Simonetti, Edoardo;
(2025)
Liquid-microjet photoelectron spectroscopy and dynamics of the photoactive yellow protein chromophore in aqueous solution.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Understanding the way complex environments influence the electronic structure and excited state dynamics of biological chromophores is crucial for uncovering the fundamental mechanisms driving photochemical processes in biological systems. Liquid-microjet photoelectron spectroscopy (LJ-PES) is an indispensable tool for the study of solutes in aqueous environments, as it enables direct measurement of electron binding energies in solution. However, a major challenge of ultraviolet (UV) LJ-PES, which allows the study of solutes at sub-mM concentrations, lies in our limited understanding of inelastic scattering of low energy electrons (<10 eV) in water, hindering the determination of accurate binding energies. The work presented in Chapter 3 describes a systematic investigation of the parameters employed in the modelling of inelastic scattering in aqueous solution. It examines the effect the scattering cross-sections, electron transmission at the liquid-vacuum interface and the concentration depth profiles of solutes on the retrieval of the genuine photoelectron distributions, using water, phenol and phenolate as benchmarks. Exploiting these results, Chapter 4 describes an investigation of the electronic structure of the photoactive yellow protein (PYP) chromophore using X-ray, extreme UV and UV LJ-PES. The first two vertical detachment energies and the adiabatic detachment energy of the chromophore were determined. Additionally, a high-lying resonance responsible for electron ejection into solution and a resonance embedded in the continuum were identified. Chapter 5 describes an investigation of the photochemical dynamics of the PYP chromophore following excitation to its first excited state using with UV LJ-PES. The measurements and analysis revealed that the chromophore moves away from the Franck-Condon region either through solvent relaxation or via rotation around the single bond adjacent to the double bond involved in isomerisation within the protein. Overall the work described in this thesis enhances our ability to interpret UV photoelectron spectra of aqueous solutions and provides new insights into the electronic structure and photochemical dynamics of the PYP chromophore.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Liquid-microjet photoelectron spectroscopy and dynamics of the photoactive yellow protein chromophore in aqueous solution |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/deed.en). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10217637 |
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