| Co-Investigator(Kenkyū-buntansha) |
NAKATA Yoshiro Gunma Univ.Dept.Physics, Prof., 工学部, 教授 (10008188)
TAKIZAWA Toshiharu Gunma Univ.Dept.Physics, Prof., 工学部, 教授 (50008158)
YABUKI Sadato Gunma Univ.Dept.Physics, Prof., 工学部, 教授 (50011581)
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| Research Abstract |
In this project, we have studied noble biological lipid micellar systems by using both synchrotron X-ray and neutron scattering techniques. Here we treat two different types of noble biological lipids. One is gangliosides and the other is phosphatidylinositol 4,5-bis(phosphaie) (PIP_2). Gangliosidis are Known to participate in various important physiological functions in cell surfaces such as self-organization of tissues, immune response and cell differntiation through a numerous variety of ganglioside structures. PIP_2 is known to be an acidic phospholipid existing at high contents in the cell membranes of brains and kidneys and recently have been attracting strong interests as the source of the second messenger in cellular signal transduction. Both of which are known to play an important role in various physiological events and signal transduction in cell surface. We found that these lipids show remarkable functionality in phase behaviors under physilolgical conditions, suggesting an
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ability of these lipids as a mimbrane active modulator that varies or regulates mimbrane-membrane interaction, protein-membrane binding, protein-protein interaction in membrane through a high conformational flexibility responding to some local perturbation in temperature, pH,ionic strength and ion species. For example, we have found that the elevation of temperature induces a significant shrinkage of the hydrophilic region of the ganglioside micelle accompanied by a slight expansion of the hydrophobic region, indicating that the oligoraccharide chains with sialic acid residues of ganglioside molecules change the conformation sensitively responding to a change of temperature. We have also found that the above shrinkage accompanies an intensive extrusion of water occluded in hydrophilic region of ganglioside micelle. In tne scattering data analyzes of the above micellar systems, we have developed a shell-modeling method combined with a repulsive interparticle interaction potential under a rescaled mean spherical approximation (RMSA) for charged particle dispersions. Wehave demonstrate successfully the high availability of this method for determining both intramicellar structure and intermicellar interaction directly from experimental scattering data. The summery of this project is given in the review paper by M.Hirai(Membrane 1998,23 : 8-16). Less
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