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dc.contributor.advisorDavid A. Weitz.en_US
dc.contributor.authorVolkmer Ward, Sabine Men_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Physics.en_US
dc.date.accessioned2009-04-29T17:40:57Z
dc.date.available2009-04-29T17:40:57Z
dc.date.copyright2008en_US
dc.date.issued2008en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/45430
dc.descriptionThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.en_US
dc.descriptionIn title on title page, "[alpha]" appears as lower case Greek letter.en_US
dc.descriptionIncludes bibliographical references (p. 49-52).en_US
dc.description.abstractThe actin cross-linker [alpha]-actinin-4 has been found indispensable for the structural and functional integrity of podocytes; deficiency or alteration of this protein due to mutations disturbs the cytoskeleton and results in kidney disease. This thesis presents rheological studies of in vitro actin networks cross-linked with wild-type and mutant a-actinin-4, which provide insight into the effect of the cross-linker on the mechanical properties of the networks. The frequency dependent viscoelasticity of the actin/[alpha]-actinin-4 networks is characterized by an elastic plateau at intermediate frequencies, and relaxation towards fluid properties at low frequencies. Since the elastic plateau is a consequence of cross-linking, its modulus increases with the [alpha]-actinin-4 concentration. Networks with wild-type and mutant a-actinin-4 differ significantly in their time scales: The relaxation frequencies of networks with the mutant cross-linker are an order of magnitude lower than that with the wild-type, suggesting a slower dissociation rate of mutant [alpha]-actinin-4 from actin, consistent with a smaller observed equilibrium dissociation constant. This difference can be attributed to an additional binding site, which is exposed as a result of the mutation. An increase in the temperature of networks with mutant [alpha]-actinin-4 appears to return the viscoelasticity to that of networks cross-linked by the wild-type. Moreover, the temperature dependence of the relaxation frequencies follows the Arrhenius equation for both cross-linkers. These results strongly support the proposition that the macroscopic relaxation of the networks directly reflects the microscopic dissociation rates of their constituents.en_US
dc.description.statementofresponsibilityby Sabine M. Volkmer Ward.en_US
dc.format.extent52 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.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.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectPhysics.en_US
dc.titleDynamic viscoelasticity of actin networks cross-linked with wild-type and mutant [alpha]-actinin-4en_US
dc.typeThesisen_US
dc.description.degreeS.M.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Dept. of Physics.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Physics
dc.identifier.oclc317880004en_US


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