Copper Environment in Artificial Metalloproteins Probed by Electron Paramagnetic Resonance Spectroscopy

Marco Flores, Tien L. Olson, Dong Wang, Selvakumar Edwardraja, Sandip Shinde, Joann Williams, Giovanna Ghirlanda, James Allen

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


The design of binding sites for divalent metals in artificial proteins is a productive platform for examining the characteristics of metal-ligand interactions. In this report, we investigate the spectroscopic properties of small peptides and four-helix bundles that bind Cu(II). Three small peptides, consisting of 15 amino acid residues, were designed to have two arms, each containing a metal-binding site comprised of different combinations of imidazole and carboxylate side chains. Two four-helix bundles each had a binding site for a central dinuclear metal cofactor, with one design incorporating additional potential metal ligands at two identical sites. The small peptides displayed pH-dependent, metal-induced changes in the circular dichroism spectra, consistent with large changes in the secondary structure upon metal binding, while the spectra of the four-helix bundles showed a predominant α-helix content but only small structural changes upon metal binding. Electron paramagnetic resonance spectra were measured at X-band revealing classic Cu(II) axial patterns with hyperfine coupling peaks for the small peptides and four-helix bundles exhibiting a range of values that were related to the specific chemical natures of the ligands. The variety of electronic structures allow us to define the distinctive environment of each metal-binding site in these artificial systems, including the designed additional binding sites in one of the four-helix bundles.

Original languageEnglish (US)
Pages (from-to)13825-13833
Number of pages9
JournalJournal of Physical Chemistry B
Issue number43
StatePublished - Oct 29 2015

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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