Presence Of Fe3 Research Articles

A microlagal-based carbonaceous sensor for enzymatic determination of glucose in blood serum

In the present work, Chlorella vulgaris, a well-known microalga was used as a carbonic precursor, to synthesis the water-soluble carbon dots (CDs) via hydrothermal method. To improve the properties, acidic carbon dots (ACDs) were also synthesized via ultrasoncation of microalgal biomass after acidic hydrolysis (using diluted acidic solution). The aqueous solution of ACDs was used as a sensor for glucose determination based on glucose oxidase enzyme (GOx) reaction and fluorescence quenching of ACDs in the presence of Fe3+ ions under the optimized conditions. The linear range of glucose in the blood serum was measured from a range of 5 µM to 500 µM with a limit of detection (LOD) 2.84 µM. Additionally, the hydrogen peroxide, as the conventional reactive oxygen species (ROS) was determined based on the Fenton reaction. The linear range of H2O2 was obtained from 10 µM to 200 µM with LOD of 975 nM. In all of these applications, fluorescence quenching of ACDs was followed according to photo-induced electron transfer (PET) mechanism in the presence of generated Fe3+ ions by Fenton reaction.

Amylopectin Regulated Mineralization of Calcium Carbonate and Its Application in Removing of Pb(II)

AbstractAs an ecological and environment‐friendly building material, sticky rice mortar has attracted the attention of many researchers. Amylopectin is the most important organic matter of it, which can improve the mechanical properties and durability of sticky rice mortar by inducing mineralization of calcium carbonate (CaCO3). However, amylopectin induced formation of CaCO3 has not been reported. In this paper, mineralization of CaCO3 induced by gelatinized amylopectin is investigated. For comparison, the different morphologies of CaCO3 are studied in the presence of Mg2+, Fe3+. Moreover, these CaCO3 products with different morphologies are used to clean the waste water. The results indicate that gelatinized amylopectin is conducive to formation of pumpkin‐like vaterite. It forms uniform rod and dumbbell‐shaped calcite in the presence of Mg2+, form calcite with stepped depressions in the presence of Fe3+. The adsorption of Pb(II) can reach extremely high level (1445.86 mg g−1) with the rod‐like calcite.

Construction of nickel- and iron-coordinated poly(5-amino-1,10-phenanthroline) film for electrocatalytic water oxidation reactions

Metalation of the electro-polymerized 5-amino-1,10-phenanthroline film (poly(5Aphen)) is carried out in methanol solutions containing nickel and iron ions, and the characterization results suggest the formation of metal complexes. The metal ion-coordinated films are able to electrochemically catalyze water oxidation reaction (WOR) in alkaline solutions. The most active electrode (Ni0.55Fe0.45-poly(5Aphen)/CP) exhibits only 264 mV overpotentials to reach 10 mA cm−2 water oxidation current densities, and is robust towards long-term galvanostatic test. Cyclic voltammetry suggests the existence of electron interactions between Fe3+ centers and the adjacent Ni2+ centers. Electrokinetic studies indicate that the presence of Fe3+ increases the adsorption energies of the water oxidation intermediates OH*, which leads to enhanced WOR catalytic activities. Ex-situ characterizations after the prolonged electrolysis suggest that the formation of amorphous metal hydroxides that are also active towards WOR. This simple preparation method can also be applied to prepare other transition metal ion-coordinated poly(5Aphen) for electrocatalysis.

High-Efficiency Anion-Exchange Membrane Water Electrolyzer Enabled by Ternary Layered Double Hydroxide Anode.

Developing high-efficiency and low-cost oxygen-evolving electrodes in anion exchange membrane (AEM) water electrolysis technology is one of the major challenges. Herein, it is demonstrated that the surface corrosion of a conventional Ni foam electrode in the presence of Fe3+ and V3+ cations can transform it into an electrode with a high catalytic performance for oxygen evolution reaction (OER). The corroded electrode consists of a ternary NiFeV layered double hydroxide (LDH) nanosheet array supported on the Ni foam surface. This NiFeV LDH electrode achieves an OER current density of 100mA cm-2 at an overpotential of 272mV in 1 m KOH, outperforming the IrO2 catalyst by 180mV. Density functional theory calculations reveal that the unique structure and the presence of vanadium in NiFeV LDH play a key role in achieving improved OER activity. When coupled with a commercial Pt/C cathode catalyst, the resulting AEM water electrolyzer achieves a cell current density as high as 2.1 A cm-2 at a voltage of only 1.8 Vcell in 1 m KOH, which is similar to the performance of the proton exchange membrane water electrolyzer obtained from the IrO2 and Pt/C catalysts pair.

