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1.
Proc Natl Acad Sci U S A ; 117(37): 22833-22840, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32873643

RESUMO

Channelrhodopsins are light-gated ion channels widely used to control neuronal firing with light (optogenetics). We report two previously unknown families of anion channelrhodopsins (ACRs), one from the heterotrophic protists labyrinthulea and the other from haptophyte algae. Four closely related labyrinthulea ACRs, named RubyACRs here, exhibit a unique retinal-binding pocket that creates spectral sensitivities with maxima at 590 to 610 nm, the most red-shifted channelrhodopsins known, long-sought for optogenetics, and more broadly the most red-shifted microbial rhodopsins thus far reported. We identified three spectral tuning residues critical for the red-shifted absorption. Photocurrents recorded from the RubyACR from Aurantiochytrium limacinum (designated AlACR1) under single-turnover excitation exhibited biphasic decay, the rate of which was only weakly voltage dependent, in contrast to that in previously characterized cryptophyte ACRs, indicating differences in channel gating mechanisms between the two ACR families. Moreover, in A. limacinum we identified three ACRs with absorption maxima at 485, 545, and 590 nm, indicating color-sensitive photosensing with blue, green, and red spectral variation of ACRs within individual species of the labyrinthulea family. We also report functional energy transfer from a cytoplasmic fluorescent protein domain to the retinal chromophore bound within RubyACRs.


Assuntos
Channelrhodopsins/química , Ativação do Canal Iônico/fisiologia , Ânions/metabolismo , Criptófitas/genética , Células HEK293 , Humanos , Canais Iônicos/química , Canais Iônicos/metabolismo , Luz , Potenciais da Membrana/fisiologia , Neurônios/metabolismo , Optogenética/métodos , Rodopsina/metabolismo
2.
Environ Res ; 188: 109872, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32846651

RESUMO

A comprehensive analysis of the chemical composition of precipitation was performed on rainwater samples collected between 1978 and 2017 over the conterminous US. A total of 86470 data records downloaded from the National Atmospheric Deposition Program were statistically analyzed and assessed in terms of precipitation chemistry. The ion abundance followed the Cl⁻ > Na⁺ > SO42⁻ > Ca2⁺ > H⁺ > NH4⁺ > NO3⁻ > Mg2⁺ > HCO3⁻ > K⁺ downward trend, showing that chloride and sodium were the most dominant among anions and cations. Ca2+, SO42- and NH4+ concentrations were notable in desert areas or in regions with significant anthropogenic activity. Frequency analysis of pH values showed that the 87.90% of the pH is acidic, exhibiting values under 5.6. According to the acidifying and neutralization potential, rainwater pH is mostly alkaline in the Western region, presenting acidic values in highly industrialized areas, in the Central and Eastern Regions. Fractional acidity showed that in the majority of the studied sampling sites 61% of the acidity in precipitation is neutralized, due to the presence of the main neutralizing agents (NH4+, Ca2+, Na+), fact sustained by the neutralization factor values. The relationship between acidic and alkaline components was thoroughly examined by ionic ratios and the ammonium availability index. Wet deposition rates of major ions confirmed the dominance of acidic species over neutralizing ones, as well as the significant imprint of regional climate and heavily industrialized areas on the precipitation chemistry. The complex major ion source apportionment, including marine and crustal enrichment factors, sea salt and non-sea salt fractions, Spearman's rank correlation analysis and Principal Component Analysis, showed that anthropogenic influences are the most significant, including coal-fired power plants, oil refineries, major industries and agricultural activities. Crustal and marine sources also presented a prominent imprint on the rainwater chemistry of the conterminous US.


