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[PMID]:28823151
[Au] Autor:Komor AJ; Rivard BS; Fan R; Guo Y; Que L; Lipscomb JD
[Ti] Título:CmlI N-Oxygenase Catalyzes the Final Three Steps in Chloramphenicol Biosynthesis without Dissociation of Intermediates.
[So] Source:Biochemistry;56(37):4940-4950, 2017 Sep 19.
[Is] ISSN:1520-4995
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:CmlI catalyzes the six-electron oxidation of an aryl-amine precursor (NH -CAM) to the aryl-nitro group of chloramphenicol (CAM). The active site of CmlI contains a (hydr)oxo- and carboxylate-bridged dinuclear iron cluster. During catalysis, a novel diferric-peroxo intermediate P is formed and is thought to directly effect oxygenase chemistry. Peroxo intermediates can facilitate at most two-electron oxidations, so the biosynthetic pathway of CmlI must involve at least three steps. Here, kinetic techniques are used to characterize the rate and/or dissociation constants for each step by taking advantage of the remarkable stability of P in the absence of substrates (decay t = 3 h at 4 °C) and the visible chromophore of the diiron cluster. It is found that diferrous CmlI (CmlI ) can react with NH -CAM and O in either order to form a P-NH -CAM intermediate. P-NH -CAM undergoes rapid oxygen transfer to form a diferric CmlI (CmlI ) complex with the aryl-hydroxylamine [NH(OH)-CAM] pathway intermediate. CmlI -NH(OH)-CAM undergoes a rapid internal redox reaction to form a CmlI -nitroso-CAM (NO-CAM) complex. O binding results in formation of P-NO-CAM that converts to CmlI -CAM by enzyme-mediated oxygen atom transfer. The kinetic analysis indicates that there is little dissociation of pathway intermediates as the reaction progresses. Reactions initiated by adding pathway intermediates from solution occur much more slowly than those in which the intermediate is generated in the active site as part of the catalytic process. Thus, CmlI is able to preserve efficiency and specificity while avoiding adventitious chemistry by performing the entire six-electron oxidation in one active site.
[Mh] Termos MeSH primário: Antibacterianos/biossíntese
Proteínas de Bactérias/metabolismo
Cloranfenicol/biossíntese
Modelos Moleculares
Ferroproteínas não Heme/metabolismo
Oxigenases/metabolismo
Streptomyces/enzimologia
[Mh] Termos MeSH secundário: Antibacterianos/química
Proteínas de Bactérias/química
Biocatálise
Domínio Catalítico
Cloranfenicol/análogos & derivados
Cloranfenicol/química
Meia-Vida
Cinética
Ferroproteínas não Heme/química
Oxirredução
Oxigênio
Oxigenases/química
Espectroscopia de Mossbauer
[Pt] Tipo de publicação:COMPARATIVE STUDY; JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Anti-Bacterial Agents); 0 (Bacterial Proteins); 0 (Nonheme Iron Proteins); 66974FR9Q1 (Chloramphenicol); EC 1.13.- (Oxygenases); S88TT14065 (Oxygen)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171003
[Lr] Data última revisão:
171003
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170822
[St] Status:MEDLINE
[do] DOI:10.1021/acs.biochem.7b00695


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[PMID]:28708835
[Au] Autor:Ateia M; Koch C; Jelavic S; Hirt A; Quinson J; Yoshimura C; Johnson M
[Ad] Endereço:Department of Civil and Environmental Engineering, Tokyo Institute of Technology, Ookayama, Tokyo, Japan.
[Ti] Título:Green and facile approach for enhancing the inherent magnetic properties of carbon nanotubes for water treatment applications.
