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 (Fe 3þ ) 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.
The paramagnetic properties of size-controlled ink particles isolated from the ink sacs of Sepia officinalis were studied by electron spin resonance (ESR) spectroscopy. Both the size-controlled ink particles and synthetic melanins seemingly yielded similar ESR spectra consisting of a singlet with a slightly asymmetrical signal. However, the progressive microwave power saturation revealed a clear difference between their paramagnetic behaviors. In comparison with synthetic melanins, the ESR spectra of the ink particles readily reached saturation, indicating a long spin–lattice relaxation time. On the other hand, the ESR linewidth depended on particle size. This implies that the particle size is related to the distance between paramagnetic species in the particles. Hence, it is reasonable that the large ink particle has the weakest spin–spin interaction among these samples. The employment of the size-controlled ink particles enabled us to determine precisely the paramagnetic parameters of Sepia inks.
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 (Fe 3+ ) compounds distributed in each fraction of the MS 1 cell. In particular, the MS fraction yielded an anisotropic FMR signal, whereas other fractions were simple FMR spectra of 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.
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