Gel filtration studies of oxyhemerythrin. I. Effects of pH on the association-dissociation equilibriums

The pH dependency of the dissociation of oxyhemerythrin has been studied by frontal gel chromatography on Sephadex G-75. The extent of dissociation is markedly pH dependent increasing below pH 6.0 and above pH 8.8. In addition, the nature of the dissociation reaction undergoes dramatic change with pH. Below pH 6.4 the rate of equilibration between species is slow relative to their time of passage through the column and they are thus resolved on chromatography. Above pH 6.6 the rate of equilibration is rapid and the various forms of hemerythrin are not resolved on migration through the column. Below pH 7.4 the dissociation is an all-or-none process with no detectable intermediates. Above pH 8.0 several intermediate species can be detected. Values for Keq and deltaG degrees are presented for various forms of oxyhemerythrin at the several pH's studied.