Becucci Lucia, Guidelli Rolando
Department of Chemistry, Florence University, Sesto Fiorentino (Firenze), Italy.
Langmuir. 2007 May 8;23(10):5601-8. doi: 10.1021/la0636560. Epub 2007 Apr 10.
The kinetics of channel formation by the polyene-like antibiotic monazomycin, both in a bilayer lipid membrane (BLM) and in a tethered BLM (tBLM), and by the peptide melittin in a tBLM, is investigated. Stepping the applied potential from a value at which channels are not formed to one at which they are formed yields current vs time curves that are sigmoidal on a BLM, while they show a maximum on a tBLM; in the latter case, sigmoidal curves are obtained by plotting the charge against time. These curves are interpreted on the basis of a general kinetic model, which accounts for the potential-dependent penetration of adsorbed monomeric molecules into the lipid bilayer, followed by their aggregation with channel formation by a mechanism of nucleation and growth. In the case of monazomycin, which is present in the solution in the form of relatively hydrophilic clusters and is adsorbed as such on top of the lipid bilayer, penetration into the bilayer following a potential jump is assumed to be preceded by a potential-independent disaggregation of the adsorbed clusters into adsorbed monomers.
研究了多烯类抗生素莫那霉素在双层脂质膜（BLM）和栓系双层脂质膜（tBLM）中形成通道的动力学，以及蜂毒肽在tBLM中形成通道的动力学。将施加的电势从不会形成通道的值跃升至会形成通道的值，得到的电流随时间变化的曲线在BLM上呈S形，而在tBLM上则出现一个最大值；在后一种情况下，通过绘制电荷随时间的变化可得到S形曲线。这些曲线是基于一个通用动力学模型来解释的，该模型考虑了吸附的单体分子在电势作用下渗透到脂质双层中，随后通过成核和生长机制聚集形成通道。对于莫那霉素，它以相对亲水的簇的形式存在于溶液中，并以这种形式吸附在脂质双层顶部，假设在电势跃变后渗透到双层中之前，吸附的簇会先发生与电势无关的解聚，形成吸附的单体。
