING GLYCOLIPIDS

Vol 3, 2025 - 329760
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Abstract

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 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 and gangliosides have a bulky headgroup consisting of a polysaccharide with a negative charge. The focus of our work is to investigate the impact of glycolipids on membrane packing, stability and liquid-ordered/liquid-disordered (Lo/Ld) phase separation. Differential scanning calorimetry (DSC) and fluorescence anisotropy were used to probe the gel-fluid transition of LUVs composed of dipalmitoyl phosphatidylcholine (DPPC) with up to 20 mol% glycolipids. First, we obtained the phase transition temperatures (Tm) of each pure glycolipid: ~67°C (cerebroside), ~43°C (sulfatide) and ~29°C (ganglioside). Then, we observed that the presence of up to 20 mol% glycolipids caused only a broadening of the peaks around 41°C, which is the Tm of pure DPPC. Fluorescence microscopy was used to detect macroscopic phase separation of GUVs (giant unilamelallar vesicles) raft-like mixtures composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), DPPC, cholesterol and glycolipids (1:1:1:1) with a probe that resides in the Ld phase. The presence of cerebroside caused the appearance of a third phase completely depleted of fluorescence, possibly a gel phase due to its high Tm. With sulfatide, the Ld phase became dominant and ganglioside abolished phase separation. To assess membrane stability, pore edge tension was measured in GUVs composed of palmitoyl oleoyl phosphatidylcholine (POPC) with up to 20 mol% glycolipids through the kinetics of macropore closure induced by electrical pulses in real time. In general, there was no significant variation in the edge tension values of POPC containing glycolipids.

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Programme
18:30 to 20:00 on 10/30/2025
UNICAMP Multidiscip…
Institutions
  • 1 Department of Biophysics, Federal University of São Paulo, São Paulo, SP, Brazil
  • 2 Unifversidade Federal de São Paulo
Track
  • 2. Biomembranes
Keywords
membranes
glycolipids
calorimetry
anisotropy
fluorescence microscopy