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1.
Chemosphere ; 257: 127223, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32534295

RESUMO

The degradation performance of trichloroethylene (TCE) by sodium percarbonate (SPC) activated with citric acid (CA) chelated Fe(II) in the presence of nonionic surfactant Tween-80 was investigated. The addition of CA successfully prevented the precipitation of iron and facilitated TCE degradation. However, Tween-80 had an inhibitory effect on TCE degradation mainly due to the competition of ∗OH between Tween-80 and TCE. The effect of SPC and Fe(II) dosage on TCE degradation was also explored and the results displayed that 87.2% of TCE could be degraded in 15 min at the SPC/Fe(II)/CA/TCE molar ratio of 3/4/2/1. Free radical probe tests confirmed that both O2-∗ and ∗OH were generated in the SPC/Fe(II)/CA system. Free radical scavenging tests implied that the degradation of TCE in the SPC/Fe(II)/CA system was mainly attributed to ∗OH, while O2-∗ was only partially involved in the degradation of TCE. In addition, TCE removal was suppressed with the raising of the initial solution pH from 3.0 to 9.0. The actual groundwater (containing Tween-80) tests confirmed that 93.2% of TCE degradation could be achieved at the SPC/Fe(II)/CA/TCE molar ratio of 30/40/10/1 and strongly demonstrated that the SPC/Fe(II)/CA process has potential for the in situ treatment of TCE contaminated groundwater in the presence of surfactant Tween-80. In conclusion, TCE degradation by Fe(II) activated SPC system in the presence of Tween-80 can be significantly enhanced with the addition of CA, and this finding offers an innovative direction for removing chlorinated organic contaminants from groundwater in contaminated site after surfactant solubilization treatment.


Assuntos
Carbonatos/química , Tensoativos/química , Tricloroetileno/química , Poluentes Químicos da Água/química , Quelantes , Ácido Cítrico , Compostos Ferrosos/química , Água Subterrânea , Ferro , Oxirredução , Polissorbatos , Surfactantes Pulmonares , Poluentes Químicos da Água/análise
2.
PLoS One ; 15(5): e0232315, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32365071

RESUMO

The INTRABEAM Carl Zeiss Surgical system (Oberkochen, Germany) is a miniature accelerator producing low energy photons (50 keV maximum). The published dosimetric characterization of the INTRABEAM was based on detectors (radiochromic films or ionization chambers) not allowing measuring the absorbed dose in the first millimeters of the irradiated medium, where the dose is actually prescribed. This study aims at determining with Magnetic Resonance Imaging (MRI) the sensitivity of a paramagnetic gel in order to measure the dose deposit produced with the INTRABEAM from 0 to 20 mm. Although spherical applicators are mostly used with the INTRABEAM system for breast applications, this study focuses on surface applicators that are of interest for cutaneous carcinomas. The irradiations at 12 different dose levels (between 2 Gy and 50 Gy at the gel surface) were performed with the INTRABEAM and a 4 cm surface applicator. The gel used in this study is a new « sensitive ¼ material. In order to compare gel sensitivity at low energy with high energy, gels were irradiated by an 18 MV photon beam produced by a Varian Clinac 2100 CD. T2 weighted multi echo MRI sequences were performed with 16 echo times. The T2 signal versus echo times was fitted with a mono-exponential function with 95% confidence interval. The calibration curve determined at low energy is a linear function (r2 = 0.9893) with a sensitivity of 0.0381 s-1.Gy-1, a similar linear function was obtained at high energy (0.0372 s-1.Gy-1 with r2 = 0.9662). The calibration curve at low energy was used to draw isodose maps from the MR images. The PDD (Percent Depth Dose) determined in the gel is within 5%-1mm of the ionization chamber PDD except for one point. The dosimetric sensitivity of this new paramagnetic ferrous gel was determined with MRI measurements. It allowed measuring the dose distribution specifically in the first millimeters for an irradiation with the INTRABEAM miniature accelerator equipped with a surface applicator.


