On Thursday, October 14, 2004, 4:00 PM Barus & Holley (Room 190) John Crocker (UPenn) presented a talk entitled:

"Mechanics of the cytoskeleton: the actin model and extensible cross-links"

as part of the Seminar Series

"Frontiers in the Interaction Between Physics and Biology"

Abstract:

While biologists have long expected the mechanical response of cells to resemble that of cross-linked networks of the biopolymer F-actin, careful experiments on both systems have consistently reported qualitatively different behavior.  We probe the mechanical response of several types of cultured cells over a wide frequency range using four different methods. Taken together, our data strongly resemble the complicated frequency and length-scale dependent response of purified F-actin, but shifted to significantly higher stiffness and frequency.  The low frequency response of cells has an interesting power-law fluid behavior, that we describewith a simple model of a network cross-linked by proteins having repeated domains that reversibly unfold in response to tension. These results constrain current engineering models of cell mechanics, and bode well for a future model based on the polymer physics of cells' molecular constituents.
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