The effect of light on plants is fundamental to our understanding of the biological world. Photo-activated processes within botanical cells are controlled by two distinct colours; red light provides the energy required for photosynthesis, and blue light stimulates responses of the cell (growth, stomatal opening, etc.) necessary for biological progression. The key step in blue-light controlled processes has recently been determined to be the formation of a covalent bond between a tightly-bound molecule of flavin and a conserved cysteine residue within a photosensitive protein domain, which causes a physical change to the protein structure upon irradiation. This research was undertaken to examine light-stimulated covalent bond formation in phototropic proteins using two approaches. Firstly, two analogues of riboflavin (5-deazariboflavin and 1-deazariboflavin) were chemically synthesised, converted to the appropriate cofactor form (flavin mononucleotide; FMN), and incorporated into the photosensitive domain. The results of this were startling; while 1-deazaFMN inactivated the photosensitive domain to all wavelengths of light, 5-deazaFMN allowed control of the domain’s behaviour using two separate wavelengths of light, creating a biophotonic nanoswitch. The second approach was based upon mutagenesis of the amino acid responsible for bond formation, introducing several alternative residues in place of the reactive cysteine. All mutants were found to be inactive to irradiation (including those incorporating either of the deazaFMN analogues), providing further evidence to support the current “radical pair” mechanism of photoadduct formation. During the synthesis of the flavin analogues, several reactions were found to be inefficient, and a large number of alternative reactions were studied. Additionally, a new route to several flavin analogues was devised and tested, and while unsuccessful, provides a foundation upon which to base a future examination of their synthesis. Finally, the synthesis of a novel riboflavin analogue (5-deaza-8-demethyl-riboflavin) was completed, allowing comparison with the synthesis of 5-deazariboflavin.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:611053 |
| Date | January 2014 |
| Creators | Wood, Andrew Craig |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/60779/ |
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