Tuning the Mobility Coupling of Quaternized Polyvinylpyridine and Anionic Phospholipids in Supported Lipid Bilayers

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• 作者：Xiaojun Shi ; Xiaosi Li ; Megan J. Kaliszewski ; Xiaodong Zhuang ; Adam W. Smith
• 刊名：Langmuir
• 出版年：2015
• 出版时间：February 10, 2015
• 年：2015
• 卷：31
• 期：5
• 页码：1784-1791
• 全文大小：417K
• ISSN：1520-5827

文摘

Binding of biomacromolecules to anionic lipids in the plasma membrane is a common motif in many cell signaling pathways. Previous work has shown that macromolecules with cationic sequences can form nanodomains with sequestered anionic lipids, which alters the lateral distribution and mobility of the membrane lipids. Such sequestration is believed to result from the formation of a lipid鈥搈acromolecule complex. To date, however, the molecular structure and dynamics of the lipid鈥損olymer interface are poorly understood. We have investigated the behavior of polycationic quaternized polyvinylpyridine (QPVP) on supported lipid bilayers doped with phosphatidylserine (PS) or phosphatidylinositol phosphate (PIP) lipids using time-resolved fluorescence microscopy, including pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). PIE-FCCS is a dual-color fluorescence spectroscopy that translates fluctuations in fluorescence signal into a measurement of diffusion and colocalization. By labeling the polymer and lipids, we investigated the adsorption-induced translational mobility of lipids and systematically studied the influence of lipid charge density and solution ionic strength. Our results show that alteration of anionic lipid lateral mobility is dependent on the net charge of the lipid headgroup and is modulated by the ionic strength of the solution, indicating that electrostatic interactions drive the decrease in lateral mobility of anionic lipids by adsorbed QPVP. At physiological salt concentration we observe that the lipid lateral mobility is weakly influenced by QPVP and that there is no evidence of stable lipid鈥損olymer complexes.