Publication Date

2013-04-25

Availability

Open access

Embargo Period

2013-04-25

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Physics (Arts and Sciences)

Date of Defense

2013-04-10

First Committee Member

Joshua L. Cohn

Second Committee Member

Neil F. Johnson

Third Committee Member

Fulin Zuo

Fourth Committee Member

Kevin Huffenberger

Fifth Committee Member

Vincent T. Moy

Abstract

Microtubules are cytoskeletal protein polymers orchestrating a host of important cellular functions including, but not limited to, cell support, cell division, cell motility and cell transport. In this thesis, we construct a toy-model of the microtubule lattice composed of vector Ising spins representing tubulin molecules, the building block of microtubules. Nearest-neighbor and next-to-nearest neighbor interactions are considered within an anisotropic dielectric medium. As a consequence of the helical topology, we observe that certain spin orientations render the lattice frustrated with nearest neighbor ferroelectric and next-to-nearest neighbor antiferroelectric bonds. Under these conditions, the lattice displays the remarkable property of stabilizing certain spin patterns that are robust to thermal fluctuations. We model this behavior in the framework of a generalized Ising model known as the J1 - J2 model and theoretically determine the set of stable patterns. Employing Monte-Carlo methods, we demonstrate the stability of such patterns in the microtubule lattice at human physiological temperatures. This suggests a novel biological mechanism for storing information in living organisms, whereby the tubulin spin (dipole moment) states become information bits and information gets stored in microtubules in a way that is robust to thermal fluctuations.

Keywords

microtubule; generalized Ising model; frustration; persistence of patterns; robustness to thermal fluctuations

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