Number Of Iron Atoms Research Articles

Isolation, purification and characterization of spleen ferritin of Gallus domesticus L.

The ferritin from the spleen of the chickens has been isolated by a method of salt fractionation and by a pH change followed by purification in sephadex G-200. 1. 2. The identification of the protein was carried out by acrylamide gel electrophoresis showing a single band. 2. 3. The characterization of ferritin has been made by determination of molecular weight, amino acids analysis and the number of iron atoms (4520) which bound the ferritin. 3. 4. The ferritin from the spleen of chicken is compared with the ferritin from the liver of pigeon.

Effect of melting conditions on the thermal expansion coefficient of alloy 36N

1. Heating melts of alloy 36N above 1700° leads to rebuilding of short-range order. During cooling of the melt this high-temperature "structure" of the liquid is retained down to the solidification temperature. 2. The condition of the melt before solidification affects the structure of the metal solidified from it. This is confirmed by the change in the coefficient of thermal expansion (TEC) and the lattice constant of samples in relation to the temperature above the liquidus to which the alloy was heated. Samples from melts heated to 1800° were characterized by larger and more consistent values of TEC than samples from the melt heated to temperatures below 1700°. 3. Data on the most probable interatomic distances lead to the assumption that with increasing overheating temperatures the composition of the solid pseudosystem Feϒ1 + Feϒ2 +36% Ni shifts toward a smaller increase in the number of iron atoms in the ϒ2 electronic condition.

Mössbauer study of atomic order inNi3Fe. I. Determination of the long-range-order parameter

By means of M\ossbauer spectroscopy we studied the structural order in a series of stoichiometric ${\mathrm{Ni}}_{3}$Fe foils, which had been given different heat treatments. The long-range-order parameter $\ensuremath{\eta}$ was determined with an accuracy of \ifmmode\pm\else\textpm\fi{}0.02 by analyzing the profiles of the outer lines of $^{57}\mathrm{Fe}$ absorption spectra, recorded at room temperature. From the analysis it appeared that the hyperfine field at $^{57}\mathrm{Fe}$ nuclei depends linearly on the numbers of iron atoms in the first and second neighboring shell, and that contributions from more distant atoms are negligible. Further anisotropic hyperfine interactions in ${\mathrm{Ni}}_{3}$Fe are small. A comparison with $\ensuremath{\eta}$ as determined from x-ray diffraction indicates that the wrongly placed atoms in partly ordered ${\mathrm{Ni}}_{3}$Fe are distributed at random over the lattice sites.

Quantitative site population in silicate minerals by the Mössbauer effect

Using the areas under Mössbauer peaks, the amount of Fe 2+ in structurally different cation positions, and the Fe 2+ Fe 3+ ratio can be calculated in silicate minerals. For a mineral containing two different types of iron atoms which give rise to different Mössbauer spectra, the area ratio A 2 A 1 equals C N 2 N 1 , where N 2 and N 1 are the number of iron atoms per formula unit and C is a constant. For a cummingtonite and a glaucophane, the calculated Fe 2+ site populations are in good agreement with those calculated by X-ray crystallography. For silicates containing Fe 2+ and Fe 3+, the ratio of Fe 3+ Fe 2+ is generally in good agreement with those calculated from chemical analyses. The assumptions and difficulties in the Mössbauer method are reviewed critically.

The number of iron atoms in the paramagnetic center (G =1.94) of reduced putidaredoxin, a nonheme iron protein.

A number of oxidation-reduction proteins, containing iron and an acid-labile form of sulfide, have been shown to exhibit low-temperature electron paramagnetic resonance (EPR) signals near g = 1.94, on reduction.l-4 These proteins include oxidases of the xanthine type, ferredoxins, and nonheme-iron and iron flavoproteins from mitochondria and bacteria. By substitution with iron5 and sulfur6' 7 isotopes having nonzero nuclear spin, both elements were conclusively shown to participate in the paramagnetic center. The nuclear magnetic moments may couple to the moment of the unpaired electron of the center, producing small positive and negative incremental local fields which act to split or broaden the EPR spectrum compared to the unsubstituted cases. The effect depends, in the simplest case of isotropic hyperfine interaction, on three variables, viz., the enrichment in isotope of nonzero nuclear spin (Fe57 of S33 in the present case), the effective local field contribution or hyperfine splitting constant of each atom, and the number of atoms of each isotope involved with a single unpaired electron. If the enrichment can be estimated, trial spectra can be calculated for various hyperfine splittings and numbers of atoms. In favorable cases comparison to the observed spectrum will reveal the values of the variables that best fit hypothesis to experiment. In this way one can determine the number and kinds of atoms interacting with the unpaired electron under the assumption of predominantly isotropic hy

Neutron Polarization and Ferromagnetic Saturation

The transmission of thermal neutrons through magnetized iron has been measured in its dependence upon the percentage deviation $\ensuremath{\epsilon}$ from saturation and upon the thickness $d$ of the sample. In agreement with the theory of Halpern and Holstein it was found that the percentage increase of transmission caused by magnetization is given by $(\frac{{n}^{2}{p}^{2}{d}^{2}}{2})f(\frac{\ensuremath{\lambda}}{\ensuremath{\epsilon}d})$, where $n$ is the number of iron atoms per unit volume. Writing for the scattering cross section of neutrons with parallel or antiparallel orientation of their spin with respect to the field, respectively ${\ensuremath{\sigma}}_{0}\ifmmode\pm\else\textpm\fi{}p$, we find $p=2.0\ifmmode\pm\else\textpm\fi{}0.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$. From the determined value of the length $\ensuremath{\lambda}=3.2\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ cm, the linear dimensions of the microcrystals can be determined to be $\ensuremath{\delta}=1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ cm. For a thickness $d=3.8$ cm a transmission effect of almost 8 percent was observed if the magnetization was brought to within 2.5 per mille of its saturation value; more than twice this effect can be expected from the same thickness at complete saturation.