One-photon and upconversion luminescence as tools to detect uranium in the environment and understand uranium-protein interactions

• Main Author: Wilson, Hannah
• Format: Dissertation
• Language: English
• Published: University of Manchester 2022
• Subjects: Actinides; Coiled coils; Environment; Fluorescence; FRET; Inner Filter; Lanthanides; Luminescence; Nanoparticles; Peptides; Proteins; Sensor; Spectroscopy; Upconversion; Uranium

Uranium is a toxic heavy metal, causing biochemical harm to humans and other living organisms if present in significant concentrations. The mechanisms behind this toxicity have been the subject of considerable investigation since the days of the Manhattan Project and remain important today with respect to the safe management of contamination arising from the nuclear energy industry. It is widely acknowledged, however, that there are gaps in understanding, particularly relating to the behaviour of uranium species in complex biological environments and the precise molecular interactions with proteins and other biomolecules. Chapter 1 introduces some fundamental uranium chemistry and photophysics, alongside a brief survey of the current analytical techniques available to monitor uranium in the environment, and of the current understanding with regards to uranium-protein interactions. Chapters 2 and 3 present the successful application of upconverting nanoparticles (UCNPs) to the quantitative detection of aqueous UVIO22+ ions. To the best of our knowledge, this is the first time that such a system has been reliably demonstrated with UCNPs, and likely one of the first UVIO22+ sensors to employ excitation within the near infrared 'biological window'. A brief introduction to the photophysics of upconversion and the wider UCNP field is presented in Chapter 2, alongside results characterising the design and synthesis of suitable nanoparticles. Chapter 3 describes the results of UVIO22+ sensing studies which combine UCNPs with one of three organic dyes: arsenazo-III, Br-PADAP and Br-PAPS. An appendix at the end of this thesis briefly investigates the possibility of luminescence energy transfer between UCNPs and uranyl(VI), in response to literature published during the course of the PhD. Chapters 4 and 5 present complementary studies investigating the interactions of UVIO22+ with a range of de novo coiled coil peptides, synthesised in collaboration with the Peacock group (University of Birmingham). In Chapter 4, the suitability of analytical techniques is assessed with an initial library of peptides; one peptide system (CS1-2) is found to exhibit remarkably bright uranyl emission at room temperature and is therefore subject to further detailed characterisation, with a focus on luminescence spectroscopy. In Chapter 5, two further studies are described, prompted by the results from Chapter 4. The first explores the impact of phosphorylation on peptide-uranyl affinity and luminescence; the second explores the selective complexation of UVIO22+ and Eu3+ within a heterobimetallic coiled coil scaffold, and the possibility of intermetallic energy transfer therein.