Lorite G S, Nobre T M, Zaniquelli M E D, de Paula E, Cotta M A
Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Departamento de Física Aplicada, Campinas, SP, Brazil.
Biophys Chem. 2009 Feb;139(2-3):75-83. doi: 10.1016/j.bpc.2008.10.006. Epub 2008 Oct 31.
In this work we report the interaction effects of the local anesthetic dibucaine (DBC) with lipid patches in model membranes by Atomic Force Microscopy (AFM). Supported lipid bilayers (egg phosphatidylcholine, EPC and dimyristoylphosphatidylcholine, DMPC) were prepared by fusion of unilamellar vesicles on mica and imaged in aqueous media. The AFM images show irregularly distributed and sized EPC patches on mica. On the other hand DMPC formation presents extensive bilayer regions on top of which multibilayer patches are formed. In the presence of DBC we observed a progressive disruption of these patches, but for DMPC bilayers this process occurred more slowly than for EPC. In both cases, phase images show the formation of small structures on the bilayer surface suggesting an effect on the elastic properties of the bilayers when DBC is present. Dynamic surface tension and dilatational surface elasticity measurements of EPC and DMPC monolayers in the presence of DBC by the pendant drop technique were also performed, in order to elucidate these results. The curve of lipid monolayer elasticity versus DBC concentration, for both EPC and DMPC cases, shows a maximum for the surface elasticity modulus at the same concentration where we observed the disruption of the bilayer by AFM. Our results suggest that changes in the local curvature of the bilayer induced by DBC could explain the anesthetic action in membranes.
在本研究中，我们通过原子力显微镜（AFM）报告了局部麻醉剂丁卡因（DBC）与模型膜中脂质斑块的相互作用效应。通过将单层囊泡融合在云母上制备支撑脂质双层（卵磷脂酰胆碱，EPC和二肉豆蔻酰磷脂酰胆碱，DMPC），并在水性介质中成像。AFM图像显示云母上EPC斑块分布和大小不规则。另一方面，DMPC形成呈现出广泛的双层区域，在其顶部形成多层斑块。在存在DBC的情况下，我们观察到这些斑块逐渐破坏，但对于DMPC双层，这个过程比EPC发生得更慢。在这两种情况下，相图像显示双层表面上形成小结构，表明当存在DBC时对双层弹性性质有影响。还通过悬滴技术对存在DBC的EPC和DMPC单层进行了动态表面张力和膨胀表面弹性测量，以阐明这些结果。对于EPC和DMPC情况，脂质单层弹性与DBC浓度的曲线在我们通过AFM观察到双层破坏的相同浓度下显示表面弹性模量的最大值。我们的结果表明，DBC引起的双层局部曲率变化可以解释其在膜中的麻醉作用。
