Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 7.225
Filtrar
1.
Bioresour Technol ; 301: 122753, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31982852

RESUMO

Phosphorus content of the digestate is crucial for evaluating its fertilizer utilization in anaerobic digestion system. The vermiculite containing rich-phosphorus is firstly used as an accelerant in anaerobic batch co-digestion system of aloe peel waste and dairy manure. After introducing vermiculite, the cumulative biogas production (295.14-353.96 mL/g VS), chemical oxygen demand removal rate (45.53%-71.03%), and volatile solid removal rate (50.70%-52.76%) are remarkably higher than those of reference reactor (234.08 mL/g VS, 39.38%, 45.10%). The thermal and fertility analyses manifest the digestates with vermiculite possess superior stability, admirable fertilizer values (5.97%-6.81%), and excellent total phosphorus content (11.44-13.29 g/kg). The improved co-digestion performance can be attributed to the addition of vermiculite. This work introduces a novel approach for improving the performance of anaerobic co-digestion and the fertilizer utilization of digestate in the co-digestion systems.


Assuntos
Aloe , Esterco , Silicatos de Alumínio , Anaerobiose , Biocombustíveis , Reatores Biológicos , Metano , Fósforo
2.
Chemphyschem ; 21(3): 188-193, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31912640

RESUMO

Tip-enhanced Raman spectroscopy (TERS) is a promising technique for structural studies of biological systems and biomolecules, owing to its ability to provide a chemical fingerprint with sub-diffraction-limit spatial resolution. This application of TERS has thus far been limited, due to difficulties in generating high field enhancements while maintaining biocompatibility. The high sensitivity achievable through TERS arises from the excitation of a localized surface plasmon resonance in a noble metal atomic force microscope (AFM) tip, which in combination with a metallic surface can produce huge enhancements in the local optical field. However, metals have poor biocompatibility, potentially introducing difficulties in characterizing native structure and conformation in biomolecules, whereas biocompatible surfaces have weak optical field enhancements. Herein, a novel, biocompatible, highly enhancing surface is designed and fabricated based on few-monolayer mica flakes, mechanically exfoliated on a metal surface. These surfaces allow the formation of coupled plasmon enhancements for TERS imaging, while maintaining the biocompatibility and atomic flatness of the mica surface for high resolution AFM. The capability of these substrates for TERS is confirmed numerically and experimentally. We demonstrate up to five orders of magnitude improvement in TERS signals over conventional mica surfaces, expanding the sensitivity of TERS to a wide range of non-resonant biomolecules with weak Raman cross-sections. The increase in sensitivity obtained through this approach also enables the collection of nanoscale spectra with short integration times, improving hyperspectral mapping for these applications. These mica/metal surfaces therefore have the potential to revolutionize spectromicroscopy of complex, heterogeneous biological systems such as DNA and protein complexes.


Assuntos
Silicatos de Alumínio/química , Materiais Biocompatíveis/química , Ouro/química , Microscopia de Força Atômica/instrumentação , DNA/análise , Microscopia de Força Atômica/métodos , Análise Espectral Raman/métodos , Ressonância de Plasmônio de Superfície/métodos
3.
Chemosphere ; 240: 124838, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31542582

RESUMO

Modified sodium vermiculite, an iron-rich clay mineral, has been used in novel heterogeneous electrochemical Fenton-based treatments, so-called electro-Fenton (EF)-vermiculite, UVA photoelectro-Fenton (PEF)-vermiculite and solar photoelectro-Fenton (SPEF)-vermiculite. Tests were made with 130 mL of 0.150 mM Ponceau SS diazo dye in 0.050 M Na2SO4 at pH 3.0, in the presence of 1.0 g L-1 catalyst microparticles. The electrolyses were performed in an undivided cell with a boron-doped diamond anode (BDD) and air-diffusion cathode for H2O2 production, at 33.3 mA cm-2. Decolorization and mineralization were upgraded in the sequence: EF-vermiculite < PEF-vermiculite < SPEF-vermiculite. The removal of organics occurred by the combined action of OH oxidant formed at the BDD surface and homogeneous and heterogeneous Fenton's reactions, along with the photolysis caused by UVA light or sunlight. The homogeneous Fenton's reaction resulted from iron ions leaching, but the heterogeneous mechanism was prevalent. Comparative treatments by anodic oxidation in the presence of H2O2 and homogeneous EF were less effective than EF-vermiculite. The diazo dye absorbance decays agreed with a pseudo-first-order kinetics. SPEF-vermiculite was the most powerful process, yielding total decolorization and 84.1% mineralization after 300 and 360 min, respectively. The influence of catalyst concentration, current density and diazo dye content on PEF-vermiculite performance was examined. Oxalic, oxamic, malic, tartronic and acetic acids were detected as final short-linear carboxylic acids.