Structural Rearrangement of Dps-DNA Complex Caused by Divalent Mg and Fe Cations.

Two independent, complementary methods of structural analysis were used to elucidate the effect of divalent magnesium and iron cations on the structure of the protective Dps-DNA complex. Small-angle X-ray scattering (SAXS) and cryo-electron microscopy (cryo-EM) demonstrate that Mg2+ ions block the N-terminals of the Dps protein preventing its interaction with DNA. Non-interacting macromolecules of Dps and DNA remain in the solution in this case. The subsequent addition of the chelating agent (EDTA) leads to a complete restoration of the structure of the complex. Different effect was observed when Fe cations were added to the Dps-DNA complex; the presence of Fe2+ in solution leads to the total complex destruction and aggregation without possibility of the complex restoration with the chelating agent. Here, we discuss these different responses of the Dps-DNA complex on the presence of additional free metal cations, investigating the structure of the Dps protein with and without cations using SAXS and cryo-EM. Additionally, the single particle analysis of Dps with accumulated iron performed by cryo-EM shows localization of iron nanoparticles inside the Dps cavity next to the acidic (hydrophobic) pore, near three glutamate residues.

Development of a Strong, Recyclable Poly(dimethylsiloxane) Elastomer with Autonomic Self‐Healing Capabilities and Fluorescence Response Properties at Room Temperature

AbstractWith the recent emphasis on environmental protection measures, there are increasingly strong demands for environment‐friendly multifunctional materials, so research regarding high‐performance, recyclable, functional materials with self‐healing abilities is of great interest. However, the comprehensive mechanical properties of most available self‐healing materials are insufficient; to date, most developed materials are either tough but brittle or flexible but weak. This report describes the application of a crosslinking strategy based on multiple dynamic bonds for the development of an autonomically self‐healing, multifunctional, boroxine‐containing poly(dimethylsiloxane) elastomer (PDMS‐BN). This approach takes advantage of well‐designed intermolecular and intramolecular nitrogen‐coordinated boroxines by using a synergetic dynamic mechanism. The elastomers exhibit enhanced comprehensive mechanical properties (with maximum strength up to 1.72 MPa, elongation at break up to 307%, Young's modulus up to 11.18 ± 0.52 MPa, and toughness up to 4.92 MJ m−3) and highly autonomic self‐healing capabilities, with ≈96% efficiency at room temperature for 48 h. Moreover, the PDMS‐BN elastomer can be recycled multiple times via crushing/molding or disassembling/casting processes, without losing their original mechanical robustness. The as‐prepared elastomers also demonstrate good adhesive properties and a unique fluorescence‐quenching response in the presence of Fe3+ ions.

A hydrolytically stable hydrogen-bonded inorganic-organic network as a luminescence turn-on sensor for the detection of Bi3+ and Fe3+ cations in water

Metal-organic materials capable of turn-on sensing of metal ions in water are highly desirable but relatively infrequently reported. Herein, a hydrogen-bonded inorganic-organic network based on Cu(I) ions and luminescent organic ligands, namely Cu-HBIBA (HBIBA = 4-[bis-(4-imidazol-1-ylphenyl)amino]benzoic acid), was synthesized and applied to detect trivalent metal ions (Fe3+ and Bi3+) in aqueous solution. Cu-HBIBA is a binuclear complex and exhibits an interesting hydrogen-bonded 1D → 2D polythreading array. Notably, Cu-HBIBA has good stability at pH values from 2 to 12 and is hardlysoluble in aqueous solution. Cu-HBIBA shows luminescence enhancement in the presence of Fe3+, and Bi3+ ions and shows high selectivity and sensitivity with detection limits of 0.16 µM and 43 nM for Fe3+ and Bi3+, respectively. The hydrolytic stability, inhibited ligand-based luminescence and uncoordinated carboxylate groups in the network may contribute to the sensing performance of Cu-HBIBA. A mechanistic study indicates that the Cu-HBIBA crystal adsorbs metal ions via the carboxyl groups on its surface, leading to inhibition of the photoelectron transfer (PET) process, recovery of the luminescent emissions of the ligand and realization of turn-on luminescence detection.

