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We are interested in the biophysical properties of the cytoskeleton of eukaryotic cells and how these regulate cell physiology. Cells generate protrusive and contractile forces in response to external chemical and mechanical stimuli and during cell migration. Improper regulation of the mechanical behavior of cells has been linked to a number of diseases, including asthma, cardiac arrhythmia and cancer metastasis.

The varied mechanical behavior of cells is determined by a dynamic and composite polymer network of > 100 proteins called the cytoskeleton. We develop tools to study the dynamic structure and biophysical behavior of macromolecular assemblies at sub-micron length scales to study how cells generate and transmit mechanical forces.

We use high resolution fluorescence microscopy to observe cytoskeletal protein dynamics in living cells and, simultaneously, measure their biophysical properties at micron length scales. By combining dynamic structure with biophysical measurements, we aim to elucidate the origins of the biophysical behavior of these assemblies. We are particularly interested in the biophysical behavior of contractile actomyosin networks and how these regulate how focal adhesions transmit force to the extracellular matrix.

Cytoskeletal material also provides quite a number of interesting problems in soft condensed matter physics. In contrast to traditional flexible polymers or rigid rods, cytoskeletal polymers are semi-flexible and the energy required to bend the filament on micron length scales is comparable to thermal energy. The competition between enthalpic and entropic effects in the dynamics and deformation of semi-flexible networks lead to extremely rich and varied mechanical response of both entangled solutions and chemically cross-linked networks. In the living cell, these networks are driven far from equilibrium by molecular motors and proteins that regulate filament cross-linking and assembly. We study the mechanical behavior of reconstituted networks of purified cytoskeletal proteins in vitro to better develop physical models of the elasticity of these dynamic semi-flexible polymer networks.