| Thu June 12th 2014 16:00 – 17:00 HR W121 | Seminar | Living soft matter Gijsje Koenderink |
Details:Driving forces such as those due to an electric field or shear can drive soft matter such as colloidal suspensions and polymer networks into fascinating non‐equilibrium patterns, such as banded or ordered steady states. By contrast, living cells naturally exhibit a unique form of internal driving in the form of chemomechanical activity. A prominent example is the cytoskeleton, a meshwork of protein polymers and force‐generating motor proteins that constitutes the scaffold of cells. The cytoskeleton is responsible for driving vital cellular functions such as growth, division, and movement. In this talk, I will show examples of our research on active cytoskeletal polymer gels. Specifically, we reconstituted a simplified model system of the actin cortex, which lies underneath the cell membrane and drives shape changes by means of myosin motors. Using a minimal system of purified proteins, we could show how myosin motors and actin filaments collectively self‐organize into force‐generating arrays. We discovered that motors contract actin networks only above a sharp threshold in crosslink density, corresponding to a connectivity percolation transition. I will also briefly discuss video particle tracking microrheology experiments on active networks which demonstrate how motor proteins generate non‐thermal fluctuations. We are currently developing microfluidic droplet techniques to encapsulate the actomyosin networks into giant unilamellar liposomes and thus build ‘minimal cells’. | ||
