| Aim:In order to supply theoretical and experimental basis for the study which is on the isolation and reconstruction of molecules of lipid rafts microdomains,we extracted and purified the ganglioside GM1,then we investigated the effect of physical and chemical factors on the phase behaviors of monolayer film of the quattuor system.Methods:1.The ganglioside GM1 were extracted from bovine brain by the Folch method and purified by silica gel and DEAE-Sephadex A-25 column chromatograph.Its structure was studied by infrared spectrum(IR) spectra,ultraviolet spectrum(UV) spectra and atomic force microscope(AFM).2.The trough area-surface pressure(π-A) isotherms under different conditions were obtained by LB technology,and the bilayer membranes were prepared by the Y-shaped deposition under certain surface pressure.3.The structure of bilayer membranes were observed by atomic force microcopy.Results:1.39.383 mg of Gls from 1000 g of wet bovine brain have certain purity,71.76%.And their absorption of Uv spectra appear at 195 nm,near to the results reported by other peoples. Compared with IR spectra of sialic acid and the experiment of content determination of it,the results showed that the structures of the products have the units of sialic acid.In order to investigate the structure of GM1.AFM technique was applied in water,and the results showed hydrophobic components of GM1 can form chain structure and hydrophilic components Of it can form ring structure which is formed by several monosaccharides.2:The trough area-surface pressure isotherms under different condition were obtained through changing the concentration,the content of cholesterol or ganglioside GM1 and the temperature,and the effects of these factors on the phase behaviors of monolayer film of supramolecular aggregates of lipid raft microdomains were investigated by the LB method:①When the concentration was increased,the self-assemblies of molecules were strengthened.②The higher temperature will result in the disorder of the self-assemblied aggregates.As a result,the phase transition will be deferred shown in theπ-A curve. ③When the concentration of ganglioside GM1 wsa increased,the self-assemblies of molecules were also strengthened.④With the increase of cholesterol concentration,two opposite trends of film pressure appeared at the point of the second phase transition,before up,and after down.3:According to the relationship between concentration,temperature,content of GM1,contnet of GM1 and membrane pressure,phase transition,the LB bilayer membranes were prepared.①According to the relationship between phase transition and concentration,membrane pressure,the LB bilayer membranes were prepared.AFM results showed that phase separation phenomenon was found at low membrane pressure under different concentration,and with the increase in membrane pressure,the phenomenon disappears completely.The filament network structure appears under different concentration,and with the increase in membrane pressure,it arranged more closely.When the concentration was same,with the increase in membrane pressure,the length and width of the filaments of the network structure were decreased,and with increasing concentrations,the width of the filaments decreases and its length did not change obviously under the same membrane pressure.The microdomain appeared under different concentration and membrane pressure.②According to the relationship between phase transition and temperature,membrane pressure, the LB bilayer membranes were prepared.AFM results showed that phase separation phenomenon was found at low membrane pressure under different concentration,and with the increase in membrane pressure,the phenomenon disappeared completely.The filament structure,network structure formed by filaments and microdomains appeared in the bilayer membranes,and with the temperature increase,number of the microdomains decreased.When the temperature was 24.5,36.4,45.2℃,with the increase in membrane pressure,The filament network structure arranged more closely;but when the temperature dropped to 15.3℃,with the increase in pressure membrane,the number of filament structure decreased and evolved in lamellar structure.③According to the relationship between phase transition and content of GM1,membrane pressure,the LB bilayer membranes were prepared.AFM results showed that when concentration of GM1 was smaller(1%),it was easy to form circular microdomains,when the membrane pressure was 10 mN/m,a little shorter strip branching structure existed in the bilayer membrane,and with the membrane pressure increased,the strip branching structure gradually disappeared,microdomains structure gradually increased,some microdomains integrated with each other;when the concentration of GM1 was 5%,there were some filament branching structures and a small number of microdomains in the bilayer membrane,but the microdomain structure had transformation trend to strip branching structure,as the increase in pressure membrane,this tendency has become even more obvious;when the concentration of GM1 was 10%,there have been substantial and a small number of microdomain structure,with the increase in membrane pressure,filament network structure arranged more closely,and there has been the phenomenon of the integration of.microdomains.④According to the relationship between phase transition and content of cholesterol,membrane pressure,the LB bilayer membranes were prepared.AFM results showed that when the content of cholesterol was 10%,20%,membrane pressure was 10,30,38 mN/m,phase separation phenomenon was found,there have been a great number of strip branching structure,a little filament network structure and microdomain.When the membrane pressure was 38 mN/m,the bilayer membrane arranged more loose than 30 mN/m.When the content of cholesterol was 20%,the arrangement of the structure was more closely than the content of 10%.When the content of cholesterol was 30%,membrane pressure was 10,30 mN/m,there has been phase separation phenomenon,microdomains structure was found,and there has been a great number of filament network structure in the bilayer membrane.With increasing the membrane pressure, the bilayer membrane structure was more compact,and there has been the phenomenon of the integration of.microdomains.Conclusion:The concentration,the temperature of sub-phase,the content of cholesterol or ganglioside GM1 all have a certain effect on the phase behaviors and structure of supramolecular aggregates of lipid raft microdomains,when the concentration is increased,the molecular number in the sub-phase is increased;the self-assemblies of molecules are strengthened,due to the stronger intermolecular interactions;the higher temperature will result in the disorder of the self-assemblied aggregates,as a result,supramolecular forces between molecules decrease;GM1 has stronger hydrogen bonding with other molecules in the system;the double role of cholesterol gives its special features.
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