Photochemical Sciences Ph.D. Dissertations

Design and Development of Metal-Peptide Nanoscaled Materials

Date of Award

2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Michael Ogawa,

Abstract

The work presented in this dissertation demonstrates how de-novo designed peptides having the double stranded á-helical coiled-coil conformation can be organized into molecular assemblies by metal coordination. The design of these peptides explores the positioning of a strong metal binding site, 4-pyridylalanine, within the hydrophilic portion of the peptides in order to coordinate the metal complexes into well-defined geometries. The effect of the peptide’s sequence on the stability of the formed metal-peptide complex has been shown through the reaction of Pal14 and Pal14n with ethylenediamine platinum (II). In particular, it was found that peptides based on an IEALEGK repeat do not form stable metals complexes. In contrast, peptides based on an IAALEQK repeat do form stable platinum complexes which in water assemble into globular structures that are 40 nm in diameter. Incorporation of a covalent crosslink into the Pal14n coiled-coil structure (Pal14C19nox) forces this peptide to form linear assemblies after the reaction with the platinum complex. The last chapter of this dissertation reveals that multiple metal binding sites on the hydrophilic exterior of the two-stranded coiled-coil Pal14Pal21n forces the formation of cyclic tetramers, rather then a polymeric product. It was also found that the conformational “plasticity” of the non-covalent coiled coil Pal14Pal21n is necessary for the formation of the platinum-peptide tetramer. In contrast, the covalently “secured” coiled-coil structure of Pal14C19Pal21nox restricts conformation changes within the molecule, which inhibits the platinum complex from orienting the peptide ligand in order to form the tetramer structure.

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