Ultrafast molecular dynamics of model biological systems

Abstract

Femtosecond time resolved photoelectron imaging spectroscopy equipment was designed, constructed, and used to reveal the non-adiabatic dynamics of model biological systems. Indole and phenol derivatives were studied as models for eumelanin, a pigment found in humans designed to protect the body from ultraviolet radiation. The photo-dynamics of these molecules was studied after excitation with ultraviolet radiation, with particular emphasis on the effect that the hydroxyl groups have on the p * dissociative state. It was found that adding a hydroxyl group onto indole to create 5-hydroxyindole had little significant effect on the photodynamics at the excitation wavelengths studied. Adding a second hydroxyl group to phenol had a strongly marked effect only when the hydroxyl groups were in close proximity to each other, in which case it dramatically increased the relaxation rate. An ultrafast optical system, imaging photoelectron spectrometer, and software to control the hardware, and collect and analyse photoelectron data were successfully implemented and used to collect and analyse data. This system will be of use for many more years and will be the basis of much future research.