Assuntos
Compostos Ferrosos/química , Radiometria/instrumentação , Géis , Fenômenos Magnéticos , Miniaturização , Aceleradores de Partículas , Doses de Radiação , Razão Sinal-Ruído , Raios X
3.
Chemistry ; 26(40): 8676-8688, 2020 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-32452579

RESUMO

Resistance to chemotherapy is a current clinical problem, especially in the treatment of microbial infections and cancer. One strategy to overcome this is to make new derivatives of existing drugs by conjugation to organometallic fragments, either by an appropriate linker, or by direct coordination of the drug to a metal. We illustrate this with examples of conjugated organometallic metallocene sandwich and half-sandwich complexes, RuII and OsII arene, and RhIII and IrIII cyclopentadienyl half-sandwich complexes. Ferrocene conjugates are particularly promising. The ferrocene-chloroquine conjugate ferroquine is in clinical trials for malaria treatment, and a ferrocene-tamoxifen derivative (a ferrocifen) seems likely to enter anticancer trails soon. Several other examples illustrate that organometallic conjugation can restore the activity of drugs to which resistance has developed.


Assuntos
Aminoquinolinas/química , Antimaláricos/uso terapêutico , Cloroquina/farmacologia , Complexos de Coordenação/química , Compostos Ferrosos/química , Malária/tratamento farmacológico , Metalocenos/química , Compostos Organometálicos/química , Compostos de Rutênio/farmacologia , Antimaláricos/farmacologia , Cloroquina/química , Complexos de Coordenação/uso terapêutico , Humanos , Estrutura Molecular , Compostos de Rutênio/síntese química
4.
Chemosphere ; 255: 126942, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387732

RESUMO

Knowledge of the geochemical behavior of uranium is critical for the safe disposal of radioactive wastes. Biotite, a Fe(II)-rich phyllosilicate, is a common rock-forming mineral and a major component of granite or granodiorite. This work comprehensively studied the sorption of U(VI) on biotite surface with batch experiments and analyzed the uranium speciation with various spectroscopic techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and time-resolved fluorescence spectra (TRFS). Our results indicated that uranyl ions could penetrate into the interlayer of biotite, this ion-exchange process was pH-dependent and only favorable under acidic condition. Instead of precipitation or reduction to uraninite, the TRFS results strongly suggests U(VI) forms surface complexes under the neutral and alkaline condition, though the number and structure of surface species could not be identified accurately. Besides, the oxidation of biotite with peroxide hydrogen showed that structural Fe(II) would have a very low redox reactivity. With leaching experiments, zeta potential analysis and thermodynamics calculation, we discussed the possible reasons for inhibition of U(VI) reduction at the biotite-water interface. Our results may provide insight on interaction mechanism of uranium at mineral-water interface and help us understand the migration behavior of uranium in natural environments.


Assuntos
Silicatos de Alumínio/química , Compostos Ferrosos/química , Urânio/química , Concentração de Íons de Hidrogênio , Troca Iônica , Minerais , Oxirredução , Espectroscopia Fotoeletrônica , Resíduos Radioativos , Dióxido de Silício , Termodinâmica
5.
Ecotoxicol Environ Saf ; 200: 110744, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32460050

RESUMO

Hematite nanoparticles (α-Fe2O3 NPs) were successfully synthesized by a low-cost solvent-free reaction using Ferrous sulfate waste (FeSO4·7H2O) and pyrite (FeS2) as raw materials and employed for the decolorization of Methyl Orange by the photo-Fenton system. The properties of α-Fe2O3 NPs before and after photo-Fenton reaction were characterized by X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS), and the optical properties of α-Fe2O3 NPs were analyzed by UV-vis diffuse reflectance spectra (UV-vis DRS) and Photoluminescence (PL) spectra. The analytic results showed that the as-formed samples having an average diameter of ~50 nm exhibit pure phase hematite with sphere structure. Besides, little differences were found by comparing the characterization data of the particles before and after the photo-Fenton reaction, indicating that the photo-Fenton reaction was carried out in solution rather than on the surface of α-Fe2O3 NPs. A 24 central composite design (CCD) coupled with response surface methodology (RSM) was applied to evaluate and optimize the important variables. A significant quadratic model (P-value<0.0001, R2 = 0.9664) was derived using an analysis of variance (ANOVA), which was adequate to perform the process variables optimization. The optimal process conditions were performed to be 395 nm of the light wavelength, pH 3.0, 5 mmol/L H2O2 and 1 g/L α-Fe2O3, and the decolorization efficiency of methyl orange was 99.55% at 4 min.


