Prepregnancy Obesity Is Not Associated with Iron Utilization during the Third Trimester.

BACKGROUND: An adequate maternal iron supply is crucial for maternal red blood cell (RBC) expansion, placental and fetal growth, and fetal brain development. Obese women may be at risk for poor iron status in pregnancy due to proinflammatory-driven overexpression of hepcidin leading to decreased iron bioavailability. OBJECTIVE: The objective of this study was to determine the impact of prepregnancy (PP) obesity on third-trimester maternal iron utilization. DESIGN: Using the stable isotope 57Fe, we measured iron utilization in the third trimester in PP obese [BMI (in kg/m2): ≥30] and nonobese (BMI: 18.5-29.9) women. We also assessed iron status, hepcidin, inflammation, erythropoietin, dietary iron intake, and gestational weight gain. Descriptive and inferential statistical tests (e.g., Student t test, Pearson correlation) were used for data analysis. RESULTS: Fifty pregnant women (21 PP obese, 29 PP nonobese) were included. Mean age was 27.6 ± 6.8 y and mean gestational age at time of 57Fe administration was 32.7 ± 0.7 wk. Anemia (hemoglobin <11 g/dL for non-black and <10.2 g/dL for black women) affected 38% of women (43% PP obese compared with 35% PP nonobese; P = 0.55). Women with PP obesity had significantly higher C-reactive protein (8.5 compared with 3.4 mg/L, P = 0.0007) and total body iron corrected for inflammation (6.0 compared with 4.3 mg/kg, P = 0.04) compared with the nonobese women. There was no difference in serum hepcidin or iron utilization between the PP BMI groups. CONCLUSION: This is the first study to assess the impact of PP obesity on maternal iron utilization. We found no difference in iron utilization in the third trimester of pregnancy in women with and without PP obesity. Despite higher frequency of anemia, women with PP obesity had less depleted body iron stores, suggesting some degree of iron sequestration. This finding should be followed up and extended to understand effects on fetal iron bioavailability.

Acute Consumption of Prebiotic Galacto-Oligosaccharides Increases Iron Absorption from Ferrous Fumarate, but not from Ferrous Sulfate and Ferric Pyrophosphate: Stable Iron Isotope Studies in Iron-Depleted Young Women.

BACKGROUND: Although acute consumption of high doses of prebiotic galacto-oligosaccharides (GOS) increases fractional iron absorption (FIA) from ferrous fumarate (FeFum), it is uncertain if low doses of GOS have this effect. Furthermore, whether GOS improve iron absorption from other commonly used iron compounds and whether ascorbic acid (AA) enhances the effect of GOS on iron absorption from FeFum is unclear. OBJECTIVES: In iron-depleted women [serum ferritin (SF) <30 µg/L], we assessed: 1) whether the acute enhancing effect of GOS on FeFum is dose dependent; 2) if GOS would affect FIA from ferrous sulfate (FeSO4) or ferric pyrophosphate (FePP); and 3) if AA and GOS given together enhance FIA from FeFum to a greater extent compared with GOS alone. METHODS: We recruited 46 women (mean age 22.0 y, mean BMI 21.3 kg/m2, median SF 17.1 µg/L), and measured FIA from 14 mg iron labeled with stable isotopes in the following conditions: 1) FIA from FeFum given with 3.5 g, 7 g GOS, and without GOS; 2) FIA from FeSO4 and FePP given with and without 15 g GOS; and 3) FIA from FeFum given with 7 g GOS with and without 93 mg AA. FIA was measured as erythrocyte incorporation of stable isotopes after 14 d. Comparisons were made using paired samples t-test or Wilcoxon rank sum test where appropriate. RESULTS: Giving 7 g of GOS significantly increased FIA from FeFum (+26%; P = 0.039), whereas 3.5 g GOS did not (P = 0.130). GOS did not significantly increase FIA from FeSO4 (P = 0.998) or FePP (P = 0.059). FIA from FeFum given with GOS and AA was significantly higher compared with FeFum given with GOS alone (+30%; P <0.001). CONCLUSIONS: In iron-depleted women, GOS does not increase FIA from FeSO4 or FePP, but it increases FIA from FeFum. Thus, a combination of FeFum and GOS may be a well-absorbed formula for iron supplements. The study was registered at clinicaltrials.gov as NCT03762148.

