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Title: The physics of free and folded polymers
Author: Craig, A. P.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2006
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This work explores the physics of self-interacting polymer chains, with an eye towards examining their behaviour in a collapsed state and to applying our results to biological systems. We begin with an extension of the classic Edwards model of chain collapse, in which chains have simple point interactions, and treat is by a Gaussian variational technique that allows us to treat chains not far from the θ-point at which they have random chain statistics. Moving from this non-specific chain collapse, we develop a model of an intrinsically curved semi-flexible chain and connect it to the helical conformations preferred by many peptides and other polymers in solution. We continue this examination of “secondary structures” by modifying the Edwards point contact potential to include a directional potential. This directional potential, meant to mimic hydrogen bonding, induces an alignment of the polymer system when it is sufficiently dense (i.e. collapsed) much like the local alignment of a α-helices or β-sheets. We pursue this analogy further by offering scaling arguments about the stability of a purely aligned β-sheet phase, amyloid fibrils, though this work may easily be generalized to include non-peptide polymers. Finally, we extent this approach to consider collapsed polymer chains under extension. We distinguish between cooperatively structured, patterned globules, and disordered, molten collapsed states, and derive different relations for each case before considering networked assemblies of such globules.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available