Robertson, Kate; (2024) Ultrafast Dynamics of Biologically Active Chromophores and their Building Blocks in Aqueous Solution. Doctoral thesis (Ph.D), UCL (University College London).

Preview

Text Robertson_10198422_PhD_thesis_final_sigs_removed.pdf Download (30MB) | Preview

Abstract

Understanding photochemical dynamics of biomolecules and their building blocks in aqueous environments is crucial for advancing our comprehension of biological processes such as photooxidation and luminescence. This understanding is essential not only for unraveling fundamental mechanisms but also for the rational design of new biotechnologies. This thesis presents studies of the excited state dynamics of molecules relevant to biology, providing insights that could aid fundamental understanding and practical applications. The first results are presented in Chapter 3 which presents an investigation of the photooxidation dynamics of phenolate, a molecular motif found in many biochromophores. Photooxidation is integral to a range of biological processes, such as the photocycle of photoactive proteins, yet the mechanism of electron emission in phenolate, had been disputed. The work described in Chapter 3 combined femtosecond transient absorption spectroscopy (TAS), with liquid-microjet photoelectron spectroscopy and high-level quantum chemistry calculations to unravel the wavelength dependant photooxidation dynamics of phenolate. Then, Chapter 4 presents a study of methyl substituted phenolates. TAS was combined with time-correlated single photon counting (TCSPC) experiments and high-level quantum chemistry calculations to understand the implications of systematic modifications to phenolate by substitution on the photooxidation mechanism. Chapter 5, then presents the first time-resolved photoelectron spectroscopy (TRPES) data recorded on the UCL liquid microjet spectrometer. This study focuses on aqueous phenolate following 1+1 resonance-enhanced photodetachment. The behavior observed in these experiments was compared to the corresponding transient absorption data from Chapter 3 and and our preliminary results hint at faster electronic relaxation dynamics for molecules near a water-vacuum interface compared to those in bulk water. Finally, Chapter 6 presents an investigation of the photoluminescence dynamics of the small molecule that lies at the heart of firefly bioluminescent (oxyluciferin). This work focused on two model bioluminescent emitters, oxyluciferin and infraoxyluciferin, studying their excited state dynamics using TAS to understand why infraluciferin is a less efficient emitter than oxyluciferin. Infraoxyluciferin is an analogue of oxyluciferin with a red-shifted emission. Bioluminescent probes have applications in in vivo imaging in medicine. To design new bioluminescent probes for deeper tissue imaging, the emission maximum of these molecules needs to be red-shifted further and made brighter. By improving our detailed understanding of the electronic relaxation of the molecular unit central to firefly bioluminescence and comparing it to the less efficient but red-shifted infraoxyluciferin, we aim to design new, more efficient tools for bioluminescent imaging.

Download activity - last month

Export as XMLCSVJSON

Download activity - last 12 months

Export as JSONCSVXML

Downloads by country - last 12 months

Export as CSVXMLJSON

Archive Staff Only

View Item