[So] Source:PLoS One;12(7):e0180636, 2017.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Current methods for preparing magnetic composites with carbon nanotubes (MCNT) commonly include extensive use of treatment with strong acids and result in massive losses of carbon nanotubes (CNTs). In this study we explore the potential of taking advantage of the inherent magnetic properties associated with the metal (alloy or oxide) incorporated in CNTs during their production. The as-received CNTs are refined by applying a permanent magnet to a suspension of CNTs to separate the high-magnetic fraction; the low-magnetic fraction is discarded with the solvent. The collected MCNTs were characterized by a suite of 10 diffraction and spectroscopic techniques. A key discovery is that metallic nano-clusters of Fe and/or Ni located in the interior cavities of the nanotubes give MCNTs their ferromagnetic character. After refinement using our method, the MCNTs show saturation magnetizations up to 10 times that of the as-received materials. In addition, we demonstrate the ability of these MCNTs to repeatedly remove atrazine from water in a cycle of dispersion into a water sample, adsorption of the atrazine onto the MCNTs, collection by magnetic attraction and regeneration by ethanol. The resulting MCNTs show high adsorption capacities (> 40 mg-atrazine/g), high magnetic response, and straightforward regeneration. The method presented here is simpler, faster, and substantially reduces chemical waste relative to current techniques and the resulting MCNTs are promising adsorbents for organic/chemical contaminants in environmental waters.
[Mh] Termos MeSH primário: Magnetismo
Nanotubos de Carbono/química
Purificação da Água/métodos
[Mh] Termos MeSH secundário: Adsorção
Atrazina/química
Ferro/química
Microscopia Eletrônica de Transmissão
Níquel/química
Espectroscopia Fotoeletrônica
Espectroscopia de Mossbauer
Análise Espectral Raman
Difração de Raios X
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Nanotubes, Carbon); 7OV03QG267 (Nickel); E1UOL152H7 (Iron); QJA9M5H4IM (Atrazine)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170926
[Lr] Data última revisão:
170926
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170715
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0180636


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[PMID]:28542723
[Au] Autor:Honarmand Ebrahimi K; Bill E; Hagedoorn PL; Hagen WR
[Ad] Endereço:Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, UK.
[Ti] Título:Spectroscopic evidence for the presence of a high-valent Fe(IV) species in the ferroxidase reaction of an archaeal ferritin.
[So] Source:FEBS Lett;591(12):1712-1719, 2017 Jun.
[Is] ISSN:1873-3468
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:A high-valent Fe(IV) species is proposed to be generated from the decay of a peroxodiferric intermediate in the catalytic cycle at the di-iron cofactor center of dioxygen-activating enzymes such as methane monooxygenase. However, it is believed that this intermediate is not formed in the di-iron substrate site of ferritin, where oxidation of Fe(II) substrate to Fe(III) (the ferroxidase reaction) occurs also via a peroxodiferric intermediate. In opposition to this generally accepted view, here we present evidence for the occurrence of a high-valent Fe(IV) in the ferroxidase reaction of an archaeal ferritin, which is based on trapped intermediates obtained with the freeze-quench technique and combination of spectroscopic characterization. We hypothesize that a Fe(IV) intermediate catalyzes oxidation of excess Fe(II) nearby the ferroxidase center.
[Mh] Termos MeSH primário: Proteínas Arqueais/metabolismo
Ceruloplasmina/metabolismo
Ferritinas/metabolismo
Ferro/química
Modelos Moleculares
Pyrococcus furiosus/enzimologia
[Mh] Termos MeSH secundário: Proteínas Arqueais/química
Biocatálise
Domínio Catalítico
Ceruloplasmina/química
Espectroscopia de Ressonância de Spin Eletrônica
Ferritinas/química
Oxirredução
Espectrofotometria
Espectroscopia de Mossbauer
Tirosina/química
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Archaeal Proteins); 42HK56048U (Tyrosine); 9007-73-2 (Ferritins); E1UOL152H7 (Iron); EC 1.16.3.1 (Ceruloplasmin)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170925
[Lr] Data última revisão:
170925
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170526
[St] Status:MEDLINE
[do] DOI:10.1002/1873-3468.12697


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[PMID]:27541495
[Au] Autor:Solti Á; Kovács K; Müller B; Vázquez S; Hamar É; Pham HD; Tóth B; Abadía J; Fodor F
[Ad] Endereço:Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, Faculty of Sciences, Eötvös Loránd University, Pázmány P. Sétány 1/C, Budapest, 1117, Hungary. adam.solti@ttk.elte.hu.
