LAUSR

Self-assembled peptide micelles and fibers demonstrate unique control over the photophysical properties of the bound, light-activated chromophore, zinc protoporphyrin IX, (PPIX)Zn. Micelles encapsulate either a mixture of uncoordinated and coordinated (PPIX)Zn or all coordinated depending on the ratio of peptide:porphyrin. As the ratio increases toward a 1:1 mi-celle:porphyrin ratio, providing the chromophore with a discrete coordination environment reminiscent of unstructured proteins, the micelles favor triplet formation. Fibers, on the other hand promote a linear array of porphyrin molecules that dictates exci-ton hopping and excimer formation at ratios as high as 60:1, peptide:porphyrin. However, even in fibers, the formation of the triplet species increases with increasing peptide:porphyrin ratio due to increased spatial separation between neighboring chromophores facilitating intersystem crossing. Full characteri-zation of the micelles structures and comparison to the fibers lead to the comparison with natural systems and the ability to control the excited populations that have utility in photocata-lytic processes. In addition, the incorporation of a second chro-mophore, heme, yields an electron transfer pathway in both micelles and fibers that highlights the utility of the peptide assemblies when engineering multichromophore arrays as in-spired by natural, photosynthetic proteins.