Related Experiment Video
Updated: Aug 24, 2026

Quantifying the Binding Interactions Between Cu(II) and Peptide Residues in the Presence and Absence of Chromophores
Published on: April 5, 2022
Spectroscopic evidence for interactions between hexacyanoiron(II/III) and an engineered purple CuA azurin
1Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathew Avenue Urbana, IL 61801, USA.
Abstract:
Interactions between hexacyanoiron(II/III) and a dinuclear, mixed valence Cu(A) center in engineered Cu(A) azurin have been investigated by UV-visible (UV-vis) and electron paramagnetic resonance (EPR) spectroscopic techniques. Addition of ferricyanide (hexacyanoiron(III)) to the Cu(A) 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)SO(4) or Cu(I)(CH(3)CN)(4)PF(6) to ferricyanide or ferrocyanide, as well as gel filtration purification of the ferricyanide-Cu(A) 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 Cu(A) centers in proteins.
Related Concept Videos
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Aryldiazonium Salts to Azo Dyes: Diazo Coupling
UV–Vis Spectroscopy of Conjugated Systems
One of the factors influencing λmax is the extent of conjugation in the...

