Development of high-sensitive multi-frequency ESR apparatus for studies on thin magnetic materials including metalloproteins

We have developed high-sensitive multi-frequency electron spin resonance (ESR) apparatus. It is composed of some home-made ESR cryostats with a TE011 cylindrical cavity and/or a Febry-Perot resonator and with a very stable matching mechanism. It is also equipped with a superconducting magnet which is capable to sweep magnetic fields up to 16T and with a vector network analyzer. We have succeeded in observing ESR signals in some metalloproteins with an integer spin(S) at several frequencies utilizing this apparatus. We have also analyzed the ESR spectra of one of them, namely Mn3+- porphyrin reconstituted myoglobin, with a spin Hamiltonian for S=2, resulting in obtaining very precise zero-field splitting parameters. (author)