We report the formation of lipid membranes supported by a soft polymeric cushion of polydopamine. First, 20 nm thick polydopamine films were formed on mica substrates. Atomic force microscopy imaging indicated that these films were also soft with a surface roughness of 2 nm under hydrated conditions. A zwitterionic phospholipid bilayer was then deposited on the polydopamine cushion by fusion of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) vesicles. Polydopamine films preserved the lateral mobility of the phospholipids as shown by fluorescence microscopy recovery after photobleaching (FRAP) experiments. Diffusion coefficients of ~5.9 and 7.2 µm2 s−1 were respectively determined for DMPC and DOPC at room temperature, values which are characteristic of lipids in a free standing bilayer system.
This nuclear plasticity, measured as projected nuclear area fluctuations, showed a non-monotonous relation to actin polymerization state. Also, myosin contractility was determined to be necessary for such nucleus plasticity. The effect of cytoskeletal organization and their active forces on chromatin plasticity was further quantified by tracking the dynamics of condensed chromatin regions, which showed increased dynamics corresponding to enhanced nuclear plasticity. In summary, using cells of defined geometries to specify cytoskeletal organization, our work demonstrates the role of active cytoskeletal forces in regulating nuclear and chromatin plasticity.
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