髓鞘碱性蛋白对细胞膜脂质分子DPPC、DPPE单层膜影响机理研究

Effect of myelin basic protein on membrane lipid monolayers composed of DPPC and DPPE molecules

本文通过Langmuir单层膜的表面压力-平均分子面积(π-A)曲线的测定与分析,分别对髓鞘碱性蛋白(MBP)与细胞膜中不同头部基团脂质分子二棕榈酰基磷脂胆碱(DPPC)和二棕榈酰基磷脂酰乙醇胺(DPPE)在空气/液体界面上的相互作用过程进行了系统研究.实验结果表明:(1)当界面上脂质含量一定时,亚相中随着MBP浓度的增大,DPPC、DPPE单层膜的等温线向平均分子面积较大的方向移动;(2)在单层膜表面压力为10 mN/m时,一个MBP分子分别结合140±3个DPPC分子和100±3个DPPE分子,随着表面压力增大,当MBP分子分别与两种磷脂分子相互作用时,MBP插入到磷脂单层界面的个数逐渐减少;(3)随着蛋白质浓度的增加,脂分子形成的单层膜变得较为疏松,且MBP分子易于插入到分子头部较小的DPPE单层膜中;(4)蛋白质的存在使DPPC单层膜的表面压力逐渐减小,且蛋白质浓度越大表面压力降低越多,DPPC被MBP带入到亚相中越多;(5)对于DPPE单层膜,蛋白质通过与DPPE相互作用插入到界面膜中,引起表面压力增大,且蛋白质浓度越高,压力变化量越大.

By analyzing the Langmuir monolayer surface pressure-mean molecular area（π-A） curves, the interaction between myelin basic protein（MBP） and dipalmitoylphosphatidyl-choline cell membranes（DPPC） and dipalmitoylphosphatidylethanolamine（DPPE）, which are the different head group of lipid molecules, has been systematically studied, respectively. The results showed that：（1） with the MBP concentration in subphase increasing, the isotherm of DPPC and DPPE monolayer moved to lager average molecular area direction when the number of the lipid on the interface was constant;（2） when the surface pressure of the monolayer reached to 10 mN/m, one MBP molecule could combined with（140 ± 3） DPPC and（100 ± 3） DPPE molecules, respectively; as the surface pressure increased, the number of proteins interacted with two kinds of phospholipid molecules inserting the interface decreased;（3） with the increase of protein concentration, the monolayer film formed by the lipid molecules becomes more loose and MBP molecules are easy to insert into DPPE with smaller head;（4） the π-T curves indicated that the presence of protein could make DPPC monolayer surface pressure decreased, and the higher the concentration of protein was, the more for decreasing values of the surface pressure. Then the DPPC was brought into the MBP subphase;（5） for DPPE monolayer, the protein combined with DPPE inserted the membrane interface, causing the increase of surface pressure, and the higher the protein concentration was, the greater change the pressure appeared.