[Ti] Título:Does a voltage-sensitive outer envelope transport mechanism contributes to the chloroplast iron uptake?
[So] Source:Planta;244(6):1303-1313, 2016 Dec.
[Is] ISSN:1432-2048
[Cp] País de publicação:Germany
[La] Idioma:eng
[Ab] Resumo:MAIN CONCLUSION: Based on the effects of inorganic salts on chloroplast Fe uptake, the presence of a voltage-dependent step is proposed to play a role in Fe uptake through the outer envelope. Although iron (Fe) plays a crucial role in chloroplast physiology, only few pieces of information are available on the mechanisms of chloroplast Fe acquisition. Here, the effect of inorganic salts on the Fe uptake of intact chloroplasts was tested, assessing Fe and transition metal uptake using bathophenantroline-based spectrophotometric detection and plasma emission-coupled mass spectrometry, respectively. The microenvironment of Fe was studied by Mössbauer spectroscopy. Transition metal cations (Cd , Zn , and Mn ) enhanced, whereas oxoanions (NO , SO , and BO ) reduced the chloroplast Fe uptake. The effect was insensitive to diuron (DCMU), an inhibitor of chloroplast inner envelope-associated Fe uptake. The inorganic salts affected neither Fe forms in the uptake assay buffer nor those incorporated into the chloroplasts. The significantly lower Zn and Mn uptake compared to that of Fe indicates that different mechanisms/transporters are involved in their acquisition. The enhancing effect of transition metals on chloroplast Fe uptake is likely related to outer envelope-associated processes, since divalent metal cations are known to inhibit Fe transport across the inner envelope. Thus, a voltage-dependent step is proposed to play a role in Fe uptake through the chloroplast outer envelope on the basis of the contrasting effects of transition metal cations and oxoaninons.
[Mh] Termos MeSH primário: Transporte Biológico Ativo/fisiologia
Cloroplastos/metabolismo
Ferro/metabolismo
[Mh] Termos MeSH secundário: Beta vulgaris/metabolismo
Beta vulgaris/fisiologia
Transporte Biológico Ativo/efeitos dos fármacos
Cádmio/metabolismo
Cloroplastos/efeitos dos fármacos
Cloroplastos/fisiologia
Diurona/farmacologia
Herbicidas/farmacologia
Manganês/metabolismo
Espectroscopia de Mossbauer
Zinco/metabolismo
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Herbicides); 00BH33GNGH (Cadmium); 42Z2K6ZL8P (Manganese); 9I3SDS92WY (Diuron); E1UOL152H7 (Iron); J41CSQ7QDS (Zinc)
[Em] Mês de entrada:1704
[Cu] Atualização por classe:171005
[Lr] Data última revisão:
171005
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160820
[St] Status:MEDLINE


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[PMID]:27227563
[Au] Autor:Montes ML; Rivas PC; Taylor MA; Mercader RC
[Ad] Endereço:Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, IFLP-CONICET, Argentina. Electronic address: lmontes@fisica.unlp.edu.ar.
[Ti] Título:Approximate total Fe content determined by Mössbauer spectrometry: Application to determine the correlation between gamma-ray-emitter activities and total content of Fe phases in soils of the Province of Buenos Aires, Argentina.
[So] Source:J Environ Radioact;162-163:113-117, 2016 Oct.
