Lipid interactions and receptor properties of glycosphingolipids in membranes
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Abstract
The glycosphingolipids (GSL) galactocerebroside, lactocerebroside and the ganglioside GMl have been studied by a number of physical techniques in single and binary hydrated systems. The thermotropic and structural properties of hydrated synthetic N-stearoyl , -oleoyl, -linoleoyl and - lignoceroyl galactosylsphingosine have been investigated by differential scanning calorimetry (DSC) and x-ray diffraction. Complex polymorphic behavior associated with crystal~liquid crystal and liquid crystal~crystal transitions were observed. The thermotropic and structural properties of hydrated synthetic N-pal mitoyl, stearoyl and lignoceroyl lactosyl dihydrosphingosine were characterized in single and mixed binary systems with dipalmitoyl phosphatidylcholine (DPPC) utilizing DSC and x - ray diffraction. The effects of increasing the hydrocarbon chain length and headgroup complexity as well as the phase behavior in DPPC bilayers were determined. The physical properties of the ganglioside GMl alone as well as various hydrated phosphatidyl choline (PC)/GMl mixtures have been determined using DSC, microcalorimetry and x-ray diffraction. The phase behavior and structural features of mixing a bilayer-forming lipid (PC's) and a nonbilayer forming lipid (GMl) were determined. Information determined in the characterization of the various GSL-PC systems was used in the preparation of GSLPC monolayers at the air/ water interface. These monolayers contained a specific GSL receptor in a PC matrix and were transferred to solid supports. Utilizing fluorescence and electron microscopy specific receptor-ligand interactions involving GM1-cholera toxin (CT), or GTlb-tetanus toxin (TT) were observed. The lateral diffusion coefficient (D) for labeled GMl and GM1-CT was determined. Utilizing these lateral diffusion properties, ordered two-dimensional crystal line arrays for both GM1-CT and GM1-CT B-subunit were demonstrated. With image analysis techniques a 30A resolution reconstruction of the GM1-CT complex was obtained .
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Dissertation (Ph.D.)--Boston University
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