Abstract
In an effort to use model fluid membranes for immunological studies, we compared the formation of planar phospholipid bilayers supported on silicon dioxide surfaces with and without incorporation of glycolipids as the antigen for in situ antibody binding. Dynamic light scattering measurements did not differentiate the hydrodynamic volumes of extruded small unilamellar vesicles (E-SUVs) containing physiologically relevant concentrations (0.5–5 mol%) of monosialoganglioside GM1 (GM1) from exclusive egg yolk l-α-phosphatidylcholine (egg PC) E-SUVs. However, quantifiable differences in deposition mass and dissipative energy loss emerged in the transformation of 5 mol% GM1/95 mol% egg PC E-SUVs to planar supported lipid bilayers (PSLBs) by vesicle fusion on thermally evaporated SiO 2, as monitored by the quartz crystal microbalance with dissipation (QCM-D) technique. Compared to the 100 mol% egg PC bilayers on the same surface, E-SUVs containing 5 mol% GM1 reached a ∼12% higher mass and a lower dissipative energy loss during bilayer transformation. PSLBs with 5 mol% GM1 are ∼18% heavier than 100 mol% egg PC and ∼11% smaller in projected area per lipid, indicating an increased rigidity and a tighter packing. Subsequent binding of polyclonal immunoglobulin G anti-GM1 to the PSLBs was performed in situ and showed specificity. The anti-GM1 to GM1 ratios at equilibrium were roughly proportional to the concentrations of anti-GM1 administered in the solution. Fluorescence recovery after photobleaching was utilized to verify the retained, albeit reduced lateral fluidity of the supported membranes. Five moles percentage of GM1 membranes (GM1 to PC ratio ∼1:19) decorated with 1 mol% N-(Texas Red sulfonyl)-1,2-dihexadecanoyl- sn-glycerol-3-phosphoethanolamine (Texas Red DHPE) exhibited an approximately 16% lower diffusion coefficient of 1.32 ± 0.06 μm 2/s, compared to 1.58 ± 0.04 μm 2/s for egg PC membranes without GM1 ( p < 0.01). The changes in vesicle properties and membrane lateral fluidity are attributed to the interactions of GM1 with itself and GM1 with other membrane lipids. This system allows for molecules of interest such as GM1 to exist on a more biologically relevant surface than those used in conventional methods such as ELISA. Our analysis of rabbit serum antibodies binding to GM1 demonstrates this platform can be used to test for the presence of anti-lipid antibodies in serum.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.