[Is] ISSN:1879-1700
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Pearson correlation coefficients between K, Ra and Th activities and the total Fe phase fractions yielded by Mössbauer spectroscopy have been calculated for soils of the Province of Buenos Aires, Argentina. Total fractions of Fe phases have been obtained from the relative fractions reported in previous works weighted by the Fe soil content and the recoilless-fraction of each Fe phase. An approximate method based on the relationship between the Mössbauer spectral absorption area (obtained from the Fe Mössbauer data) and the total Fe concentration (determined by colorimetric methods, after microwave assisted acid digestion of soil samples) has been used for the first time to determine the Fe concentration in soils with an accuracy of 15%. Protocol to extend the method for unknown samples is also discussed. The determined new coefficients differ from those reported previously. A significant and positive correlation between the total fraction of Fe and the K activity values has been obtained. This result validates the hypothesis put forward in a previous work, i.e., that illite captures the K existing in the soil. In addition, with the new approximation, the Pearson correlation coefficients for the other natural radionuclides give values that indicate that the methodology reported here is appropriate to study the correlations between the activity values with the total fractions of Fe phases.
[Mh] Termos MeSH primário: Ferro/análise
Poluentes Radioativos do Solo/análise
Solo/química
Espectroscopia de Mossbauer
[Mh] Termos MeSH secundário: Argentina
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Soil); 0 (Soil Pollutants, Radioactive); E1UOL152H7 (Iron)
[Em] Mês de entrada:1705
[Cu] Atualização por classe:171116
[Lr] Data última revisão:
171116
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160527
[St] Status:MEDLINE


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[PMID]:27166425
[Au] Autor:Netz DJ; Genau HM; Weiler BD; Bill E; Pierik AJ; Lill R
[Ad] Endereço:Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Robert-Koch-Strasse 6, 35032 Marburg, Germany.
[Ti] Título:The conserved protein Dre2 uses essential [2Fe-2S] and [4Fe-4S] clusters for its function in cytosolic iron-sulfur protein assembly.
[So] Source:Biochem J;473(14):2073-85, 2016 Jul 15.
[Is] ISSN:1470-8728
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:The cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery comprises 11 essential components and matures Fe-S proteins involved in translation and genome maintenance. Maturation is initiated by the electron transfer chain NADPH-diflavin reductase Tah18-Fe-S protein Dre2 that facilitates the de novo assembly of a [4Fe-4S] cluster on the scaffold complex Cfd1-Nbp35. Tah18-Dre2 also play a critical role in the assembly of the diferric tyrosyl radical cofactor of ribonucleotide reductase. Dre2 contains eight conserved cysteine residues as potential co-ordinating ligands for Fe-S clusters but their functional importance and the type of bound clusters is unclear. In the present study, we use a combination of mutagenesis, cell biological and biochemical as well as UV-visible, EPR and Mössbauer spectroscopic approaches to show that the yeast Dre2 cysteine residues Cys(252), Cys(263), Cys(266) and Cys(268) (motif I) bind a [2Fe-2S] cluster, whereas cysteine residues Cys(311), Cys(314), Cys(322) and Cys(325) (motif II) co-ordinate a [4Fe-4S] cluster. All of these residues with the exception of Cys(252) are essential for cell viability, cytosolic Fe-S protein activity and in vivo (55)Fe-S cluster incorporation. The N-terminal methyltransferase-like domain of Dre2 is important for proper Fe-S cluster assembly at motifs I and II, which occurs in an interdependent fashion. Our findings further resolve why recombinant Dre2 from Arabidopsis, Trypanosoma or humans has previously been isolated with a single [2Fe-2S] instead of native [2Fe-2S] plus [4Fe-4S] clusters. In the presence of oxygen, the motif I-bound [2Fe-2S] cluster is labile and the motif II-bound [4Fe-4S] cluster is readily converted into a [2Fe-2S] cluster.
