Photoelectrochemical detection of oxidative DNA damage induced by Fenton reaction with low concentration and DNA-associated Fe2+

The metal ion dependent decomposition of hydrogen peroxide, the so-called Fenton Reaction, yields hydroxyl radicals that can cause oxidative DNA damage both in vitro and in vivo. We have previously reported a photoelectrochemical sensor for the detection of oxidative DNA damage induced by an Fe(2+)-mediated Fenton Reaction, using a DNA intercalator as a photoelectrochemical signal reporter (Liang, M.; Guo, L.-H. Environ. Sci. Technol. 2007, 41, 658). The intercalator binds less to the damaged DNA in the sensor film than the native form, resulting in a reduction in the measured photocurrent. In this report, some mechanistic aspects of the sensor were investigated. It was found that Fe(2+) alone (without the coexistence of H(2)O(2)) suppressed the photocurrent of the intercalator bound to the DNA film in a pH-dependent manner. Similar pH dependence was observed for the zeta potential of the tin oxide nanoparticle colloid used in the preparation of the semiconductor electrode, leading to the hypothesis that the metal ion binds to the surface oxide groups on the electrode and quenches the photoelectrochemical response. At pH 3, the quenching effect was reduced substantially to permit the detection of DNA damage by as low as 10 muM Fe(2+) and 40 microM H(2)O(2), a concentration that is within the physiologically relevant range. It was also found that Fe2+ ions associated with the DNA in the sensor film and participated in the DNA damage reaction, a mechanism that has been implicated in previous studies on metal carcinogenesis.     

Formation of halogenated cyclopent-2-enone derivatives by interrupted Nazarov cyclizations

Allenyl vinyl ketones were exposed to titanium and indium halides in order to carry out Nazarov cyclizations. Whereas TiI₄ and InX₃ (X = Cl, Br, and I) led to cyclopentenones in which a halogen was trapped highly regioselectively, the reactions mediated by TiBr₄ gave mixtures of brominated isomers. When the allenyl vinyl ketones were treated first with Br₂ and then with TiBr₄, doubly brominated cyclopentenones resulted, and treatment with I₂ followed by TFA gave cyclopentenones bearing both hydroxyl and iodo groups.     

Catalytic hydrolysis of esters of 2-hydroxypyridine derivatives for Cu2+ detection

Hydrolysis of activated esters, e.g., picolinic acid and alpha-amino acid esters, in the presence of Cu(2+) salts is a stoichiometric process because products of this reaction bind the catalytic metal ion substantially stronger than starting materials do. Herein we report improved ester substrates, which are cleaved in the presence of catalytic amounts of Cu(2+); 55 turnovers of hydrolysis are observed for the best substrate, acetic acid 2-hydroxypyridine ester. We demonstrate that this reaction can be used for sensitive and selective detection of Cu(2+) by using both absorption and fluorescence spectroscopy.     

A pyrene-based dual chemosensor for colorimetric detection of Cu2+ and fluorescent detection of Fe3+

A pyrene based chemosensor was designed and synthesized. The pyrene fluorophore was connected with a pyridine unit through a Schiff base structure to give the sensor (L). L was tested with a variety of metal ions and exhibited high colorimetric selectivities for Cu²⁺ and Fe³⁺ over other ions. Upon binding with Cu²⁺ or Fe³⁺, L showed an obvious optical color change from colorless to pink for Cu²⁺ or orange for Fe³⁺ over a wide pH range from 3 to 12. Moreover, the fluorescence of L at 370 nm decreased sharply after bonding with Fe³⁺, while other metal ions including Cu²⁺ had no apparent interference. Thus, using such single chemosensor, Cu²⁺ and Fe³⁺ can be detected independently with high selectivity and sensitivity. The limits of detection toward Cu²⁺ and Fe³⁺ were 8.5 and 2.0 μM, respectively. DFT calculation results also proved the formation of stable coordination complexes and the phenomenon of fluorescence quenching by Fe³⁺. Furthermore, L was also successfully used as a bioimaging reagent for detection of Fe³⁺ in living cells.     

