Bin Xiaomin, Lipkowski Jacek
Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
J Phys Chem B. 2006 Dec 28;110(51):26430-41. doi: 10.1021/jp0660132.
Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was employed to investigate the interaction of cholesterol with the headgroups of dimyristoylphosphatidycholine (DMPC) molecules under a static electric field. DMPC/cholesterol (7:3 molar ratio) mixtures form a bilayer on a Au(111) electrode surface by fusion and spreading of small unilamellar vesicles. PM-IRRAS experiments provided detailed information concerning the conformation and hydration of headgroups of DMPC bilayers in the presence and absence of 30% cholesterol. The presence of 30% cholesterol increases the space between the headgroups of DMPC molecules and hence increases the hydration of the DMPC/cholesterol mixed bilayer. The conformational state of the headgroups of DMPC molecules in the mixed bilayer is also significantly changed. The phosphate group is closer to the surface compared with the pure DMPC bilayer. The conformation of the -O-C-C-N moiety changes from gauche to trans in the presence of cholesterol.
采用偏振调制红外反射吸收光谱法(PM - IRRAS)研究了在静电场下胆固醇与二肉豆蔻酰磷脂酰胆碱(DMPC)分子头部基团的相互作用。DMPC/胆固醇(摩尔比7:3)混合物通过小单层囊泡的融合和铺展在Au(111)电极表面形成双层膜。PM - IRRAS实验提供了有关在存在和不存在30%胆固醇的情况下DMPC双层膜头部基团的构象和水合作用的详细信息。30%胆固醇的存在增加了DMPC分子头部基团之间的间距,从而增加了DMPC/胆固醇混合双层膜的水合作用。混合双层膜中DMPC分子头部基团的构象状态也发生了显著变化。与纯DMPC双层膜相比,磷酸基团更靠近表面。在存在胆固醇的情况下,-O - C - C - N部分的构象从 gauche 变为 trans。