Spectroscopic evidence for interactions between hexacyanoiron(II/III) and an engineered purple CuA azurin

Hee Jung Hwang, Yi Lu

Research output: Contribution to journalArticlepeer-review


Interactions between hexacyanoiron(II/III) and a dinuclear, mixed valence CuA center in engineered CuA azurin have been investigated by UV-visible (UV-vis) and electron paramagnetic resonance (EPR) spectroscopic techniques. Addition of ferricyanide (hexacyanoiron(III)) to the CuA azurin resulted in a new absorption band around 500 nm in the UV-vis and an isotropic line at g=2.16 in the EPR spectra. Control experiments, including additions of Cu(II)SO4 or Cu(I)(CH3CN)4PF 6 to ferricyanide or ferrocyanide, as well as gel filtration purification of the ferricyanide-CuA azurin adduct indicate complex formation between cupric ion and ferrocyanide ion in the protein. Solvent or small molecule accessibility, metal oxidation state and the presence of more than one metal ion are potential factors important for the complex formation. These findings must be taken into consideration when using ferricyanide or ferrocyanide as redox agents for studying CuA centers in proteins.

Original languageEnglish (US)
Pages (from-to)797-802
Number of pages6
JournalJournal of Inorganic Biochemistry
Issue number5
StatePublished - May 1 2004


  • Copper
  • Cu center
  • EPR
  • Ferricyanide
  • Ferrocyanide

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry


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