Assuntos
Silicatos de Alumínio/química , Compostos Azo/química , Técnicas Eletroquímicas/métodos , Catálise
4.
J Forensic Sci ; 64(6): 1698-1706, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31674673

RESUMO

During antemortem and postmortem comparison of dental records of carbonized victims, restorations may be part of such records. The objective of this study was to evaluate the effect of heat on the fluorescence behavior of contemporary tooth-colored restorative materials and natural tooth structure when subjected to range of temperatures, using illumination with 405 nm wavelength light. A total of 132 human extracted teeth restored with tooth-colored restorative materials were exposed to heat (200, 500, 900, 1200°C) in an oven for 30 min. Samples were imaged before and after heat treatment. All tooth-colored restorative materials underwent changes in color and in fluorescence properties, at each of the temperatures used. Resin-based restorative materials still fluoresced at 200°C, and at 500°C underwent major color changes due to volatilization of resin. Materials containing inorganic fluorophores still fluoresced at 900°C, while at 1200°C, none of the materials tested in this study showed any fluorescence.


Assuntos
Materiais Dentários , Restauração Dentária Permanente , Fluorescência , Temperatura Alta , Silicatos de Alumínio , Cor , Resinas Compostas , Porcelana Dentária , Odontologia Legal , Cimentos de Ionômeros de Vidro , Humanos , Cerâmicas Modificadas Organicamente , Compostos de Potássio
5.
Dent Mater ; 35(12): 1706-1717, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31575490

RESUMO

BACKGROUND: In an effort to design novel zirconia reinforced mica glass ceramics for dental restorations, clinically relevant properties such as wear, coefficient of thermal expansion, optical transmittance, and cytocompatibility with human gingival fibroblast cell lines were investigated in the present study. MATERIALS & METHODS: Microstructure analysis of two body wear of heat treated mica glass ceramic ceramics (47.2 SiO2-16.7 Al2O3-9.5 K2O-14.5 MgO-8.5 B2O3-6.3F wt.%) reinforced with 20wt.% YSZ, were evaluated against a steatite antagonist in a chewing simulator following Willytec Munich method. In addition, Coefficient of thermal expansion (CTE), total transmittance, scattering coefficient and cytocompatibility on human gingival fibroblast cell lines were performed and compared to the commercially available dental ceramic systems. RESULTS: The experimental mica glass ceramic demonstrate micro-ploughing, pull out and debris formation along the cutting surface, indicating abrasive wear mechanism. Thermal expansion of mica glass ceramic composite was recorded as 5×10-6/°C, which is lower than the thermal expansion of commercially available core and veneering ceramics. Further, significant differences of transmittance and scattering coefficient of mica glass ceramics with 20wt.% YSZ with commercial dental ceramics was found and extensive fibroblast cell spreading with filopodial extension, cell-to-cell bridges and proliferation with human gingival fibroblast cell lines. CONCLUSION: With acceptable cytocompatibility with human gingival fibroblast cells and better wear properties with respect to commercial IPS emax Press, the mica glass ceramic composites (47.2 SiO2-16.7Al2O3-9.5 K2O-14.5 MgO-8.5 B2O3-6.3F wt.%) with 20wt.% YSZ have the potential for dental restorative applications as machinable veneering ceramics.


