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Human ferritin homopolymers with H or L subunits (rHF and rLF) were genetically engineered in E coli. Apoferritins were then reconstituted with 2000 Fe atoms. A big difference was observed in the rates of iron uptake, whereas the mean core size was similar in rHF and rLF. Magnetization of the recombinant human ferritins were measured as functions of temperature and field. The blocking temperature TB(H) at low fields is considerably higher in rLF than in rHF. From the fit of M(H) data to a modified Langevin function: M(H)=M0L(μpH/kBT)+χaH, the effective magnetic moment μp is found to be much larger in rLF than in rHF. Experimental data demonstrate that the magnetic properties, in particular, the uncompensated spins of ferritin core are related to the biomineralization process in ferritins. [ABSTRACT FROM AUTHOR]

We report ¹H and [sup 23]Na nuclear magnetic resonance (NMR) and relaxation measurements in two variants of the V6 cluster with formula [CH[sub 3]H[sub 6][sub 4]Na[sub 2][H[sub 4]{V[sub 3]L}[sub 2]P[sub 4]O[sub 4]]·14H[sub 2]O and Na[sub 6][H[sub 4]{V[sub 3]L}[sub 2]P[sub 4]O[sub 4]]· 18H[sub 2]O, respectively. Both the NMR linewidth and the spin-lattice relaxation (NSLR) data can be explained semiquantitatively by assuming a dipolar coupling between the proton (sodium) nuclei and the three V(IV) magnetic moments forming an almost equilateral triangle with nearest neighbor antiferromagnetic exchange interactions. From the temperature dependence of the [sup 23]Na NSLR we obtain the value of the two gaps separating the lower energy total spin states. [ABSTRACT FROM AUTHOR]

We report [sup 1]H nuclear magnetic resonance spin-lattice relaxation rate (NSLR) measurements as a function of temperature (1.5–4.2 K) and as a function of applied magnetic field (0.2–8.2 T) in the molecular magnet [(PhSiO[sub 2])[sub 6]Cu[sub 6](O[sub 2]SiPh)[sub 6]] in short Cu6. The results are explained in terms of a simple model whereby the NSLR is driven by the fluctuations of the local hyperfine field due to the reorientation of the total spin of the molecule in its ground state. From the analysis of the data, we infer the temperature and field dependence of the characteristic rate of the fluctuations of the total magnetization of the Cu6 ring in its ground state. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Rotational bands in 110,112Ru and 108Mo have been investigated by means of γ-γ-γ and γ-γ(θ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. New ΔI = 1 negative parity doublet bands are found. These bands in 110,112Ru and 108Mo have all the properties expected for chiral vibrations. Microscopic calculations that combine the TAC mean-field with random phase approximation support this interpretation. [ABSTRACT FROM AUTHOR]

We report an investigation of the magnetic core of the biomolecule ferritin by means of proton nuclear magnetic resonance (NMR) and relaxation, magnetic susceptibility and scanning electron microscope (SEM) measurements. SEM images show that the outer protein shell is taken out completely by an appropriate chemical treatment and indicate particle sizes ranging from 102 to 104 nm. Susceptibility measurements show a maximum in the zero-field-cooled data which is strongly field-dependent and can be ascribed to superparamagnetic behavior, whereas the hysteresis curve is different from normal ferritin. Proton NMR and spin-lattice relaxation data as a function of temperature at 4.7 T suggest the presence of an antiferromagnetic transition around 100 K. [ABSTRACT FROM AUTHOR]

We have developed a nonconventional broadband electron spin resonance (ESR) spectrometer operating continuously in the frequency range from 0.5 to 9 GHz. Dual antenna structure and the microwave absorbing environment differentiate the setup from the conventional one and enable broadband operation with any combination of frequency or magnetic field modulation and frequency or magnetic field sweeping. Its performance has been tested with the measurements on a 1,1-diphenyl-2-picrylhydrazyl (DPPH) sample and with the measurements on the single molecular magnet, V6, in solid state at low temperature. [ABSTRACT FROM AUTHOR]

We utilize a nonconventional (i.e., without resonance cavity) broadband electron spin resonance (ESR) spectrometer operating continuously in the frequency range 0.3-9 GHz to investigate the ground state of the magnetic molecule {V6} at low temperature. There exist two different varieties of {V6} molecules with small differences in the organic part and in the crystal packing. We find differences in the width and hyperfine structure of the ESR line in the two compounds. However, the central frequency of the broad ESR line measured vs H down to 0.3 GHz shows a linear behavior in both compounds indicating a g value close to 2 and a zero field gap no larger than 30 × 10-3 K. The result is in contrast with a level scheme for the ground state previously reported for one of the two varieties of {V6}. We propose an alternative scenario for the structure of the magnetic ground state. [ABSTRACT FROM AUTHOR]

The structural identity of the biomineralized iron core nanoparticles in Helicobacter pylori ferritins (Hpf's) has been determined by employing soft x-ray absorption spectroscopy and soft x-ray magnetic circular dichroism. Valence states of Fe ions are nearly trivalent in all Hpf's, indicating that the amount of magnetite (Fe3O4) is negligible. With increasing filling of Fe ions, the local configurations of Fe3+ ions change from the mixture of the tetrahedral and octahedral symmetries to the octahedral symmetry. These results demonstrate that the biomineralization of the ferritin core changes from maghemite-like (γ-Fe2O3) formation to hematite-like (α-Fe2O3) formation with increasing Fe content. [ABSTRACT FROM AUTHOR]

A correction to the article “Broadband electron spin resonance at low frequency without resonance cavity” that was published in the July 11, 2008 issue is presented.