Measuring Electron Transfer Rates in Protein
Crystals with Transient Absorption Spectroscopy
Brian R. Crane
Cornell University
Rates of long-range electron transfer (ET) in proteins depend on many factors which include redox properties of donor and acceptor sites, conformation of the bridging polypeptide and solvent structure. Protein crystals are an excellent medium to study ET because the crystal lattice can associate proteins in fixed orientations and X-ray diffraction can be used to characterize structures of ET reactive states. We have developed photochemical systems and spectroscopic instrumentation for measuring long-range ET in single protein crystals. Challenges of microsecond ET experiments in protein crystals will be discussed, along with recent results from studies of redox reactions between the biological partners cytochrome C peroxidase and cytochrome C.