Assuntos
Porcelana Dentária , Dióxido de Silício , Silicatos de Alumínio , Cerâmica , Humanos , Teste de Materiais , Propriedades de Superfície , Zircônio
6.
Braz Oral Res ; 33: e095, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31618283

RESUMO

This study evaluates the shear bond strength (SBS) of various resin cements to different ceramics. Composite resin cylinders of Z100 were fabricated and cemented to disks of feldspathic ceramic (Creation), leucite-reinforced feldspathic ceramic (Empress I), and densely sintered aluminum oxide ceramic (Procera AllCeram) using five resin cements: Panavia F (PAN), RelyX ARC (ARC), RelyX Unicem (RXU), RelyX Veneer, and Variolink II. SBS was measured after three days of water storage (baseline) and after artificial aging (180 days of water storage along with 12,000 thermal cycles). Failure mode of fractured specimens also was evaluated. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α=0.05). RXU showed 1) the lowest baseline median SBS to feldspathic ceramic, which was not statistically different from PAN; 2) the lowest median baseline SBS to leucite-reinforced feldspathic and densely sintered aluminum-oxide ceramics. All cements performed similarly after aging, except for ARC (median 0.0 MPa) and PAN (median 16.2 MPa) in the densely sintered aluminum-oxide ceramic group. Resin cements perform differently when bonded to different ceramic substrates. While all test resin cements worked similarly in the long-term to feldspathic and leucite-reinforced feldspathic ceramics, only the MDP-containing resin cement provided durable bonds to densely sintered aluminum-oxide ceramic.


Assuntos
Cerâmica/química , Colagem Dentária/métodos , Cimentos de Resina/química , Alumínio/química , Silicatos de Alumínio/química , Teste de Materiais , Compostos de Potássio/química , Valores de Referência , Reprodutibilidade dos Testes , Resistência ao Cisalhamento , Estatísticas não Paramétricas , Propriedades de Superfície
7.
Chemosphere ; 226: 907-914, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31509920

RESUMO

The isomorphous substitution in the structure of phyllosilicate minerals plays an important role in regulating of surface chemical properties. In this work, iron muscovite nanoparticles with various Al species were successfully prepared to explore the structural Fe and Al species on the capture of Cd(II) from solutions. The synthesized nanocrystals have irregular shapes with diameters of 10-50 nm. The incorporation of Al(III) into the iron muscovite nanostructure has slight effect on the species of Fe and the crystal phase of the products. The degree of Al(III) substituting Si(IV) in the tetrahedral sheets of the minerals obviously increased with increasing of Al doping levels. For the samples with low Al doping levels (5% and 10%), the adsorption capacity of the iron muscovite nanoparticles for Cd(II) increased slightly. With increasing of Al doping ratio to 15%, the obtained iron muscovite nanoparticles exhibited a maximal uptake of 41.4 mg g-1 for Cd(II), which is about two times that of the undoped samples (22.8 mg g-1). The solution pH had a slight effect on the Cd (II) capture at a wide pH range from 4 to 8. The adsorption of Cd(II) is very fast and reached a steady state within 5 min. Desorption results showed that the binding strength between Cd(II) and iron muscovite nanoparticles was obviously enhanced by incorporation of Al at a high level. The ion exchange and surface complexation are principal mechanisms in the Cd(II) capture by the iron muscovite nanomaterials with various structural Al species.


Assuntos
Silicatos de Alumínio/química , Alumínio/química , Cádmio/isolamento & purificação , Ferro/química , Nanopartículas/química , Adsorção , Cádmio/química , Concentração de Íons de Hidrogênio , Propriedades de Superfície
8.
Environ Sci Technol ; 53(19): 11251-11259, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31478650

