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.
