A Ferromagnetic Resonance Study of Iron Complexes as Biologically Synthesized in Magnetic Bacteria

Abstract

In order to analyze the magnetic behaviors of iron complexes biologically synthesized in magnetic bacteria MS-1, we performed FMR (Ferromagnetic Resonance) measurements for each fraction of the cell. We observed FMR spectra from the ferric iron (Fe3+) compounds distributed in each fraction of the MS-1 cell. In particular, the magnetosome fraction yielded an anisotropic FMR signal, whereas other fractions were simple FMR spectra of a Gaussian type.Upon counting the numbers of spins in various cell fractions, we compared them with the iron population as determined by the 1.10-phenanthroline method. We found a good correlation between the number of spins and the iron population in several cell fractions. We concluded that the cell fractions, other than those fractions containing magnetite, consist mostly of ferric irons rather than ferrous irons.