Force Field Parameters for Fe2+4S2-4 Clusters of Dihydropyrimidine Dehydrogenase, the 5-Fluorouracil Cancer Drug Deactivation Protein: A Step towards In Silico Pharmacogenomics Studies.

The dimeric dihydropyrimidine dehydrogenase (DPD), metalloenzyme, an adjunct anti-cancer drug target, contains highly specialized 4 × Fe2+4S2−4 clusters per chain. These clusters facilitate the catalysis of the rate-limiting step in the pyrimidine degradation pathway through a harmonized electron transfer cascade that triggers a redox catabolic reaction. In the process, the bulk of the administered 5-fluorouracil (5-FU) cancer drug is inactivated, while a small proportion is activated to nucleic acid antimetabolites. The occurrence of missense mutations in DPD protein within the general population, including those of African descent, has adverse toxicity effects due to altered 5-FU metabolism. Thus, deciphering mutation effects on protein structure and function is vital, especially for precision medicine purposes. We previously proposed combining molecular dynamics (MD) and dynamic residue network (DRN) analysis to decipher the molecular mechanisms of missense mutations in other proteins. However, the presence of Fe2+4S2−4 clusters in DPD poses a challenge for such in silico studies. The existing AMBER force field parameters cannot accurately describe the Fe2+ center coordination exhibited by this enzyme. Therefore, this study aimed to derive AMBER force field parameters for DPD enzyme Fe2+ centers, using the original Seminario method and the collation features Visual Force Field Derivation Toolkit as a supportive approach. All-atom MD simulations were performed to validate the results. Both approaches generated similar force field parameters, which accurately described the human DPD protein Fe2+4S2−4 cluster architecture. This information is crucial and opens new avenues for in silico cancer pharmacogenomics and drug discovery related research on 5-FU drug efficacy and toxicity issues.

Biochemical properties of extracellular protease from Staphylococcus epidermidis isolated from Harbin dry sausages and its hydrolysis of meat protein

This study aimed to explore biochemical properties of extracellular protease from Staphylococcus (S.) epidermidis BP9 isolated from Harbin dry sausages and its future potential application in Harbin dry sausages. The protease was purified by 80% ammonium sulfate, ion exchange, and gel filtration chromatography to obtain a 24 kDa extracellular protease. The protease reached maximal activity at pH 6.0 and 50 °C and was stable at pH 4.0–9.0 and 20–40 °C. Its protease activity was inhibited in the presence of Fe2+. The enzymatic characterization of the protease revealed a Vmax 62.5 U/mL·min, Km 11.76 mg/mL, and the half-life = 62.44 min, ΔH*d = 72.11 kJ/mol, ΔG*d = 91.40 kJ/mol, and ΔS*d = −59.60 J/mol·K at 50 °C. In addition, the protease hydrolysed myofibrillar protein into small particles and produced soluble peptides. This study provides a basis for understanding the biochemical characteristics of the S. epidermidis BP9 protease and its future application for Harbin dry sausages.

Synthesis of novel benzothiazole based fluorescent and redox-active organic nanoparticles for their application as selective and sensitive recognition of Fe3+ ions

A novel benzothiazole based compound (1) has been synthesized and further employed for the fabrication of fluorescent as well as redox active organic nanoparticles (1-ONPs) by adopting a nano-re-precipitation method. The formation of 1-ONPs was confirmed by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) techniques, where the size was found to be ~42.84 nm in the optimized conditions. The resulting 1-ONPs acted as selective and sensitive sensor for recognition of Fe3+ ions in dual transduction mode. The nanoparticles underwent quenching of fluorescence intensity as well as an amplified stripping current response in the presence of Fe3+. The high surface charge density worked as a tool for enhancing the current response of nanoparticles over bulk solution mode and hence is extended to in-field analysis.