[Mh] Termos MeSH primário: Citosol/metabolismo
Proteínas com Ferro-Enxofre/metabolismo
Proteínas de Saccharomyces cerevisiae/metabolismo
Saccharomyces cerevisiae/citologia
Saccharomyces cerevisiae/metabolismo
[Mh] Termos MeSH secundário: Sobrevivência Celular/genética
Sobrevivência Celular/fisiologia
Cisteína/química
Cisteína/metabolismo
Proteínas com Ferro-Enxofre/química
Proteínas com Ferro-Enxofre/genética
Mutagênese
Saccharomyces cerevisiae/genética
Saccharomyces cerevisiae/fisiologia
Proteínas de Saccharomyces cerevisiae/química
Proteínas de Saccharomyces cerevisiae/genética
Espectroscopia de Mossbauer
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Dre2 protein, S cerevisiae); 0 (Iron-Sulfur Proteins); 0 (Saccharomyces cerevisiae Proteins); K848JZ4886 (Cysteine)
[Em] Mês de entrada:1705
[Cu] Atualização por classe:170515
[Lr] Data última revisão:
170515
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160512
[St] Status:MEDLINE
[do] DOI:10.1042/BCJ20160416


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[PMID]:27009567
[Au] Autor:Miller EP; Auerbach H; Schünemann V; Tymon T; Carrano CJ
[Ad] Endereço:Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, USA. ccarrano@mail.sdsu.edu.
[Ti] Título:Surface binding, localization and storage of iron in the giant kelp Macrocystis pyrifera.
[So] Source:Metallomics;8(4):403-11, 2016 Apr.
[Is] ISSN:1756-591X
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Iron is an essential element for all living organisms due to its ubiquitous role in redox and other enzymes, especially in the context of respiration and photosynthesis. Although the iron uptake and storage mechanisms of terrestrial/higher plants have been well-studied, the corresponding systems in marine algae have received far less attention. While the iron many marine algae take up from the environment, irrespective of its detailed internalization mechanism, arrives at the cell surface by diffusion, there is growing evidence for more "active" means of concentrating this element prior to uptake. It has been well established in both laboratory and environmentally derived samples, that a large amount of iron can be "non-specifically" adsorbed to the surface of marine algae. While this phenomenon is widely recognized and has prompted the development of experimental protocols to eliminate its contribution to iron uptake studies, its potential biological significance as a concentrated iron storage source for marine algae is only now being recognized. In this study, using an interdisciplinary array of techniques, we show that the giant kelp Macrocystis pyrifera also displays significant cell surface bound iron although less than that seen with the related brown alga Ectocarpus siliculosus. The iron on the surface is likely bound to carboxylate groups and once inside the iron is found to localize differently depending on cell type. Iron appears to be stored in an as yet undefined mineral phase.
[Mh] Termos MeSH primário: Membrana Celular/metabolismo
Ferro/metabolismo
Macrocystis/metabolismo
[Mh] Termos MeSH secundário: 3,3'-Diaminobenzidina/metabolismo
Azóis/metabolismo
Fluorescência
Espaço Intracelular/metabolismo
Cinética
Espectroscopia de Mossbauer
Termodinâmica
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Azoles); 2RV4T6KHQI (3,3'-Diaminobenzidine); E1UOL152H7 (Iron)
[Em] Mês de entrada:1701
[Cu] Atualização por classe:170104
[Lr] Data última revisão:
170104
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160325
[St] Status:MEDLINE
[do] DOI:10.1039/c6mt00027d


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[PMID]:27002973
[Au] Autor:Kovács K; Pechousek J; Machala L; Zboril R; Klencsár Z; Solti Á; Tóth B; Müller B; Pham HD; Kristóf Z; Fodor F
[Ad] Endereço:Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest, 1512, Hungary. kkriszti@chem.elte.hu.
[Ti] Título:Revisiting the iron pools in cucumber roots: identification and localization.
[So] Source:Planta;244(1):167-79, 2016 Jul.
