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1.
Top Curr Chem (Cham) ; 377(6): 33, 2019 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-31664531

RESUMO

Separation of hydrocarbon mixtures into single components is a very important industrial process because all represent very important energy resources/raw chemicals in the petrochemical industry. The well-established industrial separation technology highly relies on the energy-intensive cryogenic distillation processes. The discovery of new materials capable of separating hydrocarbon mixtures by adsorbent-based separation technologies has the potential to provide more energy-efficient industrial processes with remarkable energy savings. Porous metal-organic frameworks (MOFs), also known as porous coordination polymers, represent a new class of porous materials that offer tremendous promise for hydrocarbon separations because of their easy tunability, designability, and functionality. A number of MOFs have been designed and synthesized to show excellent separation performance on various hydrocarbon separations. Here, we summarize and highlight some recent significant advances in the development of microporous MOFs for hydrocarbon separation applications.


Assuntos
Hidrocarbonetos/isolamento & purificação , Estruturas Metalorgânicas/química , Alcenos/química , Alcenos/isolamento & purificação , Etilenos/química , Etilenos/isolamento & purificação , Hidrocarbonetos/química , Parafina/química , Parafina/isolamento & purificação , Porosidade
2.
Plant Mol Biol ; 101(3): 269-296, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31338671

RESUMO

KEY MESSAGE: The first transcriptome coupled to metabolite analyses reveals major trends during acerola fruit ripening and shed lights on ascorbate, ethylene signalling, cellular respiration, sugar accumulation, and softening key regulatory genes. Acerola is a fast growing and ripening fruit that exhibits high amounts of ascorbate. During ripening, the fruit experience high respiratory rates leading to ascorbate depletion and a quickly fragile and perishable state. Despite its growing economic importance, understanding of its developmental metabolism remains obscure due to the absence of genomic and transcriptomic data. We performed an acerola transcriptome sequencing that generated over 600 million reads, 40,830 contigs, and provided the annotation of 25,298 unique transcripts. Overall, this study revealed the main metabolic changes that occur in the acerola ripening. This transcriptional profile linked to metabolite measurements, allowed us to focus on ascorbate, ethylene, respiration, sugar, and firmness, the major metabolism indicators for acerola quality. Our results suggest a cooperative role of several genes involved in AsA biosynthesis (PMM, GMP1 and 3, GME1 and 2, GGP1 and 2), translocation (NAT3, 4, 6 and 6-like) and recycling (MDHAR2 and DHAR1) pathways for AsA accumulation in unripe fruits. Moreover, the association of metabolites with transcript profiles provided a comprehensive understanding of ethylene signalling, respiration, sugar accumulation and softening of acerola, shedding light on promising key regulatory genes. Overall, this study provides a foundation for further examination of the functional significance of these genes to improve fruit quality traits.


Assuntos
Ácido Ascórbico/química , Etilenos/química , Frutas/fisiologia , Malpighiaceae/genética , Malpighiaceae/metabolismo , Transcriptoma , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Plantas/metabolismo , Análise de Componente Principal , Transdução de Sinais
3.
Molecules ; 24(11)2019 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-31159332

RESUMO

Herein, we report the homo- and co-polymerization of ethylene (E) with norbornene (NB) catalyzed by vanadium(III) phosphine complexes of the type VCl3(PMenPh3-n)2 [n = 2 (1a), 1 (1b)] and VCl3(PR3)2 [R = phenyl (Ph, 1c), cyclohexyl (Cy, 1d), tert-butyl (tBu, 1e)]. In the presence of Et2AlCl and Cl3CCOOEt (ETA), 1a-1e exhibit good activities for the polymerization of ethylene, affording linear, semicrystalline PEs with a melting temperature of approximately 130 °C. Mainly alternating copolymers with high comonomer incorporation were obtained in the E/NB copolymerization. A relationship was found between the electronic and steric properties of the phosphine ligands and the catalytic performance. Overall, the presence of electron-withdrawing ligand substituents increases the productivity, complexes with aryl phosphine (weaker σ-donor character) exhibiting a higher (co)polymerization initiation rate than those with alkyl phosphines (stronger σ-donor character). Steric effects also seem to play a key role since 1d and 1e, having large size phosphines (PCy3 θ = 170° and PtBu3 θ = 182°, respectively) are more active than 1a (PMe2Ph θ = 122°). In this case, the larger size of PtBu3 and PCy3 likely compensates for their higher donor strength compared to PMe2Ph.