RESUMO

Mineral-soil organic matter (SOM including DNA, proteins, and polysaccharides) associations formed through various interactions, play a key role in regulating long-term SOM preservation. The mechanisms underlying DNA-mineral and DNA-protein/polysaccharide interactions at nanometer and molecular scales in environmentally relevant solutions remain uncertain. Here, we present a model mineral-SOM system consisting of mineral (mica)-nucleic acid (environmental DNA, eDNA)/protein (bovine serum albumin)/polysaccharide (alginate), and combine atomic force microscopy (AFM)-based dynamic force spectroscopy and PeakForce quantitative nanomechanical mapping using DNA-decorated tips. Single-molecule binding and adhesion force of eDNA to mineral and to mineral adsorbed by protein/polysaccharide reveal the noncovalent bonds and that systematically changing ion compositions, ionic strength, and pH result in significant differences in organic-organic and organic-mineral binding energies. Consistent with the bond-strength measurements, protein, rather than polysaccharide, promotes mineral-bound DNA molecules by ex situ AFM deposition observations in relatively high concentrations of divalent cation-containing acidic solutions. These molecular-scale determinations and nanoscale observations should substantially improve our understanding of how environmental factors influence the organic-mineral interfacial interactions through the synergy of collective noncovalent and/or covalent bonds in mineral-organic associations.


Assuntos
Silicatos de Alumínio , DNA , Adsorção , Microscopia de Força Atômica , Propriedades de Superfície
9.
Environ Sci Technol ; 53(19): 11588-11596, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31478655

RESUMO

Clay minerals abound in sedimentary formations and the interaction of reservoir gases with their submicron features have direct relevance to many geoenergy applications. The quantification of gas uptake over a broad range of pressures is key toward assessing the significance of these physical interactions on enhancing storage capacity and gas recovery. We report a systematic investigation of the sorption properties of three source clay minerals-Na-rich montmorillonite (SWy-2), illite-smectite mixed layer (ISCz-1), and illite (IMt-2)-using CO2 and CH4 up to 30 MPa at 25-115 °C. The textural characterization of the clays by gas physisorption indicates that micropores are only partly accessible to N2 (77 K) and Ar (87 K), while larger uptakes are measured with CO2 (273 K) in the presence of illite. The supercritical excess sorption experiments confirm these findings while revealing differences in uptake capacities that originate from the clay-specific pore size distribution. The lattice density functional theory model describes accurately the measured sorption isotherms by using a distribution of properly weighted slit pores and clay-specific solid-fluid interaction energies, which agree with isosteric heats of adsorption obtained experimentally. The model indicates that the maximum degree of pore occupancy is universal to the three clays and the two gases, and it depends solely on temperature, reaching values near unity at the critical temperature. These observations greatly support the model's predictive capability for estimating gas adsorption on clay-bearing rocks and sediments.


Assuntos
Dióxido de Carbono , Argila , Adsorção , Silicatos de Alumínio , Minerais , Silicatos
10.
Dent Mater ; 35(10): 1498-1505, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31400983

RESUMO

OBJECTIVES: Understand how cooling protocols control the microstructure and mechanical properties of veneering porcelains. METHODS: Two porcelain powders were selected, one used to veneer metallic frameworks (VM13) and one for zirconia frameworks (VM9). After the last firing cycle, the monolithic specimens were subjected to two cooling protocols: slow and fast. Flexural strength (FS) was evaluated by three-point beam bending and fracture toughness (KIC) was evaluated by the single-edge V-notch beam (SEVNB) method. Scanning electron microscopy (SEM) was performed to determine the leucite crystal volume fraction (%), particle size, and matrix microcrack density. The results were compared by analysis of variances (ANOVA) and Tukey's multiple comparison test. RESULTS: The mechanical properties were significantly (p<0.05) higher for the VM13 porcelain (FS=111.0MPa, KIC=1.01MPa.√m) compared to VM9 (FS=79.6MPa, KIC =0.87MPa.√m) regardless of cooling protocol due to ∼250% higher volume fraction of leucite crystals. The slow cooled VM13 and fast cooled VM9 resulted in the highest and lowest mechanical properties, respectively, while the VM9 slow cooled properties were similar to the VM13 fast cooled. The SEM revealed that the slow cooling significantly increased the volume fraction of leucite crystals by 33-41 %. Across both porcelains, a significant linear correlation between both mechanical properties (strength and toughness) and leucite crystal content was found. Slow cooling was also associated with increased crystal growth resulting in more matrix microcracking. SIGNIFICANCE: Controlled crystallization using slow cooling can be applied as a means of strengthening dental porcelains. However, the benefits of slow cooling may be partially offset by increasing the microcrack density in the glass matrix. To achieve the maximum benefit of slow cooling, it is recommending to develop heat treatments to produce porcelain with fine-grained and homogenously dispersed leucite crystals to achieve minimal glass matrix microcracking.