Extreme Differences in the Interactions of `Bare' Fe+ and Fe2+ with Hydrogen Peroxide: Fenton Chemistry in the Gas Phase

The interaction of bare iron mono‐ and dications with hydrogen peroxide in the gas phase is studied by ab initio calculations employing the B3LYP/6‐311+G* level of theory. For the monocation, the quartet and sextet coordination complexes Fe(H₂O₂) are high‐energy isomers that easily interconvert to the more stable iron dihydroxide monocation Fe(OH) and hydrated iron oxide (H₂O)FeO⁺ (quartet) or dissociate into FeOH⁺+OH^. (sextet). On the dication surface, however, the order of stabilities is reversed in that Fe(H₂O₂)²⁺ (quintet) corresponds to the most stable doubly charged species, while the formal Fe^IV compounds Fe(OH) and (H₂O)FeO²⁺ are higher in energy.     

Bimetallic AuRu aerogel with enzyme-like activity for colorimetric detection of Fe2+ and glucose

Aerogels have become a hot topic of research due to their extremely low density and special interconnected structure as well as their enzyme-like activity. The development of new multifunctional nano-enzyme aerogels with high activity and good stability is still a considerable challenge. In this paper, AuRu aerogels with peroxidase and oxidase activities were synthesized using a simple one-step method and successfully used to construct colorimetric sensors for the detection of Fe²⁺ and glucose based on their enzyme-like activities. Furthermore, we are fortunate to find that AuRu aerogels have good photothermal properties. This suggests that AuRu aerogels can be used not only for in vitro testing but also for promising applications such as disease treatment.     

浅谈检验Fe~(2+)与Fe~(3+)的误区

空白试验证明,用浓度大于1mol/L的盐酸溶液做Fe~(3+)的提取液,或用过浓盐酸溶液酸化试液,盐酸中的Fe~(3+)都会给检验试液中的Fe~(3+)带来干扰;检验食品中的铁元素时,若铁是以Fe~(2+)形式存在,如果加入硝酸将其氧化为Fe~(3+),硝酸中Fe~(3+)会对检验试液中的Fe~(3+)带来干扰。     

羧甲基壳聚糖对亚铁离子的吸附

壳聚糖是由甲壳素经脱乙酰基后得到的一种天然高分子氨基多糖 ,它是金属离子的良好配体 ,其配合物在工业、农业、食品、环保、医药等方面的应用已有许多研究 [1～ 4 ] .脱乙酰基后的壳聚糖溶解性有很大改善 ,但仍只能溶于酸或酸性水溶液 ,限制了它的推广应用 .通过化学改性的羧甲基壳聚糖 ( CMCS)具有良好的水溶性、保湿性、乳化性 ,其分子中含有— OH、— NH2 、—COOH等基团 ,能有效络合金属离子 [5] .人体对壳聚糖 -亚铁络合物的吸收远远大于传统的 Fe SO4 药物 [6 ] ,壳聚糖及其衍生物与 Fe2 的络合物有可能用于治疗缺铁性贫血 …     

Anion influence on the hydrated oxides formed by Fe3+ and Fe2+ precipitation

The anion influence on the hydrated oxides formed by Fe³⁺ and Fe²⁺ precipitation simulating the aqueous radioactive waste treatment has been investigated by Mössbauer spectroscopy. Fe₃(SO₄)₂, Fe(NO₃)₃, FeCl₃, FeSO₄ and FeCl₂ were used as iron sources and neutralized by NaOH. The obtained products contain several kinds of amorphous and/or poorly crystallized hydrated oxides, depending on the anion type which exists in solution and on the initial iron valence. The pH influence on the final precipitate is taken into account.     

Selective detection of Fe2+ by combination of CePO4:Tb3+ nanocrystal-H2O2 hybrid system with synchronous fluorescence scan technique

A new method for quenching kinetic discrimination of Fe(2+) and Fe(3+), and sensitive detection of trace amount of Fe(2+) was developed by using synchronous fluorescence scan technique. The principle of this assay is based on the quenching kinetic discrimination of Fe(2+) and Fe(3+) in CePO(4):Tb(3+) nanocrytals-H(2)O(2) hybrid system and the Fenton reaction between Fe(2+) and H(2)O(2). Stable, water-soluble and well-dispersible CePO(4):Tb(3+) nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy (TEM) and electron diffraction spectroscopy (EDS). We found that both Fe(2+) and Fe(3+) could quench the synchronous fluorescence of CePO(4):Tb(3+) nanocrytals-H(2)O(2) system, but their quenching kinetics velocities were quite different. In the presence of Fe(3+), the synchronous fluorescent intensity was unchanged after only one minute, but in the presence of Fe(2+), the synchronous fluorescent intensity decreased slowly until 28 min later. The Fenton reaction between Fe(2+) and H(2)O(2) resulted in hydroxyl radicals which effectively quenched the synchronous fluorescence of the CePO(4):Tb(3+) nanocrystals due to the oxidation of Ce(3+) into Ce(4+) by hydroxyl radicals. Under optimum conditions, the linear range for Fe(2+) is 3 nM-2 μM, and the limit of detection is 2.0 nM. The method was used to analyze water samples.     

