The diphenylalanine (FF) dipeptide is the core recognition motif of the Alzheimer’s amyloid beta (Aß) polypeptide, as well as being important in other amyloidogenic proteins. The Aß polypeptide self assembles to form fibrils and these fibrils are found in the brains of patients with Alzheimer’s disease. FF itself is also known to self-assemble to form fibres and there has been much interest in the FF motif since Reches and Gazit made this observation. The structures it forms are biocompatible and have a high aspect ratio. Under different conditions of humidity and concentration it can form various morphologies such as nanovesicles and ribbons. Despite the great interest in this area, the self-assembly mechanism of these fibres is not known. The motivation throughout this work has been to understand the assembly of the elongated FF fibres in order to be able to control it for the variety of applications that have been suggested. Several experimental and theoretical techniques were used to this end. Molecular and metadynamics simulations were employed to investigate the early stages of the fibres assembly. Optical spectrocopy was used to investigate their assembly kinetics and mechanism in situ. New linear dichroism (LD) methods were developed in order to study the FF fibres which grow into large rigid structures. A new electronic LD sequencer was created which made it possible to automate kinetics measurements over long periods of time, and a new capillary was designed and built which could be cleaned more thoroughly than the previous models. These experiments showed that FF fibres assemble by nucleation driven assembly, with secondary nucleation taking place. They also showed that 40 °C is an important temperature in the onset of fibre formation. Electron and optical microscopy were used to quantify the heterogeneity of the fibres and to observe their growth in real time. It was found that the fibres were more heterogenous than had previously been reported. The results of these experiments elucidated new information about the characteristics and the self-assembly of FF fibres, as well as developed techniques in order to probe them, and similar biological fibres, further.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:682889 |
| Date | January 2015 |
| Creators | Montgomery, Caroline Beryl |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/77370/ |
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