Various Sources Of Iron Research Articles

Optimizing Fe-N-C Electrocatalysts for PEMFCs: Influence of Constituents and Pyrolysis on Properties and Performance

Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen reduction reaction (ORR) of the cathode side, prevents their widespread incorporation. Fe-N-C electrocatalysts have emerged as viable alternatives to platinum. In this study, different precursor components were investigated for the way that they affect the pyrolysis process, which is crucial for tailoring the final catalyst properties. In particular, carbon allotropes such as carbon Vulcan, Ketjenblack, and carbon nanotubes were selected for their unique structures and properties. In addition, various sources of iron (FeCl2, FeCl3, and K[Fe(SCN)4]) were evaluated. The influence of the pyrolysis atmosphere on the resulting Fe-N-C catalyst structures was also assessed. Through an integrated structure and surface chemistry analyses, as well as electrochemical tests with rotating disk electrode experiments in acidic media, the ORR performance and stability of these catalysts were defined. By examining the relationships between carbon sources and iron precursors, this research provides valuable information for the optimization of Fe-N-C catalysts in fuel cell applications.

Bacterial Siderophores: Structure, Functions, and Role in the Pathogenesis of Infections

This review systematizes and analyzes the data published over the past decade, devoted to the study of low-molecular-weight high affinity iron chelators – siderophores. Siderophores, which are found in bacteria, fungi and mammals, are able to extract iron from insoluble inorganic compounds, and in the host organism – from complexes with proteins that perform the function of nonspecific protection of mammals from infections. The extracted iron is delivered to cells through surface protein receptors specific for each siderophore, as well as various protein transport systems that make up membranes. Siderophores play an important role in virulence in pathogenic bacteria, performing many functions in the host organism, in addition to providing microbes with iron and other biological metals. They participate in the storage of excess iron, toxic to cells, protect bacteria from reactive oxygen compounds, compete for iron with phagocytes, and have a harmful effect on host cells, acting as secreted bacterial toxin in some cases. Bacterial siderophores perform a signaling function and regulate both, their own synthesis and the synthesis of other virulence factors. Many pathogenic bacteria produce several siderophores that are active under different conditions, against various sources of iron in the host organism and at different stages of infectious process. The review presents the results of the experimental studies aimed at elucidating the structure and diverse functions of bacterial siderophores, the mechanisms of their biosynthesis and regulation of expression, as well as the role of these molecules in the physiology and virulence of pathogenic bacteria. Special emphasis is put on siderophores of bacteria causing particularly dangerous infections.

Iron Sources Effects on Growth, Physiological Parameters and Nutrition of Cacao

Productivity and sustainability of cacao (Theobroma cacao L.) in tropical soils are affected by levels of iron. Information is lacking on the cacao response to various sources of iron (Fe). A greenhouse experiment was conducted to evaluate the effects of five iron sources iron sulfate heptahydrate, ferric ethylenediamine-N,N’-bis(2-hydroxyphenylacetic acid), ferric diethylenetriaminepentaacetic acid, ferric ethylenediaminetetraacetic acid, fiesta herbicide (FeSO4 · 7H2O, FeEDDHA, FeDTPA, FeEDTA,) at 10 mg Fe kg−1 soil on growth, photosynthesis, content of photosynthetic pigments and starch and macro- and micronutrient nutrition of cacao. The various iron sources had significant effects on shoot and root dry biomass accumulation, leaf chlorophyll a and b content, carotenoid levels, SPAD index and PN. These parameters were significantly correlated with concentration, uptake, influx, and transport and use efficiency of Fe. In cacao net photosynthesis, stomatal conductance, internal carbon dioxide (CO2), and transpiration in leaf level responded differently to the sources of Fe. Invariably, macro and micronutrient uptake, influx, transport, and use efficiency showed differential responses to sources of iron but significant effects were only observed for copper (Cu), Fe, manganese (Mn), and zinc (Zn). Overall, FeDTPA, FeEDTA and FeHEDTA could be the best sources of Fe in improving, growth, photosynthesis and macro and micro nutrition of cacao.

An update on the transport and metabolism of iron in Listeria monocytogenes: the role of proteins involved in pathogenicity.

Listeria monocytogenes is a Gram-positive bacterium that causes a rare but severe human disease with high mortality rate. The microorganism is widespread in the natural environment where it shows a saprophytic lifestyle. In the human body it infects many different cell types, where it lives intracellularly, however it may also temporarily live extracellularly. The ability to survive and grow in such diverse niches suggests that this bacterium has a wide range of mechanisms for both the acquisition of various sources of iron and effective management of this microelement. In this review, data about the mechanisms of transport, metabolism and regulation of iron, including recent findings in these areas, are summarized with focus on the importance of these mechanisms for the virulence of L. monocytogenes. These data indicate the key role of haem transport and maintenance of intracellular iron homeostasis for the pathogenesis of L. monocytogenes. Furthermore, some of the proteins involved in iron homeostasis like Fri and FrvA seem to deserve special attention due to their potential use in the development of new therapeutic antilisterial strategies.

Ocean chemistry: Fingerprints of a trace nutrient.