Assuntos
Cerâmica , Facetas Dentárias , Silicatos de Alumínio , Cristalização , Porcelana Dentária , Análise do Estresse Dentário , Teste de Materiais , Microscopia Eletrônica de Varredura , Propriedades de Superfície
11.
Environ Sci Pollut Res Int ; 26(28): 28860-28870, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31385252

RESUMO

Nowadays, most of mineral-based adsorbents are powder form, which makes them inconvenient to collect and always easy to cause secondary pollution. In this work, an organic rectorite composite nanofiber membrane (SRt-PAN) was designed and prepared by electrospinning technique. The as-received composite nanofiber membranes were characterized by XRD and SEM analysis, proving the homodisperse and existence of SRt in PAN nanofiber membrane. A series of batch experiments for BPA adsorption were carried out to investigate the effect of different adsorption parameters, including initial concentration, pH, and temperature of pollutant solution. The influences of modifier dosage and adsorbent dosage on the adsorption performance were investigated as well. On the basis of the experiment results, the adsorption process could be well described by the pseudo-second-order model and the Langmuir isotherm. In addition, the thermodynamic parameters indicate that this adsorption process is exothermic and spontaneous. Moreover, compared with pure nanofiber membranes and organic rectorite powders, the resultant SRt-PAN adsorbents exhibited higher adsorption capacity, superior reusability, and adsorption stability. It is indicated that the hydrophobicity surface of organic rectorite should be the key factor to not only the intimate interfacial combination between the mineral and PAN, but also the enhancement of BPA adsorption capacity.


Assuntos
Silicatos de Alumínio/síntese química , Compostos Benzidrílicos/química , Minerais/síntese química , Nanofibras/química , Fenóis/química , Adsorção , Silicatos de Alumínio/química , Cinética , Minerais/química , Temperatura Ambiente , Termodinâmica
12.
Nat Commun ; 10(1): 3448, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-31371725

RESUMO

Today the terrestrial surface drives biogeochemical cycles on Earth through chemical weathering reactions mediated by the biological influence of soils. Prior to the expansion of life on to land, abiotic weathering may have resulted in different boundary conditions affecting the composition of the biosphere. Here we show a striking difference in weathering produced minerals preserved in the Mesoproterozoic Velkerri Formation. While the bulk chemistry and mineralogy is dominated by illite similar to many modern mudstones, application of a novel microbeam technology reveals that the initial detrital minerals were composed of mica (28%) and feldspar (45%) with only a trace amount (<2%) of typical soil formed clay minerals. The majority of illite and the high Al2O3 fraction previously interpreted as a weathering signal, is present as a replacement of feldspar and mica. These sediments record physical erosion with limited pedogenic clay mineral formation implying fundamentally different weathering pathways.


Assuntos
Minerais/química , Oceanos e Mares , Solo/química , Oligoelementos/química , Tempo (Meteorologia) , Silicatos de Alumínio , Austrália , Fenômenos Químicos , Química Física , Argila , Monitoramento Ambiental , Fenômenos Geológicos , Geologia , Compostos de Potássio
13.
Environ Sci Pollut Res Int ; 26(27): 28294-28308, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31368068

RESUMO

Stable Hg(II)-containing flue gas has been successfully simulated by the plasma oxidation of Hg(0), and an effective solution for Hg(0) mercury fumes was obtained by combining the plasma with a ceramic nanomaterial. Characterization tests showed that the ceramic nanomaterial was mainly composed of silicon dioxide (SiO2) with other minor constituents, including potassium mica (KAl3Si3O11), iron magnesium silicate (Fe0.24Mg0.76SiO3) and dolomite (CaMg(CO3)2). The nanomaterial had many tube bank structures inside with diameters of approximately 8-10 nm. The maximum sorption capacity of Hg(II) was 5156 µg/g, and the nanomaterial can be regenerated at least five times. During the adsorption, chemical adsorption first occurred between Hg(II) and sulfydryl moieties, but these were quickly exhausted, and Hg(II) was then removed by surface complexation and wrapped into Fe moieties. The pseudo-first-order kinetic model and the Langmuir equation had the best fitting results for the kinetics and isotherms of adsorption. This work suggests that the ceramic nanomaterial can be used as an effective and recyclable adsorbent in the removal of gaseous Hg(II).


