Identification of the cyanide stretching frequency in the cyano derivative of Cu/Zn-superoxide dismutase by IR and Raman spectroscopy

Jane Han, Ninian Blackburn, Thomas M. Loehr

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Abstract

Cyanide has been investigated as a potential ligand-directed probe of the coordination chemistry of Cu(II) and Cu(I) active sites via vibrational spectroscopic studies of CN- coordinated to the metal centers in non-blue copper proteins. Native superoxide dismutase (SOD) was found to bind one CN- that had IR and Raman frequencies at 2137 cm-1. The assignment of this band was confirmed by using 13CN-, which gave the theoretically expected isotope shift, and by comparison with an inorganic model complex, [Cu(PMAS)]2+, which was found to form a monocyano complex with νCN = 2125 cm-1. Ultrafiltration experiments definitively identified the 2137-cm-1 band as νCN of a protein-bound species. These results are consistent with a linear end-on-bonded CN- on Cu(II)-SOD as proposed from earlier EPR and EXAFS experiments. Replacing H2O in the medium by D2O gave no isotope shift of the 2137-cm-1 band, indicating that CN- is most likely not involved in hydrogen-bonding interactions in the active-site cavity. With increasing concentrations of cyanide, the 2137-cm-1 band became weaker and was accompanied by the appearance of strong vibrational modes characteristic of di-, tri-, and tetracyano Cu(I) complexes arising from Cu removal from the protein. These studies demonstrate the potential importance of cyanides (and isocyanides) as ligand-directed vibrational spectroscopic probes of non-blue copper proteins.

Original languageEnglish (US)
Pages (from-to)3223-3229
Number of pages7
JournalInorganic Chemistry
Volume31
Issue number15
StatePublished - 1992

Fingerprint

inorganic peroxides
Cyanides
cyanides
Stretching
Raman spectroscopy
Infrared spectroscopy
Derivatives
proteins
Isotopes
isotope effect
spectroscopy
Superoxide Dismutase
Copper
Proteins
Ligands
copper
ligands
probes
Ultrafiltration
Paramagnetic resonance

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Identification of the cyanide stretching frequency in the cyano derivative of Cu/Zn-superoxide dismutase by IR and Raman spectroscopy. / Han, Jane; Blackburn, Ninian; Loehr, Thomas M.

In: Inorganic Chemistry, Vol. 31, No. 15, 1992, p. 3223-3229.

Research output: Contribution to journalArticle

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