Formation of Artificial Metal-Peptide Assemblies

1. Formation of Artificial Metal-Peptide Assemblies Brandon Young, Mikhail V Tsurkan, and Michael Y Ogawa Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University Ohio Science and Engineering Conference

2. Why? • To Control Metal-directed Protein Folding and Assembly • To Make synthetic metalloenzymes and proteins that could be used in organic applications: • Diabetes • Cystic fibrosis • Prion disease (Mad Cow) • Sickle cell • Utilized for Drug delivery systems • "nanomachines"

3. Solid Phase Peptide Synthesis Scheme Peptide Synthesizer AC-QIAALEQKIAALECysKIAALEQKIAALEQKGGY—CONH2 AC-QIAALEQKIAALECysKIAALEQKIAALEQKGGY—CONH2

4. Structures Based on the Synthetic Peptide (C-14) S S S S S S HS SH AC-QIAALEQKIAALECysKIAALEQKIAALEQKGGY—CONH2 AC-QIAALEQKIAALECysKIAALEQKIAALEQKGGY—CONH2 (“Coiled-coil”) The sequence of the synthetic peptide (C-14) was designed to provide: • A rigid linear (“coiled-coil”) structure • Metal-binding cysteine (-SH) residues in middle of structure • Self-assembly properties in Hydrophobic atmosphere

5. Metal-peptides Monomer Structures CO CO Re S OC + 2 HS Peptide S Br NH + 2 HS Peptide Pt S NH S In this project we applied metals and peptides to create new and innovative structures. [NEt4]2Re(CO)3Br3 + 2 HS Peptide Au

6. Self-Assembly Process by formation of coiled-coils CO CO Re S OC OC S Br CO S Re CO Br S NH NH Pt Pt S S Br S NH NH CO S Re S S S Br CO OC OC S Re CO NH S CO S Pt NH Au Au To utilize directional bonding properties that would be conducive to our study we worked with linear (Au) and square planar (Re and Pt) metal complexes. Also the synthetic peptide (C-14) was sequenced to provide properties which would be favorable in our experimental conditions. Formation of a 180º metal-peptide complex (Gold) Au+ 2C-14 Formation of a 90º metal-peptide complex ( Rhenium & Platinum) Pt+ 2C-14 Re+2C-14

7. Characterization of metal-peptide assemblies bySDS-PAGE Ideal Nanotube SDS-PAGE 27 kDa 17 kDa 14 kDa 6 kDa Trimers Dimer Monomer Re+2C-14 Au+ 2C-14 Standard Pt+ 2C-14 Peptide C-14 Metal “Coiled-coil” peptide With this combination of metals and peptide, we test for metal-peptide structures that may contain two or more units of the metal-peptide complex. The principle idea of this work is to construct metal-peptide complexes; for example, dimers, trimers, and tube structures.

8. Purification of metal-peptide complex SDS-PAGE 27 kDa 17 kDa 14 kDa 6 kDa SDS-PAGE results showing the presence of discrete higher molecular weight metal-peptide assemblies upon reacting C-14 with Platinum and Rhenium in methanol. Pt1 Pt2 Pt3 Re1 Re2 Re3 Re4 St 2 2 1 1 3 4 3

9. Conclusion • Results indicate that new peptide assemblies can be form through cross-linking (covalent capture) of the peptide of coiled-coil structure. • Related work, which focus on the formation of metal-peptide complex, with determined geometry, shows that evidence for formation of metal-peptide nanoassemblies. • Purification of the metal-peptide structures is possible.

10. Future work • Future work will include purification of a stable metal-peptide complexes and following characterization of possible metal-peptide assemblies.