Assuntos
Etilenos/química , Norbornanos/química , Fosfinas/química , Vanádio/química , Catálise , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Polimerização
4.
Molecules ; 24(12)2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31234313

RESUMO

Oligonucleotides are key compounds widely used for research, diagnostics, and therapeutics. The rapid increase in oligonucleotide-based applications, together with the progress in nucleic acids research, has led to the design of nucleotide analogs that, when part of these oligomers, enhance their efficiency, bioavailability, or stability. One of the most useful nucleotide analogs is the first-generation bridged nucleic acids (BNA), also known as locked nucleic acids (LNA), which were used in combination with ribonucleotides, deoxyribonucleotides, or other analogs to construct oligomers with diverse applications. However, there is still room to improve their efficiency, bioavailability, stability, and, importantly, toxicity. A second-generation BNA, BNANC (2'-O,4'-aminoethylene bridged nucleic acid), has been recently made available. Oligomers containing these analogs not only showed less toxicity when compared to LNA-containing compounds but, in some cases, also exhibited higher specificity. Although there are still few applications where BNANC-containing compounds have been researched, the promising results warrant more effort in incorporating these analogs for other applications. Furthermore, newer BNA compounds will be introduced in the near future, offering great hope to oligonucleotide-based fields of research and applications.


Assuntos
Hidrocarbonetos Aromáticos com Pontes/química , Oligonucleotídeos/química , Etilenos/química
5.
Mol Biotechnol ; 61(9): 650-662, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31201604

RESUMO

1-Aminocyclopropane carboxylic acid oxidase (ACCO) catalyzes the last step of ethylene biosynthesis in plants. Although some sets of structures have been described, there are remaining questions on the active conformation of ACCO and in particular, on the conformation and potential flexibility of the C-terminal part of the enzyme. Several techniques based on the introduction of a probe through chemical modification of amino acid residues have been developed for determining the conformation and dynamics of proteins. Cysteine residues are recognized as convenient targets for selective chemical modification of proteins, thanks to their relatively low abundance in protein sequences and to their well-mastered chemical reactivity. ACCOs have generally 3 or 4 cysteine residues in their sequences. By a combination of approaches including directed mutagenesis, activity screening on cell extracts, biophysical and biochemical characterization of purified enzymes, we evaluated the effect of native cysteine replacement and that of insertion of cysteines on the C-terminal part in tomato ACCO. Moreover, we have chosen to use paramagnetic labels targeting cysteine residues to monitor potential conformational changes by electron paramagnetic resonance (EPR). Given the level of conservation of the cysteines in ACCO from different plants, this work provides an essential basis for the use of cysteine as probe-anchoring residues.


Assuntos
Aminoácido Oxirredutases/química , Aminoácidos Cíclicos/química , Cisteína/química , Etilenos/química , Lycopersicon esculentum/enzimologia , Óxidos de Nitrogênio/química , Proteínas de Plantas/química , Aminoácido Oxirredutases/genética , Aminoácido Oxirredutases/metabolismo , Substituição de Aminoácidos , Aminoácidos Cíclicos/metabolismo , Sítios de Ligação , Clonagem Molecular , Cisteína/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Escherichia coli/genética , Escherichia coli/metabolismo , Etilenos/biossíntese , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Cinética , Lycopersicon esculentum/química , Modelos Moleculares , Mutagênese Sítio-Dirigida , Óxidos de Nitrogênio/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Marcadores de Spin , Especificidade por Substrato
6.
Phys Chem Chem Phys ; 21(19): 9957-9968, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-31041955