Assuntos
Compostos Azo/química , Corantes/química , Compostos Férricos/química , Nanopartículas Metálicas/química , Catálise , Compostos Férricos/síntese química , Compostos Ferrosos/química , Ferro/química , Solventes , Sulfetos/química
6.
Chemistry ; 26(43): 9430-9444, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32227537

RESUMO

The last decade has witnessed the rapid development of high-valent Pd-involved organic transformations. This has also led to a steadily growing number of publications concerning the preparation of isolable and characterizable palladium(III) and palladium(IV) complexes. A variety of one-electron and two-electron oxidants have been employed to give access to high-oxidation-state Pd compounds. Undoubtedly, the study of these stoichiometric reactions has great implications for relevant Pd-mediated catalysis. In this minireview, the focus is on the synthetic approaches to structurally determined PdIII/IV complexes starting from their PdII precursors, and the advances in this research area from early 2010 to late 2019 will be highlighted. Chemical oxidations exploiting various oxidizing agents including 1) hypervalent iodine reagents; 2) halogens; 3) electrophilic fluorination reagents; 4) alkyl/aryl halides; 5) ferrocenium salts; 6) peroxides/O2 ; 7) sulfonyl chlorides; and 8) others are covered. A "greener" electrooxidation manner has also been reviewed.


Assuntos
Compostos Ferrosos/química , Paládio/química , Catálise , Elétrons , Halogenação , Halogênios/química , Indicadores e Reagentes/química , Iodo/química , Oxirredução
7.
Biochim Biophys Acta Proteins Proteom ; 1868(6): 140413, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32179182

RESUMO

Only recently it was discovered that haemoglobin (Hb) belongs to the standard gene repertoire of insects, although their tracheal system is used for respiration. A classical oxygen-carrying function of Hb is only obvious for hexapods living in hypoxic environments. In other insect species, including the common fruit fly Drosophila melanogaster, the physiological role of Hb is yet unclear. Here, we study recombinant haemoglobin from the European honeybee Apis mellifera (Ame) and the malaria mosquito Anopheles gambiae (Aga). Spectroscopic evidence shows that both proteins can be classified as hexacoordinate Hbs with a strong affinity for the distal histidine. AgaHb1 is proposed to play a role in oxygen transport or sensing based on its multimeric state, slow autoxidation, and small but significant amount of five-coordinated haem in the deoxy ferrous form. AmeHb appears to behave more like vertebrate neuroglobin with a complex function given its diversified distribution in the genome.


Assuntos
Anopheles/metabolismo , Abelhas/metabolismo , Hemoglobinas/análise , Sistema Respiratório/metabolismo , Análise Espectral/métodos , Animais , Anopheles/genética , Abelhas/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Evolução Molecular , Compostos Férricos/química , Compostos Ferrosos/química , Genoma , Heme/metabolismo , Hemoglobinas/genética , Insetos/genética , Insetos/metabolismo , Ligantes , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Modelos Moleculares , Oxigênio
8.
Chemosphere ; 251: 126362, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32151808

RESUMO

In this manuscript, Fe(II) inhibition of anammox and its recovery were investigated, and the performance, kinetics and statistical features were comprehensively studied simultaneously. Anammox was suppressed and completely inhibited by the addition of 109.29 and 378.57 mg/L Fe(II), respectively, via uncompetitive inhibition. Nitrite inhibition of anammox was best fitted by the Edwards model and Aiba model. EDTA-2Na wash (0.5, 1.0, 1.5, and 2.0 mM) had a limited effect on anammox recovery, while the addition of 2.0 mM betaine accelerated anammox recovery. Prolonged betaine addition caused an unintended reduction of anammox activity, though it self-recovered after the withdrawal of betaine. The modified Boltzmann model most accurately simulated the processes of anammox recovery using the EDTA-2Na wash, betaine regulation and self-recovery, and the modified Stover-Kincannon model was able to assess the results of anammox recovery. The one-sample t-test was successfully applied to determine the effects of these three recovery strategies on inhibited anammox, which were short-term disinhibition or long-term recovery effects. The above-mentioned results demonstrate that an intermittent addition of betaine, which is a better alternative to frequently-used but poorly-degradable EDTA, may be a useful and environmentally friendly recovery strategy for Fe(II)-inhibited anammox reactor.


