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Resolved Hyperfine at L-band for High-Spin CoEDTA, A Model for Co Sites in Proteins
1Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA. wantholi@mcw.edu.
Abstract:
Low-frequency electron paramagnetic resonance (EPR) spectra were obtained for the Co complex of ethylene diamine tetraacetic acid (CoEDTA). It was found that the cobalt hyperfine at -mid is better resolved at a low frequency, L-band (1.37 GHz), and not resolved at X-band (9.631 GHz), which is the conventional frequency used for most spectra for metal complexes. Resolved cobalt hyperfine lines lead to additional EPR parameters like -mid for cobalt and a more-accurate determination of -mid. Resolved hyperfine lines in the L-band, but not the S-band, spectra were obtained at a concentration of 1 mM. Knowing these additional EPR parameters provides a means to better determine the electron density in the ground state orbital for each cobalt complex, as well as to determine differences upon a change of ligation. If zinc sites can be replaced by cobalt, the cobalt spectra for these sites will enhance the characterization of the zinc sites.
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