Assuntos
Poluentes Atmosféricos , Chuva , Poluentes Atmosféricos/análise , Ânions/análise , Cátions , Cloretos , Monitoramento Ambiental , Estações do Ano , Estados Unidos
3.
Proc Natl Acad Sci U S A ; 117(35): 21740-21746, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817533

RESUMO

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) anion channel is essential for epithelial salt-water balance. CFTR mutations cause cystic fibrosis, a lethal incurable disease. In cells CFTR is activated through the cAMP signaling pathway, overstimulation of which during cholera leads to CFTR-mediated intestinal salt-water loss. Channel activation is achieved by phosphorylation of its regulatory (R) domain by cAMP-dependent protein kinase catalytic subunit (PKA). Here we show using two independent approaches--an ATP analog that can drive CFTR channel gating but is unsuitable for phosphotransfer by PKA, and CFTR mutants lacking phosphorylatable serines--that PKA efficiently opens CFTR channels through simple binding, under conditions that preclude phosphorylation. Unlike when phosphorylation happens, CFTR activation by PKA binding is completely reversible. Thus, PKA binding promotes release of the unphosphorylated R domain from its inhibitory position, causing full channel activation, whereas phosphorylation serves only to maintain channel activity beyond termination of the PKA signal. The results suggest two levels of CFTR regulation in cells: irreversible through phosphorylation, and reversible through R-domain binding to PKA--and possibly also to other members of a large network of proteins known to interact with the channel.


Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Canais de Ânion Dependentes de Voltagem/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Ânions/metabolismo , Fenômenos Biofísicos , Proteínas Quinases Dependentes de AMP Cíclico/fisiologia , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/fisiologia , Ativação do Canal Iônico/fisiologia , Mutagênese Sítio-Dirigida , Nucleotídeos/metabolismo , Oócitos/metabolismo , Técnicas de Patch-Clamp/métodos , Fosforilação , Ligação Proteica/fisiologia , Serina/metabolismo , Canais de Ânion Dependentes de Voltagem/fisiologia , Proteínas de Xenopus/metabolismo , Xenopus laevis/metabolismo
4.
J Environ Radioact ; 222: 106372, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32771856

RESUMO

There are few effective technologies for the sequestration of highly water-soluble pertechnetate (TcO4-) from contaminated water despite the urgency of environmental and public health concerns. In this work, anion exchanged and cetyltrimethylammonium bromide (CTAB) functionalized MIL-101-Cr-NO3 were investigated for perrhenate (ReO4-), a surrogate of TcO4-, sequestration from artificial groundwater. Cl-, I-, and CF3SO3- exchanged MIL-101-Cr proved more effective at ReO4- removal than the parent MIL-101-Cr-F. Compared to the parent framework, CTAB functionalized MIL-101-Cr-NO3 increased ReO4- removal capacity from 39 to 139 mg/g, improved the reaction kinetics from ~30 to <10 min to reach full adsorption capacity and the selectivity for ReO4- over competing NO3-, CO32-, SO42-, and Cl-. Spectroscopic data indicated that the chemical speciation of Re in the exchanged MIL-101-Cr remained ReO4-, indicating synergistic sequestration through both anion exchange and non-ion exchange binding with the positively charged ligand of CTAB. These studies foreshadow potential applications of MOFs for the remediation of 99TcO4- from contaminated environments.


Assuntos
Compostos de Amônio , Água Subterrânea , Estruturas Metalorgânicas , Monitoramento de Radiação , Ânions
5.
Water Sci Technol ; 81(11): 2441-2449, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784287

RESUMO

Municipal sludge disposal and recycle has become a prominent research theme. In this study, a sequential process for integral treatment of municipal sludge was primarily presented, combining acid leaching, anion exchange and aerobic composting. The aim of the process was to remove chromium (Cr) from the sludge and reuse the sludge as manure. Firstly, Cr was removed from municipal sludge via the acid leaching process; the removal rate was up to 57.43%. Then, ion exchange resin was used to remove Cr from leachate; the removal rate reached 95%. Aluminum sheet was used to replace the Cr from eluent; the replacement rate was 63.3%. The aerobic composting process could be successfully warmed up to above 55 °C and lasted for 4 days; the seed germination index reached 68.3%. After the composting process, the residual Cr in sludge mainly existed at a more stable residual state and organic binding state. Overall, this novel sequential process serves as a potential high-efficiency, green, low-energy way for municipal sludge recycle.


