Hemoglobin oxidative addition model

Figure 20. Oxidative addition model of 02-bvnding to hemoglobin...

Of greatest interest are those compounds that attempt to model hemoglobin directly. Simple iron(II) porphyrins are readily autoxidized first to superoxo species, then to //-peroxo dimers and finally to /x-oxo dimers, as represented in equation (60). Bridge formation must be prevented if carrier properties are to be observed. This has been achieved by the use of low temperature and sterically hindered or immobilized iron(II) porphyrins. Irreversible oxidation is also hindered by the use of hydrophobic environments. In addition, model porphyrins should be five-coordinate to allow the ready binding of 02 this requires that one side should be protected with a hydrophobic structure. Attempts have also been made to investigate the cooperative effect by studying models in which different degrees of strain have been introduced. 

We propose that the two-electron oxidative addition 02-binding model developed for hemerythrin can be generalized to hemoglobin, as shown in Figure 20. The deoxy form is presumed to have weak axial... 

Dioxygen O2. reversibly binds hemoglobin, myoglobin and their models (bent Fe-0-0) dihapto side-on (M-t -02) peroxide complexes, resulting from oxidative addition of O2, are also known. Superoxo- and peroxo ligands bridging two metals (p ) can be r or rf. 

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