Assuntos
Carbonato de Cálcio/química , Ferro/química , Magnésio/química , Mercúrio/análise , Nanoestruturas/química , Dióxido de Silício/química , Adsorção , Silicatos de Alumínio/química , Cerâmica/química , Gases , Cinética , Mercúrio/química , Minerais/química
14.
Dent Mater ; 35(10): 1430-1438, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31387743

RESUMO

OBJECTIVE: This study evaluated the influence of preheating different composite resins on their viscosity and strengthening yielded to ceramic. METHODS: Modulus of elasticity, Poisson's ratio, and degree of CC conversion were measured for three restorative composite resins (Z100-microhybrid; Empress Direct-nanohybrid; Estelite Omega-supranano) and one photoactivated resin cement (RelyX Veneer). Viscosity was measured during a heating-cooling curve (25°C-69°C-25°C) and also using isothermal analyses at 25°C and 69°C. Feldspar ceramic disks simulating veneers were bonded with the luting materials. Biaxial flexural strength, characteristic strength, and Weibull modulus were calculated at axial positions (z=0 and z=-t2) of the bilayers. Film thickness was measured and morphology at the bonded interfaces was observed. Data were statistically analyzed (α=0.05). RESULTS: A gradual decrease in viscosity was noticed as the rheometer temperature gradually increased. Viscosity differences between the composite resins were large at the beginning of the analysis, but minor at 69°C. At 25°C, the composites were up to 38 times more viscous than the resin cement; at 69°C the difference was 5-fold. CC conversion was similar between all resin-based agents. The resin cement yielded lower film thickness than the composites. All resin-based agents were able to infiltrate the ceramic porosities at the interface and strengthen the ceramic. However, the magnitude of the strengthening effect was higher for the preheated composite resins, particularly at z=-t2. SIGNIFICANCE: Selection of composite resin impacts its response to preheating and the resulting viscosity, film thickness, and magnitude of ceramic strengthening.


Assuntos
Cerâmica , Resinas Compostas , Silicatos de Alumínio , Porcelana Dentária , Teste de Materiais , Compostos de Potássio , Cimentos de Resina , Propriedades de Superfície
15.
J Microbiol Biotechnol ; 29(7): 1071-1077, 2019 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-31337188

RESUMO

Natural gamma-decalactone (GDL) produced by biotransformation is an essential food additive with a peach-like aroma. However, the difficulty of effectively controlling the concentration of the substrate ricinoleic acid (RA) in water limits the biotransformation productivity, which is a bottleneck for industrialization. In this study, expanded vermiculite (E-V) was utilized as a carrier of RA to increase its distribution in the medium. E-V and three commonly used organic compounds were compared with respect to their effects on the biotransformation process, and the mechanism was revealed. Scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis indicated that RA was physically adsorbed onto the surface of and inside E-V instead of undergoing a chemical reaction, which increased the opportunity for interactions between microorganisms and the substrate. The highest concentration of GDL obtained in the medium with E-V was 6.2 g/l, which was 50% higher than that in the reference sample. In addition, the presence of E-V had no negative effect on the viability of the microorganisms. This study provides a new method for producing natural GDL through biotransformation on an industrial scale.


Assuntos
Silicatos de Alumínio/química , Biotransformação , Lactonas/metabolismo , Ácidos Ricinoleicos/química , Ácidos Ricinoleicos/metabolismo , Adsorção , Microbiologia Industrial , Viabilidade Microbiana , Yarrowia/metabolismo , Yarrowia/fisiologia
16.
J Phys Chem Lett ; 10(15): 4192-4196, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31305079

RESUMO

We report the successful one-pot synthesis of adenosine mono-, di-, and triphosphate in the confined space of a mordenite zeolite. This is also the first report of ATP synthesized onto a porous mineral surface. The results revealed a plausible prebiotic route to ribonucleotides and highlighted the contribution of microporous minerals in the origins of life.