Assuntos
Compostagem , Ânions , Esterco , Reciclagem , Esgotos
6.
Ecotoxicol Environ Saf ; 205: 111187, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32853869

RESUMO

Ionic liquids have been becoming new 'green solvent' because of the low saturation vapor pressure, less volatilization and more recycling utilization. Since most ILs are soluble in water, it should be indispensable to evaluate the ecotoxicology effect of ILs on aquatic environment before using them widely. Based on the concept of norm index, a set of norm descriptors were proposed for anions, cations and ILs. The whole IL structure optimization method has been used to build a predictive norm index-based quantitative structure-toxicity relationship model for the toxicity of ILs on Vibrio fischeri. Statistical results indicated that norm descriptors were reliable and robust in expressing the relationship between structural information and toxicity of ILs. Meanwhile, a series of ILs without experimental values were predicted based on this stable QSTR model. The results indicated that for imidazole-based ILs, an increase in the length of substituent in the branch could enhance the toxicity of ILs on Vibrio fischeri, and the branch contains hydroxyl group, double bond or triple bonds might reduce the toxicity of ILs. Results obtained in this present work would be valuable for the molecular design and the toxicity evaluation toward aquatic organism of ILs.


Assuntos
Aliivibrio fischeri/efeitos dos fármacos , Imidazóis , Líquidos Iônicos , Modelos Teóricos , Solventes , Ânions/química , Cátions/química , Ecotoxicologia/métodos , Imidazóis/química , Imidazóis/toxicidade , Líquidos Iônicos/química , Líquidos Iônicos/toxicidade , Valor Preditivo dos Testes , Relação Quantitativa Estrutura-Atividade , Solventes/química , Solventes/toxicidade
7.
J Chromatogr A ; 1628: 461444, 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32822983

RESUMO

The effect of bead and ligand structure on protein adsorption was investigated for multimodal anion exchangers combining a quaternary ammonium ion group with hydrophobic moieties: Nuvia aPrime 1 and aPrime 2, based on a 54 µm diameter polymeric bead, and Capto Adhere ImpRes and Capto Adhere, based on agarose beads 51 and 78 µm diameter, respectively. Bovine serum albumin (BSA) monomer, BSA dimer, and thyroglobulin (Tg) were used as model proteins. Based on TEM imaging and iSEC, the Nuvia resins have a microgranular structure and large pores (110 nm radius), while the Capto resins have a fibrous structure and smaller pores (32-36 nm radius). Comparable binding capacities (80-110 mg/mL), decreasing as salt is added, are observed for all three proteins on the Nuvia resins. Higher capacities (110-130 mg/mL), also decreasing as salt is added, are observed for BSA monomer and dimer on the Capto resins. However, the Tg binding capacity is very low in this case and increases as salt is added. Confocal laser scanning microscopy show that the kinetics are controlled by pore diffusion for all four resins, but with diffusivities that decrease as the protein size increases especially for the Capto resins. For Tg at low salt, binding is restricted to a thin shell close to the bead surface for both Capto resins. The ratio of effective and free diffusivity is about 0.30, 0.18, and 0.08 for BSA monomer, BSA dimer, and Tg, respectively, on the Nuvia resin. These values decrease to about 0.11, 0.04, and 0.01, respectively, for the Capto resins as a result of diffusional hindrance. Dynamic binding capacities are consistent with the equilibrium and rate behaviors.


