Determination of metal state from protein X-ray structure
X-ray diffraction experiments, regardless if about small molecules or proteins / RNA / DNA, are usually one element characterizing a sample.  On occasion, you may infer the oxidation state from the transition metals environment: how many closest neighbors, their distance, their number, their spatial arrangement.
You are free to complement findings by any other technique either using the same crystal sample as mounted on the diffractometer (e.g., UV-Vis), or with sample material from the same batch characterized at the same temperature as the crystal mounted on the diffractometer: spin characterization by EPR, Moessbauer, NMR (your are not constrained to CHN) and SQUID  to mention a selection. Because PubMed includes records about the structure characterization of large biomolecules, this database may serve as a source of inspiration how this was done, e.g., for heme