Push–Pull Mechanism for Lipid Raft Formation

A quantitative assessment has been made of the interaction between exchangeable mimics of 1-palmitoyl-2-oleoyl-<i>sn</i>-glycero-3-phosphocholine (POPC) and cholesterol in the liquid-ordered (<i>l</i>₀) and the liquid-disordered (<i>l</i>_d) states using the nearest-neighbor recognition (NNR) method. This assessment has established that these lipids mix ideally in the <i>l</i>₀ phase (i.e., they show no net attraction or repulsion toward each other) but exhibit repulsive interactions in the <i>l</i>_d phase. The implications of these findings for the interactions between unsaturated phospholipids and cholesterol in eukaryotic cell membranes are briefly discussed

Stimulated Release of Cholesterol from Liposomal Membranes by a PEGylated Phospholipid

PEGylated phospholipids are commonly used to increase the blood-circulation time of liposomes by providing a steric barrier around them. This paper documents a fundamentally new property of these lipidsan ability to stimulate the release of cholesterol from phospholipid membranes. Evidence for such stimulation has been obtained by measuring the transport of dehydroergosterol (DHE), a fluorescent simulant of cholesterol, from donor liposomes made from 1-palmitoyl-2-oleoyl-<i>sn</i>-glycero-3-phosphocholine (POPC), 1,2-distearoyl-<i>sn</i>-glycero-3-phosphoethanolamine-<i>N</i>-[methoxy­(polyethylene glycol)-2000 (DSPE-PEG₂₀₀₀), and DHE to acceptor liposomes made from POPC, 1-palmitoyl-2-oleoyl-<i>sn</i>-glycero-3-phosphoglycerol (POPG), and cholesterol. The potential of PEGylated lipids to serve as novel cholesterol-lowering agents is briefly discussed