Judging phase purity of hematite (α-Fe2O3) nanoparticles through structural and magnetic studies

The effect of post-growth annealing on the phase transformation leading to phase pure hematite (α-Fe2O3) nanoparticles is reported in this work. Co-precipitation technique was used to synthesise iron oxide nanoparticles by adjusting the pH of the solution. The xerogel was dried at 80 °C and the obtained powder was calcined in the temperature range 400–800 °C for 3 h. in air. Annealing temperature was prefixed on the basis of the thermal degradation pattern of the starting precursor. X-ray diffraction (XRD) study endorsed the presence of mixed phases FeO, FeO2 and α-Fe2O3 in the as-prepared sample. On annealing, the minor phases transform gradually to α-Fe2O3, as confirmed through thermal studies. Performed Rietveld analysis confirms the presence of impurity phases in samples annealed at low temperature. Phase pure sample crystallizes in the rhombohedral corundum structure (space group, R-3c) with a = 5.04044 Å, c = 13.7628 Å and c/a = 2.73048. FT-Raman spectral investigations allowed for a clear assignment of the α-Fe2O3 phase. Chemical analysis advocated the only presence of Fe3+ ions that octahedrally coordinated with hexagonally close packed O2- ions that constitute corundum structure. Electron microscopy (TEM) images proved the non-spherical particle distribution in the range 80–100 nm with mean particle size of 93 nm. Structural phase transition with annealing temperature was further confirmed through the fluctuations in the magnetic structure. In analogues to XRD, magnetic study also served as a judging tool to identify purity and the presence of mixed phases in hematite.

Effect of iron ions as assistant depressant of citric acid on the flotation separation of scheelite from calcite

The flotation separation of scheelite and calcite is challenging, because of the similarities in their surface chemical properties, solution chemical properties, calcium ion active sites, and, consequently, floatability. Efficient flotation depressants are required to separate scheelite and calcite by flotation. Citric acid (CA) has recently been investigated as a flotation depressant; however, its depressing action toward calcite is limited owing to its low number of polar groups (i.e., carboxyl and hydroxyl groups). In this study, iron ions (Fe3+) were used to improve the depressing action and selectivity of CA toward calcite. The microflotation behavior of scheelite and calcite was investigated under the influence of different depressant systems. Wettability, Fourier transform infrared, X-ray photoelectron spectroscopy, thermodynamic, and atomic force microscopy analyses revealed the selective depression mechanism of the depressant mixture comprising Fe3+ and CA (denoted Fe3+/CA). The microflotation results indicate that although the flotation separation of the two minerals is difficult using CA on its own, good separation effect is achieved using Fe3+/CA. Fe3+/CA chemically co-adsorbs on the calcite surface more strongly than on the scheelite surface. The iron ions and CA form ferric citrate (where L here denotes that the citrate ion is a ligand) that is then adsorbed at the oxygen sites on the surface of calcite in the flotation slurry. In the presence of Fe3+/CA, the adsorbed complexes form a dense layer on calcite, but a sparse layer on scheelite. The proposed depressant system realizes the efficient flotation separation of scheelite from calcite, which has theoretical and practical significance for the efficient development and utilization of scheelite resources.

Evidence for Local Structural Distortion and Mixed States of Fe in <i>β</i>-NaFeO<sub>2</sub>: A Bond Valence Sum Analysis

We have analyzed the crystal structure, interatomic distances and bond valence sums in β-phase of sodium ferrite based on neutron diffraction measurement at room temperature. The Rietveld analysis performed using Pna21 space group obtains smaller lattice constants compared to the previous reports. This discrepancy is attributed to the sodium deficiency. We notice that the Na-O bonds are shortened, while Fe-O bonds are elongated. The calculated bond valence sum around the sodium and the iron ions are 1.08 and 2.64, respectively. This indicates the presence of Fe2+-Fe3+ mixed valence state.

A green path to extract carbon quantum dots by coconut water: Another fluorescent probe towards Fe3+ ions

In recent years, carbon quantum dots (CQDs) have been of great enthrallment in the fluorescent probe field. Carbon precursors with interesting physicochemical properties may be derived from natural sources. In this research, for the first time, coconut water has been used as a source of carbon to prepare blue fluorescent CQDs without any modification and functionalization. The preparation of CQDs is very simple and cost-effective, when compared with other conventional techniques. The reaction parameters temperature and pH were varied to obtain monodispersed spherical CQDs with an average grain size of ∼5nm. The CQDs exhibit blue emission with a wavelength of 487nm with an excitation wavelength of 390nm and are used for Fe3+ ions detection. Fe3+ ions have been observed to quench the fluorescence intensity of the CQDs than other heavy metals. In the presence of Fe3+ ions, the fluorescent CQDs are quenched due to the interaction of CQDs and Fe3+ ions. A spectroscopic result shows that Fe3+ ions can be observed within a concentration of 0–700μM, as well as the detection limit is 0.30μM. The CQDs provide a unique pathway for potential application in the environmental monitoring of heavy metal ions.