Zum System H2O2, Fe2+-, Fe3+-Ion

Ohne Zusammenfassung     

基于联萘酚衍生物的荧光传感器对Ca~(2+)的选择性测定

设计了基于联萘酚衍生物(LZ)的高选择性的荧光化学传感器,分别采用荧光光谱和紫外-可见光谱法研究了其对Ca~(2+)的识别.结果显示,与其他金属离子,如Ag~+、Al ~(3+)、Bi ~(3+)、Cd~(2+)、Co~(3+)、Cr~(3+)、Cu~(2+)、Fe~(3+)、Hg~(2+)、K~+、Mg~(2+)、Mn~(2+)、Ni ~(2+)、Pb~(2+)、Zn~(2+)相比,探针LZ对Ca~(2+)呈现良好的选择性.并且该探针在486nm处的荧光强度与Ca~(2+)浓度在2~7μmol/L范围内呈现良好的线性关系,其回归系数为0.994,检测限为0.8μmol/L,多次测定的相对标准偏差为2%.     

Local tilting angles tau for Fe+ in Cd2+ site and Fe3+ in Si4+ site of CdSiP2 semiconductor

The EPR parameters (g factors, g(parallel), g(perdendicular) and zero-field splitting D) for Fe+ in Cd2+ site and Fe3+ in Si4+ site of CdSiP2 semiconductor are calculated from the distinct high-order perturbation formulas. From the calculations, the local tetragonal distortions and hence the local tilting angles tau (which are different from the corresponding host values) for both paramagnetic centers are estimated. The results are discussed.     

Simultaneous Determinations of Fe2+ and Fe3+ in Ferrous Sulfate Destined for Pharmaceutical Preparations

ABSTRACT

Only the simultaneous analysis of the amount of Fe^2? and the possible presence of Fe³⁺ in ferrous sulfate heptahydrated (FeSO_4. 7 H₂O) can guarantee covered tablets, drops or syrups with insured quality. This work suggests that these analysis are accomplished through spectrophotometric method by use of the 1, 10-phenanthroline as chelate. Thus, at 510 nm the absorption is only due to the complex of the ligand with Fe^2? and at 390 nm the absorption is indicative of Fe^2+/3+ coordinated. Pharmaceutical raw matter and covered tablets were analyzed. Techniques of thermogravimetric analysis (TG-DTG) were used for the knowledge of the regions of loss of water of the FeSO₄. 7 H₂O for the relationship to its stoichiometry.     

Terbium hybrid particles with spherical shape as luminescent probe for detection of Cu2+ and Fe3+ in water

A novel green emissive terbium inorganic-polymeric hybrid particle was designed and this material could detect cations in water. Polyvinyl alcohol as an amphiphilic surfactant rendered the powders dispersible in water with regular round shape (10-20 μm). Interestingly, we noticed that not only Cu(2+) (detection limit 10(-4)M) but also Fe(3+) (detection limit 10(-4) M) can give rise to emission quenching to this target material in comparison with K(+), Na(+), Fe(2+), Mn(2+), Pd(2+), Cd(2+) and Co(2+) (10(-3) mol L(-1)). We regarded that the coordination interactions between ligand and metal ions resulted in these quenching processes. Additionally, it was found that the sensing material can be repeatedly used at least 5 cycles. More importantly, this novel material demonstrated higher thermal-stability in aqueous media than pure silica hybrid material.     