57Fe enrichment in mice for ß-thalassaemia studies via Mössbauer spectroscopy of blood samples.

In this work, wild-type and heterozygous ß-thalassaemic mice were enriched with 57Fe via gastrointestinal absorption to characterize in greater detail the iron complexes then identifiable via Mössbauer spectroscopy. The 57Fe enrichment method was validated and Mössbauer spectra were obtained at 80 K from blood samples from wild-type and ß-thalassaemic mice at 1, 3, 6, and 9 months of age. As expected, the haemoglobin levels of the thalassaemic mice were lower than from normal mice, indicating anaemia. Furthermore, significant amounts of ferritin-like iron were observed in the thalassaemic mice samples, which decreased with mouse age, reflecting the pattern of reticulocyte count reduction reported in the literature.

A Nitric Oxide Storage and Transport System That Protects Activated Macrophages from Endogenous Nitric Oxide Cytotoxicity.

Nitric oxide (NO) is integral to macrophage cytotoxicity against tumors due to its ability to induce iron release from cancer cells. However, the mechanism for how activated macrophages protect themselves from endogenous NO remains unknown. We previously demonstrated by using tumor cells that glutathione S-transferase P1 (GSTP1) sequesters NO as dinitrosyl-dithiol iron complexes (DNICs) and inhibits NO-mediated iron release from cells via the transporter multidrug resistance protein 1 (MRP1/ABCC1). These prior studies also showed that MRP1 and GSTP1 protect tumor cells against NO cytotoxicity, which parallels their roles in defending cancer cells from cytotoxic drugs. Considering this, and because GSTP1 and MRP1 are up-regulated during macrophage activation, this investigation examined whether this NO storage/transport system protects macrophages against endogenous NO cytotoxicity in two well characterized macrophage cell types (J774 and RAW 264.7). MRP1 expression markedly increased upon macrophage activation, and the role of MRP1 in NO-induced 59Fe release was demonstrated by Mrp1 siRNA and the MRP1 inhibitor, MK571, which inhibited NO-mediated iron efflux. Furthermore, Mrp1 silencing increased DNIC accumulation in macrophages, indicating a role for MRP1 in transporting DNICs out of cells. In addition, macrophage 59Fe release was enhanced by silencing Gstp1, suggesting GSTP1 was responsible for DNIC binding/storage. Viability studies demonstrated that GSTP1 and MRP1 protect activated macrophages from NO cytotoxicity. This was confirmed by silencing nuclear factor-erythroid 2-related factor 2 (Nrf2), which decreased MRP1 and GSTP1 expression, concomitant with reduced 59Fe release and macrophage survival. Together, these results demonstrate a mechanism by which macrophages protect themselves against NO cytotoxicity.

A higher proportion of iron-rich leafy vegetables in a typical Burkinabe maize meal does not increase the amount of iron absorbed in young women.

Food-to-food fortification can be a promising approach to improve the low dietary iron intake and bioavailability from monotonous diets based on a small number of staple plant foods. In Burkina Faso, the common diet consists of a thick, cereal-based paste consumed with sauces composed of mainly green leaves, such as amaranth and jute leaves. Increasing the quantity of leaves in the sauces substantially increases their iron concentration. To evaluate whether increasing the quantity of leaves in sauces would provide additional bioavailable iron, an iron absorption study in 18 young women was conducted in Zurich, Switzerland. Burkinabe composite test meals consisting of the maize paste tô accompanied by an iron-improved amaranth sauce, an iron-improved jute sauce, or a traditional amaranth sauce were provided as multiple meals twice a day for 2 consecutive days. Iron absorption was measured as erythrocyte incorporation of stable iron isotopes. Mean fractional iron absorption from maize paste consumed with an iron-improved amaranth sauce (4.9%) did not differ from the same meal consumed with an iron-improved jute sauce (4.9%; P = 0.9), resulting in a similar quantity of total iron absorbed (679 vs. 578 µg; P = 0.3). Mean fractional iron absorption from maize paste accompanied by a traditional amaranth sauce (7.4%) was significantly higher than that from the other 2 meal types (P < 0.05), but the quantity of total iron absorbed was similar (591 µg; P = 0.4 and 0.7, respectively). A food-to-food fortification approach based on an increase in leafy vegetables does not provide additional bioavailable iron, presumably due to the high phenolic compound concentration of the leaves tested. Alternative measures, such as adding iron absorption enhancers to the sauces, need to be investigated to improve iron nutrition from Burkinabe maize meals.

