Dynamic viscoelasticity of actin networks cross-linked with wild-type and mutant [alpha]-actinin-4
Name
317880004-MIT.pdf
Description
Full printable version
Size
8.49 MB
Format
Adobe PDF
Checksum (MD5)
19a43bfbd84eede53e7d89d69756c7d9
Author(s)
Volkmer Ward, Sabine M
Advisor(s)
David A. Weitz.
Date Issued
2008
Publisher
Massachusetts Institute of Technology
Abstract
The 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.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.
In title on title page, "[alpha]" appears as lower case Greek letter.
Includes bibliographical references (p. 49-52).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Terms of Use
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.
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.
Persistent DSpace Link