Assuntos
Betaína/química , Compostos Ferrosos/química , Modelos Químicos , Anaerobiose , Reatores Biológicos , Cinética , Nitrogênio , Oxirredução
9.
PLoS One ; 15(3): e0228740, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32214347

RESUMO

Parasitic diseases are a neglected and serious problem, especially in underdeveloped countries. Among the major parasitic diseases, Leishmaniasis figures as an urgent challenge due to its high incidence and severity. At the same time, the indiscriminate use of antibiotics by the population is increasing together with resistance to medicines. To address this problem, new antibiotic-like molecules that directly kill or inhibit the growth of microorganisms are necessary, where antimicrobial peptides (AMPs) can be of great help. In this work, the ferrocene molecule, one active compound with low levels of in vivo toxicity, was coupled to the N-terminus of the RP1 peptide (derived from the human chemokine CXCL4), aiming to evaluate how this change modifies the structure, biological activity, and toxicity of the peptide. The peptide and the conjugate were synthesized using the solid phase peptide synthesis (SPPS). Circular dichroism assays in PBS showed that the RP1 peptide and its conjugate had a typical spectrum for disordered structures. The Fc-RP1 presented anti-amastigote activity against Leishmania amazonensis (IC50 = 0.25 µmol L-1). In comparison with amphotericin B, a second-line drug approved for leishmaniasis treatment, (IC50 = 0.63 µmol L-1), Fc-RP1 was more active and showed a 2.5-fold higher selectivity index. The RP1 peptide presented a MIC of 4.3 µmol L-1 against S. agalactiae, whilst Fc-RP1 was four times more active (MIC = 0.96 µmol L-1), indicating that ferrocene improved the antimicrobial activity against Gram-positive bacteria. The Fc-RP1 peptide also decreased the minimum inhibitory concentration (MIC) in the assays against E. faecalis (MIC = 7.9 µmol L-1), E. coli (MIC = 3.9 µmol L-1) and S. aureus (MIC = 3.9 µmol L-1). The cytotoxicity of the compounds was tested against HaCaT cells, and no significant activity at the highest concentration tested (500 µg. mL-1) was observed, showing the high potential of this new compound as a possible new drug. The coupling of ferrocene also increased the vesicle permeabilization of the peptide, showing a direct relation between high peptide concentration and high carboxyfluorescein release, which indicates the action mechanism by pore formation on the vesicles. Several studies have shown that ferrocene destabilizes cell membranes through lipid peroxidation, leading to cell lysis. It is noteworthy that the Fc-RP1 peptide synthesized here is a prototype of a bioconjugation strategy, but it still is a compound with great biological activity against neglected and fish diseases.


Assuntos
Peptídeos Catiônicos Antimicrobianos/química , Peptídeos Catiônicos Antimicrobianos/farmacologia , Compostos Ferrosos/química , Metalocenos/química , Sequência de Aminoácidos , Animais , Peptídeos Catiônicos Antimicrobianos/metabolismo , Peptídeos Catiônicos Antimicrobianos/toxicidade , Bactérias/efeitos dos fármacos , Leishmania/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Permeabilidade
10.
Inorg Chem ; 59(5): 3304-3311, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32064865

RESUMO

The water-compatible optically pure metallohelices made by self-assembly of simple nonpeptidic organic components around Fe(II) ions are now recognized as a distinct subclass of helicates that exhibit similar architecture to some natural cationic antimicrobial peptides. Notably, a new series of metallohelices was recently shown to exhibit biological activity, displaying high, structure-dependent activity against bacteria. It is also important that, thanks to their properties, such metallohelices can exhibit specific interactions with biomacromolecules. Here, following our prior report on the metallohelices that have high, structure-dependent activity against bacteria, we investigated the interactions of the series of iron(II) metallohelices with DNA, which is a potential pharmacological target of this class of coordination compounds. The results obtained with the aid of biophysical and molecular biology methods show that the investigated metallohelices accumulate in eukaryotic cells and that a significant fraction of the metallohelices accumulates in the cell nucleus, allowing them to interact also with nuclear DNA. Additionally, we have demonstrated that some metallohelices have a high affinity to DNA and are able to condense/aggregate DNA molecules more efficiently than conventional DNA-condensing agents, such as polyamines. Moreover, this capability of the metallohelices correlates with their efficiency to inhibit DNA-related enzymatic activities, such as those connected with DNA transcription, catalysis of DNA relaxation by DNA topoisomerase I, and cleavage by restriction enzymes.


