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Title: Design, construction and biophysical applications of optical tweezers
Author: Theofanidou, Eirini
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2004
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The first part of this work is dedicated to technical issues and system developments; the design and construction of an open microscope which forms the base for an optical tweezers set-up, is described. Subsequently the creation of a generic optical tweezers set-up is presented. This set-up was used in combination with two photon fluorescence to investigate the deteriorating of the quality of the trap due to optical aberrations. It is shown that using adaptive optics (i.e. a deformable membrane), the aberrations are partially corrected. Furthermore, it was demonstrated that using the deformable membrane one can achieve the axial-position control of the trapped particle. The same open microscope was used in combination with a ferroelectric liquid crystal spatial light modulator to construct multiple trap tweezers. The fast switching speeds of the ferroelectric device, compared to the conventional nematic systems, is shown to enable very rapid reconfiguration of trap geometries, controlled, high speed particle movement, and the firs tweezers array multiplexing. The second part of the work focuses on biophysical applications. A commercial microscope combined with fluorescence imaging is used to analyse the stretching and unwinding of DNA, as well as DNA condensation. Stretching and unwinding of polymers under flow is a very important phenomenon associated with the rheological properties of dilute polymer solutions. Scaling theory predicts two broad regimes for the overall shape of the deformed DNA molecule: the ‘trumpet’ regime at low flow velocities and a ‘stem and flower’ regime at high flow velocities. I studied the DNA shape at different velocities using optical trapping of single DNA molecules tethered on polystyrene beads. The results show clearly the two theoretically predicted regimes of ‘trumpet’ and ‘stem and flower’.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available