Structural modification of natural fibers for fluorescent probe application

In situ chemical polymerization of acid fuchsin (AF) dye in the presence of Fe3+ as a complexing and oxidizing agent in the presence of two different textile fibers such as silk and rayon were carried out by varying the experimental conditions in the N2 ambiance. The synthesized polymer systems were subjected to various analytical measurements such as FT‐IR, FES, SEM, TEM, GPC, UV‐visible spectroscopy, cyclic voltammetry, and water contact angle to assess their structure‐property relation. The electrical conductivity values of the AF grafted natural fibers were measured. The rate of grafting (RG) was calculated by using the absorption and emission spectra. The SO2 stretching of AF is seen at 1230 cm−1 in the FT‐IR spectrum. The order of grafting reaction was calculated as 0.99 based on absorbance spectrum, which proved the first‐order reaction with respect to Fe3+ concentration. The binding site and binding constant values were determined. The energy of activation (Ea) for the AF grafted rayon fiber was estimated as 30.72 kJ/mole. A plausible reaction mechanism was proposed based on the obtained experimental results.

Iron enhances the binding rates and translational efficiency of iron responsive elements (IREs) mRNA with initiation factor eIF4F.

Interaction of iron responsive elements (IRE) mRNA with the translational machinery is an early step critical in the initiation of protein synthesis. To investigate the binding specificity of IRE mRNA for eIF4F, kinetic rates for the eIF4F·IRE RNA interactions were determined and correlated with the translational efficiency. The observed rate of eIF4F·FRT IRE RNA interactions was 2-fold greater as compared to eIF4F·ACO2 IRE RNA binding. Addition of iron enhanced the association rates and lowered the dissociation rates for the eIF4F binding to both IRE RNAs, with having higher preferential binding to the FRT IRE RNA. The binding rates of both eIF4F·IRE RNA complexes correlated with the enhancement of protein synthesis in vitro. Presence of iron and eIF4F in the depleted WGE significantly enhanced translation for both IRE RNAs. This suggests that iron promotes translation by enhancing the binding rates of the eIF4F∙IRE RNA complex. eIF4F·IRE RNA binding is temperature-dependent; raising the temperature from 5 to 25°C, enhanced the binding rates of eIF4F·FRT IRE (4-fold) and eIF4F·ACO2 IRE (5-fold). Presence of Fe2+ caused reduction in the activation energy for the binding of FRT IRE and ACO2 IRE to eIF4F, suggesting a more stable platform for initiating protein synthesis. In the presence of iron, lowered energy barrier has leads to the faster association rate and slower rate of dissociation for the protein-RNA complex, thus favoring efficient protein synthesis. Our results correlate well with the observed translational efficiency of IRE RNA, thereby suggesting that the presence of iron leads to a rapid, favorable, and stable complex formation that directs regulatory system to respond efficiently to cellular iron levels.

Influence of various Cu/Fe ratios on the surface properties of green synthesized Cu-Fe-BTC and it`s relation to methylene blue adsorption

The incorporation of different percentages of Fe2+ into copper benzene-1,3,5-tricarboxylate (CuBTC) was successfully carried out at room-temperature synthesis with water as the only solvent. The XRD and XPS analysis shows that the Fe2+ were substituted into the paddlewheel structure. The incorporation of 18% Fe2+ into CuBTC can increase the surface area and porosity of the framework. The BET surface area of Cu82Fe18BTC (1240 m2/g) was significantly higher than CuBTC (708 m2/g). Further increase in the Fe2+ percentage will reduce the surface area of the compound. The presence of Fe2+ in the framework successfully disturbs the pore formation and widens the pore size on the surface of these compounds. This as well as the pHpzc, which is related to the surface acidity of the resulting bimetallic organic framework (BMOF), play an important role in the adsorption process. Cu53Fe47BTC with an adsorption capacity of 94.42 mg/g shows approximately 6 times greater adsorption capacity against MB compared to CuBTC. This shows that by utilizing a different ratio of Cu and a second metal, it is possible to effectively design the surface morphology of BMOF for specific applications.

