STRUCTURE OF HEME IN PYRIDINE-WATER MIXTURES AND ITS IMPLICATION IN STUDIES OF HEME CATABOLISM

The nature of the changes in the heme pyridine/water system at around 10% (v/v) pyridine was evaluated to correlate them with studies on heme degradation. A study of heme spectra in pyridine/water mixtures at low pyridine concentrations revealed changes in hemeochrome structure consistent with an aggregation process. No corresponding change in the structure of the hemeochrome species was observed. This aggregation was correlated with a previously observed sharp decrease in the rate of coupled oxidation (degradation) of heme as pyridine concentration is decreased. The decrease appears to be due primarily to heme aggregation and not to changes in the hydrophobic nature of the solvent. The effect of ethanol and butanone addition was examined and supports this conclusion. Evidence is presented that coupled oxidation occurs via the Fe(II) species (hemochrome).