RESUMO

The ethylene-forming enzyme (EFE) is a unique member of the Fe(ii)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenases. It converts 2OG into ethylene plus three CO2 molecules (ethylene-forming reaction) and also catalyzes the C5 hydroxylation of l-arginine coupled to the oxidative decarboxylation of 2OG (l-Arg hydroxylation reaction). To uncover the mechanisms of the dual transformations by EFE, quantum mechanical/molecular mechanical (QM/MM) calculations were carried out. Based on the results, a branched mechanism was proposed. An FeII-peroxysuccinate complex with a dissociated CO2 generated through the nucleophilic attack of the superoxo moiety of the Fe-O2 species on the keto carbon of 2OG is the key common intermediate in both reactions. A competition between the subsequent CO2 insertion (a key step in the ethylene-forming pathway) and the O-O bond cleavage (leading to the formation of succinate) governs the product selectivity. The calculated reaction barriers suggested that the CO2 insertion is favored over the O-O bond cleavage. This is consistent with the product preference observed in experiments. By comparison with the results of AsqJ (an Fe/2OG oxygenase that leads to substrate oxidation exclusively), the protein environment was found to be crucial for the selectivity. Further calculations demonstrated that the local electric field of the protein environment in EFE promotes ethylene formation by acting as a charge template, exemplifying the importance of the electrostatic interaction in enzyme catalysis. These findings offer mechanistic insights into the EFE catalysis and provide important clues for better understanding the unique ethylene-forming capability of EFE compared with other Fe/2OG oxygenases.


Assuntos
Arginina/metabolismo , Etilenos/biossíntese , Ácidos Cetoglutáricos/metabolismo , Liases/metabolismo , Arginina/química , Biocatálise , Teoria da Densidade Funcional , Etilenos/química , Hidroxilação , Ácidos Cetoglutáricos/química , Liases/química , Estrutura Molecular , Oxirredução
7.
Molecules ; 24(8)2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30999618

RESUMO

Suppressing the amount of ethylene during storage has been of interest as a method to enhance shelf life of fruit. In this work, ethylene removal by adsorption using cobalt oxide-impregnated nanoporous carbon has been studied. Nanoporous carbon with a high surface area up to 2400 m2 g-1 was prepared by carbonization process biomass and synthetic polymer at 850 °C. Dispersion of cobalt oxide on porous carbon surface was carried out by an incipient wetness procedure followed by calcination process at 200 °C. Ethylene adsorption test was performed using a volumetric method in an ultrahigh vacuum rig constructed by Swagelok VCR® fittings. The results showed that the cobalt oxide/carbon system had significant ethylene adsorption capacity. Ethylene uptake increases with the increasing cobalt oxide loading on the carbon. The highest ethylene capacity of 16 mol kg-1 adsorbent was obtained by using 30 wt.% (weight percentage) of cobalt oxide dispersed in polymer-derived carbon. In closed storage, the ratio of 15 g adsorbent/kg fruit may extend the storage life up to 12 d, higher than that without adsorbent (3 d). Therefore, the results demonstrate the great potential use of cobalt oxide-impregnated nanoporous carbon as an adsorbent for ethylene removal during storage of fruit.