Novel bioanalytical strategy using isotope pattern deconvolution and ICP-QMS for the study of iron incorporation in erythrocytes: An insight to better assessment.

Iron is an essential element for human life and its nutritional status in the human body is directly linked to human health. More than 1015 atoms of iron per second are necessary for the maintenance of haemoglobin formation. To predict iron bioavailability three approaches are normally employed: (a) faecal recovery; (b) plasma appearance; and (c) erythrocyte incorporation (the most used). Isotope Pattern Deconvolution (IPD) is a mathematical tool that allows the isolation of distinct isotope signatures from mixtures of natural abundance and enriched tracers. In this work we propose a novel strategy to assess erythrocyte iron incorporation, based on the use of an iron stable isotope (57Fe) and the IPD concept. This strategy allows direct calculation of the exogenous concentration of 57Fe incorporated into RBCs after supplementation. In this way, to determine the mass of iron incorporated into erythrocytes, the unique prediction that must be made is the blood volume, estimate to reproduce the natural dilution of the tracer (57Fe) in the blood. This novel bioanalytical approach was applied for the measurements of iron incorporation and further iron absorption studies in humans, using a group of twelve healthy participants, that should be further evaluated for the assessment of other chemical elements that could be of health concerns and directly impact society.

Tissue-variation of iron stable isotopes in marine fish coupled with speciation analysis using X-ray absorption fine structure.

The Fe stable isotope ratio (δ56Fe) in tissues is a potential parameter for examining the Fe metabolism in marine fish. Although the effect of ferritin storage has been proposed as a possible cause of heavy isotope (56Fe) enrichment in the liver, no speciation and stable isotope ratio coupling data are available. Here, we report the δ56Fe values measured by multicollector ICP-MS and the result of Fe K-edge X-ray absorption near-edge structure (XANES) analysis of multiple tissues obtained from a skipjack tuna (Katsuwonus pelamis) and a chub mackerel (Scomber japonicus). Apparent isotopic fractionation between the liver and the muscle samples (Δ56FeL-M = Î´56Feliver - Î´56Femuscle) from these species was observed (0.85 ‰ and 0.57 ‰, respectively). The dominant Fe species in the muscle was heme Fe (the sum of methemoglobin, oxyhemoglobin, and deoxyhemoglobin), while ferritin was not detected according to the linear combination fitting of the XANES spectra. In the liver, ferritin contribution was ca. 28 %-54 % of the total Fe content. The apparent difference in δ56Fe between heme Fe and ferritin was estimated to range from 1.41 ‰ to 1.52 ‰ based on the tissue-specific δ56Fe values and the XANES results. These results indicate that the Fe storage as ferritin does not induce the lowering of δ56Fe in the muscle, considering the low contribution of the liver Fe to the total Fe content in the body.

Iron isotopic fractionation driven by low-temperature biogeochemical processes.

