High-spin Fe1+ sites are potentially important in iron-sulfur proteins but are rare in synthetic compounds and unknown in metalloproteins. Here, we demonstrate a spectroscopically characterized example of high-spin non-heme Fe1+ in a protein environment. Cryoreduction of Fe 2+-substituted azurin at 77 K with 60Co γ radiation generates a new species with a S = 3/2 (high-spin) Fe 1+ center having D > 0 and E/D ∼ 0.25. This transient species is stable in a glycerol-water glass only up to ∼170 K. A combination of electron paramagnetic resonance and Mössbauer spectroscopies provides a powerful means of identifying a transient high-spin Fe1+ site in a protein scaffold.
ASJC Scopus subject areas
- Inorganic Chemistry
- Physical and Theoretical Chemistry