Assuntos
Cobalto/química , Etilenos/química , Conservação de Alimentos/métodos , Frutas , Óxidos/química , Adsorção , Porosidade
8.
Spectrochim Acta A Mol Biomol Spectrosc ; 218: 171-177, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-30991293

RESUMO

In this work, a novel probe D-HBT-NBD (1O) based on diarylethene to detect biothiols (including Cys, Hcy and GSH) was synthesized and the relative colorimetric and fluorescent properties were tested. The probe exhibited excellent photochromic properties and showed apparent colorimetric and fluorescent signals for Cys, Hcy and GSH. The probe can selectively detect Cys, Hcy and GSH by naked eyes for its open-ring isomer 1O and can discriminate Cys from Hcy/GSH by apparent color change from light orange to dark pink at the closed-ring state under the irradiation of UV light. At the excitation wavelength of 465 nm, the probe could be used to discriminate GSH from Cys/Hcy with no fluorescent emission at 570 nm. Taking advantage of the photochromic property of the diarylethene moiety and the different fluorescent properties of NBD derivatives of GSH and Cys/Hcy, 1O could be used as a novel probe to discriminate Cys, Hcy and GSH from each other simultaneously. Meanwhile, a logic gate was constructed based on the colorimetric and fluorescent properties of 1O.


Assuntos
Cisteína/análise , Etilenos/química , Corantes Fluorescentes/química , Glutationa/análise , Homocisteína/análise , Técnicas de Química Sintética , Colorimetria/métodos , Etilenos/síntese química , Corantes Fluorescentes/síntese química , Espectrometria de Fluorescência/métodos
9.
Methods Mol Biol ; 1973: 59-89, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31016696

RESUMO

This chapter describes procedures for (1) the synthesis of six 2'-C,4'-C-ethyleneoxy-bridged thymidine phosphoramidites, i.e., methylene-EoDNA-T, (R)-Me-methylene-EoDNA-T, (S)-Me-methylene-EoDNA-T, EoDNA-T, (R)-Me-EoDNA-T, and (S)-Me-EoDNA-T phosphoramidites, (2) the introduction of the phosphoramidites into oligonucleotides, (3) UV-melting experiments of the duplexes of the modified oligonucleotides and complementary RNA, and (4) nuclease degradation experiments of the modified oligonucleotides.


Assuntos
Compostos Bicíclicos com Pontes/química , DNA/biossíntese , DNA/química , Desoxirribonucleases/metabolismo , Etilenos/química , Timina/química , Estabilidade Enzimática
10.
Int J Mol Sci ; 20(7)2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30939780

RESUMO

donor⁻acceptorDonor⁻acceptor⁻π⁻acceptor⁻donor (D1-A1-π-A2/A3-D2)-type small molecules, such TPA-MC-2 and TPA-MC-3, were designed and synthesized starting from donor-substituted alkynes (TPA-MC-1) via [2 + 2] cycloaddition-retroelectrocyclization reaction with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) units, respectively. TPA-MC-2 and TPA-MC-3 chromophores differ on the A2/A3 acceptor subunit, which is 1,1,4,4-tetracyanobutadiene (TCBD) and a dicyanoquinodicyanomethane (DCQDCM), respectively. Both the derivative bearing same donors D1 (triphenylamine) and D2 (trimethylindolinm) and also same A1 (monocyano) as an acceptor, tetracyano with an aryl rings as the π-bridging moiety. The incorporation of TCNE and TCNQ as strong electron withdrawing units led to strong intramolecular charge-transfer (ICT) interactions, resulting in lower LUMO energy levels. Comparative UV⁻Vis absorption, fluorescence emission, and electrochemical and computational studies were performed to understand the effects of the TCNE and TCNQ subunits incorporated on TPA-MC-2 and TPA-MC-3, respectively.


Assuntos
Compostos de Anilina/química , Benzopiranos/química , Reação de Cicloadição/métodos , Elétrons , Indóis/química , Absorção de Radiação , Etilenos/química , Nitrilos/química , Raios Ultravioleta
11.
Molecules ; 24(6)2019 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-30909457

RESUMO

Ethylene is a classical plant hormone and has appeared as a strong molecule managing many physiological and morphological reactions during the life of a plant. With laser-based photoacoustic spectroscopy, ethylene can be identified with high sensitivity, at a high rate and with very good selectivity. This research presents the dynamics of trace gases molecules for ethylene released by cherry flowers, apple flowers and strawberry flowers. The responses of distinctive organs to ethylene may fluctuate, depending on tissue sensitivity and the phase of plant development. From the determinations of this study, the ethylene molecules at the flowers in the nitrogen flow were established in lower concentrations when the value is correlated to the ethylene molecules at the flowers in synthetic air flow.