Iron is geologically important and biochemically crucial for all microorganisms, plants and animals due to its redox exchange, the involvement in electron transport and metabolic processes. Despite the abundance of iron in the earth crust, its bioavailability is very limited in nature due to its occurrence as ferrihydrite, goethite, and hematite where they are thermodynamically stable with low dissolution kinetics in neutral or alkaline environments. Organisms such as bacteria, fungi, and plants have evolved iron acquisition mechanisms to increase its bioavailability in such environments, thereby, contributing largely to the iron cycle in the environment. Biogeochemical cycling of metals including Fe in natural systems usually results in stable isotope fractionation; the extent of fractionation depends on processes involved. Our review suggests that significant fractionation of iron isotopes occurs in low-temperature environments, where the extent of fractionation is greatly governed by several biogeochemical processes such as redox reaction, alteration, complexation, adsorption, oxidation and reduction, with or without the influence of microorganisms. This paper includes relevant data sets on the theoretical calculations, experimental prediction, as well as laboratory studies on stable iron isotopes fractionation induced by different biogeochemical processes.

Change in the characteristics of ferritin induces iron imbalance in prion disease affected brains.

Prion disease associated neurotoxicity is mainly attributed to PrP-scrapie (PrP(Sc)), the disease associated isoform of a normal protein, the prion protein (PrP(C)). Participation of other proteins and processes is suspected, but their identity and contribution to the pathogenic process is unclear. Emerging evidence implicates imbalance of brain iron homeostasis as a significant cause of prion disease-associated neurotoxicity. The underlying cause of this change, however, remains unclear. We demonstrate that iron is sequestered in heat and SDS-stable protein complexes in sporadic-Creutzfeldt-Jakob-disease (sCJD) brains, creating a phenotype of iron deficiency. The underlying cause is change in the characteristics of ferritin, an iron storage protein that becomes aggregated, detergent-insoluble, and partitions with denatured ferritin using conventional methods of ferritin purification. A similar phenotype of iron deficiency is noted in the lumbar spinal cord (SC) tissue of scrapie infected hamsters, a site unlikely to be affected by massive neuronal death and non-specific iron deposition. As a result, the iron uptake protein transferrin (Tf) is upregulated in scrapie infected SC tissue, and increases with disease progression. A direct correlation between Tf and PrP(Sc) suggests sequestration of iron in dysfunctional ferritin that either co-aggregates with PrP(Sc) or is rendered dysfunctional by PrP(Sc) through an indirect process. Surprisingly, amplification of PrP(Sc)in vitro by the protein-misfolding-cyclic-amplification (PMCA) reaction using normal brain homogenate as substrate does not increase the heat and SDS-stable pool of iron even though both PrP(Sc) and ferritin aggregate by this procedure. These observations highlight important differences between PrP(Sc)-protein complexes generated in vivo during disease progression and in vitro by the PMCA reaction, and the significance of these complexes in PrP(Sc)-associated neurotoxicity.

Nutritional iron supplementation studies based on enriched (57) Fe, added to milk in rats, and isotope pattern deconvolution-ICP-MS analysis.

Enriched stable iron isotopes in combination with isotope pattern deconvolution and ICP-MS have been used to study the absorption and bioavailability of iron from supplemented formula milk administrated to lactating rats. The use of two enriched stable isotope tracers, one as the metabolic tracer (here (57) Fe) and the other ((54) Fe) as quantitation tracer, is shown to provide quantitative data about endogenous and exogenous (supplemented) total Fe distribution in rat feces, urine, red blood cells (RBCs), serum, liver, and kidney. The proposed analytical methodology was validated using reference materials (serum, urine, and liver) spiked with both (54) Fe and (57) Fe. Quantitative information about iron absorption/bioavailability and/or metabolism can be obtained from the amounts of endogenous and exogenous iron found in the tissues and fluids analyzed, and about its kinetic after 2 weeks of iron supplementation. The obtained results are discussed in terms of iron exchanged and its half-life in lactating rats and the observed iron levels in serum, RBCs, liver, and kidney comparing nonsupplemented rats and maternal feed rats.

Mobilization of storage iron is reflected in the iron isotopic composition of blood in humans.

