Influence of biologically active compounds on the monomolecular gramicidin channel function in phospholipid monolayers
Influence of biologically active compounds on the monomolecular gramicidin channel function in phospholipid monolayers
复制标题
生物活性化合物对磷脂单层中单分子短杆菌肽通道功能的影响
作者：
A. Nelson
通过检查一些生物活性化合物和短杆菌肽修饰的脂质单层之间的相互作用（作为不同阳离子浓度和组成的溶液中的膜模型），研究了生物活性化合物对自组装脂质单层系统内离子通道传输的影响。使用的技术是交流伏安法来测量层的电容，以及循环伏安法（CV）和计时电流法来研究Tl电化学。 CV 结果倾向于支持所提出的模型，即在实验时间尺度内 Tl 的电化学中非线性扩散效应并不显着。因此，电极过程被视为 CE 机制，其中速率限制步骤是离子在通道中的易位。由于电活性离子 Tl + 和单价电解质离子在施加的电势场的影响下进入通道之间存在竞争，因此出现了复杂化。渗透率常数的值是从电化学数据得出的。结果表明，脂质层中的许多疏水添加剂，特别是聚芳族化合物和聚共轭化合物，选择性地引起短杆菌肽修饰的DOPC单层对T1 + 的渗透性的改变。在添加视黄醇的单层中，短杆菌肽介导的通透性增加了高达 5 倍，这与层中存在相似浓度的带负电荷的脂质 (PS) 时所观察到的情况相似。氯代芳香族杀虫剂DDT会导致渗透性明显降低。据建议，由于层中的添加剂导致的对Tl + 的渗透性的变化主要是由单层内的化合物对通道内离子易位的能垒的影响引起的。发生这种情况是因为这些化合物改变了作用在通过通道的离子上的图像力以及与离子本身直接相互作用的图像力。
The effect of biologically active compounds on ion channel transport within a self-assembled lipid monolayer system was investigated by examining interactions between some bioactive compounds and the gramicidin-modified lipid monolayer as a membrane model in solutions of different cation concentration and composition. Techniques used were ac voltammetry to measure the capacitance of the layers and cyclic voltammetry (CV) and chronoamperometry to study Tl electrochemistry. The CV results tend to support the proposed model that nonlinear diffusion effects are not significant in the electrochemistry of Tl within the time scale of the experiment. As a result the electrode process is treated as a CE mechanism where the rate limiting step is the translocation of the ion in the channel. Complications arise because there is competition between the electroactive ion, Tl + , and the univalent electrolyte ion to enter the channel under the influence of the applied potential field. Values of the permeability rate constants have been derived from the electrochemical data. Results indicate that many hydrophobic additives in the lipid layer in particular polyaromatic and polyconjugated compounds selectively give rise to an alteration in the permeability of gramicidin-modified DOPC monolayers to Tl + . Up to 5-fold increase in gramicidin-mediated permeability is noted in monolayers with added retinol, which is similar to that seen in the presence of a similar concentration of negatively charged lipids (PS) in the layer. The chlorine-substituted aromatic pesticide DDT causes an apparent depression in the permeability. It is proposed that the variations of permeability to Tl + due to additives in the layer are predominantly caused by the effect of the compounds within the monolayer on the energy barrier to the translocation of the ion within the channel. This occurs because the compounds alter the image forces acting on the ion passing through the channel as well as directly interacting with the ion itself.