Phase Transitions and the Principle of Detailed Balance in Living Systems
The Center for Theoretical Biological Physics PRESENTS Dr. Fred MacKintosh Abercrombie Professor of Chemical & Biomolecular Engineering Professor of Physics & Astronomy Center for Theoretical Biological Physics Rice University Abstract: The mechanics of cells and tissues are largely governed by scaffolds of filamentous proteins that make up the cytoskeleton, as well as extracellular matrices. Evidence is emerging that such networks can exhibit rich mechanical phase behavior. A classic example of a mechanical phase transition was identified by Maxwell for macroscopic engineering structures: networks of struts or springs exhibit a continuous, second-order phase transition at the isostatic point, where the number of constraints imposed by connectivity just equals the number of mechanical degrees of freedom. We will present recent theoretical predictions and experimental evidence for mechanical phase transitions in both synthetic and biopolymer networks. Living systems typically operate far from thermodynamic equilibrium, which affects both their dynamics and mechanical response. Due to enzymatic activity at the molecular scale, living systems characteristically violate detailed balance, a fundamental principle of equilibrium statistical mechanics. We discuss violations of detailed balance at the meso-scale of whole cells. Bio: Fred MacKintosh received his PhD in Theoretical Physics from Princeton University in 1989. Following a two-year postdoc at Exxon Research and Engineering, he joined the Physics faculty at the University of Michigan in 1991. In 2001, Fred joined the Physics Faculty of the Vrije Universiteit in Amsterdam as Professor of Theoretical Complex Systems. Since mid-2016, Fred is Abercrombie Professor of Chemical & Biomolecular Engineering, with joint appointments also in Chemistry and in Physics & Astronomy. He is also a member of the CTBP.
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