[Is] ISSN:1432-2048
[Cp] País de publicação:Germany
[La] Idioma:eng
[Ab] Resumo:MAIN CONCLUSION: Fe deficiency responses in Strategy I causes a shift from the formation of partially removable hydrous ferric oxide on the root surface to the accumulation of Fe-citrate in the xylem. Iron may accumulate in various chemical forms during its uptake and assimilation in roots. The permanent and transient Fe microenvironments formed during these processes in cucumber which takes up Fe in a reduction based process (Strategy I) have been investigated. The identification of Fe microenvironments was carried out with (57)Fe Mössbauer spectroscopy and immunoblotting, whereas reductive washing and high-resolution microscopy was applied for the localization. In plants supplied with (57)Fe(III)-citrate, a transient presence of Fe-carboxylates in removable forms and the accumulation of partly removable, amorphous hydrous ferric oxide/hydroxyde have been identified in the apoplast and on the root surface, respectively. The latter may at least partly be the consequence of bacterial activity at the root surface. Ferritin accumulation did not occur at optimal Fe supply. Under Fe deficiency, highly soluble ferrous hexaaqua complex is transiently formed along with the accumulation of Fe-carboxylates, likely Fe-citrate. As (57)Fe-citrate is non-removable from the root samples of Fe deficient plants, the major site of accumulation is suggested to be the root xylem. Reductive washing results in another ferrous microenvironment remaining in the root apoplast, the Fe(II)-bipyridyl complex, which accounts for ~30 % of the total Fe content of the root samples treated for 10 min and rinsed with CaSO4 solution. When (57)Fe(III)-EDTA or (57)Fe(III)-EDDHA was applied as Fe-source higher soluble ferrous Fe accumulation was accompanied by a lower total Fe content, confirming that chelates are more efficient in maintaining soluble Fe in the medium while less stable natural complexes as Fe-citrate may perform better in Fe accumulation.
[Mh] Termos MeSH primário: Cucumis sativus/metabolismo
Ferro/metabolismo
Raízes de Plantas/metabolismo
Xilema/metabolismo
[Mh] Termos MeSH secundário: Cucumis sativus/ultraestrutura
Compostos Férricos/metabolismo
Immunoblotting
Compostos de Ferro/metabolismo
Microscopia Eletrônica
Oxirredução
Raízes de Plantas/ultraestrutura
Espectroscopia de Mossbauer
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Ferric Compounds); 0 (Iron Compounds); 1K09F3G675 (ferric oxide); 63G354M39Z (ferric citrate); E1UOL152H7 (Iron)
[Em] Mês de entrada:1704
[Cu] Atualização por classe:171005
[Lr] Data última revisão:
171005
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160323
[St] Status:MEDLINE
[do] DOI:10.1007/s00425-016-2502-x


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[PMID]:26948644
[Au] Autor:Magro M; Moritz DE; Bonaiuto E; Baratella D; Terzo M; Jakubec P; Malina O; Cépe K; de Aragao GM; Zboril R; Vianello F
[Ad] Endereço:Department of Comparative Biomedicine and Food Science, University of Padua, Italy; Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Palacký University in Olomouc, Czech Republic.
[Ti] Título:Citrinin mycotoxin recognition and removal by naked magnetic nanoparticles.
[So] Source:Food Chem;203:505-12, 2016 Jul 15.
[Is] ISSN:0308-8146
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Citrinin is a nephrotoxic mycotoxin which can be synthesized by Monascus mold during the fermentation process in foods. Monascus, generally described as red mold, is a red-pigmented filamentous fungus attracting a great interest for the production of natural dyes and cholesterol-lowering statins. We individuated a specie of Monascus producing high amount of natural dyes. However, this high pigmentation was correlated with the production of citrinin. Peculiar magnetic nanoparticles, synthesized in-house and called "Surface Active Maghemite Nanoparticles" (SAMNs), are proposed as an efficient and reliable mean for citrinin removal from Monascus treated foods. The nanomaterial efficiency for citrinin binding was proved on Monascus suspensions, and SAMN@citrinin complex was characterized by MÓ§ssbauer spectroscopy and magnetization measurements, showing that SAMNs resulted structurally and magnetically well conserved after citrinin binding. SAMNs are excellent and stable magnetic nano-carrier for toxin removal, which can be applied in food industry.