Assuntos
Difosfato de Adenosina/síntese química , Monofosfato de Adenosina/síntese química , Trifosfato de Adenosina/síntese química , Silicatos de Alumínio/química , Nanopartículas/química , Técnicas de Síntese em Fase Sólida/métodos , Zeolitas/química , Adenina/química , Organofosfatos/química , Origem da Vida , Porosidade , Ribose/química , Propriedades de Superfície , Termodinâmica , Fatores de Tempo
17.
Nature ; 571(7764): 251-256, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31292559

RESUMO

The ability of proteins and other macromolecules to interact with inorganic surfaces is essential to biological function. The proteins involved in these interactions are highly charged and often rich in carboxylic acid side chains1-5, but the structures of most protein-inorganic interfaces are unknown. We explored the possibility of systematically designing structured protein-mineral interfaces, guided by the example of ice-binding proteins, which present arrays of threonine residues (matched to the ice lattice) that order clathrate waters into an ice-like structure6. Here we design proteins displaying arrays of up to 54 carboxylate residues geometrically matched to the potassium ion (K+) sublattice on muscovite mica (001). At low K+ concentration, individual molecules bind independently to mica in the designed orientations, whereas at high K+ concentration, the designs form two-dimensional liquid-crystal phases, which accentuate the inherent structural bias in the muscovite lattice to produce protein arrays ordered over tens of millimetres. Incorporation of designed protein-protein interactions preserving the match between the proteins and the K+ lattice led to extended self-assembled structures on mica: designed end-to-end interactions produced micrometre-long single-protein-diameter wires and a designed trimeric interface yielded extensive honeycomb arrays. The nearest-neighbour distances in these hexagonal arrays could be set digitally between 7.5 and 15.9 nanometres with 2.1-nanometre selectivity by changing the number of repeat units in the monomer. These results demonstrate that protein-inorganic lattice interactions can be systematically programmed and set the stage for designing protein-inorganic hybrid materials.


Assuntos
Silicatos de Alumínio/química , Proteínas Imobilizadas/química , Biossíntese de Proteínas , Nanofios/química , Ligação Proteica
18.
Chemosphere ; 235: 670-678, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31276880

RESUMO

Extracellular DNA (eDNA) is widely present in soil, with potential ecological impacts. Metal cations are naturally present on the surface of soil clay minerals, although the adsorption mechanism of eDNA on clay minerals saturated with metal cations is still not fully understood. The research investigated the adsorption of eDNA, using salmon sperm DNA as a representative, on metal cation (Na+, Ca2+, and Fe3+)-saturated montmorillonites (Mt). Metal cation-saturated Mt have higher adsorption capacities for DNA. Compared with Mt (3500 mg⋅kg-1), the amounts of DNA adsorption on metal cation-saturated Mt (pH = 7.0) were increased by 0.74-5.38 times, and followed the descending order of Fe-Mt > Na-Mt > Ca-Mt > Mt. A temperature of 25 °C was found to be more suitable than 15 and 35 °C for DNA adsorption, while an increasing pH value (3.0-9.0) reduced DNA adsorption on Mt and metal cation-saturated Mt. Microscopic and spectroscopic analyses, together with a model computation technique, confirmed that metal cations saturated on the surface of Mt work like a "cation bridge" linking oxygen atoms in the phosphate groups of DNA and the negatively charged moieties of Mt, which were predominantly bound through electrostatic forces, thus, facilitating DNA adsorption at pH > 5. The results of this investigation provide valuable insight into eDNA adsorption on soil clay minerals and the transport and fate of eDNA in the natural soil environment.


