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Coupled Effects of Mechanics, Geometry, and Chemistry on Bio-Membrane Behavior


Giang, Ha Thanh (2013) Coupled Effects of Mechanics, Geometry, and Chemistry on Bio-Membrane Behavior. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/BVSK-K782.

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Lipid bilayer membranes are models for cell membranes--the structure that helps regulate cell function. Cell membranes are heterogeneous, and the coupling between composition and shape gives rise to complex behaviors that are important to regulation. This thesis seeks to systematically build and analyze complete models to understand the behavior of multi-component membranes.

We propose a model and use it to derive the equilibrium and stability conditions for a general class of closed multi-component biological membranes. Our analysis shows that the critical modes of these membranes have high frequencies, unlike single-component vesicles, and their stability depends on system size, unlike in systems undergoing spinodal decomposition in flat space. An important implication is that small perturbations may nucleate localized but very large deformations. We compare these results with experimental observations.

We also study open membranes to gain insight into long tubular membranes that arise for example in nerve cells. We derive a complete system of equations for open membranes by using the principle of virtual work. Our linear stability analysis predicts that the tubular membranes tend to have coiling shapes if the tension is small, cylindrical shapes if the tension is moderate, and beading shapes if the tension is large. This is consistent with experimental observations reported in the literature in nerve fibers. Further, we provide numerical solutions to the fully nonlinear equilibrium equations in some problems, and show that the observed mode shapes are consistent with those suggested by linear stability. Our work also proves that beadings of nerve fibers can appear purely as a mechanical response of the membrane.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:lipid bilayer, membrane, stability, heterogeneous
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bhattacharya, Kaushik
Thesis Committee:
  • Lapusta, Nadia (chair)
  • Ravichandran, Guruswami
  • Phillips, Robert B.
  • Bhattacharya, Kaushik
Defense Date:30 May 2013
Record Number:CaltechTHESIS:06062013-102758695
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7851
Deposited By: Ha Giang
Deposited On:06 Jun 2013 22:43
Last Modified:04 Oct 2019 00:02

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