Two transformation pathways of Acetaminophen with Fe3+ saturated clay particles in dark or light

Acetaminophen (AP) has been frequently detected in different environments due to its wide usage as a common analgesic and antipyretic pharmaceutical. Excess residual of AP in the environment may cause biological risk. However, information about its environmental behaviors was limited, especially the interactions with clay minerals. In this study, AP transformation mediated by Fe3+ saturated clay particles was systematically investigated. The results showed 47.6 ± 1.1% or 78.9 ± 0.5% of AP was removed in the presence of Fe3+-montmorillonite respectively in dark or under simulated sunlight irradiation after 10 h. The hypothesized mechanism was that exchangeable ferric ions can either obtain electron from AP to form AP radical, or produce •OH under light, which can further react with AP. In dark condition, AP radicals could cross-couple with each other to form dimers, while oxidation products were also detected under light irradiation due to •OH attacking. Moreover, higher concentration of dissolved oxygen (DO) facilitated Fe3+ regeneration on clay surfaces and more reactive Fe species distributed in lower pH, which could significantly enhance the removal of AP both in dark and light. Results of this study revealed that clay minerals played important roles in the abiotic transformation of AP either in dark or under light irradiation, and oligomerization other than mineralization were the dominant processes.

Melting phase relation of Fe-bearing Phase D up to the uppermost lower mantle

Abstract Dense hydrous magnesium silicates (DHMSs) are considered important water carriers in the deep Earth. Due to the significant effect of Fe on the stability of DHMSs, Fe-bearing Phase D (PhD) deserves much attention. However, few experiments have been conducted to determine the stability of PhD in different bulk compositions. In this study, we provide experimental constraints for the stability of PhD in the AlOOH-FeOOH-Mg1.11Si1.89O6H2.22 system between 18 and 25 GPa at 1000–1600 °C, corresponding to the P-T conditions of the mantle transition zone and uppermost lower mantle. Fe3+-bearing PhD was synthesized from the FeOOH-Mg1.11Si1.89O6H2.22 binary system with two different Fe3+ contents. The resultant Al,Fe3+-bearing compositions are close to analog specimens of the fully oxidized mid-ocean ridge basalt (MORB) and pyrolite in the AlOOH-FeOOH-Mg1.11Si1.89O6H2.22 ternary system. The substitution mechanism of Fe is shown to be dependent on pressure, and Fe3+ occupies both Mg and Si sites in PhD at pressures below 21 GPa. In contrast, Fe3+ only occupies Si site at pressures exceeding 21 GPa. The presence of Fe3+ results in a slight reduction in the thermal stability field of PhD in the FeOOH-Mg1.11Si1.89O6H2.22 system in comparison to Mg-bearing, Fe-free PhD. In contrast, Al,Fe3+-bearing PhD is more stable than Mg-bearing PhD in both MORB and pyrolite compositions. In this regard, Al,Fe3+-bearing PhD could act as a long-term water reservoir during subduction processes to the deep mantle.

Effect of Physiological Concentrations of Vitamin C on the Inhibitation of Hydroxyl Radical Induced Light Emission from Fe2+-EGTA-H2O2 and Fe3+-EGTA-H2O2 Systems In Vitro.

Ascorbic acid (AA) has antioxidant properties. However, in the presence of Fe2+/Fe3+ ions and H2O2, it may behave as a pro-oxidant by accelerating and enhancing the formation of hydroxyl radicals (•OH). Therefore, in this study we evaluated the effect of AA at concentrations of 1 to 200 µmol/L on •OH-induced light emission (at a pH of 7.4 and temperature of 37 °C) from 92.6 µmol/L Fe2+—185.2 µmol/L EGTA (ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid)—2.6 mmol/L H2O2, and 92.6 µmol/L Fe3+—185.2 µmol/L EGTA—2.6 mmol/L H2O2 systems. Dehydroascorbic acid (DHAA) at the same range of concentrations served as the reference compound. Light emission was measured with multitube luminometer (AutoLumat Plus LB 953) for 120 s after automatic injection of H2O2. AA at concentrations of 1 to 50 µmol/L and of 1 to 75 µmol/L completely inhibited light emission from Fe2+-EGTA-H2O2 and Fe3+-EGTA-H2O2, respectively. Concentrations of 100 and 200 µmol/L did not affect chemiluminescence of Fe3+-EGTA-H2O2 but tended to increase light emission from Fe2+-EGTA-H2O2. DHAA at concentrations of 1 to 100 µmol/L had no effect on chemiluminescence of both systems. These results indicate that AA at physiological concentrations exhibits strong antioxidant activity in the presence of chelated iron and H2O2.