Grant: Discovery Grants Program - Individual

The goal of the proposed research is to gain a fundamental understanding of the factors governing the energetics and efficiency of photochemical energy conversion in both natural and artificial photosynthetic systems. The phenomenon of electron-spin polarization, which is associated with the early events that occur following the absorption of light, provides an observable that gives very detailed information on a molecular and electronic level. Our suite of modern time-resolved electron paramagnetic resonance (EPR) instruments allows us to use the spin polarization of light-induced paramagnetic species to study these events in detail and to learn how to control them. In photosynthetic organisms, the energy conversion takes place in large membrane-bound protein complexes known as photosynthetic reaction centres, which are astoundingly efficient and function under an enormous range of conditions. The key reaction initiated by light absorption in these systems is a trans-membrane electron transfer, which generates a series of spin polarized radical pairs that can be followed using time-resolved EPR techniques. Competing and unproductive reactions such as the formation of molecular triplet states can also be studied in this manner. Our close collaborations with groups in the US, Germany, Russia and Japan give us access to a wide range of complementary spectroscopic, theoretical, biochemical and molecular biology techniques. Using this broad array of methods, we are putting together an exquisitely detailed picture of the energetics, kinetics and dynamics of these vitally important systems. We are now using this knowledge to aid in the design and characterization of artificial mimics of the natural systems.