Correlation of Kβ´ intensity and formal unpaired Fe(d) spin count. Data points refer to Kβ spectra in Fig. 2 (Left) and SI Appendix, Fig. S7 (nonporphyrin compounds). Kβ data for dehydrated deoxy, carboxy, and oxy HB and met (at Fe(d) = 1) MB/HB (solid asterisks) and solid hemin (solid square) at room temperature derived from ref. 45 were scaled to our data at Fe(d) = 0. Fe(d) spins correspond to: 0, LS Fe(II); 1, LS Fe(III); 4, HS Fe(II), and 5, HS Fe(III). Kβ´ intensities for oxy MB/HB were placed at Fe(d) = 2 for a formal IS Fe(II) (solid or dashed lines, linear fits to porphyrin/nonporphyrin or porphyrin data, R = 0.99). (Inset) Data from Kβ spectra in Fig. 2, Right (for Fe(d) count calculation see the text; line, linear fit to porphyrin data, R = 0.98).