Assuntos
Etilenos/química , Flores/química , Frutas/química , Respiração Celular , Etilenos/análise , Flores/metabolismo , Frutas/metabolismo , Reguladores de Crescimento de Planta/análise , Reguladores de Crescimento de Planta/química , Análise Espectral
12.
Phytopathology ; 109(7): 1102-1114, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30880572

RESUMO

Tomato gray mold disease caused by Botrytis cinerea is a serious disease that threatens tomato production around the world. Clonostachys rosea has been used successfully as a biocontrol agent against divergent plant pathogens, including B. cinerea. To understand the signal transduction pathway of C. rosea-induced resistance to tomato gray mold disease, the effects of C. rosea on gray mold tomato leaves along with changes in the activities of three defense enzymes (phenylalanine ammonialyase [PAL], polyphenol oxidase [PPO], and catalase [CAT]), second messengers (nitric oxide [NO], hydrogen peroxide [H2O2], and superoxide anion radical [O2-]), and stress-related genes (mitogen-activated protein kinase [MAPK], WRKY, Lexyl2, and atpA) in four different hormone-deficient (jasmonic acid [JA], ethylene [ET], salicylic acid [SA], and gibberellin) tomato mutants were investigated. The results revealed that C. rosea significantly inhibited the growth of mycelia and spore germination of B. cinerea. Furthermore, it reduced the incidence of gray mold disease, induced higher levels of PAL and PPO, and induced lower levels of CAT activities in tomato leaves. Moreover, it also increased NO, H2O2, and O2- levels and the gene expression levels of WRKY, MAPK, atpA, and Lexyl2. The incidence of gray mold disease in four hormone-deficient mutants was higher than that in the corresponding wild-type tomato plants. Among all of these hormone-deficient tomato mutants, JA had the most significant effect in regulating the different signal molecules. Additional study suggested that JA upregulated the expression of Lexyl2, MAPK, and WRKY but downregulated atpA. Furthermore, JA also enhanced the activity of PAL, PPO, and CAT and the production of NO and H2O2. SA downregulated CAT and PAL, whereas ET upregulated PAL but downregulated CAT. This study is of significance in understanding the regulatory pathways and biocontrol mechanism of C. rosea against B. cinerea.


Assuntos
Ciclopentanos/farmacologia , Peróxido de Hidrogênio/química , Lycopersicon esculentum , Oxilipinas/farmacologia , Ácido Salicílico/farmacologia , Botrytis , Ciclopentanos/química , Etilenos/química , Oxilipinas/química , Doenças das Plantas , Transdução de Sinais
13.
Macromol Rapid Commun ; 40(11): e1900015, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30892758

RESUMO

Ultrathin single crystal γ-Al(OH)3 (Gibbsite) nanoplatelets with average thickness <20 nm and length <800 nm, pretreated with trimethylaluminum (TMA), represent highly efficient activators and supports bis(imino)pyridine iron (II) (FeBIP) complex to produce high density polyethylene (HDPE) as well as gibbsite/HDPE nanocomposites in exceptionally high yields. Opposite to both methylaluminoxane (MAO)-activated homogeneous FeBIP catalyst and heterogenous silica-supported single site catalysts, no addition of MAO is required. At low TMA/Fe = 50 molar ratio, the superior catalyst activity (up to 6500 kg mol-1 h-1 bar-1 ) of FeBIP@TMA@Gibbsite is paralleled by controlled polyethylene particle growth without encountering reactor-fouling problems typical for homogeneous catalysts. TMA@Gibbsite is compared with other AlR3 @Gibbsite activators. The Al/Fe molar ratio governs catalyst activity as well as molar mass, molar mass distribution, and thermal properties of polyethylene. Moreover, hexagonal gibbsite nanoplatelets are uniformly dispersed in polyethylene to yield agglomerate-free polyethylene/gibbsite nanocomposites.


