COMBINING MOSSBAUER-SPECTROSCOPY WITH INTEGER SPIN ELECTRON-PARAMAGNETIC-RESONANCE

Integer spin EPR will become an important tool for the studies of the active sites of iron-containing metalloproteins. Laboratories have focused on combined EPR and Mössbauer studies of systems yielding Mössbauer spectra that could be analyzed with high accuracy and confidence in the framework of the spin Hamiltonian formalism. Using zerofield splitting parameters from the Mössbauer analysis, it is possible to assign EPR transitions with confidence and refine the methods of EPR data analysis. Integer spin EPR, in turn, has aided in recognizing the fundamental features of some systems; in particular, it has helped to solve the problem of the P cluster state pox. Some of the iron-containing proteins and model complexes for which integer spin EPR has been observed are presented in the chapter. A survey of the literature on Mössbauer spectroscopy suggests that a variety of other iron-containing proteins are likely to exhibit integer spin EPR at either X- or Q-band frequencies. Based on the progress that has been made in the past it is anticipated that this technique will be a valuable tool for the biochemist and biophysicist. By applying Mössbauer and EPR spectroscopy to proteins with multiple iron-containing sites and using the methodology discussed above, one should be able to untangle quite complex situations. © 1993, Elsevier Inc. All rights reserved.