Benjamin Meaker Visiting Professor Stephen Bradforth, University of Southern California, USA

Profile picture of Professor Stephen BradforthExploring energy and charge-transfer in aromatic amino-acids and DNA using ultrafast spectroscopy

3 - 23 September 2018


Professor Stephen Bradforth joined the Department of Chemistry in 1996. He is currently USC Dornsife Divisional Dean for Natural Sciences and Mathematics, in which position he coordinates strategic planning, faculty appointments and research advancement. As a Physical Chemist, Bradforth’s lab designs experiments to gain a deeper understanding of how the inter-connected motions of molecules impact chemical reactions in complex but frequently encountered environments – such as the aqueous milieu of cells or in functional molecular materials. His research applies ultrafast laser techniques to address contemporary scientific challenges from solar energy conversion, damage to DNA and cancer nanomedicine.

In education, he is active in recent national efforts, spearheaded by the Research Corporation for Scientific Advancement and the Association of American Universities, to reform undergraduate STEM education in research-intensive US universities. Following undergraduate studies at Cambridge, Bradforth earned his PhD at the University of California, Berkeley and carried out postdoctoral research at the University of Chicago. His honours include a David and
Lucile Packard Fellowship in Science and Engineering, and he is a Cottrell Scholar of the Research Corporation for Scientific Advancement and a Fellow of the American Physical Society and of the Royal Society of Chemistry.

Project Summary

The ultraviolet (UV) component of solar light poses significant risks to all life on Earth. If UV light is absorbed by deoxyribonucleic acids (DNA), the genetic source code for all life on Earth, or amino-acids key for biological processes, deleterious photochemical reactions can be induced and lead to significant oxidative damage and carcinogenesis. These processes occur on very short timescales, on the order of femtoseconds to picoseconds.

One femtosecond = 1 x 10-15 fs: there are more femtoseconds in one second than there are years in the age of the known Universe. Current leading ultrafast laser spectroscopic methods are unable to determine the first steps in the excited state dynamics that underpin the molecular mechanisms of photodamage, such as electronic energy transfer between adjacent DNA bases, or charge-transfer leading to highly reactive solvated electron species- the primary reducing agent in radiation chemistry.

To gain a more detailed picture of these events requires the development of new spectroscopic tools, which Prof. Bradforth and Dr. Oliver are poised
to develop, utilising their complimentary expertise: Prof. Stephen Bradforth is a world-leading authority on photoinduced DNA damage and state-of-the-art deep-UV laser generation, and Dr Tom Oliver has innovated world-leading multidimensional ultrafast spectroscopic techniques. Together they will develop the blue-prints for a brand-new experiment, two-dimensional ultraviolet-vibrational spectroscopy, which will be able to directly probe and infer the initial steps in the molecular mechanisms that drive and dictate potentially dangerous photoinduced reactions in DNA. Furthermore, Prof. Bradforth and Dr. Oliver will generate a unified picture of the ultrafast photochemistry of the UV chromophore of tryptophan, a key biological amino-acid and the implications for damage inside proteins that are abundant in nature.