Assuntos
Resinas de Troca de Ânions/química , Cromatografia por Troca Iônica , Proteínas/metabolismo , Adsorção , Ânions/química , Difusão , Interações Hidrofóbicas e Hidrofílicas , Cinética , Ligantes , Polímeros/química , Sefarose/química , Soroalbumina Bovina/química
8.
J Chromatogr A ; 1627: 461378, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823092

RESUMO

Downstream processing (DSP) of large bionanoparticles is still a challenge. The present study aims to systematically compare some of the most commonly used DSP strategies for capture and purification of enveloped viruses and virus-like particles (eVLPs) by using the same staring material and analytical tools. As a model, Human Immunodeficiency Virus-1 (HIV-1) gag VLPs produced in CHO cells were used. Four different DSP strategies were tested. An anion-exchange monolith and a membrane adsorber, for direct capture and purification of eVLPs, and a polymer-grafted anion-exchange resin and a heparin-affinity resin for eVLP purification after a first flow-through step to remove small impurities. All tested strategies were suitable for capture and purification of eVLPs. The performance of the different strategies was evaluated regarding its binding capacity, ability to separate different particle populations and product purity. The highest binding capacity regarding total particles was obtained using the anion exchange membrane adsorber (5.3 × 1012 part/mL membrane), however this method did not allow the separation of different particle populations. Despite having a lower binding capacity (1.5 × 1011 part/mL column) and requiring a pre-processing step with flow-through chromatography, Heparin-affinity chromatography showed the best performance regarding separation of different particle populations, allowing not only the separation of HIV-1 gag VLPs from host cell derived bionanoparticles but also from chromatin. This work additionally shows the importance of thorough sample characterization combining several biochemical and biophysical methods in eVLP DSP.


Assuntos
Convecção , HIV-1/isolamento & purificação , Adsorção , Animais , Ânions , Células CHO , Cromatina/metabolismo , Cromatografia de Afinidade , Cricetinae , Cricetulus , HIV-1/ultraestrutura , Histonas/metabolismo , Humanos , Microesferas , Nanopartículas/química , Nanopartículas/ultraestrutura , Polímeros/química , Porosidade , Vírion/isolamento & purificação , Vírion/ultraestrutura
9.
Proc Natl Acad Sci U S A ; 117(29): 17381-17388, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32632018

RESUMO

Adiponectin (Acrp30) is an adipokine associated with protection from cardiovascular disease, insulin resistance, and inflammation. Although its effects are conventionally attributed to binding Adipor1/2 and T-cadherin, its abundance in circulation, role in ceramide metabolism, and homology to C1q suggest an overlooked role as a lipid-binding protein, possibly generalizable to other C1q/TNF-related proteins (CTRPs) and C1q family members. To investigate this, adiponectin, representative family members, and variants were expressed in Expi293 cells and tested for binding to lipids in liposomes using density centrifugation. Binding to physiological lipids were also analyzed using gradient ultracentrifugation, liquid chromatography-mass spectrometry, and shotgun lipidomics. Interestingly, adiponectin selectively bound several anionic phospholipids and sphingolipids, including phosphatidylserine, ceramide-1-phosphate, glucosylceramide, and sulfatide, via the C1q domain in an oligomerization-dependent fashion. Binding to lipids was observed in liposomes, low-density lipoproteins, cell membranes, and plasma. Other CTRPs and C1q family members (Cbln1, CTRP1, CTRP5, and CTRP13) also bound similar lipids. These findings suggest that adiponectin and CTRPs function not only as hormones, but also as lipid opsonins, as may other C1q family proteins.


Assuntos
Adiponectina/metabolismo , Complemento C1q/metabolismo , Fosfolipídeos/metabolismo , Esfingolipídeos/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Adipocinas/metabolismo , Adiponectina/genética , Animais , Ânions , Membrana Celular , LDL-Colesterol , Humanos , Metabolismo dos Lipídeos , Lipidômica , Lipoproteínas/metabolismo , Lipossomos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Opsonizantes/metabolismo , Plasma
10.
J Chromatogr A ; 1625: 461301, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709344

RESUMO

In this work we utilized basic and acidic analytes to investigate the ionic interaction participation in retention behavior of selected reversed-phase and polar columns. The test analytes included nitrate, benzenesulfonate and trimethylphenylammonium ions. The fully aqueous mobile phase comprising 10 mM dichloroacetic acid buffered with ammonia solution to desirable pH was used for retention experiments. Developed method was utilized to study the ionic interactions of stationary phases in pH range between 2.5 and 9.0. We demonstrate that selected sorbents used for reversed-phase and hydrophilic interaction chromatography separations exhibit cation- or anion-exchange interactions. We compare the results to novel Atlantis PREMIER BEH C18 AX mixed-mode column that combines reversed-phase and anion-exchange interaction modes. We evaluated the relative retention strength of selected columns for anionic and cationic analytes.


