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dc.contributor.authorHanke, Felix.en_US
dc.date.accessioned2014-10-21T12:38:40Z
dc.date.available2014-10-21T12:38:40Z
dc.date.issued2007en_US
dc.identifier.otherAAINR27196en_US
dc.identifier.urihttp://hdl.handle.net/10222/54902
dc.descriptionThis thesis develops theoretical aspects of stretching single polymer molecules using an Atomic Force Microscope. Particular emphasis is placed on the difference between controlled force and controlled position modes of the experiment, corresponding to the Gibbs and Helmholtz ensembles in statistical mechanics.en_US
dc.descriptionInitially, an analytic model for conformational transitions in thermodynamic equilibrium is developed and applied to Dextran. The observed force response is fitted, resulting in the two dominant conformers for Dextran, allowing a prediction of the proper thermal equation of state as well as a direct calculation of the observed thermal fluctuations.en_US
dc.descriptionA second part of the thesis deals with the fast stretching of polymer molecules. The results of Transfer Matrix calculations are used in a Master Equation approach to predict fast non-equilibrium effects in polymer stretching. The time scale is fixed by an expansion of the Master Equation, which can be fitted to relaxation time measurements on DNA. The predicted response of a molecule to fast stretching is qualitatively similar to the equilibrium force-extension curve, but occurs at much higher forces. This result is linked to memory effects in the thermal fluctuations of the molecule-cantilever system is much more pronounced in the Helmholtz (constant pulling velocity) regime. A calculation of non-equilibrium molecular relaxation is also presented in this work.en_US
dc.descriptionFollowing the discussions of polymers stretched in and out of thermodynamic equilibrium, the thesis considers the ultimate non-equilibrium process - breaking a single molecule. It is shown how the survival rate of a bond under the application of stress depends on the applied force. Moreover, the potential barrier is calculated analytically for the case of a Morse potential and is used to fit spectra obtained from breaking an ensemble of Terpyridine-Ru2+-Terpyridine complexes. The theory allows the determination of three microscopic parameters: the depth V0 of the unperturbed potential, the attempt frequency A and the width of the unperturbed potential gamma. Finally, the necessity of using data at many different loading rates is discussed and it is shown that these loading rates need to vary at least two orders of magnitude to enable quantitative fitting.en_US
dc.descriptionThesis (Ph.D.)--Dalhousie University (Canada), 2007.en_US
dc.languageengen_US
dc.publisherDalhousie Universityen_US
dc.publisheren_US
dc.subjectPhysics, Molecular.en_US
dc.titleThe mechanical response of macromolecules in and out of equilibrium.en_US
dc.typetexten_US
dc.contributor.degreePh.D.en_US
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