A Spectrophotometric Study of the Reaction of Ferric Iron and Citric Acid

Lanford, Oscar E.; Quinan, James R.

doi:10.1021/ja01189a020

Cited by 29 publications

(13 citation statements)

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“…A number of iron-citrate species have been reported from potentiometric, polarographic, spectrophotometric, and magnetic susceptibility data (42)(43)(44)(45)(46)(47).…”

Section: Phosphate As a Synergistic Anionmentioning

confidence: 99%

Specificity of the Synergistic Anion for Iron Binding by Ferric Binding Protein from Neisseria gonorrhoeae

et al. 2004

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Ferric binding protein in Neisseria gonorrhoeae (nFbpA) transports iron from outer membrane receptors for host proteins across the periplasm to a permease in an alternative pathway to the use of siderophores in some pathogenic bacteria. Phosphate and nitrilotriacetate, both at pH 8, and vanadate at pH 9 are shown to be synergistic in promoting ferric binding to nFbpA, in contrast to carbonate and sulfate. Interestingly, only phosphate produces the fully closed conformation of nFbpA as defined by native electrophoresis. The role of phosphate was probed by constructing three mutants: Q58E, Q58R, and G140H. The anion and iron binding properties of the Q58E mutant are similar to the wild-type protein, implying that one phosphate oxygen is a hydrogen bond donor and may in part define the specificity of nFbpA for phosphate over sulfate. Phosphate is a weakly synergistic anion in the Q58R and G140H mutants, and these mutants do not form completely closed structures. Ferric binding was investigated by both isothermal titration and differential scanning calorimetry. The apparent affinity of nFbpA for iron in a solution of 30 mM citrate is 1 order of magnitude larger in the presence (K(app)= 1.7 x 10(5) M(-1)) of phosphate than in its absence (K(app) = 1.6 x 10(4) M(-1)) at pH 7. Similar results were obtained at pH 8. This increase in affinity with phosphate as well as the formation of closed structure allows nFbpA to compete for free ferric ions in solution and suggests that ferric binding to nFbpA is regulated by the synergistic phosphate anion at sites of iron uptake.

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“…A number of iron-citrate species have been reported from potentiometric, polarographic, spectrophotometric, and magnetic susceptibility data (42)(43)(44)(45)(46)(47).…”

Section: Phosphate As a Synergistic Anionmentioning

confidence: 99%

Specificity of the Synergistic Anion for Iron Binding by Ferric Binding Protein from Neisseria gonorrhoeae

et al. 2004

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“…When citrates are present in the nutrient solution, the ferric ions form the complex compound Fe(H citr)* (Lanford and Quinan 1948) which Bitcover and Sieling (1951) suggest to be the form in which iron is taken up by plants, while other authors (Pringsheim 1952) are of the opinion that only the free ions (of iron and manganese) are absorbed and replaced by others according to the laws of equilibrium. Consequently the fate of the complex compounds in the nutrition of plants seems still to require detailed investigations.…”

Section: Coininentsmentioning

confidence: 99%

The Significance for Algae of Chelating Substances in the Nutrient Solutions

Waris

1953

Physiologia Plantarum

119

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“…In addition, the additional adsorption of these molecules on the surface of the formed hydro complexes prevents their aggregation. Most early studies claim that in neutral environments, formed hydro complexes of iron citrate are in a stoichiometric ratio of 1:1 [24], and the degree of hydrolysis for the charge of such a complex may vary [25,26]. The formation of hydro complexes of FeL, Fe 2 L 2, and Fe 3 L 3 at close molar ratios of 1:1 of Fe 3+ ions and citric acid anions in solution was also observed in Ref.…”

Section: Structural and Morphological Characteristicsmentioning

confidence: 72%

Structurally Dependent Electrochemical Properties of Ultrafine Superparamagnetic ‘Core/Shell’ γ-Fe2O3/Defective α-Fe2O3 Composites in Hybrid Supercapacitors

et al. 2021

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The paper presents a method for obtaining electrochemically active ultrafine composites of iron oxides, superparamagnetic ‘core/shell’ γ-Fe2O3/defective α-Fe2O3, which involved modifying sol-gel citrate synthesis, hydrothermal treatment of the formed sol, and subsequent annealing of materials in the air. The synthesized materials’ phase composition, magnetic microstructure, and structural, morphological characteristics have been determined via X-ray analysis, Mossbauer spectroscopy, scanning electron microscopy (SEM), and adsorption porometry. The mechanisms of phase stability were analyzed, and the model was suggested as FeOOH → γ-Fe2O3 → α-Fe2O3. It was found that the presence of chelating agents in hydrothermal synthesis encapsulated the nucleus of the new phase in the reactor and interfered with the direct processes of recrystallization of the structure with the subsequent formation of the α-Fe2O3 crystalline phase. Additionally, the conductive properties of the synthesized materials were determined by impedance spectroscopy. The electrochemical activity of the synthesized materials was evaluated by the method of cyclic voltammetry using a three-electrode cell in a 3.5 M aqueous solution of KOH. For the ultrafine superparamagnetic ‘core/shell’ γ-Fe2O3/defective α-Fe2O composite with defective hematite structure and the presence of ultra-dispersed maghemite with particles in the superparamagnetic state was fixed increased electrochemical activity, and specific discharge capacity of the material is 177 F/g with a Coulomb efficiency of 85%. The prototypes of hybrid supercapacitor with work electrodes based on ultrafine composites superparamagnetic ‘core/shell’ γ-Fe2O3/defective α-Fe2O3 have a specific discharge capacity of 124 F/g with a Coulomb efficiency of 93% for current 10 mA.

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A Spectrophotometric Study of the Reaction of Ferric Iron and Citric Acid

Cited by 29 publications

References 0 publications

Specificity of the Synergistic Anion for Iron Binding by Ferric Binding Protein from Neisseria gonorrhoeae

Specificity of the Synergistic Anion for Iron Binding by Ferric Binding Protein from Neisseria gonorrhoeae

The Significance for Algae of Chelating Substances in the Nutrient Solutions

Structurally Dependent Electrochemical Properties of Ultrafine Superparamagnetic ‘Core/Shell’ γ-Fe2O3/Defective α-Fe2O3 Composites in Hybrid Supercapacitors

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