Kelusky E C, Smith I C
Mol Pharmacol. 1984 Sep;26(2):314-21.
The influence of the local anesthetics tetracaine (TTC) and procaine (PRC) on bilayers of specifically deuterated phosphatidylethanolamines (PE) has been studied by 2H and 31P NMR. Dimyristoylphosphatidylethanolamines (DMPE), deuterated at positions 2, 4, and 14 of the sn-2 chain, position 2 of the sn-1 chain, and in the ethanolamine headgroup, were mixed 1:1 with a semisynthetic egg PE and the effect of measured quantities of TTC and PRC on the 2H quadrupole splittings, spin-lattice relaxation times, and 31P chemical shift anisotropy were observed. Experiments were performed at pH 5.5, when the anesthetics are primarily charged, and at pH 9.5, when they are uncharged. Tetracaine was observed to disorder the hydrocarbon region of the bilayer and to induce a conformational change in the PE headgroup. Conversely, procaine had little or no effect on the hydrocarbon region and induced only a small change in the headgroup. These conformational changes and disordering effects, when adjusted for anesthetic partitioning, are essentially independent of the charge on the anesthetic. However, at pH 5.5 and low TTC/PE molar ratios (less than 0.1), the 2H NMR spectra showed two lipid environments--one corresponding to free PE and the other to PE in contact with TTC. Continued addition of TTC resulted in the eventual disappearance of the free PE signal and the corresponding growth of the signal from PE in contact with TTC. At pH 9.5, when TTC is uncharged, only one signal is observed. This indicates that at low pH, when TTC is primarily charged, it has a much slower rate of lateral diffusion in the PE bilayer. In mixtures of PE and phosphatidylserine, a conformational change in the headgroup was noted which was similar to that seen in the pure PE; however, there was no evidence for slow lateral diffusion of the anesthetics. The effects of TTC and PRC on the PE bilayer, when combined with our earlier study of the labeled anesthetics [Kelusky, E.C., and I.C.P. Smith, Biochemistry, 22:6011-6017 (1983)], indicate that TTC penetrates into the hydrocarbon portion of the bilayer whereas PRC sites only in the headgroup region.
利用2H和31P核磁共振技术研究了局部麻醉剂丁卡因（TTC）和普鲁卡因（PRC）对特定氘代磷脂酰乙醇胺（PE）双层膜的影响。将在sn-2链的2、4和14位、sn-1链的2位以及乙醇胺头部基团进行氘代的二肉豆蔻酰磷脂酰乙醇胺（DMPE）与半合成鸡蛋PE按1:1混合，观察了定量的TTC和PRC对2H四极分裂、自旋晶格弛豫时间以及31P化学位移各向异性的影响。实验分别在pH 5.5（此时麻醉剂主要带电荷）和pH 9.5（此时麻醉剂不带电荷）条件下进行。观察到丁卡因会扰乱双层膜的烃区，并引起PE头部基团的构象变化。相反，普鲁卡因对烃区几乎没有影响，仅引起头部基团的微小变化。当对麻醉剂的分配进行校正时，这些构象变化和扰乱效应基本上与麻醉剂上的电荷无关。然而，在pH 5.5和低TTC/PE摩尔比（小于0.1）时，2H核磁共振谱显示出两种脂质环境——一种对应于游离PE，另一种对应于与TTC接触的PE。持续添加TTC会导致游离PE信号最终消失，以及与TTC接触的PE信号相应增强。在pH 9.5时，丁卡因不带电荷，仅观察到一个信号。这表明在低pH值下，当丁卡因主要带电荷时，它在PE双层膜中的横向扩散速率要慢得多。在PE和磷脂酰丝氨酸的混合物中，观察到头部基团的构象变化与纯PE中的相似；然而，但没有证据表明麻醉剂存在缓慢的横向扩散。丁卡因和普鲁卡因对PE双层膜的影响，结合我们早期对标记麻醉剂的研究[Kelusky, E.C., and I.C.P. Smith, Biochemistry, 22:6011 - 6017 (1983)]，表明丁卡因可穿透双层膜的烃部分，而普鲁卡因仅位于头部基团区域。
