HIGH-FREQUENCY EPR PREDICTIONS FOR THE NONHEME IRON PROTEIN LIPOXYGENASE

Soybean lipoxygenase-1 high frequency (greater than or equal to 70 GHz ) EPR spectra at low magnetic field strengths (<2 Tesla) are predicted to have interdoublet transitions. Analysis of these transitions, if t hey are observed, will accurately measure all the zero field splitting (ZFS) terms for the second order spin Hamiltonian. The combination of interdoublet transitions with Kramers doubler transitions can be used as a sensitive, direct, measurement of D. The non-heme iron protein, lipoxygenase, in its activated S = 5/2 Fe+3 state, exhibits distributi ons in E/D. The effect of distributions in ZFS parameters on Kramers d oublet transitions and interdoublet transitions are very different. Th ese differences can be used to separate the components of the distribu tion in E/D: distributions in E and D. A first estimate of the separat ed distributions can be obtained from the relative amplitudes of the l owest Kramers doublet to the interdoublet transitions.