Membrane cholesterol-doped

Another peculiarity of DOPC-cholesterol GUVs is that they are destabilized and collapse when exposed to DC pulses at which cholesterol-free vesicles (e.g., made of egg phosphatidylcholine (egg PC) or pure DOPC) preserve their stability and only porate and reseal. The cholesterol-doped GUVs burst and disintegrated in a fashion reminiscent of that of charged membranes [142] (see Figure 7.6 for an example of a collapsing charged vesicle). As a quantitative characteristic of mem-... 

Cationic lipids can destabilize a cellular membrane because of its intrinsic detergent property. Therefore, destabilization of endosomal and/or lysosomal membrane may be a contribution from the cationic lipids itself In the same context, it was shown that the cationic lipid/DOPE or cationic lipid/cholesterol liposome formulation exhibit surface anisotropies in terms of increased liposomal surface pH (161,162). The surface pH of the liposomal formulations exhibits at least two pH units higher than the pH of the solution at which they are made. Therefore, a liposomal solution made at physiological pH may in reality exhibit a surface pH > 9, which is detrimental for both the stability of endosome and activity of lysosomal enzymes. Endosomal disruptions were also done with fusogenic peptides, which promote pH-dependent fusion of small liposomes when associated with lipid bilayer. When these peptides were co-delivered with lipid/DNA complex, they imparted formidable endosomal disruption by changing its usual random coil conformation into amphipathic a-helix conformation at lower pH, resulting in consequent cytoplasmic delivery of DNA (163). 

Fig. 3 - a) Current fluctuations in oxidized cholesterol membranes modified with PVh. One can observe the current jumps, followed by 0N 0FF fluctuations, resulting from the formation of some channels, at different membrane potentials. Applied voltage and changes in membrane conductance are reported. (The figure is taken from (7)). b) Steady state current voltage and conductance-voltage curves of PVh doped bilayer membranes. One can notice that I-V characteristic is linear and therefore G-V is a constant. 

The object of this study is to examine temperature-induced control of affinity of liposomes to cell surfaces using thermosensitive polymers. In this study, we prepared various liposomes consisting of egg yolk phosphatidylcholine (EYPC), dioleoylphosphatidylethanolamine (DOPE), and 3p-[N-(N ,N -dimethylaminoethane)carbamoyl]cholesterol (DC-Chol), which is a cationic lipid, and modified these liposomes with thermosensitive polymers, homopolymer and copolymers of N-acryloylpyrrolidine (APr), having anchors to liposome membranes. Their interactions with model membranes and cells were investigated. Suppression and enhancement of these interactions, depending on temperature, are described. 

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