Assuntos
Núcleo Celular/química , DNA Topoisomerases Tipo I/metabolismo , DNA/antagonistas & inibidores , Compostos Ferrosos/farmacologia , Inibidores da Topoisomerase I/farmacologia , Núcleo Celular/metabolismo , DNA/genética , DNA/metabolismo , Compostos Ferrosos/síntese química , Compostos Ferrosos/química , Células HCT116 , Humanos , Estrutura Molecular , Fenômenos Ópticos , Inibidores da Topoisomerase I/síntese química , Inibidores da Topoisomerase I/química
11.
Chemosphere ; 248: 126123, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32059334

RESUMO

The immobilization of selenate (SeO42-) using metal oxides (CaO and MgO) and ferrous salt as the immobilization reagents were examined by the leaching test and solid-phase analysis via XRD, XAFS, TGA, and XPS. The results indicated that nearly all of SeO42- was reduced to SeO32- in the CaO-based reaction within 7 days. Then, the generated SeO32- was mainly sorbed onto the iron-based minerals (Fe2O3 and FeOOH) through the formation of both bidentate mononuclear edge-sharing (1E) and monodentate mononuclear corner-sharing (1V) inner-sphere surface complexes, suggested by PHREEQC simulation and EXAFS analysis. Differently, less amount of SeO42- (approximately 45.50%) was reduced to SeO32- for the MgO-based reaction. However, if the curing time increases to a longer time (more than 7 days), the further reduction could occur because there are still Fe(II) species in the matrix. As for the associations of Se in the solid residue, most of the selenium (SeO32- and SeO42-) was preferentially distributed onto the Mg(OH)2 through outer-sphere adsorption. Definitely, this research can provide a deep understanding of the immobilization of selenium using alkaline-earth metal oxide related materials and ferrous substances.


Assuntos
Compostos de Cálcio/química , Poluentes Ambientais/análise , Compostos Ferrosos/química , Óxido de Magnésio/química , Óxidos/química , Ácido Selênico/análise , Adsorção , Poluentes Ambientais/química , Modelos Teóricos , Ácido Selênico/química , Purificação da Água/métodos
12.
Curr Pharm Biotechnol ; 21(7): 587-595, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31893988

RESUMO

OBJECTIVE: The current study reports a green, rapid and one-pot synthesis of FeSO4 nanoparticles using Hibiscus rosasinensis floral extract as a reducing and capping agent. 0.5M of FeSO4 was stirred with the floral extract of H. rosasinensis for around 20 minutes at 37ºC and pH 7. METHODS: The development of pink color was considered as the endpoint of reduction and the nanoparticles were characterized by UV-Vis spectrum, EDAX, DLS, FTIR, FESEM, and XRD. UV-Vis spectral analysis indicated a peak at 530 nm and EDAX measurement revealed the presence of Fe, S, O and C elements in the nanoparticle sample. The FTIR analysis showed amines, alcohol and alkene groups that act as capping agents for the produced nanoparticles. FESEM and XRD determination presented FeSO4 nanoparticles of 40-60 nm in size. The synthesized nanoparticles were found to have antibacterial activity against 6 pathogenic bacteria with MIC and MBC of 40 mg/mL. RESULTS: To determine the toxicity at the eukaryotic level, brine shrimp toxicity assay was conducted and 100% mortality was found at concentrations >0.06 mg/mL. Gel shift assay suggested the mechanism of toxicity of FeSO4 NPs by binding and degradation of DNA molecules. CONCLUSION: From the results, the authors demonstrate the ease of green synthesis of FeSO4 nanoparticles and its bioactivity that may have potential applications as drugs and drug delivery systems against various diseases.


Assuntos
Antibacterianos/química , Antineoplásicos/química , Dano ao DNA , Compostos Ferrosos/química , Química Verde/métodos , Nanopartículas/química , Animais , Antibacterianos/farmacologia , Antibacterianos/toxicidade , Antineoplásicos/farmacologia , Antineoplásicos/toxicidade , Artemia/efeitos dos fármacos , Artemia/genética , Biofilmes/efeitos dos fármacos , Biofilmes/crescimento & desenvolvimento , Ensaio de Desvio de Mobilidade Eletroforética , Compostos Ferrosos/farmacologia , Compostos Ferrosos/toxicidade , Flores/química , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Hibiscus , Testes de Sensibilidade Microbiana , Extratos Vegetais/química , Espectroscopia de Infravermelho com Transformada de Fourier , Análise de Sobrevida
13.
Mater Sci Eng C Mater Biol Appl ; 108: 110371, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31924004

RESUMO

The objective of this paper is to demonstrate the potential of nanostructured polypyrrole formed by template free as platform for amperometric detection of DNA. The nanowires of polypyrrole (nw-PPy) are formed through electrochemical polymerization and chemically modified by electrochemical oxidation of ethylene diamine or dendrimers PAMAM to obtain aminated surface. The DNA probe and ferrocenyl group, as redox reporter, were covalently linked to the surface of nw-PPy. The chemical structure of nanostructured platform was characterized through SEM, FT-IR and XPS and the electrochemical properties through cyclic voltammetry and electrochemical impedance spectroscopy (EIS). We show that the properties of nw-PPy such as, hydrophilic character and large surface area have large effect on the electronic properties. Thus, the electrochemical performance is increased compared to others nanomaterials considering the obtained value of the rate of electron transfer of 18 s-1. These properties allow enhanced DNA sensing where detection limit of 0.36 atomolar without any amplification step. The biosensor can be applied in detection of genomic DNA of Mycobacterium tuberculosis and the mutated one which present the resistance to rifampicin and large selectivity was demonstrated. We believe that nw-PPy modified with redox marker is a promising platform for electrochemical biosensors and can be applied for various diagnosis prospects.


