LIQUID CRYSTALLINE LIPID BILAYER MEMBRANES

四苯基卟啉铜（II）（CuTPP）已被发现分配 有利地进入二肉豆蔻酰磷脂酰胆碱（DMPC）双层膜。 取向的顺磁共振（EPR）谱 液晶DMPC膜表明，对于高（约 1/25）CuTPP/DMPC摩尔比时，CuTPP与DMPC的平面取向。 分子平行于双层表面。 这一结果是明确的 与我们先前的观察相反，在低（小于或等于 至1/100）CuTPP/DMPC摩尔比，分子的平面为 优选垂直于膜表面（M. Pasenkiewicz-Gierula，W. K. Subczynski和W. E. 03 The Dog（1997） Phys. 101，5596-5606）。 碰撞率的测量 在CuTPP和硬脂酸自旋标记物的氮氧部分之间 位于膜的不同深度， 电子顺磁共振谱的结果表明， 高CuTPP/DMPC摩尔比下的取向与 脂质附近CuTPP分子的自缔合（结晶） 双层中心 对这一结论的进一步证实来自 CuTPP在DMPC液晶中EPR谱的比较 膜与CuTPP晶体和聚集体的那些。 的 自缔合过程取决于CuTPP/DMPC的摩尔比 以及样品制备后的时间。

Copper(II) tetraphenylporphine (CuTPP) has been found to partition favorably into dimyristoylphosphatidylcholine (DMPC) bilayer membrane. Electron paramagnetic resonance (EPR) spectra of oriented liquid-crystalline DMPC membranes indicate that for a high (about 1/25) CuTPP/DMPC molar ratio, CuTPP is oriented with the plane of the molecule parallel to the bilayer surface. This result is in clear contrast to our previous observation that at low (less than or equal to 1/100) CuTPP/DMPC molar ratio, the plane of the molecule is preferentially perpendicular to the membrane surface (M. Pasenkiewicz-Gierula, W. K. Subczynski, and W. E. Antholine (1997) J. Phys. Chem. 101, 5596-5606). Measurements of the collision rate between CuTPP and the nitroxide moiety of stearic acid spin labels located at different depths in the membrane using saturation-recovery EPR spectroscopy lead to the conclusion that the change of the CuTPP orientation at a high CuTPP/DMPC molar ratio is coupled with self-association (crystallization) of CuTPP molecules near the lipid bilayer center. Additional confirmation of this conclusion comes from comparison of EPR spectra of CuTPP in liquid-crystalline DMPC membranes with those of CuTPP crystals and aggregates. The self-association process depends both on the CuTPP/DMPC molar ratio and the time after sample preparation.