Assuntos
Cromatografia Líquida/métodos , Adsorção , Ânions , Cromatografia de Fase Reversa , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Dióxido de Silício/química , Água/química
11.
Chemosphere ; 259: 127421, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32603965

RESUMO

Nanocomposites with ultrahigh adsorption capabilities are highly desired for efficient wastewater remediation. Unfortunately, most of the nanomaterial based adsorbents showing inevitable limitation such as leaching and agglomeration led to the emerging field of carbonaceous hybrid materials with nanocomposites. Herein, we demonstrated a simple and low-temperature hydrothermal assisted preparation of Fe-Al based nanocomposites immobilized using carbon spheres. Towards this, we have approached two different routes one is hybridizing with nanocomposite and another is doping on the surface of the carbon spheres. Iron doping played a dual-faceted role of active site for robust adsorption as well as induce magnetic property to the composites. The micro-cleaners have been extensively characterized for their physicochemical properties and adsorption capacities using FTIR, Raman, XRD, BET isotherms and XPS techniques. Remarkably, microcleaners shows robust adsorption where >99% removal was obtained within 10 min for 50 mg L-1 concentrated Eriochrome Black T (EBT) dye using 0.01 g of materials. Further, adsorption data followed the pseudo second order kinetics while the equilibrium data fitted perfectly into the Langmuir adsorption equation. As synthesized user friendly microcleaner (HTC-2) exhibits maximum adsorption capacity (qmax) of 564.97 mg g-1 for EBT dye at pH 4. Hence, the preliminary results highlight the potential of the composites to be used in pretreatment steps of industry effluents.


Assuntos
Corantes/química , Nanocompostos/química , Poluentes Químicos da Água/química , Adsorção , Ânions , Compostos Azo , Carbono , Concentração de Íons de Hidrogênio , Ferro , Cinética , Águas Residuárias , Poluentes Químicos da Água/análise
12.
Artigo em Inglês | MEDLINE | ID: mdl-32615055

RESUMO

The effect of the presence of minerals in natural soil polluted with lead (II) was investigated to verify the efficiency of the electrokinetic remediation method. Natural soil "Sebkha of Oran" containing high calcite minerals and characterized by high salinity was used in experimental studies. This study investigates the effects of alkaline soil pH conditions on the transport and removal of lead by the electrokinetic treatment. XRD analyses were performed on the soil sample before and after electrokinetic treatment to determine any changes in mineral phases. Mathematical models using experimental data are developed to describe the mobility and diffusion coefficient of lead ions through the soil. Mathematical models were generated based on the physicochemical parameters characterizing the movement of cations and anions.


Assuntos
Técnicas Eletroquímicas/métodos , Recuperação e Remediação Ambiental/métodos , Chumbo/análise , Modelos Teóricos , Poluentes do Solo/análise , Solo/química , Ânions , Cátions , Minerais/química
13.
Environ Pollut ; 266(Pt 2): 115102, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32650200

