Circular dichroism and magnetic circular dichroism studies on methemoglobin and its derivatives.

CD and MCD spectra of human methemoglobin and its derivatives were studied with special reference to the relation of CD and MCD spectra to the magnetic moments. The intensities of MCD peaks of methemoglobin derivatives at 270 nm were inversely proportional to their magnetic susceptibility, and there was a linear relationship between magnetic ellipticity and magnetic susceptibility. The MCD peak intensity of methemoglobin peroxide compound was close to that of methemoglobin cyanide complex, suggesting that the methemoglobin peroxide compound is in a low-spin state.