The unique composition and dynamic nature of biological membranes enables phenomena such as formation of transient domains, assembly of protein complexes, and local changes in mechanical properties. For characterization of fundamental aspects of cellular membranes, the biomimetic supported lipid bilayer (SLB) presents a stable, well-defined platform for experimentation. However, the underlying support dampens undulations and fluctuations of the membrane. Softening the interactions by polymer cushions can be beneficial for some applications. Here, we discuss two <i>in situ </i>methods of tuning membrane structure, lipid mobility, and mechanics in polyacrylic acid (PAA)-cushioned SLBs: (i) By changing environmental pH and (ii) by specific binding of streptavidin protein to the surface of the lipid bilayer. The PAA cushion is pH responsive and deprotonates and swells under alkaline conditions. Neutron reflectivity and fluorescence recovery after photobleaching (FRAP) reveal that lipid mobility diminishes when the PAA cushion is collapsed (pH&lt;6), but is restored when the cushion is swollen. Under alkaline conditions, the supported membrane is still conformal to the cushion, but the interaction is weakened.  We find that binding of streptavidin to a gel-phase PAA-cushioned bilayer stiffens the membrane and reduces undulations on the swollen cushion, offering insight into mechanical responses of lipid bilayers to potential stimuli in biological settings.

<i>In situ</i> methods for tuning membrane structure and lipid mobility in polyacrylic acid-cushioned supported lipid bilayers

255th National Meeting (2018)

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In situ methods for tuning membrane structure and lipid mobility in polyacrylic acid-cushioned supported lipid bilayers