Solvent effects on myoglobin conformational substates as studied by electron paramagnetic resonance

Electronic paramagnetic resonance spectra of frozen horse myoglobin solutions at two different pH values and with different added organic solvents are analyzed by computer simulation in terms of Gaussian distributions of some ferric ion crystal field parameters. The mean values and the corresponding variances of these distributions, thought as arising from a distribution of the protein conformational substates, are found to be affected by both the pH and the addition of organic solvents. The significant narrowing of the conformational substate distribution, induced by large addition of glycerol, is discussed.