RESUMO

Current study deals with the surface modification of acid activated carbon (prepared from Pongamia pinnata shells) with Cetyltrimethylammonium bromide (CTAB) and its role as an adsorbent in eliminating anionic azo dyes viz. Congo red (CR) and Direct blue 6 (DB) from single and binary adsorptive systems. Binary adsorptive system involved the synergistic and antagonistic influence of one dye over the adsorption of other dye. Physico-chemical alterations due to surfactant modification and post adsorption were studied using atomic force microscopy (AFM), Zeta Potential, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), surface area analysis and Fourier-transformed infrared spectroscopy (FTIR). Process parameters influencing efficient adsorption of CR and DB species viz. initial pH of dye solution, adsorbent dosage, incubation temperature and initial concentration of dye species were optimised. Sorbate-sorbent interaction studies for single adsorptive system revealed sorbate's monolayer formation over adsorbent's surface and the involvement of chemisorption, as verified by Langmuir isotherm model and pseudo-second order model, respectively. Langmuir maximum adsorption capacity of the adsorbent was 555.56 mg/g for CR and 625.00 mg/g for DB. Meanwhile, for binary adsorptive system, competitive Langmuir model verified both CR and DB had antagonistic/competitive effect over each other's adsorption. Thermodynamic analysis revealed the adsorptive process as exothermic, spontaneous and thermodynamically favourable with an elevated degree of dis-orderedness. Co-existing cations and anions has nominal effect on the adsorption capacity of dyes. Recyclability studies verified a modest efficiency of 62.52% for CR and 50.47% for DB species after the end of 4th adsorption-desorption cycle; thus affirming its recyclability potential. Phytotoxic assay affirmed the effectivity of the adsorbent in adsorbing dye species from aqueous solutions using Vigna mungo seeds as the model.


Assuntos
Carvão Vegetal , Poluentes Químicos da Água/análise , Adsorção , Ânions , Compostos Azo , Corantes , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
14.
J Chromatogr A ; 1625: 461331, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709357

RESUMO

In this work, a novel imidazolium bonding method was proposed for the synthesis of hydrophilic interaction liquid chromatography (HILIC) stationary phases. One obtained stationary phase (SilprAprImCl) was derived from direct reaction between N-(3-aminopropyl)-imidazole and 3-chloropropylated silica gel. Other two materials (SilprAprImBF4 and SilprAprImTf2N) were obtained from SilprAprImCl by ion exchange reaction, respectively. Fourier-transform infrared spectroscopy and elemental analysis afforded the proofs of successful imidazolium immobilization and satisfied bonding efficiency. Various polar compounds such as saccharides, nucleosides, and nucleobases were utilized to evaluate the retention behaviours of these materials in HILIC mode. Different effects from mobile composition, column temperature, imidazolium unite and paired anions (Cl-, BF4-, and Tf2N-) in imidazolium were proved and discussed. Separation mechanism and the role of the imidazolium ions were also investigated in mobile phases with different pH. Moreover, chromatographic stability was evaluated by consecutive injections. Finally, the reliability of these stationary phases was demonstrated by the separation of oligosaccharides in real fructooligosaccharides samples.


Assuntos
Cromatografia Líquida/métodos , Interações Hidrofóbicas e Hidrofílicas , Imidazóis/química , Propanóis/química , Ânions , Concentração de Íons de Hidrogênio , Imidazóis/síntese química , Líquidos Iônicos/química , Nucleosídeos/química , Nucleosídeos/isolamento & purificação , Oligossacarídeos/química , Propanóis/síntese química , Reprodutibilidade dos Testes , Temperatura
15.
J Chromatogr A ; 1625: 461338, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709362

RESUMO

Until today, ion-pair reversed-phase chromatography is still the dominating method for analytical characterization of synthetic oligonucleotides. Its hyphenation with mass spectrometry, however, has some drawbacks such as ion-suppression in electrospray ionization. To overcome this problem, we present in this work a multiple heart-cutting (MHC) two-dimensional liquid chromatography (2D-LC) method with ultra-violet (UV) and electrospray ionization (ESI) mass spectrometry (MS) detection. A reversed-phase/weak anion-exchange (RP/WAX) stationary phase in the first dimension (1D) provides the selectivity for separation of structurally closely related oligonucleotide sequences and deletions (shortmers), respectively, using a mixed pH/triethylammonium phosphate buffer gradient at constant organic modifier content. Heart cuts of the oligonucleotide peaks are transferred to the second dimension (2D) via a multiple heart-cutting valve which is equipped with two loop decks. The 2D RP column is used for desalting via a diverter valve. Active solvent modulation enables to refocus the oligonucleotide peak into a sharp zone by 2D RP entirely free of non-volatile buffer components and ion-pair agents. Oligonucleotides can thus be sensitively detected by ESI-QTOF-MS under MS-compatible conditions.


