Abstract
-
Natural selection in photosynthesis has engineered tetrapyrrole based, nanometer scale, light harvesting
and energy capture in light-induced charge separation. By designing and creating nanometer scale
artificial light harvesting and charge separating proteins, we have the opportunity to reengineer and
overcome the limitations of natural selection to extend energy capture to new wavelengths and to tailor
efficient systems that better meet human as opposed to cellular energetic needs. While tetrapyrrole
cofactor incorporation in natural proteins is complex and often assisted by accessory proteins for
cofactor transport and insertion, artificial protein functionalization relies on a practical understanding of
the basic physical chemistry of protein and cofactors that drive nanometer scale self-assembly.
Patterning and balancing of hydrophobic and hydrophilic tetrapyrrole substituents is critical to avoid
natural or synthetic porphyrin and chlorin aggregation in aqueous media and speed cofactor partitioning
into the non-polar core of a man-made water soluble protein designed according to elementary first
principles of protein folding. This partitioning is followed by site-specific anchoring of tetrapyrroles to
histidine ligands strategically placed for design control of rates and efficiencies of light energy and
electron transfer while orienting at least one polar group towards the aqueous phase