Seminars and Events
Nanostructures, Surfaces, and Coatings and Molecular Astrophysics
Coordinator: Rául Gago
18 January 2019, 16:00 h. Sala de Seminarios, 182
Probing the cell membrane organization in living cells using Atomic Force Microscopy
Andra C. Dumitru
Louvain Institute of Biomolecular Science and Technology, Belgium
Red blood cells (RBCs) feature remarkable mechanical properties while navigating through microcirculation vessels and during spleen filtration. An unusual combination of plasma membrane (PM) and cytoskeleton physical properties allows RBCs to undergo extensive deformation. Our goal is to get a better understanding of key aspects regarding the role of submicrometric assemblies in the PM machinery, such as their stabilization mechanism and their role in cell elasticity. To this aim, we use multifunctional high-resolution force-distance based atomic force microscopy (FD-based AFM), which allows to simultaneously map nanoscale structural features of the cell surface along with physical and biological properties. Our multiparametric approach reveals spatially correlated structural and mechanical heterogeneities at the surface of living cells, while correlated AFM-fluorescence imaging is used to identify sub-micrometric sphingomyelin-enriched lipid domains of variable stiffness at the red blood cell surface. Our experiments provide novel insights into the interplay between nanoscale organization of RBCs plasma membrane and their nanomechanical properties. To unambiguously identify lipid-enriched domains on the RBC surface and to correlate them with local nanomechanical heterogeneities, we developed a method to graft a toxin fragment (either lysenin or theta-D4) to the AFM tip. We were able to image and specifically probe cholesterol- and sphingomyelin-enriched domains within DOPC bilayers and on the surface of living cells at high-resolution. The combination of AFM topography and nanomechanical mapping with specific probes for molecular recognition of lipids represents a novel approach to identify lipid-enriched domains in synthetic bilayers and offers a unique perspective to directly observe lipid assemblies in cells.