And oxygen autoxidation

The complex formed from hematin a and native globin (from crystalline hemoglobin) possesses an approximate ratio of 4 to 1 and shows low spin characteristics in both oxidized and reduced forms. The reduced complex, when oxidized by either oxygen or ferricyanide, is converted to a yellow compound whose spectra differ from those of the initial compound. The conversion is reversed by dithionite but not by prolonged deaeration. We concluded that the hematin a-gZo fn complex is autoxidizable but possesses no oxygenative property and is not reduced by ferrocyto-chrome c. The hematin di-polyhistidine complex also shows low spin characteristics. Its reduced form is even more autoxidizable than hematin Si-globin. The implications of these observations are discussed, with heme protein interactions and the structural specificities required for oxygenation and autoxidation. 

With these considerations in mind, we have studied the spectral characteristics, oxygenation, and autoxidation of the hematin a-globin and the hematin a-polyhistidine complexes. This report communicates some results along these lines. 

To demonstrate reversible oxygenation and autoxidation, a scheme as shown in Figure 1 was designed. The solution was placed in a Thun-berg cuvette. Whenever deaeration was employed, the cuvette was evacuated and subsequently flushed with helium the cycle was repeated three times and ended in a helium atmosphere. Ferricyanide or dithio-nite, always in a very slight excess, was added under helium atmosphere without contamination of air. 

PE are very sensitive to oxygen and autoxidize faster than PC, a process accompanied by an intense brown discoloration. Studies to reduce the oxidation of the PUEA with dietary supplementation of rosemary extract and tocopherols showed a higher oxidative stability of n-3 PA (Galobart et al., 2001 Cherian et al., 1996). 

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