We recently showed in an animal model that iron isotopic composition varies substantially between different organs. For instance, iron in ferritin-rich organs--such as the major storage tissues liver, spleen, and bone marrow--contain a larger fraction of the heavy iron isotopes compared with other tissues, including blood. As a consequence, partitioning of body iron into red blood cells and storage compartments should be reflected in the isotopic pattern of blood iron. To confirm this hypothesis, we monitored blood iron isotope patterns in iron-overloaded subjects undergoing phlebotomy treatment by multicollector inductively coupled plasma mass spectrometry. We found that bloodletting and consequential replacement of lost blood iron by storage iron led to a substantial increase of the heavy isotope fraction in the blood. The progress of iron depletion therapy and blood loss was quantitatively traceable by isotopic shifts of as much as +1‰ in δ((56)Fe). These results show that--together with iron absorption efficiency--partitioning of iron between blood and iron storage tissues is an important determinant of blood iron isotopic patterns, which could make blood iron isotopic composition the first composite measure of iron metabolism in humans.

Quantitating Iron Transport across the Mouse Placenta In Vivo using Nonradioactive Iron Isotopes.

Iron is essential for maternal and fetal health during pregnancy, with approximately 1 g of iron needed in humans to sustain a healthy pregnancy. Fetal iron endowment is entirely dependent on iron transfer across the placenta, and perturbations of this transfer can lead to adverse pregnancy outcomes. In mice, measurement of iron fluxes across the placenta traditionally relied on radioactive iron isotopes, a highly sensitive but burdensome approach. Stable iron isotopes (57Fe and 58Fe) offer a nonradioactive alternative for use in human pregnancy studies. Under physiological conditions, transferrin-bound iron is the predominant form of iron taken up by the placenta. Thus, 58Fe-transferrin was prepared and injected intravenously in pregnant dams to directly assess placental iron transport and bypass maternal intestinal iron absorption as a confounding variable. Isotopic iron was quantitated in the placenta and mouse embryonic tissues by inductively coupled plasma mass spectrometry (ICP-MS). These methods can also be employed in other animal model systems of physiology or disease to quantify in vivo iron dynamics.

Measurement of the enriched stable isotope 58Fe in iron related disorders- comparison of INAA and MC-ICP-MS.

As a safer alternative for the use of radioactive tracers, the enriched stable 58Fe isotope has been introduced in studies of iron metabolism. In this study this isotope is measured with instrumental neutron activation analysis (INAA) in blood samples of patients with iron related disorders and controls after oral ingestion of a 58Fe containing pharmaceutical. Results were compared with those derived from MC-ICP-MS, applied on the same samples, and analytical and practical aspects of the two techniques were compared. Both techniques showed an increased absorption and incorporation in red blood cells of the 58Fe isotope in iron deficient patients in contrast to the controls. In all individuals results of INAA measurements were in good agreement with those of MC-ICP-MS (|zeta| < 2). Uncertainties in INAA are substantially higher than those achievable by MC-ICP-MS but the INAA technique offers a high specificity and selectivity for iron close to 100%. In contrast to INAA, sample preparation before measurement is very critical in MC-ICP-MS and interferences with 58Ni and 54Cr may hamper the measurement of 58Fe and 54Fe respectively. Since it takes at least five days after irradiation to reduce the activity of interfering radionuclides (mainly 24Na), INAA is a more time consuming procedure; the need of a nuclear reactor facility makes it also less accessible than MC-ICP-MS. Costs are comparable. Both INAA and MC-ICP-MS are able to adequately measure changes in iron isotope composition in blood when an enriched stable iron isotope is applied in clinical research. Although MC-ICP-MS is more sensitive, is faster and has easier access, in INAA preparative steps before measurement are simpler and there are hardly demands on the kind and size of the samples. This may be relevant working with biomaterials in a clinical setting.

Iron bioavailability of a casein-based iron fortificant compared with that of ferrous sulfate in whole milk: a randomized trial with a crossover design in adult women.

