| MSB3c | |
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| Paul Janmey |
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| Departments of Physiology, Physics, Bioengineering, University of Pennsylviana |
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| Title | Assembly and mechanics of intermediate filaments |
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| Abstract | One cellular function of intermediate filaments is to provide cells with compliance to small deformations while strengthening them when large stresses are applied. IFs accomplish this mechanical role because of the unusual non-linear elasticity of the gels they form and the very large strains that single IFs can accommodate without breaking. These filaments have persistence lengths less than one micron and form networks with mesh sizes on the same order. Therefore much of the elasticity can be accounted for by entropic models that predict the forces needed to extend the filaments' end-to-end distance. IFs are unique among cytoskeletal filaments in withstanding large deformations. Single filaments can stretch to more than 3 times their initial length before breaking, and gels of IF withstand strains greater than 100% without damage. Even after mechanical disruption of gels formed by crosslinked neuronal IFs, for example, the elastic modulus of these gels rapidly recovers under conditions where gels formed by other cytoskeletal filaments are irreversibly ruptured. Assembly of individual IFs into crosslinked networks occurs in large part due to electrostatic interactions between these highly anionic polyelectrolytes and polycationic ligands The strength and reversibility of these labile crosslinks contributes to network elasticity in a manner that has yet to be thoroughly modeled. Recent studies of IF network rheology and self-assembly by multivalent counterions reveals some of the unique properties of these cytoskeletal elements. These experimental data can help distinguish among different theoretical models for network elasticity of crosslinked semiflexible polymers. |
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| Location | Woodward 3 |
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