Mechanical properties of F-actin network

Cells sense, generate and respond to forces in their surroundings through cytoskeletal dynamics. Actin, the most abundant protein found in eukaryotic cells, is organized into various cytoskeletal structures that provide physical support for the cell and play important roles in numerous cellular processes. Assembly of F-actin into higher-order structures is regulated by over 100 actin binding proteins (ABPs). Although extensive measurements to estimate the mechanical properties of ABP/F-actin networks showed that they are nonlinear and viscoelastic, a full understanding of the origin of such fascinating behaviors is lacking. This thesis presents a multi-scale approach to identify the factors that determine the mechanical properties of F-actin networks from the macroscopic level to the single-molecule level. The mechanical properties of F-actin networks were probed by passive and active methods using optical tweezers. For the passive approach the thermal fluctuations of colloidal spheres are monitored to estimate the frequency-dependent complex shear modulus of an F-actin network. In the active approach, the response of an embedded microsphere to a driving force is tracked to obtain the strain-dependent viscoelasticity. The developed methods were applied to F-actin networks cross-linked with various ABPs such as filamin and a -actinin, with and without gelsolin to control filament length. Microstructures of those networks were also characterized in terms of filament length, mesh size, and degree of bundling.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Lee, Hyungsuk

Advisor dc:contributor.advisor

• Roger D. Kamm.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/50588

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/50588