BACKGROUND: A highly soluble iron-casein complex has been developed for food fortification purposes with the aim to provide high iron bioavailability. OBJECTIVE: We aimed to determine the iron bioavailability of the iron-casein complex relative to that of ferrous sulfate (control) when given with whole milk in healthy young women. METHODS: A randomized comparator-controlled trial with a crossover design was conducted using the erythrocyte incorporation dual stable isotope (57Fe, 58Fe) technique. Iron absorption from the iron-casein complex was compared with that from ferrous sulfate in 21 healthy women aged 20-38 y with normal iron status. RESULTS: Fractional iron absorption (geometric mean; -SD, +SD) from the iron-casein complex (3.4%; 1.4%, 5.4%) and from ferrous sulfate (3.9%; 1.7%, 6.1%) were not statistically different (P > 0.05). The relative bioavailability value of the iron-casein complex to ferrous sulfate was determined to be 0.87 (-1 SD, +1 SD: -0.90, +2.64). CONCLUSIONS: The iron-casein complex has iron bioavailability comparable to that of ferrous sulfate in healthy young women. This trial was registered at www.anzctr.org.au as ACTRN12615000690550.

Mass-dependent and -independent signature of Fe isotopes in magnetotactic bacteria.

Magnetotactic bacteria perform biomineralization of intracellular magnetite (Fe3O4) nanoparticles. Although they may be among the earliest microorganisms capable of biomineralization on Earth, identifying their activity in ancient sedimentary rocks remains challenging because of the lack of a reliable biosignature. We determined Fe isotope fractionations by the magnetotactic bacterium Magnetospirillum magneticum AMB-1. The AMB-1 strain produced magnetite strongly depleted in heavy Fe isotopes, by 1.5 to 2.5 per mil relative to the initial growth medium. Moreover, we observed mass-independent isotope fractionations in (57)Fe during magnetite biomineralization but not in even Fe isotopes ((54)Fe, (56)Fe, and (58)Fe), highlighting a magnetic isotope effect. This Fe isotope anomaly provides a potential biosignature for the identification of magnetite produced by magnetotactic bacteria in the geological record.

Extrinsic Labeling of Staple Food Crops with Isotopic Iron Does Not Consistently Result in Full Equilibration: Revisiting the Methodology.

Extrinsic isotopic labeling of food Fe has been used for over 50 years to measure Fe absorption. This method assumes that complete equilibration occurs between the extrinsic and the intrinsic Fe prior to intestinal absorption. The present study tested this assumption via in vitro digestion of varieties of maize, white beans, black beans, red beans, and lentils. Prior to digestion, foods were extrinsically labeled with (58)Fe at concentrations of 1, 10, 50, and 100% of the intrinsic (56)Fe. Following an established in vitro digestion protocol, the digest was centrifuged and the Fe solubilities of the extrinsic (58)Fe and the intrinsic (56)Fe were compared as a measure of extrinsic/intrinsic equilibration. In the beans, significantly more of the extrinsic Fe (up to 2-3 times, p < 0.001) partitioned into the supernatant. The effect varied depending upon the seed coat color, the harvest, and the concentration of the extrinsic Fe. For lentils and maize the extrinsic Fe tended to partition into the insoluble fraction and also varied depending on variety and harvest. There was no crop that consistently demonstrated full equilibration of the extrinsic Fe with the intrinsic Fe. These observations challenge the accuracy of Fe absorption studies in which isotopic extrinsic Fe was used to evaluate Fe absorption and bioavailability.

Iron Absorption from Two Milk Formulas Fortified with Iron Sulfate Stabilized with Maltodextrin and Citric Acid.

BACKGROUND: Fortification of milk formulas with iron is a strategy widely used, but the absorption of non-heme iron is low. The purpose of this study was to measure the bioavailability of two iron fortified milk formulas designed to cover toddlers´ nutritional needs. These milks were fortified with iron sulfate stabilized with maltodextrin and citric acid. METHODS: 15 women (33-47 years old) participated in study. They received on different days, after an overnight fast, 200 mL of Formula A; 200 mL of Formula B; 30 mL of a solution of iron and ascorbic acid as reference dose and 200 mL of full fat cow's milk fortified with iron as ferrous sulfate. Milk formulas and reference dose were labeled with radioisotopes (59)Fe or (55)Fe, and the absorption of iron measured by erythrocyte incorporation of radioactive Fe. RESULTS: The geometric mean iron absorption corrected to 40% of the reference dose was 20.6% for Formula A and 20.7% for Formula B, versus 7.5% of iron fortified cow's milk (p < 0.001). The post hoc Sheffé indeed differences between the milk formulas and the cow's milk (p < 0.001). CONCLUSION: Formulas A and B contain highly bioavailable iron, which contributes to covering toddlers´ requirements of this micronutrient.