Assuntos
Bentonita/química , DNA/química , Metais/química , Poluentes do Solo/química , Adsorção , Silicatos de Alumínio/química , Cátions/química , Argila , Minerais/química , Fosfatos , Sódio , Solo
19.
Environ Res ; 175: 449-456, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31158563

RESUMO

BACKGROUND: A vermiculite processing plant in a Minneapolis, Minnesota neighborhood utilized asbestos-containing ore from Libby, Montana from the late 1930's until 1989. Multiple pathways of exposure to Libby asbestos were characterized in a cohort of over 6000 plant workers and residents living near the plant. OBJECTIVE: We conducted a cohort linkage study to assess the impact of cumulative low dose exposure and the role of occupational history on asbestos-related mortality and cancer morbidity among cohort members residing near a vermiculite plant. METHODS: Cohort members alive in 1988 (n = 5848) were linked to the Minnesota Cancer Surveillance System to identify incident cases of mesothelioma, lung cancer, and all-cancer diagnosed from 1988 to 2010. Proportional incidence ratios (PIRs) were calculated for mesothelioma and lung cancer. Vital status and cause of death were ascertained from Minnesota vital records and the National Death Index (1988-2011). Mortality rates of the cohort (2001-2011) for asbestos-related outcomes were compared to the Minnesota population to estimate standardized mortality ratios (SMRs) and stratified by gender, exposure, and occupational history categories. RESULTS: We identified seven cases of mesothelioma, with elevated incidence only in females (PIR = 11.76, 95% CI: 3.17, 30.12). Lung cancer was elevated in both genders: PIR = 1.54 (95% CI: 1.19, 2.0) in males and 1.62 (95% CI: 1.21, 2.12) in females. We found elevated mortality from COPD, lung cancer, and mesothelioma among females (SMR for mesothelioma in females = 18.97, CI: 3.91, 55.45), among the 546 deaths identified. All four deaths from mesothelioma occurred in the >75th percentile of exposure (>0.0156 fiber/cc x months). The SMR for lung cancer and all respiratory cancer was elevated even after controlling for occupation. CONCLUSIONS: Community exposure to Libby amphibole asbestos from a vermiculite processing plant is associated with increased risk of COPD, lung cancer and mesothelioma incidence and mortality, most notably among females, and is likely to remain a public health issue for years to come.


Assuntos
Silicatos de Alumínio , Asbestos , Neoplasias Pulmonares/epidemiologia , Mesotelioma/epidemiologia , Exposição Ocupacional/estatística & dados numéricos , Amiantos Anfibólicos , Feminino , Humanos , Incidência , Masculino , Minnesota/epidemiologia , Montana
20.
Int J Mol Sci ; 20(12)2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31234409

RESUMO

Crystallite aluminosilicates are inorganic microporous materials with well-defined pore-size and pore-structures, and have important industrial applications, including gas adsorption and separation, catalysis, etc. Crystallite aluminosilicates are commonly synthesized via hydrothermal processes, where the oligomerization of silicic acids is crucial. The mechanisms for the oligomerization of poly-silicic acids in neutral aqueous solution were systematically investigated by extensive first-principles-based calculations. We showed that oligomerization of poly-silicic acid molecules proceeds through the lateral attacking and simultaneously proton transfer from the approaching molecule for the formation of a 5-coordinated Si species as the transition state, resulting in the ejection of a water molecule from the formed poly-silicic acid. The barriers for this mechanism are in general more plausible than the conventional direct attacking of poly-silicic acid with reaction barriers in the range of 150-160 kJ/mol. The formation of linear or branched poly-silicic acids by intermolecular oligomerization is only slightly more plausible than the formation of cyclic poly-silicic acids via intramolecular oligomerization according to the reaction barriers (124.2-133.0 vs. 130.6-144.9 kJ/mol). The potential contributions of oligomer structures, such as the length of the linear oligomers, ring distortions and neighboring linear branches, etc., to the oligomerization were also investigated but found negligible. According to the small differences among the reaction barriers, we proposed that kinetic selectivity of the poly-silicic acids condensation would be weak in neutral aqueous solution and the formation of zeolite-like structures would be thermodynamics driven.


Assuntos
Ácido Silícico/química , Água/química , Zeolitas/química , Silicatos de Alumínio/química , Dimerização , Cinética , Modelos Moleculares , Soluções , Termodinâmica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA