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Title: The assembly and artificial fossilisation of novel complex protocells
Author: Fothergill, James Thomas
ISNI:       0000 0004 6057 8517
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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This thesis describes work that was undertaken to investigate the design of novel protocellular systems based on simple, positively charged polydiallyldimethylammonium chloride (PDDA)/adenosine triphosphate (ATP) or negatively charged PDDA/polyacrylic acid (PAA) coacervate phases. Coacervate phases were stabilised by encapsulation within a colloidosome formed from partially hydrophobised silica nanoparticles. The coacervate core colloidosomes were assembled via the formation of a Pickering emulsion, in which the coacervate bulk phase was suspended in a continuous phase of anhydrous dodecane. The colloidosomes were transferred out of the dodecane and into alternative solvents (acetone, ethanol and water) by cross-linking the colloidal particles with tetra methyl orthosilicate. The silica microstructures that were formed when the PDDA/PAA coacervate phase was used as the template had a homogeneous core, which was solidified throughout by the condensation of silica. Occasionally oil droplets were able to ingress into the coacervate phase, however they remained in close proximity to the coacervate/oil interface. Destabilisation of the Pickering emulsion interface was achieved by charge matching the positive PDDA/ATP coacervate phase with the negatively charged silica nanoparticles. This lead to significant ingress of oil droplets throughout the silica microstructures. The structures with complex interiors were characterised by a range of microscopy and X-ray tomographic techniques. Separately, photo active chloroplasts were extracted from Spinacia oleracea leaves into phosphate buffer, and then incorporated into coacervate microdroplets in aqueous suspensions. The activity of the chloroplasts within the coacervates was characterised by spectroscopic tracking of the reduction of the redox dye 2,6-dichorophenolindophenol from its blue form to its colourless form. A comparison of the stability and activity of the chloroplasts before and after sequestration into the coacervates was performed. Finally, artificial fossilisation experiments were attempted using a hydrothermal bomb or cold seal press on protocells formed from FMOC-tyrosine hydro gelled vesicles, yeast cells and the coacervate core microstructures. These systems were analysed by electron microscopy to check for evidence of the formation of microfossils.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available