Affinity, speciation, and molecular features of copper(II) complexes with a prion tetraoctarepeat domain in aqueous solution: Insights into old and new results

Giuseppe Di Natale, Katalin Osz, Csilla Kállay, Giuseppe Pappalardo, Daniele Sanna, Giuseppe Impellizzeri, Imre Sóvágó, Enrico Rizzarelli

Research output: Contribution to journalArticle

14 Citations (Scopus)


Characterization of the copper(II) complexes formed with the tetraoctarepeat peptide at low and high metal-to-ligand ratios and in a large pH range, would provide a breakthrough in the interpretation of biological relevance of the different metal complexes of copper(II)-tetraoctarepeat system. In the present work, the potentiometric, UV/Vis, circular dichroism (CD), and electron paramagnetic resonance (EPR) studies were carried out on copper(II) complexes with a PEG-ylated derivative of the tetraoctarepeats peptide sequence (Ac-PEG27-(PHGGGWGQ)4-NH2) and the peptide Ac-(PHGGGWGQ)2-NH2. Conjugation of tetraoctarepeat peptide sequence with polyethyleneglycol improved the solubility of the copper(II) complexes. The results enable a straightforward explanation of the conflicting results originated from the underestimation of all metal-ligand equilibria and the ensuing speciation. A complete and reliable speciation is therefore obtained with the released affinity and binding details of the main complexes species formed in aqueous solution. The results contribute to clarify the discrepancies of several studies in which the authors ascribe the redox activity of copper(II)-tetraoctarepeat system considering only the average effects of several coexisting species with very different stoichiometries and binding modes.

Original languageEnglish
Pages (from-to)3751-3761
Number of pages11
JournalChemistry - A European Journal
Issue number11
Publication statusPublished - Mar 11 2013



  • UV/Vis spectroscopy
  • circular dichroism
  • coordination modes
  • copper
  • peptides

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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