Oxymyoglobin stability

A hydrogen bond (dotted green line) donated by the distal histidine residue to the bound oxygen molecule helps stabilize oxymyoglobin. 

It is important to note that in these studies of vitamin E supplementation, it is the stability of oxymyoglobin that is improved. There does not appear to be any effect of vitamin E supplementation on the absolute concentration of myoglobin. In addition, consumers often associate discolored meat with a high microbial load. While meat color is not necessarily an adequate indicator of bacteriological quality (Faustman et al., 1990), Arnold et al. (1992a) have shown that bacterial growth on meat from vitamin E supplemented cattle is similar to that of meat from control animals. Thus, while the color stability of vitamin E supplemented beef may be improved, microbial growth is unaffected. The question of whether such enhanced color stability masks a natural deteriorative process must be addressed and requires further research. 

LFe(II)-02 adducts derived from a porphyrinic complex L constitute models of oxymyoglobin. Nevertheless, their stability is limited in classical conditions by the accessibility of the first coordination sphere to water molecules. 

Fig. 11. A hypothetical picture to account for the stability of oxyhemoglobin and oxymyoglobin. The non-polar environment of each binding site retards oxidation, which involves charge separation, but leaves the deoxygenation process unhindered.

There are many important spectral and chemical differences between this synthetic model and hemoglobin and myoglobin, but these results do support the above suggested explanation of the stability of oxyhemoglobin and oxymyoglobin. 

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