Assuntos
Técnicas Biossensoriais , DNA Bacteriano/análise , Técnicas Eletroquímicas/métodos , Mycobacterium tuberculosis/genética , Nanoestruturas/química , Polímeros/química , Pirróis/química , Dendrímeros/química , Eletrólitos/química , Compostos Ferrosos/química , Ouro/química , Cinética , Metalocenos/química , Mycobacterium tuberculosis/isolamento & purificação , Nanoestruturas/ultraestrutura , Nanofios/química , Nanofios/ultraestrutura , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier
14.
Dalton Trans ; 49(5): 1545-1554, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31930254

RESUMO

Ferritins are multimers comprised of 4 α-helical bundle monomers that co-assemble to form protein shells surrounding an approximately spherical internal cavity. The assembled multimers acquire Fe2+ from their surroundings by utilising channels that penetrate the protein for the transportation of iron to diiron catalytic centres buried within the monomeric units. Here oxidation of the substrate to Fe3+ is coupled to the reduction of O2 and/or peroxide to yield the precursor to a ferric oxy hydroxide mineral that is stored within the internal cavity. The rhombic dodecahedral quaternary structure results in channels of 4-fold and 3-fold symmetry, located at the vertices, which are common to all 24mer-ferritins. Ferritins isolated from higher eukaryotes have been demonstrated to take up Fe2+via the 3-fold channels. One of the defining features of ferritins isolated from prokaryotes is the presence of a further 24 channels, the B-channels, and these are thought to play an important role in Fe2+ uptake in this sub-family. SynFtn is an unusual ferritin isolated from the marine cyanobacterium Synechococcus CC9311. The reported structure of SynFtn derived from Fe2+ soaked crystals revealed the presence of a fully hydrated Fe2+ associated with three aspartate residues (Asp137 from each of the three symmetry related subunits) within each three-fold channel, suggesting that it might be the route for Fe2+ entry. Here, we present structural and spectro-kinetic data on two variants of SynFtn, D137A and E62A, designed to assess this possibility. Glu62 is equivalent to residues demonstrated to be important in the transfer of iron from the inner exit of the 3-fold channel to the catalytic centre in animal ferritins. As expected replacing Asp137 with a non-coordinating residue eliminated rapid iron oxidation by SynFtn. In contrast the rate of mineral core formation was severely impaired whilst the rate of iron transit into the catalytic centre was largely unaffected upon introducing a non-coordinating residue in place of Glu62 suggesting a role for this residue in release of the oxidised product. The identification of these two residues in SynFtn maps out major routes for Fe2+ entry to, and exit from, the catalytic ferroxidase centres.


Assuntos
Ceruloplasmina/metabolismo , Ferritinas/metabolismo , Compostos Ferrosos/metabolismo , Células Procarióticas/metabolismo , Synechococcus/química , Biocatálise , Domínio Catalítico , Ceruloplasmina/química , Espectroscopia de Ressonância de Spin Eletrônica , Ferritinas/química , Ferritinas/isolamento & purificação , Compostos Ferrosos/química , Modelos Moleculares , Células Procarióticas/química , Synechococcus/metabolismo
15.
Molecules ; 25(2)2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31936620

RESUMO

Two novel coordination compounds containing heterocyclic bidentate N,N-donor ligand 2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (fpo) were synthesized. A general formula for compounds originating from perchlorates of iron, cobalt, and fpo can be written as: [M(fpo)2(H2O)2](ClO4)2 (M = Fe(II) for (1) Co(II) for (2)). The characterization of compounds was performed by general physico-chemical methods-elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) in case of organics, and single crystal X-ray diffraction (sXRD). Moreover, magneto-chemical properties were studied employing measurements in static field (DC) for 1 and X-band EPR (Electron paramagnetic resonance), direct current (DC), and alternating current (AC) magnetic measurements in case of 2. The analysis of DC magnetic properties revealed a high spin arrangement in 1, significant rhombicity for both complexes, and large magnetic anisotropy in 2 (D = -21.2 cm-1). Moreover, 2 showed field-induced slow relaxation of the magnetization (Ueff = 65.3 K). EPR spectroscopy and ab initio calculations (CASSCF/NEVPT2) confirmed the presence of easy axis anisotropy and the importance of the second coordination sphere.


