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Direct Measurement of Charge Reversal on Lipid Bilayers Using Heterodyne-Detected Second Harmonic Generation Spectroscopy.
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-01-21 , DOI: 10.1021/acs.jpcb.9b09341
HanByul Chang 1 , Paul E Ohno 1 , Yangdongling Liu 1 , Emilie H Lozier 1 , Naomi Dalchand 1 , Franz M Geiger 1
Affiliation  

We report the detection of charge reversal induced by the adsorption of an aqueous cationic polyelectrolyte, poly(allylamine hydrochloride) (PAH), to supported lipid bilayers (SLBs) used as idealized model biological membranes. Through the use of an α-quartz reference crystal, we quantify the total interfacial potential at the interface in absolute units using heterodyne-detected second harmonic generation (HD-SHG) as an optical voltmeter. This quantification is made possible by isolating the phase-shifted potential-dependent third-order susceptibility from other contributions to the total SHG response. We detect the sign and magnitude of the surface potential and the point of charge reversal at buried interfaces without prior information or complementary data. Isolation of the second-order susceptibility contribution from the overall SHG response allows us to directly characterize the Stern and diffuse layers over single-component SLBs. We apply the method to SLBs formed from three different zwitterionic lipids having different gel-to-fluid phase transition temperatures (Tm's). We determine whether the surface potential changes with the physical phase state (gel, transitioning, or fluid) of the SLB. Furthermore, we incorporate 20% of negatively charged lipids to the zwitterionic SLB to investigate how the surface potential and the second-order nonlinear susceptibility χ(2) change with surface charge.

中文翻译:

使用异戊二烯检测的第二谐波发生光谱法直接测量脂质双层的电荷逆转。

我们报告了检测到的电荷反转的检测,该电荷反转是通过将水性阳离子聚电解质,聚(烯丙胺盐酸盐)(PAH)吸附到支持的脂质双层(SLB)用作理想模型生物膜而引起的。通过使用α石英参考晶体,我们使用外差检测到的二次谐波生成(HD-SHG)作为光电电压表,以绝对单位对界面上的总界面电势进行了量化。通过将相移后的电位相关的三阶磁化率与对总SHG响应的其他贡献隔离开来,可以实现这种量化。我们在没有先验信息或补充数据的情况下,检测了掩埋界面的表面电势的符号和大小以及电荷反转点。从整体SHG响应中分离出二阶磁化率影响,使我们能够直接表征单组分SLB上的船尾和扩散层。我们将该方法应用于由三种不同的两性离子脂质形成的SLB,它们具有不同的凝胶-流体相变温度(Tm)。我们确定表面电位是否随SLB的物理相态(凝胶,过渡或流体)而变化。此外,我们将带负电荷的20%的脂质掺入两性离子SLB中,以研究表面电势和二阶非线性磁化率χ(2)随表面电荷的变化。我们将该方法应用于由三种不同的两性离子脂质形成的SLB,它们具有不同的凝胶-流体相变温度(Tm)。我们确定表面电位是否随SLB的物理相态(凝胶,过渡或流体)而变化。此外,我们将带负电荷的20%的脂质掺入两性离子SLB中,以研究表面电势和二阶非线性磁化率χ(2)随表面电荷的变化。我们将该方法应用于由三种不同的两性离子脂质形成的SLB,它们具有不同的凝胶-流体相变温度(Tm)。我们确定表面电位是否随SLB的物理相态(凝胶,过渡或流体)而变化。此外,我们将带负电荷的20%的脂质掺入两性离子SLB中,以研究表面电势和二阶非线性磁化率χ(2)随表面电荷的变化。
更新日期:2020-01-22
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