[Mh] Termos MeSH primário: Citrinina/análise
Indústria Alimentícia/métodos
Nanopartículas de Magnetita/química
Monascus/metabolismo
[Mh] Termos MeSH secundário: Fermentação
Corantes de Alimentos/metabolismo
Contaminação de Alimentos/prevenção & controle
Microscopia Eletrônica de Transmissão
Monascus/crescimento & desenvolvimento
Espectroscopia de Mossbauer
Propriedades de Superfície
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Food Coloring Agents); 0 (Magnetite Nanoparticles); 3S697X6SNZ (Citrinin)
[Em] Mês de entrada:1610
[Cu] Atualização por classe:161230
[Lr] Data última revisão:
161230
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160308
[St] Status:MEDLINE


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[PMID]:26841310
[Au] Autor:Blaszczyk AJ; Silakov A; Zhang B; Maiocco SJ; Lanz ND; Kelly WL; Elliott SJ; Krebs C; Booker SJ
[Ti] Título:Spectroscopic and Electrochemical Characterization of the Iron-Sulfur and Cobalamin Cofactors of TsrM, an Unusual Radical S-Adenosylmethionine Methylase.
[So] Source:J Am Chem Soc;138(10):3416-26, 2016 Mar 16.
[Is] ISSN:1520-5126
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:TsrM, an annotated radical S-adenosylmethionine (SAM) enzyme, catalyzes the methylation of carbon 2 of the indole ring of L-tryptophan. Its reaction is the first step in the biosynthesis of the unique quinaldic acid moiety of thiostrepton A, a thiopeptide antibiotic. The appended methyl group derives from SAM; however, the enzyme also requires cobalamin and iron-sulfur cluster cofactors for turnover. In this work we report the overproduction and purification of TsrM and the characterization of its metallocofactors by UV-visible, electron paramagnetic resonance, hyperfine sublevel correlation (HYSCORE), and Mössbauer spectroscopies as well as protein-film electrochemistry (PFE). The enzyme contains 1 equiv of its cobalamin cofactor in its as-isolated state and can be reconstituted with iron and sulfide to contain one [4Fe-4S] cluster with a site-differentiated Fe(2+)/Fe(3+) pair. Our spectroscopic studies suggest that TsrM binds cobalamin in an uncharacteristic five-coordinate base-off/His-off conformation, whereby the dimethylbenzimidazole group is replaced by a non-nitrogenous ligand, which is likely a water molecule. Electrochemical analysis of the protein by PFE indicates a one-electron redox feature with a midpoint potential of -550 mV, which is assigned to a [4Fe-4S](2+)/[4Fe-4S](+) redox couple. Analysis of TsrM by Mössbauer and HYSCORE spectroscopies suggests that SAM does not bind to the unique iron site of the cluster in the same manner as in other radical SAM (RS) enzymes, yet its binding still perturbs the electronic configuration of both the Fe/S cluster and the cob(II)alamin cofactors. These biophysical studies suggest that TsrM is an atypical RS enzyme, consistent with its reported inability to catalyze formation of a 5'-deoxyadenosyl 5'-radical.
[Mh] Termos MeSH primário: Proteínas com Ferro-Enxofre/química
Metiltransferases/química
S-Adenosilmetionina/química
Vitamina B 12/química
[Mh] Termos MeSH secundário: Coenzimas/química
Eletroquímica/métodos
Espectroscopia de Ressonância de Spin Eletrônica
Espectroscopia de Mossbauer
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, N.I.H., EXTRAMURAL; RESEARCH SUPPORT, NON-U.S. GOV'T; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Nm] Nome de substância:
0 (Coenzymes); 0 (Iron-Sulfur Proteins); 7LP2MPO46S (S-Adenosylmethionine); EC 2.1.1.- (Methyltransferases); P6YC3EG204 (Vitamin B 12)
[Em] Mês de entrada:1612
[Cu] Atualização por classe:161230
[Lr] Data última revisão:
161230
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160204
[St] Status:MEDLINE
[do] DOI:10.1021/jacs.5b12592



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