Assuntos
Cobalto/química , Complexos de Coordenação/química , Compostos Ferrosos/química , Ferro/química , Anisotropia , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Furanos/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Oxidiazóis/química , Espectroscopia de Infravermelho com Transformada de Fourier , Espectroscopia de Mossbauer
16.
J Phys Chem Lett ; 11(3): 1030-1037, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-31967828

RESUMO

Very recently, the bulk synthesis of cyclo-N5- from arylpentazole through the treatment with m-chloroperbenzonic acid (m-CPBA) and ferrous bisglycinate ([Fe(Gly)2]) (Zhang, C., et al. Science 2017, 355, 374) has greatly promoted the application of pentazolate anion as a novel high-performance energetic material. Yet the mechanism for this reaction is still unexplored. Herein we perform mechanistic studies on the selective C-N bond cleavage in arylpentazole by using density functional theory methods. The direct C-N bond activation by m-CPBA was computed to be kinetically inaccessible. Instead, the oxidation of [Fe(Gly)2] by m-CPBA is much favorable, which leads to the generation of a high-valent iron(IV)-oxo product. The Fe(IV)-oxo intermediate has been examined by UV-vis absorption spectra experiments and further verified by excited-state calculations. It is found that the Fe(IV)-oxo serves as the key intermediate for the C-N bond activation of arylpentazole and the cyclo-N5- generation. Our calculations clarified the key mechanistic details of the cyclo-N5- generation, and the factors that affect the production yield are further discussed.


Assuntos
Clorobenzoatos/química , Compostos Ferrosos/química , Glicina/química , Modelos Moleculares , Pentilenotetrazol/química , Carbono/química , Nitrogênio/química , Oxirredução , Teoria Quântica , Espectrofotometria , Termodinâmica
17.
Chemosphere ; 247: 125804, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31931311

RESUMO

Fe(II)/persulfate process has been proven to be a promising technique for disintegrating sludge, while during the Fe(II)/persulfate treatment the direct information about the variation of extracellular polymeric substances (EPS) properties, which is a key factor affecting sludge dewatering, is still lacked. In this work, different dosages of Fe(II)/persulfate were employed to treat EPS fractions extracted from waste activated sludge. The experiment results showed that EPS fractions were modified by Fe(II)/persulfate process. An oxidation/flocculation process was raised to unveil how Fe(II)/persulfate modified EPS fractions: Firstly, SO4- and OH were formed by chemical reactions of Fe(II) activating persulfate and radical interconversion, respectively. Then these species nonselectively fragmented EPS fractions through decomposing their components, which facilitated decrement of the hydrophilic components and high/mid molecular weight of organics in EPS fractions. Furthermore, these radicals transformed the secondary structure of EPS proteins by affecting the hydrogen bonds at specific positions and inducing the cleavage of the S-S bonds in cysteine residues of proteins, which led to loose layout of protein molecules and thus increased exposure of the hydrophobic groups hidden in EPS protein molecules. Secondly, Fe(III), i.e., the oxidation product of Fe(II), assembled the ruptured colloids particles through lessening electronegativity. Consequently, Fe(II)/persulfate process elevated the flocculability and hydrophobicity of EPS fractions, which would improve physicochemical and rheological properties of sludge to facilitate its dewaterability.


Assuntos
Matriz Extracelular de Substâncias Poliméricas/química , Compostos Ferrosos/química , Esgotos/química , Floculação , Radicais Livres/química , Oxirredução , Sulfatos/química , Eliminação de Resíduos Líquidos/métodos
18.
Bioelectrochemistry ; 132: 107412, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31889632

RESUMO

The synthesis of a series of methyl 2-alkyl-5-aryl-4-ferrocenoylpyrrolidine-2-carboxylates has been achieved by [3 + 2] dipolar cycloaddition of azomethine ylides to acryloylferrocene. The electrochemical properties of novel products were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These techniques revealed the quasi-reversible one-electron oxidation process. The DNA-binding capacity of all the products was also studied using CV and DPV, and significant interactions between synthesized compounds and nucleic acid, mostly of the electrostatic type, were disclosed. DFT calculations and molecular docking tests were carried out to gain a more exhaustive insight into the interactions of the obtained products with nucleic acid. A detailed characterization of the new compounds was performed by IR, NMR and elemental analyses, followed by single-crystal X-ray diffraction experiments for two representatives.