Lack of dissolved iron in the sea limits biological productivity and the uptake of carbon dioxide. The sources of dissolved iron in the North Atlantic Ocean have been identified from isotopic variations of this trace nutrient. See Letter p.212 Iron availability limits phytoplankton growth throughout the oceans, acting as a key influence on the global carbon cycle and the oceanic response to changing climate. But large uncertainties remain as to the relative importance of the various sources of iron, including windblown dust and hydrothermal vents. This paper presents a high-resolution transect of seawater dissolved stable iron isotope ratios and iron concentrations in the North Atlantic Ocean. Saharan dust aerosol emerges as the dominant source of dissolved iron along the section, with sediments and hydrothermal vents also significant. Changes in these sources through time may have wide-ranging implications for the global carbon cycle.

Iron-Containing Intermetallic Phases in Al-Si Based Casting Alloys

Iron is the most common impurity in aluminium and its alloys. It is not easily removed and it can cause adverse effects to ductility and castability, particularly in the popular Al-Si based casting alloys. The choice of whether to use alloys based on primary aluminium (low Fe levels, high cost) or secondary aluminium (moderate/high Fe levels, cheaper) for a cast product is often a commercial decision. However, a compromise may be necessary between the desire for reduced metal cost and the need to maximise casting productivity via reduced defect formation and to minimise the deleterious effect of iron on mechanical properties. This paper discusses the various sources of iron, how it enters aluminium alloys, the way that iron leads to the formation of complex intermetallic phases during solidification and how these phases can adversely affect mechanical properties (especially ductility) and lead to the formation of excessive shrinkage defects. The formation of the iron-containing β phase will be highlighted using the latest in situ solidification study using synchrotron X-radiation. The paper offers guidelines to the practical levels of iron that can be tolerated and how to minimise the negative effects of iron.

Iron(II)‐Catalyzed Asymmetric Hydrosilylation of Acetophenone

AbstractFour new ligands containing a pentasubstituted cyclopentadiene tethered to a stereogenic diamine unit have been prepared and used in the iron‐catalyzed enantioselective hydrosilylation of acetophenone. Catalytically active species have been generated in situ starting from various sources of iron. Fe(acac)2 was the catalyst precursor of choice, whereas other simple FeII or FeIII compounds resulted in significantly lower or no catalytic activity. Quantitative conversions were obtained working with 4 mol‐% Fe at room temp. and phenylsilane as the reducing agent. Under these conditions, ligand 4 afforded an enantioselectivity of 37 % ee. Attempts to isolate the single‐component Fe complexes containing ligands 3–6 have failed so far.

Fertilizer Source Affects Iron, Manganese, and Zinc Leaching, Nutrient Distribution, and Geranium Growth#

The effect of various sources of iron (Fe), manganese (Mn), and zinc (Zn) on growth and visual quality of geranium (Pelargonium X hortorum L. “Orbit Red”) seedlings, nutrient leaching, and nutrient distribution in the growing medium was determined in two experiments. In the first experiment, Fe, Mn, and Zn were applied as a commercially formulated water‐soluble fertilizer (WSF), granular incorporated fertilizer (GIF), or no micronutrient (NOM) fertilizer was applied. In the second experiment, the commercially formulated GIF was applied, but WSF was specially formulated to apply the same amount of each element from the same chemical sources as the GIF. Also a 50% GIF and 50% WSF (50 GIF/50 WSF) treatment was included. In both experiments, shoot relative growth rate (RGR) tended to be greater when WSF was applied than when GIF was used. Plant visual quality did not differ regardless of fertilizer used in either experiment, but plants receiving NOM fertilizer were of lower quality than plants receiving any micronutrient fertilizer. The amount of Fe, Mn, and Zn leached from the medium was greater with GIF than with WSF or 50 GIF/50 WSF when the same amount of each element was applied regardless of fertilizer source. Analysis of the growing medium at the end of each experiment revealed higher amounts of Fe, Mn, and Zn in the upper portion than in the middle or lower portions of the medium with WSF. The micronutrients studied were evenly distributed throughout the medium when applied as a GIF. #Approved for publication by the Director, Oklahoma Agricultural Experiment Station. This research was supported by project H‐2324.

Binding and utilization of human transferrin by Prevotella nigrescens.

To survive and multiply within their hosts, pathogens must possess efficient iron-scavenging mechanisms. In the present study, we investigate the capacity of Prevotella nigrescens and Prevotella intermedia to use various sources of iron for growth and characterize the transferrin-binding activity of P. nigrescens. Iron-saturated human transferrin and lactoferrin, but not ferric chloride and the iron-free form of transferrin, could be used as sources of iron by P. nigrescens and P. intermedia. Neither siderophore activity nor ferric reductase activity could be detected in P. nigrescens and P. intermedia. However, both species showed transferrin-binding activity as well as the capacity to proteolytically cleave transferrin. To various extents, all strains of P. nigrescens and P. intermedia tested demonstrated transferrin-binding activity. The activity was heat and protease sensitive. The capacity of P. nigrescens to bind transferrin was decreased when cells were grown in the presence of hemin. Preincubation of bacterial cells with hemin, hemoglobin, lactoferrin, fibrinogen, immunoglobulin G, or laminin did not affect transferrin-binding activity. The transferrin-binding protein could be extracted from the cell surface of P. nigrescens by treatment with a zwitterionic detergent. Subjecting the cell surface extract to affinity chromatography on an agarose-transferrin column revealed that it contained a protein having an estimated molecular mass of 37 kDa and possessing transferrin-binding activity. The transferrin-binding activity of P. nigrescens and P. intermedia may permit the bacteria to obtain iron for survival and growth in periodontal pockets.