278439 Carbon Nanotubes As Mechanical Probes of Equilibrium and Non-Equilibrium Biopolymer Networks

Tuesday, October 30, 2012: 9:00 AM
Butler West (Westin )
Nikta Fakhri1, Matteo Pasquali2, Frederick C. MacKintosh3 and Christoph Schmidt1, (1)Third Institute of Physics-Biophysics, University of Göttingen, Göttingen, Germany, (2)Chemical and Biomolecular Engineering, Rice University, Houston, TX, (3)Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, Netherlands

A biological cell is a soft material with complex mechanical properties arising from a composite and highly dynamic intracellular protein polymer network (consisting of actin, microtubules and intermediate filaments). Equilibrium soft materials show strain fluctuations due to random thermal stresses; living biological materials exhibit, in addition, non-equilibrium, internal stress fluctuations generated by active force generators (e.g. motor proteins). Understanding the dynamic properties of such heterogeneous and structurally complex networks requires probes that span length-scales from nanometers to micrometers.

We use single-walled carbon nanotubes (SWNTs) as multi-scale micro-probes. SWNTs are nanometer-diameter hollow carbon filaments with micrometer lengths and a tunable bending stiffness. Their persistence length varies between 20 – 100 microns. Therefore they show significant thermal fluctuations on the micron scale.

We study the motion of individual SWNTs in reconstituted actin (equilibrium) and actin-myosin (non-equilibrium) networks by near infrared fluorescence microscopy. At long times, SWNTs reptate in the networks. At short times SWNTs can sample the spectrum of local stresses in both equilibrium and non-equilibrium networks. We can calculate complex shear moduli from recorded fluctuations and observed power-law scaling in equilibrium actin networks. In the non-equilibrium networks we observed strong local shape fluctuations reflecting the activity of the molecular motors.


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See more of this Session: Polymer Networks and Gels I
See more of this Group/Topical: Materials Engineering and Sciences Division