Self-assembling light harvesting systems templated by the tobacco mosaic virus coat protein

A light harvesting (LH) system has been constructed based on the self-assembly of chromophore-labeled monomers of the tobacco mosaic virus coat protein (TMVP). The installation of a cysteine residue on the 5' surface of the coat protein allowed for the site selective attachement of maleimide-functionalized chromphores. Simple adjustments in pH and ionic strength cause these conjugates to assemble into disk- and rod-shaped materials capable of efficient energy transfer between chromophores. The capability of the system to integrate different types of chromophores is demonstrated, allowing light collection over a broad range of wavelengths in the visible spectrum.;Picosecond time-resolved fluorescence spectroscopy was employed to characterize the energy transfer pathways within these LH systems. Due to the occurrence of both donor-to-donor and donor-to-acceptor transfer pathways, a global lifetime analysis was required to describe the system accurately. Energy transfer from donor to acceptor chromophores was shown to occur in 187 ps with an efficiency of 36%. A faster decay component of 70 ps was also observed from global lifetime analysis and is attributed to donor-to-donor transfer.;For LH arrays containing a high ratio of donors to acceptors, rod and disk assemblies derived from a single stock of chromophore-labeled TMVP exhibited significantly different levels of energy transfer, with rods significantly outperforming disks. For systems with equal amounts of donors and acceptors, disk and rod assemblies showed more similar efficiencies. Three potential mechanisms were proposed that might explain this behavior. The first postulates that disks may exhibit a great susceptibility to defects, and a second suggests that there may exist a greater redundancy of energy transfer pathways in rods. A third explanation proposes a difference in the rates of vertical and horizontal transfer within the TMV assembly due to variations in the chromophore geometries.;Finally, attempts were made to improve the material aspects of the TMV scaffold through genetic modification. To allow for the incorporation other functionalities onto TMV assemblies, a genetically-encoded aldehyde tag was inserted into the pore of the protein. However, constructs were not expressed. In addition, three lengths of RNA containing the origin of assembly were created to control rod length.