Position-Dependent Energy Transfer Between Ruthenium(II) and Osmium(II) Modified Coiled-coil α-Helical Peptides & Oligoproline Recognition by a β-Hairpin Peptide

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  • Position-dependent energy transfer between ruthenium(II) and osmium(II) modified coiled-coil alpha-helical peptides and oligoproline recognition by a beta-hairpin peptide
Last Modified
  • March 21, 2019
Creator
  • Wilger, Dale Joseph
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • Two different research projects are discussed throughout this dissertation. The first project relates to the study of position-dependent energy transfer between specially synthesized metallopeptides that contain RuII and OsII bipyridyl complexes. The second project relates to the measurement of aromatic-prolyl interactions in a model peptide system. The study of excited-state energy transfer processes is of interest due to its implications in natural and artificial photosynthesis. In this work, a series of coiled-coil alpha-helical metallopeptides were designed, synthesized, and characterized. The metallopeptides contain RuII and OsII bipyridyl complexes that serve as excited-state energy donors and acceptors, respectively. Rates for energy transfer between the metallopeptides are position dependent and intimately linked with the structure of the peptide scaffold itself. The results indicate that energy transfer phenomena can be fine-tuned using peptide primary sequence and secondary structure. The metallopeptide system could be used to better understand the mechanisms of RuII to OsII excited-state energy transfer, and may potentially be applied to the construction of synthetic light-harvesting antenna, or as a sensitizer for dye-sensitized solar cells. As a second project, aromatic-prolyl interactions were studied in a model peptide system composed of a beta-hairpin peptide motif known as a tryptophan zipper (trpzip). Interactions between the amino acid proline and aromatic amino acids are of importance in the context of both protein folding and protein-protein interactions. The intermolecular recognition of the polyproline type II (PPII) helix peptide secondary structure by aromatic residues is important in a large number of cellular signaling events. Also, the cis-trans isomerization of amide bonds containing proline is often rate-limiting during protein folding. A disulfide exchange system was designed for studying aromatic-prolyl interactions between a trpzip peptide and a series of oligoproline peptides which adopt the PPII helix conformation. Favorable aromatic-prolyl interactions with energies up to 2.3 kcal middotmol-1 were measured. A beta-hairpin peptide which also contains tryptophan, WKWK, does not have favorable interactions with the oligoproline peptides. The WKWK beta-hairpin peptide contains a different configuration of tryptophan residues and demonstrates the importance of structure when considering aromatic-prolyl interactions in the context of complex peptide environments.
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  • In Copyright
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  • "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry."
Advisor
  • Waters, Marcey
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  • Chapel Hill, NC
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  • Open access
Date uploaded
  • March 18, 2013

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