Saito H, Araiso T, Shirahama H, Koyama T
Department of Chemistry, Faculty of Science, Hokkaido University.
J Biochem. 1991 Apr;109(4):559-65. doi: 10.1093/oxfordjournals.jbchem.a123419.
The motion of the head group of phospholipid molecules in the bilayer structure was investigated by a picosecond fluorescence anisotropy technique using a newly synthesized fluorescent phospholipid, dipalmitoyl-L-alpha-phosphatidyl-(3-p-methoxyphenyl)umbelliferone (DPPU). In this phospholipid, a coumarin derivative is attached covalently to the phosphate moiety. The motion of the acyl chain of the phospholipid was also investigated by the same method using 1-palmitoyl-2-(3-diphenylhexatrienyl)-propanoyl-L-alpha-phospha tid ylcholine (DPHpPC). From fluorescence anisotropy decay the wobbling diffusion rate (Dw) of DPPU and DPHpPC in DPPC vesicles at 45 degrees C was calculated to be 2.7 x 10(9) s-1 and 5.1 x 10(7) s-1 using the wobbling-in-cone-model. The range of the motion was calculated as the cone angle (theta c), which is half of the angle of the cone in which the fluorophore can diffuse. The cone angle of the coumarin skeleton of DPPU in DPPC vesicles at 45 degrees C was 64 degrees, which was larger than that of the DPH skeleton of DPHpPC, 40 degrees. These results indicate that the motion of the head group is much faster and wider than that of the acyl chain. When cholesterol was added to the DPPC vesicles, the range of motion of the acyl chain decreased, but that of the head group increased. These facts show that cholesterol restricts the motion of the acyl chain but enhances that of the head group in the phospholipid bilayer.
使用新合成的荧光磷脂二棕榈酰-L-α-磷脂酰-(3-对甲氧基苯基)伞形酮（DPPU），通过皮秒荧光偏振技术研究了双层结构中磷脂分子头部基团的运动。在这种磷脂中，香豆素衍生物共价连接到磷酸部分。还使用1-棕榈酰-2-(3-二苯基己三烯基)-丙酰-L-α-磷脂酰胆碱（DPHpPC），通过相同方法研究了磷脂酰基链的运动。根据荧光偏振衰减，使用锥体内摆动模型计算出45℃时DPPU和DPHpPC在二棕榈酰磷脂酰胆碱（DPPC）囊泡中的摆动扩散速率（Dw）分别为2.7×10⁹ s⁻¹和5.1×10⁷ s⁻¹。运动范围计算为锥角（θc），即荧光团能够扩散的圆锥角度的一半。45℃时DPPU在DPPC囊泡中香豆素骨架的锥角为64°，大于DPHpPC的二苯基己三烯骨架的锥角40°。这些结果表明，头部基团的运动比酰基链的运动更快且范围更广。当向DPPC囊泡中加入胆固醇时，酰基链的运动范围减小，但头部基团的运动范围增加。这些事实表明，胆固醇限制了磷脂双层中酰基链的运动，但增强了头部基团的运动。
