Browsing by Subject "Lipid bilayers"
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Item Domain formation in choleterol/POPE/POPC lipid bilayer membranes(Texas Tech University, 2005-08) Thiagarajan, Visveswaran; Vaughn, Mark W.; Dai, Lenore L.; Cheng, Kelvin K.The regulation of several activities of the cell membranes has been associated with the formation of membrane domains. Self assembling lipid bilayers that serve as model cell membranes have been used to study their lateral organization and the formation of such lateral membrane domains. A recently proposed Superlattice (SL) model and several experimental studies have shown that Cholesterol and several lipids molecules tend to form an ordered domain at certain critical compositions as predicted by the SL model. Cholesterol/POPE/POPC lipid bilayers were used in this work and their lateral organization and the formation of membrane domains was studied using steady state and time-resolved fluorescence spectroscopy. The peaks and dips obtained in the values of the steady state anisotropy and the parameters obtained from the time-resolved studies serve as evidence indicating the formation of ordered domains at the head group and acyl chain level. An attempt was made to study the effect of the formation of such membrane domains on the binding of proteins to the membrane. A glass microfluidic chip was fabricated for this purpose. The binding of the proteins to the supported bilayers in the microchannels of the biochip was studied using total internal refraction fluorescence microscopy.Item Synthesis of giant unilamellar vesicles (GUV) from RSE liposomes in high and low ionic strength buffers(2010-08) Saremi, Bahar; Huang, Juyang; Lichti, Roger L.; Park, SoyeunA cell’s plasma membrane separates the interior and exterior media of cell, along with contributing to many vital functions, such as maintaining gradients across the cell and signal transductions. Lipid bilayers, the most important constituents of the cell membranes, have been subject of numerous studies. Synthetic liposomes have been widely used as model systems of cell membranes. However, the size of typical liposomes is less than 0.5 microns, too small for most microscopy studies. On the other hand, giant unilamellar vesicles (GUV) are a special type of liposome sized 10 to 200 microns, particularly suited for studying complex phase behaviors of biomembranes using fluorescence microscopy. In this study, the synthesis of GUVs from much smaller liposomes produced by the rapid solvent exchange (RSE) method in solutions of high and low ionic strength was investigated. Such GUVs have a unique property: the lipid composition is very uniform throughout the sample, unlike GUVs prepared by other methods. The detailed procedures of the electroformation method in high and low ionic strength buffers were systematically tested and refined. The optimized procedure was able to produce high quality DOPC/DSPC/cholesterol multi-component GUVs, which clearly showed coexisting lipid phases. The procedure can also be further adapted to produce GUVs containing native membrane proteins.