Comparison of Experimental and Broken Symmetry Density Functional Theory Calculated Electron Paramagnetic Resonance Parameters for the Manganese Catalase Active Site in the Superoxidized Mn III /Mn IV State.

Broken symmetry density functional theory has been used to calculate g-tensor, 55 Mn, 14 N, and 17 O hyperfine couplings for active site models of superoxidized MnIII /MnIV manganese catalase both in its native and azide-inhibited form. While a good agreement is found between the calculated and experimental g-tensor and 55 Mn hyperfine couplings for all models, the active site geometry and Mn ion oxidation state can only be readily distinguished based on a comparison of the calculated and experimental 14 N azide and 17 O HFCs. This comparison shows that only models containing a Jahn-Teller distorted 5-coordinate (MnIII )2 site and a 6-coordinate (MnIV )1 site can satisfactorily reproduce the experimental 14 N and 17 O hyperfine couplings.