Magnetic Susceptibilities of Horse Erythrocyte Catalase and Its Derivatives in the Range from Room Temperature to 4.2°K

Abstract

The magnetic susceptibilities of horse erythrocyte catalase [EC 1.11.1.6] and its derivatives were measured in the range from room temperature to 4.2°K. spin compounds, such as free catalase and the fluoride compound, the dependence of the magnetic susceptibility was calculated assuming that the fine structure of the ground state of the iron ion can be expressed by a spin Hamiltonian, DS². In this calculation, the paramagnetic saturation effect was taken into consideration. The values of the parameter, D, of the spin Hamiltonian were estimated to be 12 cm⁻¹ for free catalase and 9 cm⁻¹ for the fluoride compound. The values of E were determined to be 0.3 cm⁻¹ for free catalase and 0.23cm⁻¹ for the fluoride compound, using the values of E/D previously determined from the EPR signals. From these values, the energy differences of the dε orbitals, E_y—E_x, were calculated to be 700cm⁻¹ for free catalase and 500cm⁻¹for the fluoride compound. With low spin compounds, such as the azide and cyanide compounds, the values of the effective numbers of the Bohr magneton, n_eff were estimated to be 2.63 for the azide compound and 2.39 for the cyanide compound from measurements in an extremely low temperature range. These large apparent values of n_eff may be due to the contribution of a small amount of high spin compound remaining in the test sample.