Absorption of stable isotopes of iron, copper, and zinc during oral contraceptives use.

The absorption of iron, copper, and zinc was determined in 22 women 19 to 25 years of age from the difference between intake and fecal output of the stable isotopes 58Fe, 65Cu, and 70Zn, as measured by neutron activation analysis. Of the 22 women, 14 were using oral contraceptive agents, and the other eight were not. Absorption in the group using oral contraceptive agents did not differ significantly from the group not using oral contraceptive agents. The overall iron absorption averaged 14%, copper 57%, and zinc 38%.

PIP: Absorption of iron, copper, and zinc was determined in 22 women (19-25 years old) from the difference between intake (regulated by testers) and fecal output of the stable isotopes Fe-58, Cu-65, and Zn-70, as measured by neutron activation analysis. Of the 22, 14 were using oral contraceptives (OCs) (1 sequential and the rest combined), and 8 were not. Absorption values did not differ significantly between the OC users and the nonusers. These data suggest that stable isotopes of elements offer promise as a means of measuring mineral absorption without the undesirable aspects of feeding radioactive materials to humans. Disadvantages include difficulty obtaining hardward, expense of radioactive isotopes, and requirement for additional radiochemical separations for zinc, and possibly other minerals.

The dynamics of (57)Fe nuclei in Fe(III)-DNA condensates.

The dynamics of iron nuclei in the condensates obtained by interaction of Fe(III) with DNA, Fe(III)(DNA monomer)(2), have been investigated by variable temperature (57)Fe Mössbauer spectroscopy. Studies were effected on gel and freeze-dried samples, obtaining nearly coincident values of the parameters isomer shift and nuclear quadrupole splitting in T ranges 20-260 K. Functions ln(A(T)/A(77.3)) vs. T, here employed to investigate the dynamics of Fe nuclei, showed linear trends in the T ranges 20-150 and 150-260 K, respectively, the latter with larger slopes. Data coincided for gelled and freeze-dried specimens. No variation of delta or Delta E parameters occurred at the two T intervals, which suggests constancy of structure and bonding with the temperature changes. Functions (T) showed trends analogous to the corresponding functions determined for iron proteins, which were attributed to the occurrence of 'conformational substates'.

The role of bacterial consortium and organic amendment in Cu and Fe isotope fractionation in plants on a polluted mine site.

Copper and iron isotope fractionation by plant uptake and translocation is a matter of current research. As a way to apply the use of Cu and Fe stable isotopes in the phytoremediation of contaminated sites, the effects of organic amendment and microbial addition in a mine-spoiled soil seeded with Helianthus annuus in pot experiments and field trials were studied. Results show that the addition of a microbial consortium of ten bacterial strains has an influence on Cu and Fe isotope fractionation by the uptake and translocation in pot experiments, with an increase in average of 0.99 ‰ for the δ(65)Cu values from soil to roots. In the field trial, the amendment with the addition of bacteria and mycorrhiza as single and double inoculation enriches the leaves in (65)Cu compared to the soil. As a result of the same trial, the δ(56)Fe values in the leaves are lower than those from the bulk soil, although some differences are seen according to the amendment used. Siderophores, possibly released by the bacterial consortium, can be responsible for this change in the Cu and Fe fractionation. The overall isotopic fractionation trend for Cu and Fe does not vary for pot and field experiments with or without bacteria. However, variations in specific metabolic pathways related to metal-organic complexation and weathering can modify particular isotopic signatures.