Spectroscopic studies of protein-heme interactions accompanying the allosteric transition in methemoglobins.

To gain an understanding of the energetics of cooperativity in methemoglobin, we have studied the effect of IHP on the optical absorption spectra, resonance Raman spectra, and circular dichroism of a series of human and carp methemoglobins. We found resonance Raman markers for the spin equilibrium and from these we have determined that those derivatives which exist in a spin equilibrium are shifted to higher spin in the carp derivatives.