Our research focuses on using
modern time-resolved electron spin resonance (ESR) spectroscopy to study
the structure and function of photosynthetic reaction centres and porphyrin-based
model systems. Light excitation of these systems leads to energy and electron
transfer reactions involving short-lived paramagnetic intermediates. The
spin polarized transient EPR spectra of these species can be used to deduce
both structural as well as kinetic information about the functional states.
Our interest in photosynthesis involves
understanding how plants and bacteria capture and store sunlight. In particular,
we are trying to elucidate the role that protein-cofactor interactions
play in controlling the effeciency and rate of the transmembrane
electron transfer in photosynthetic reaction centres. Transient ESR
is especially well-suited for studying the quinone acceptors in these systems
and shown that their properties are dramatically different although they
are structurally very similar. Recently, we have begun studying deletion
mutants of cyanobacteria which allow both the protein and cofactors to
be altered in a controlled way.
The work on porphyrin-based model systems
is directed primarily towards understanding the influence of paramagnetic
transition metals such as Cu2+ on energy transfer in systems of coupled
chromophores. Our goal is to use the spin polarization generated
in these processes to study metallo-proteins which are not otherwise photoactive.
