Alexandria Digital Research Library

Single molecule studies of polyelectrolyte structure

Berezney, John Paul
Degree Grantor:
University of California, Santa Barbara. Materials
Degree Supervisor:
Omar A. Saleh
Place of Publication:
[Santa Barbara, Calif.]
University of California, Santa Barbara
Creation Date:
Issued Date:
Biophysics, Physics, and Materials science
Magnetic tweezers
Locked nucleic acid
Hyaluronic acid
Branched polymer
Dissertations, Academic and Online resources
Ph.D.--University of California, Santa Barbara, 2016

As our understanding of the physics of soft matter grows, the materials we design become more complex. This complexity can be understood through new length scales which describe the system. We are motivated to characterize these lengths to understand how material properties emerge from constituent components. To this end, we employ the magnetic tweezers to resolve structural changes in polymer configuration through measurements of elasticity. We demonstrate this technique can be extended to polymers with stiffness greater than has been previously established. First, through direct measurements of the low force crossover to the Pincus blob regime, we measure the bending rigidity of hyaluronic acid. By varying the ionic strength, we show the stiffness of this molecule varies linearly with the Debye length as predicted by Barrat-Joanny. Next, we show magnetic tweezers may be used to characterize polymers with more complex architectures.

Here, we present the first measurements of comb polymers using magnetic tweezers and characterize the effects of branching in several force regimes. At the lowest forces, we develop the effective exponent analysis technique which estimates Pincus blob regime crossover behavior when such transitions are not directly resolvable. At higher forces, we show predominant ideal chain models such as the wormlike chain and freely jointed chain are not sufficient to describe the behavior of densely branched comb polymers. Instead we introduce a modified wormlike chain model which incorporates the internal tension caused by neighboring branch interactions. Together, these measurements show the structure and behavior of polymers is not uniform at all length scales and models which treat polymers homogenously over many length scales may fail to fully capture observed phenomena.

Finally, we present a new method of functionalizing DNA using triplex-forming locked nucleic acids and characterize their stability and specificity with magnetic tweezers. This functionalization approach offers potential for the creation of new materials as well as widening the experimental possibilities for single molecule manipulation instruments.

Physical Description:
1 online resource (132 pages)
UCSB electronic theses and dissertations
Catalog System Number:
Inc.icon only.dark In Copyright
Copyright Holder:
John Berezney
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