Assuntos
Cromatografia de Fase Reversa/métodos , Oligonucleotídeos/química , Oligonucleotídeos/isolamento & purificação , Espectrometria de Massas por Ionização por Electrospray/métodos , Ânions , Cromatografia por Troca Iônica , Oligonucleotídeos/análise , Polímeros/química
16.
Water Res ; 182: 115963, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32622126

RESUMO

Electrochemically mediated adsorption is an emerging technology that utilizes redox active (or Faradaic) materials and has exhibited high salt adsorption capacity and superb ion selectivity. Here, we use a redox polymer polyvinylferrocene (PVFc) as the anode and a conducting polymer polypyrrole doped with a large anionic surfactant (pPy-DBS) as the cathode for selective electrochemical removal of inorganic and organic components. We fabricated a flow system with alternating adsorption/desorption steps incorporating an electrosorption cell and inline probes (ultraviolet-visible spectroscopy, conductivity and pH sensors) to demonstrate on-the-fly quantification of the ion adsorption performance. The flow system provides a more realistic evaluation of dynamic selectivity for the active materials during cyclic operation than that based on a single equilibrium adsorption step in batch. Our results show a three-fold (cycle) selectivity toward the removal of benzoate, as a representative organic anion, against a 50-fold abundance of perchlorate supporting anion, indicating that electrochemically mediated adsorption is a promising technology for waste water remediation applications.


Assuntos
Polímeros , Purificação da Água , Adsorção , Ânions , Eletrodos , Oxirredução , Pirróis
17.
J Chromatogr A ; 1625: 461226, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709310

RESUMO

In this work, an easy and fast procedure for the selective multiresidue determination of 14 highly polar pesticides (including glyphosate, glufosinate, ethephon and fosetyl) and metabolites in beverages is presented. After an initial sample dilution (1:1, v/v), the extract is shaken and centrifuged, further diluted and then injected directly into the LC-MS/MS system, using hydrophilic interaction liquid chromatography (HILIC) and tandem mass spectrometry. No clean-up procedure was needed. The method was validated according to the current European guidelines for pesticide residue analysis in food and feed and linearity, limits of detection and quantification, matrix effects, trueness and precision were assessed. For plant-based milk, wine and beer samples, 10, 11 and 12 analytes, respectively, out of 14 were fully validated at 10 µg kg-1, the lowest spike level tested. The matrix effect was negative in most of the cases, showing for some compounds, such as HEPA, up to 80% suppression when compared to the response from standards in solvent. The use of isotopically labelled internal standards is required for the optimal quantification, as it compensates for high and varying matrix effects and also for recovery losses during extraction.


Assuntos
Cerveja/análise , Cromatografia Líquida de Alta Pressão/métodos , Substitutos do Leite/química , Resíduos de Praguicidas/análise , Espectrometria de Massas em Tandem/métodos , Vinho/análise , Animais , Ânions/química , Interações Hidrofóbicas e Hidrofílicas , Leite de Soja/química
18.
Food Chem ; 333: 127493, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32659659

RESUMO

The effects of the addition of salt ions and molecular weights (Mw) of CH on Mesona chinensis polysaccharide (MCP)-chitosan (CH) hydrogel were investigated. Result indicated both low concentration of monovalent salt ions (Na+ and K+), divalent cations (Ca2+) and oxoanions (SO42-) could promote the gel properties of MCP-CH hydrogel. The Mw of CH has huge impact on the formation and properties of hydrogel. Combining the relationship between rheology and structural, monovalent salt ions such as Na+ and K+ affect gel formation and its properties by influencing electrostatic interaction and chain conformation. Both divalent cations (Ca2+) and oxoanions (SO42-) facilitated the formation of gel networks via electrostatic interaction, coordination bonds and hydrogen bonds. Moreover, Mw of CH influenced formation and texture of MCP-CH hydrogel via affecting the conformation of CH molecular chain. These findings will provide a few theoretical bases to understand the formation mechanism of MCP-CH hydrogel.


