Ultrafast dynamics of the NH bond and its significance towards the photoresistive mechanism of nucleic bases and base-pairs

Processes which involve the absorption of light play an integral role in our day-to-day lives. Nature has carefully chosen our molecular building blocks so that the potentially devastating effects of ultraviolet radiation are by-passed. The nucleic bases adenine, thymine, guanine and cytosine, which constitute the building blocks of our genetic code, DNA, absorb ultraviolet radiation very readily. Once absorbed, this energy is very efficiently diffused through harmless molecular relaxation pathways reducing the risk of molecular breakdown and therefore photochemical damage. The timescales of these photoresistive pathways must be very fast for them to compete effectively with the detrimental paths. It is becoming increasingly clear however that, although ultrafast measurements with lasers reveal very fast relaxation pathways, more refined experiments are required to test the ever increasingly sophisticated calculations that model the theory behind these pathways. The work described here is two-fold: Firstly, to build an experimental apparatus which allows introduction of the nucleic bases into an isolated molecular environment. Secondly, interrogate these molecules with sequences of ultrafast laser pulses so that we identify these pathways and completely characterize them. Having looked at the isolated nucleic bases, the experiments will then be extended to look at a more realistic scenario such as a nucleic base-pair and try to understand why nature has chosen the nucleic bases of our genetic code to be paired in such a unique way. For instance, do base-pairs show more photoresistance than the individual nucleic bases? The results of these studies will allow us to develop some basic principles governing the photochemical processes occurring in DNA bases and base-pairs and validate the theoretical models already present on these systems. The results will also lend themselves to fields such as biochemistry and biophysics, illustrating the interdisciplinary nature of this work. The majority of the funds requested are on essential equipment to help start-up the research career of the PI. Funds are also requested for a research student although postdoctoral support is not sought as the PI holds a Royal Society University Fellowship and will take the role of the postdoctoral researcher. The apparatus itself will far exceed the timescale of the proposal, provide continuity to the PI's research and bring the Department of Chemistry to the forefront of U.K. experimental ultrafast chemical dynamics.