Assuntos
DNA/metabolismo , Técnicas Eletroquímicas/métodos , Compostos Ferrosos/metabolismo , Metalocenos/metabolismo , Cristalografia por Raios X , Teoria da Densidade Funcional , Compostos Ferrosos/química , Espectroscopia de Ressonância Magnética , Metalocenos/química , Estrutura Molecular , Oxirredução , Espectrofotometria Infravermelho
19.
Chemosphere ; 244: 125473, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31790996

RESUMO

In this study, Fe(II)-activated persulfate-assisted hydrothermal treatment (Fe(II)-PS-HT) was used to improve the efficiency of removing nitrogen (N) from the sewage sludge (SS) under relatively mild conditions (i.e., at 150 °C, for 20min), and the N transformation mechanism was investigated. The total N content in the solid residue was used to evaluate the N removal efficiency. Further, the redistribution of N in the solid and liquid products was characterized and quantified to obtain a N transformation mechanism during sequential persulfate oxidation (Fe(II) and persulfate) assisted hydrothermal treatment (HT). The experimental results denote that the N removal efficiency obtained from the Fe(II)-PS-HT (persulfate/C = 0.085 and Fe(II)/persulfate = 0.5) treated SS was increased by 35.0% at a relatively mild temperature (i.e., 150 °C) when compared with that obtained by treating SS using normal HT. Elevating Fe(II)/persulfate ratio to 1.25 promoting the N removal efficiency by 59.9%-65.9%. Furthermore, the electron paramagnetic resonance (EPR) and scanning electron microscopy (SEM) results clearly denote a N removal mechanism where the sulfate radicals (SO4∙-) produced by Fe(II)-PS destroy the sludge structure and destructed extracellular polymers (EPS). In the absence of EPS protection, proteins were directly exposed to extreme hydrothermal circumstances, and were rapidly transformed from the SS into the liquid residue. The free radicals also provided energy for the denitrification of Heterocycle-N. Consequently, a high N removal efficiency was obtained by Fe(II)-PS-HT with persulfate/C = 0.085 and Fe(II)/persulfate = 1.25 at 150 °C for 20 min.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Compostos Ferrosos/química , Nitrogênio , Oxirredução , Esgotos/química , Sulfatos , Temperatura
20.
Biochim Biophys Acta Proteins Proteom ; 1868(2): 140335, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31785381

RESUMO

Pyranose oxidase (POx) catalyzes the oxidation of d-glucose to 2-ketoglucose with concurrent reduction of oxygen to H2O2. POx from Trametes ochracea (ToPOx) is known to react with alternative electron acceptors including 1,4-benzoquinone (1,4-BQ), 2,6-dichlorophenol indophenol (DCPIP), and the ferrocenium ion. In this study, enzyme variants with improved electron acceptor turnover and reduced oxygen turnover were characterized as potential anode biocatalysts. Pre-steady-state kinetics of the oxidative half-reaction of ToPOx variants T166R, Q448H, L545C, and L547R with these alternative electron acceptors were evaluated using stopped-flow spectrophotometry. Higher kinetic constants were observed as compared to the wild-type ToPOx for some of the variants. Subsequently, the variants were immobilized on glassy carbon electrodes. Cyclic voltammetry measurements were performed to measure the electrochemical responses of these variants with glucose as substrate in the presence of 1,4-BQ, DCPIP, or ferrocene methanol as redox mediators. High catalytic efficiencies (Imaxapp/KMapp) compared to the wild-type POx proved the potential of these variants for future bioelectrocatalytic applications, in biosensors or biofuel cells. Among the variants, L545C showed the most desirable properties as determined kinetically and electrochemically.


Assuntos
Desidrogenases de Carboidrato/metabolismo , Técnicas Eletroquímicas/métodos , 2,6-Dicloroindofenol/química , Benzoquinonas/química , Biocatálise , Desidrogenases de Carboidrato/química , Desidrogenases de Carboidrato/genética , Domínio Catalítico , Eletrodos , Compostos Ferrosos/química , Glucose/química , Glucose/metabolismo , Cinética , Metalocenos/química , Mutagênese Sítio-Dirigida , Oxirredução , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Trametes/enzimologia
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