The first Mn L-edge absorption spectra of a Mn metalloprotein are
presented in this paper. Both reduced
and superoxidized Mn catalase have been examined by
fluorescence-detected soft X-ray absorption spectroscopy,
and their Mn L-edge spectra are dramatically different. The
spectrum of reduced Mn(II)Mn(II) catalase has
been
interpreted by ligand field atomic multiplet calculations and by
comparison to model compound spectra. The analysis
finds a 10 Dq value of ∼1.1 eV, consistent with
coordination by predominately nitrogen and oxygen donor
ligands.
For interpretation of mixed valence Mn spectra, an empirical
simulation procedure based on the addition of homovalent
model compound spectra has been developed and was tested on a variety
of Mn complexes and superoxidized Mn
catalase. This routine was also used to determine the oxidation
state composition of the Mn in
[Ba8Na2ClMn16(OH)8(CO3)4L8]·53H2O
(L =
1,3-diamino-2-hydroxypropane-N,N,N‘,N‘-tetraacetic
acid).
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