Driving Charge Transport in Chromophore-Protein Complexes through Tryptophan Pathways

Sequential photoinduced charge transport along tryptophan-based "hopping" pathways will be investigated in protein (azurin) constructs containing a covalently attached organometallic photosensitizer, as well as in molecular donor-acceptor assemblies. In azurins, we will investigate hole hopping dynamics through two different pathways as a function of their composition, cofactor distances and orientation, and spectroscopically characterize tryptophan radical-cationic intermediates. Combination of system design/synthesis, cutting edge ultrafast time-resolved spectroscopic experiments (namely structure-sensitive femtosecond stimulated Raman and IR absorption), and high-level quantum mechanical dynamical simulations will provide deep insight into electron/hole hopping mechanism and unravel critical factors controlling charge-separation kinetics and yields. This new knowledge will be applied to propose a functional azurin-based "photoenzyme" whose demonstration will pave the way toward future development of enzymatic photocatalysis relevant to artificial photosynthesis.