Surface Potential of a Planar Charged Lipid-Water Interface. What Do Vibrating Plate Methods, Second Harmonic and Sum Frequency Measure?
Surface Potential of a Planar Charged Lipid-Water Interface. What Do Vibrating Plate Methods, Second Harmonic and Sum Frequency Measure?
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DOI：
10.1021/acs.jpclett.8b02093
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发表时间：
2018-10-04
影响因子：
5.7
通讯作者：
Bonn, M.
中科院分区：
文献类型：
--
作者：
Dreier, L. B.;Bemhard, C.;Bonn, M.
界面电势是影响膜上电化学反应和生物分子相互作用的重要参数。因此，更深入地理解测量与表面势有关的量的不同方法具有重大的科学和技术意义。我们使用具有不同电荷密度的脂单分子膜，并彻底比较了用振动板电容法和二次谐波发生光谱进行的表面电位测量的结果。作为表面电荷的函数，这两种技术提供了非常不同的结果。利用和频发生光谱提供的脂链、脂头基团和界面水的分子信息，我们理清了不同技术对表面电势的不同贡献。我们的结果表明，这两种不同的途径是由不同的分子部分和效应所主导的。虽然斑点方法的响应形状作为电荷密度的函数是由脂类羰基控制的，但倍频结果包含了界面水分子、脂类和超瑞利散射的贡献。
The interfacial electrical potential is an important parameter influencing, for instance, electrochemical reactions and biomolecular interactions at membranes. A deeper understanding of different methods that measure quantities related to the surface potential is thus of great scientific and technological relevance. We use lipid monolayers with varying charge density and thoroughly compare the results of surface potential measurements performed with the vibrating plate capacitor method and second harmonic generation spectroscopy. The two techniques provide very different results as a function of surface charge. Using the molecular information on lipid alkyl chain, lipid headgroup, and interfacial water provided by sum frequency generation spectroscopy, we disentangle the different contributions to the surface potential measured by the different techniques. Our results show that the two distinct approaches are dominated by different molecular moieties and effects. While the shape of the SPOT method response as a function of charge density is dominated by the lipid carbonyl groups, the SHG results contain contributions from the interfacial water molecules, the lipids and hyper-Rayleigh scattering.