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. Author manuscript; available in PMC: 2014 Jan 15.
Published in final edited form as: Coord Chem Rev. 2012 Jun 6;257(2):511–527. doi: 10.1016/j.ccr.2012.05.008

Figure 11.

Figure 11

Experimental νFeN/νNO pattern for Fe(III)NO porphyrin adducts having thiolate (bottom left region) or imidazole (upper right region) proximal residue. Thiolate adducts describe a positive correlation for cysteinate heme proteins [67,122-124] (red dots and dashed red line) and model compounds (red circles), with (SR-HB) and without (SR) an internal H-bond to the thiolate ligand[121]. Histidine-ligated heme proteins fall between the two negative backbonding correlations describing Mb variants with (black line) and without (blue line) a distal histidine (Fig. 9). A number of representatives fall between the lines (green triangles), due to variable lone pair interactions, or to variations in proximal ligand donor strength [ref. 29 and references therein].