Seantier Bastien, Kasemo Bengt
Chalmers University of Technology, Chemical Physics Group, Applied Physics, Fysikgränd 3, Gothenburg, Sweden.
Langmuir. 2009 May 19;25(10):5767-72. doi: 10.1021/la804172f.
We have used the quartz crystal microbalance with dissipation monitoring (QCM-D) technique to investigate how mono- and divalent cations influence the formation of supported (phospho)lipid bilayers (SPB, SLB), occurring via deposition of nanosized palmitoyloleoyl phosphatidylcholine (POPC) vesicles on a SiO2 support. This process is known to proceed via initial adsorption of intact vesicles until a critical surface coverage is reached, where the combination of vesicle-surface and vesicle-vesicle interaction causes the vesicles to rupture. New vesicles then rupture and the lipid fragments fuse until a final continuous bilayer is formed. We have explored how this process and the critical coverage are influenced by different mono- and divalent ions and ion concentrations, keeping the anions the same throughout the experiments. The same qualitative kinetics is observed for all cations. However, different ions cause quite different quantitative kinetics. When compared with monovalent ions, even very small added concentrations of divalent cations cause a strong reduction of the critical coverage, where conversion of intact, adsorbed vesicles to bilayer occurs. This bilayer promoting effect increases in the order Sr2+<Ca2+<Mg2+. Monovalent cations exhibit a much weaker but similar effect in the order Li+>Na+>K+. The results are of practical value for preparation of lipid bilayers and help shed light on the role of ions and on electrostatic effects at membrane surfaces/interfaces.
我们使用了具有耗散监测功能的石英晶体微天平（QCM-D）技术，来研究一价和二价阳离子如何影响支撑（磷酸）脂质双层（SPB，SLB）的形成，该过程是通过将纳米尺寸的棕榈酰油酰磷脂酰胆碱（POPC）囊泡沉积在SiO2载体上实现的。已知这个过程是通过完整囊泡的初始吸附进行的，直到达到临界表面覆盖率，此时囊泡-表面和囊泡-囊泡相互作用的结合会导致囊泡破裂。然后新的囊泡破裂，脂质片段融合，直到形成最终的连续双层。我们研究了这个过程和临界覆盖率如何受到不同的一价和二价离子以及离子浓度的影响，在整个实验过程中保持阴离子相同。所有阳离子都观察到相同的定性动力学。然而，不同的离子会导致截然不同的定量动力学。与一价离子相比，即使添加非常低浓度的二价阳离子也会导致临界覆盖率大幅降低，即完整的吸附囊泡转化为双层的覆盖率降低。这种双层促进作用按Sr2+<Ca2+<Mg2+的顺序增加。一价阳离子表现出弱得多但类似的作用，顺序为Li+>Na+>K+。这些结果对于脂质双层的制备具有实际价值，并有助于阐明离子的作用以及膜表面/界面处的静电效应。