Assuntos
Quitosana/química , Hidrogéis/química , Lamiaceae/química , Extratos Vegetais/química , Polieletrólitos/química , Sais/química , Ânions/química , Cálcio/química , Hidrogéis/síntese química , Peso Molecular , Polissacarídeos/química , Potássio/química , Reologia , Sódio/química
19.
Chemosphere ; 260: 127624, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32683029

RESUMO

Soil organic matter (SOM) is known to exert a major control on the mobility and bioavailability of cationic nutrients. However, the role of SOM in the fate of anionic nutrients, especially phosphorus (P), is less well characterized. The objectives of this study were to (1) compare the formation of binary complexes of calcium (Ca) with humic acids (HA) extracted from two contrasting soils, and (2) determine if binary HA-Ca complexes could incorporate P by forming ternary HA-Ca-P complexes. The Ca binding capacities of the HA extracted from an agricultural organic soil (AOS) and a pristine riparian soil (RS) were measured via potentiometric titrations; the formation of ternary complexes was analyzed by size fractionation using MWCO tubes. Proton and Ca binding capacities of RS-HA were higher than AOS-HA, and pH had a weaker effect on Ca binding to RS-HA. These differences are consistent with lower proportions of aromatic groups, and a higher proportion of alkyl groups derived from 13C NMR spectroscopy. Together, the NMR, titration and MWCO data indicate that Ca binds to RS-HA through monodentate complexes and electrostatic attraction that are capable of binding P producing ternary complexes. In contrast, at pH 8.5 Ca forms bidentate complexes with AOS-HA, which do not provide bridging positions to incorporate P. Overall, our results imply that the formation of HA-Ca and HA-Ca-P complexes depend on the structure of the HA, and that complexation to HA may play an important role in the fate of P in terrestrial and aquatic environments.


Assuntos
Cálcio/química , Fósforo/análise , Poluentes do Solo/análise , Ânions , Cálcio na Dieta , Cátions , Substâncias Húmicas/análise , Minerais , Solo/química , Poluentes do Solo/química
20.
Proc Natl Acad Sci U S A ; 117(31): 18224-18230, 2020 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-32680959

RESUMO

Utilizing an ionic liquid strategy, we report crystal structures of salts of free anionic nucleobases and base pairs previously studied only computationally and in the gas phase. Reaction of tetrabutylammonium ([N4444]+) or tetrabutylphosphonium ([P4444]+) hydroxide with adenine (HAd) and thymine (HThy) led to hydrated salts of deprotonated adenine, [N4444][Ad]·2H2O, and thymine, [P4444][Thy]·2H2O, as well as the double salt cocrystal, [P4444]2[Ad][Thy]·3H2O·2HThy. The cocrystal includes the anionic [Ad-(HThy)] base pair which is a stable formation in the solid state that has previously not even been suggested. It exhibits Watson-Crick connectivity as found in DNA but which is unusual for the free neutral base pairs. The stability of the observed anionic bases and their supramolecular formations and hydrates has also been examined by electronic structure calculations, contributing to more insight into how base pairs can bind when a proton is removed and highlighting mechanisms of stabilization or chemical transformation in the DNA chains.


Assuntos
Adenina/química , Pareamento de Bases , Timina/química , Ânions , Cristalografia , Ligação de Hidrogênio , Modelos Moleculares , Estrutura Molecular , Conformação de Ácido Nucleico
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