A fluorescent sensor based on quinazoline ketone derivatives for selectivity of Fe3+

In this work, we provided a fluorescent sensor based on a compound containing fluorophore quinazoline ketone for detecting metal ions. 2-Methyl-4(3 H)-quinazoline thione was synthesised as a fluorescent probe for tervalent ferric ion (Fe³⁺) detection. Fluorescent determination of 2-methyl-4(3 H)-quinazoline thione indicated its maximum emission wavelength of 306.5 nm. The fluorescence interference and titration experiments have shown that the compound has a high selective fluorescence response to Fe³⁺. With an increase in the Fe³⁺ ion concentration, the fluorescence emission strength gradually weakened, and a slight red shift appeared. With Job’s method, 2-methyl-4(3 H)-quinazoline thione was proved to form a 1:2 complex with Fe³⁺. The results revealed that 2-methyl-4(3 H)-quinazoline thione could be used as a fluorescent probe for the recognition of Fe³⁺ with high selectivity.     

Highly selective colorimetric and electrochemical Pb2+ detection based on TTF-pi-pyridine derivatives

[reaction: see text] The pyridineethenyl-substituted tetrathiafulvalene (TTF) compounds, 4-(4-pyridineethenyl)tetrathiafulvalene (1a) and 4,4'(5')-[bis-(4-pyridineethenyl)]tetrathiafulvalene (2a) together with the styryl-substituted TTF compounds, 4-styryltetrathiafulvalene (1b) and 4,4'(5')-bis-styryltetrathiafulvalene (2b), have been designed and synthesized. All these compounds exhibit strong absorption bands in the range of 370 to 550 nm, which are assigned to the intramolecular charge-transfer transition from the HOMO in TTF to the LUMO in the pyridyl or phenyl group. Compared to compounds 1b and 2b, the pyridineethenyl-substituted TTF compounds 1a and 2a show remarkable sensing and coordinating properties to Pb2+. With the addition of micromolar concentrations of Pb2+ to the solution, 1a or 2a displays dramatic changes in the UV-vis absorption spectrum, 1H NMR spectrum, and redox property.     

Colorimetric detection of Fe3+/2+ and fluorescent detection of Al3+ in aqueous media: applications and DFT calculations

Abstract

A new multifunctional colorimetric and fluorescent chemosensor 1 for Fe^3+/2+ and Al³⁺ has been synthesized in the one-step procedure. The sensor 1 detected both Fe²⁺ and Fe³⁺ through the color change from yellow to brown and Al³⁺ via turn-on fluorescence. The binding stoichiometries of sensor 1 with Fe^3+/2+ and Al³⁺ were proposed to be 1:1 with the analyses of ESI-mass and Job plot. Importantly, the detection limits of 1 for Fe^3+/2+ (2.11 and 2.70 μM) and Al³⁺ (3.44 μM) were lower than the EPA guideline (5.37 μM) for Fe^3+/2+ and WHO guideline (7.41 μM) for Al³⁺. Compound 1 was used to quantify ferric species (Fe³⁺) in real samples. Moreover, the sensing processes for Fe^3+/2+ and Al³⁺ were proposed with the spectroscopic studies and theoretical calculations.     

Topological structural alerts modulations of mammalian cell mutagenicity for halogenated derivatives

Genotoxicity is a key toxicity endpoint for current regulatory requirements regarding new and existing chemicals. However, genotoxicity testing is time-consuming and costly, and involves the use of laboratory animals. This has motivated the development of computational approaches, designed to predict genotoxicity without the need to conduct laboratory tests. Currently, many existing computational methods, like quantitative structure–activity relationship (QSAR) models, provide limited information about the possible mechanisms involved in mutagenicity or predictions based on structural alerts (SAs) do not take statistical models into account. This paper describes an attempt to address this problem by using the TOPological Substructural MOlecular Design (TOPS-MODE) approach to develop and validate improved QSAR models for predicting the mutagenicity of a range of halogenated derivatives. Our most predictive model has an accuracy of 94.12%, exhibits excellent cross-validation and external set statistics. A reasonable interpretation of the model in term of SAs was achieved by means of bond contributions to activity. The results obtained led to the following conclusions: primary halogenated derivatives are more mutagenic than secondary ones; and substitution of chlorine by bromine increases mutagenicity while polyhalogenation decreases activity. The paper demonstrates the potential of the TOPS-MODE approach in developing QSAR models for identifying structural alerts for mutagenicity, combining high predictivity with relevant mechanistic interpretation.