Mizuno, DaisukeDaisukeMizunoTardin, CatherineCatherineTardinSchmidt, ChristophChristophSchmidtMacKintosh, F. C.F. C.MacKintosh2017-09-072017-09-072007https://resolver.sub.uni-goettingen.de/purl?gro-2/1071Cells both actively generate and sensitively react to forces through their mechanical framework, the cytoskeleton, which is a nonequilibrium composite material including polymers and motor proteins. We measured the dynamics and mechanical properties of a simple three-component model system consisting of myosin II, actin filaments, and cross-linkers. In this system, stresses arising from motor activity controlled the cytoskeletal network mechanics, increasing stiffness by a factor of nearly 100 and qualitatively changing the viscoelastic response of the network in an adenosine triphosphate-dependent manner. We present a quantitative theoretical model connecting the large-scale properties of this active gel to molecular force generation.journal_article10.1126/science.1134404172349460002435354000403143545