Comparison of the core size distribution in iron dextran complexes using Mössbauer spectroscopy and X-ray diffraction.

Mössbauer spectra of a series of iron dextran complexes in the intermediate temperature range where both sextet and doublet coexist may be used to obtain a qualitative description of the distribution of core sizes in these samples. Eight samples from five suppliers have been examined at 100 and 77 K. These differ markedly in the relative doublet contribution to the total spectral area and also in the hyperfine fields characterizing the sextets. The results indicate three distinct types of distribution. One sample from each type has also been examined at 4 K, where the doublet component has vanished and the hyperfine field distribution has become narrow and symmetric. These data are compared with estimates of average core diameters from X-ray line broadening.

Fluoroacetate content of some species of the toxic Australian plant genus, Gastrolobium, and its environmental persistence.

Gas chromatography confirmed the relatively high concentrations of fluoroacetate found in toxic Gastrolobiums, a genus of indigenous Australian plants. Fluoroacetate concentration in these plants ranged from 0.1 to 3875 micrograms/g (ppm) dry weight, with young leaves and flowers containing the highest concentrations. However, there was considerable intrastand variation between individual plants of at least two species with coefficients of variation ranging from 94% to 129%. Despite the high concentrations of fluoroacetate in many species, only one of nine soil samples collected from beneath these plants contained fluoroacetate. None of the 16 water samples collected from nearby streams and catchment dams contained fluoroacetate. This suggests that fluoroacetate does not persist in this environment. Fluoroacetate was also found in the genus Nemcia, and very low levels of fluoroacetate (ng/g) were detected in the foodstuffs, tea and guar gum. The latter indicates that other plant species may produce biologically insignificant amounts of fluoroacetate.

The recharacterization of a polysaccharide iron complex (Niferex).

An oral hematinic marketed as "Niferex," the active component of which is a polysaccharide-iron complex (PIC), has recently been recharacterized. PIC is synthesized by the neutralization of an FeCl3 carbohydrate solution. Original characterization of this complex by Mössbauer spectroscopy and X-ray powder diffraction suggested that the iron-rich core was similar in structure to the mineral ferrihydrite. Higher precision X-ray powder diffraction now indicates that the core has a long-range order more similar to the mineral akaganéite, beta-FeOOH, than to ferrihydrite. This structure has been found for other similar ferric iron-carbohydrate polymers, especially those synthesized by the hydrolysis of FeCl3. Also discussed are the variable temperature (24-295 K) Mössbauer spectroscopic data for PIC. The first example of EXAFS data for polysaccharide iron complexes confirms that the iron is in an octahedral environment, coordinated to oxygen, with a short-range order similar to that for ferritin. The second iron shells in the PIC samples are less ordered than the second shell in ferritin. The size of the PIC core was found to be approximately 5 nm by X-ray powder diffraction, and is of the same order of magnitude as the ferritin core.

A Mössbauer and X-ray powder diffraction study of some ferrous hematinics.

Iron deficiency anemia is a relatively common illness that can arise from a number of different causes. Three ferrous salts are usually used in its treatment: ferrous fumarate, gluconate, and sulfate. They are administered orally and are relatively well tolerated. These hematinics have been studied by Mössbauer spectroscopy and X-ray powder diffraction, and can easily be distinguished by both techniques. It was found that the two ferrous sulfates studied (Eckerd and SmithKline Beckman Co.) most closely resemble the monohydrate by comparison of the X-ray powder pattern with those of the JCPDS. Both the ferrous fumarate (Femiron) and gluconate (Spring Valley) had approximately 10% ferric iron present. To the authors' knowledge, this is the first reported Mössbauer spectrum for ferrous fumarate.

Comparison of polysaccharide iron complexes used as iron supplements.

An oral hematinic marketed as "water soluble polysaccharide iron complex" (Vitaline Formulas) has been characterized using x-ray powder diffraction and Mössbauer spectroscopy. Another polysaccharide iron complex marketed as Niferex (Central Pharmaceuticals) has been previously studied by us and found to have a core similar to ferrihydrite, but with some long-range order of the mineral akaganéite, beta-FeOOH. The latter is seen in other ferric carbohydrate complexes synthesized by the hydrolysis of FeCl3. This commercial product, however, is very different and has a mixture of iron components including hematite (alpha-Fe2O3) magnetite (Fe3O4), goethite (alpha-FeOOH), iron metal, and a ferrous salt.

Structural variations in soluble iron complexes of models for ferritin: an x-ray absorption and Mössbauer spectroscopy comparison of horse spleen ferritin to Blutal (iron-chondroitin sulfate) and Imferon (iron-dextran).

Variations in the turnover of storage iron have been attributed to differences in apoferritin and in the cytoplasm but rarely to differences in the structure of the iron core (except size). To explore the idea that the iron environment in soluble iron complexes could vary, we compared horse spleen ferritin to pharmaceutically important model complexes of hydrous ferric oxide formed from FeCl3 and dextran (Imferon) or chondroitin sulfate (Blutal), using x-ray absorption (EXAFS) and Mössbauer spectroscopy. The results show that the iron in the chondroitin sulfate complex was more ordered than in either horse spleen ferritin or the dextran complex (EXAFS), with two magnetic environments (Mössbauer), one (80%-85%) like Fe2O3 X nH2O (ferritinlike) and one (15%-20%) like Fe2O3 (hematite); since sulfate promotes the formation of inorganic hematite, the sulfate in the chondroitin sulfate most likely nucleated Fe2O3 and hydroxyl/carboxyls, which are ligands common to chondroitin sulfate, ferritin and dextran most likely nucleated Fe2O3 X nH2O. Differences in the structure of the iron complexed with chondroitin sulfate or dextran coincide with altered rates of iron release in vivo and in vitro and provide the first example relating function to local iron structure. Differences might also occur among ferritins in vivo, depending on the apoferritin (variations in anion-binding sites) or the cytoplasm (anion concentration).