Mooney, C; (2015) Spectroscopy and Dynamics of Fluorescent Protein Chromophore Anions. Doctoral thesis , UCL (University College London).

Text Ciarán Roger Samuel Mooney corrected_thesis.pdf Available under License : See the attached licence file. Download (17MB)

Abstract

Gas-phase photoelectron imaging spectroscopy has been combined with electrospray ionisation to examine the electronic structure and dynamics of a variety of biologically relevant chromophores. Both nanosecond and femtosecond spectroscopy techniques have been employed and many of these experimental measurements have been complimented by ab initio calculations. The photodetachment spectra of model chromophore anions of Green Fluorescent Protein (GFP) and Cyan Fluorescent Protein (CFP) along with their constituent moieties, phenol and indole, have been recorded at 269 nm and 330 nm. This study provided measurements of the vertical and adiabatic detachment energies of the ground and first excited state radicals of all four molecules. A detailed nanosecond photoelectron spectroscopy study of the GFP model chromophore anion was then undertaken using a range of wavelengths between 315 nm and 328 nm. This has revealed the interplay between direct and indirect detachment processes and their influence on the photoelectron spectra. A femtosecond time-resolved study of the model GFP chromophore anion was also performed along with ab initio calculations to identify key molecular structures. This study revealed that the ultrafast decay dynamics of the gas-phase model anion have similar timescales as those measured in solution. In another study, photodetachment spectra of chemically modified GFP model chromophore anions were measured at 350 nm. The addition of strongly electron donating or withdrawing groups on the phenoxide moiety of the chromophore demonstrates how chemistry can be exploited to tune the electron emission properties the chromophore. Finally, a study of model chromophore anions of Photoactive Yellow Protein (PYP) was undertaken. This work examined the photoelectron spectra of three isomers of the PYP model chromophore at a wide variety of wavelengths between 315 nm and 364 nm. The vibrationally resolved spectra allow us to identify the predominate anion isomer produced by electrospray ionisation and highlights the importance of direct and indirect photodetachment pathways in anion spectroscopy.

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