Assuntos
Etilenos/química , Ferro/química , Nanocompostos/química , Nanotecnologia/métodos , Polímeros/química , Catálise
14.
Org Lett ; 21(5): 1538-1541, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30779589

RESUMO

A ketene [2 + 2]-addition, an intramolecular aldol reaction, a Suzuki-Miyaura coupling, and a chemoselective lactam reduction were used to prepare a late-stage precursor of haouamine A. Exposure to acid led to a Grob-type fragmentation of the strained 3-aza[7]paracyclophane ring, followed by a tandem Pictet-Spengler reaction of the intermediate iminium ion and conversion to a novel 1,4a-propanocyclopenta[ b]pyridine. This cascade reaction might also be relevant for the mechanism of action of the natural product.


Assuntos
Aldeídos/química , Etilenos/química , Compostos Heterocíclicos de 4 ou mais Anéis/química , Cetonas/química , Piridinas/química , Estrutura Molecular
15.
J Chromatogr A ; 1593: 73-80, 2019 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-30718060

RESUMO

A series of ethylene/1-octene copolymers with different chemical composition was separated in six binary mobile phases using solvent gradients and a column packed with porous graphite Hypercarb™. It was found that the elution volumes of the samples were to a larger extent influenced by the choice of desorption promoting solvent (desorli: 1,2-dichlorobenzene vs. 1,2,4-trichlorobenzene) than by the choice of adsorption promoting solvent (2-ethyl-1-hexanol, 1-decanol, n-decane). Elution volumes increased with decreasing number of chlorine atoms in the desorlis as well as with increasing polarity of the adsorlis. The resolution of HPLC systems depended pronouncedly on the choice of solvent pair: While in the majority of the tested HPLC systems, the chromatograms of the polymer samples indicate a shoulder, in n-decane→TCB the samples eluted without indication of a shoulder. In addition to the influence of different solvents on the samples elution behavior, the response of the employed detector, an evaporative light scattering detector (ELSD), was investigated. Its response was found to depend pronouncedly on the nature of the used solvents. Overall, the solvent pair 1-decanol→TCB appears to be the optimal compromise between the considered parameters and thus the best choice for HPLC of ethylene/1-octene copolymers.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Elastômeros/química , Polienos/química , Solventes/química , Alcenos/química , Etilenos/química , Polímeros/química
16.
Org Lett ; 21(3): 758-761, 2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30632762

RESUMO

The C3-C21 segment of aflastatin A has been synthesized by converging three segments including the C3-C8 segment, the C9-C15 segment, and the C16-C21 segment. Each segment has been synthesized from a vinylketene silyl N,O-acetal possessing a chiral auxiliary by a wide-range stereocontrol strategy. The C3-C8 segment was constructed in seven steps including the stereoselective vinylogous Mukaiyama alkylation, while the C9-C15 segment and the C16-C21 segment were synthesized using the vinylogous Mukaiyama aldol reaction in seven and eight steps, respectively.


Assuntos
Cetonas , Pirrolidinonas , Técnicas de Química Sintética , Etilenos/química , Cetonas/química , Pirrolidinonas/síntese química , Pirrolidinonas/química , Estereoisomerismo
17.
J Chromatogr A ; 1585: 192-195, 2019 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-30482432

RESUMO

This study demonstrated a novel method for determining the melting point (MP) of industrial grade alkyl ketene dimer (AKD) wax by an automated headspace gas chromatographic (HS-GC) technique, in which methanol was used as the tracer. It was based on measuring the GC signal of methanol released from an aqueous solution during the temperature increasing. When the temperature of AKD MP reached, the AKD granules floated on the surface aqueous solution was liquidized and completely isolated the methanol transfer from the solution to the headspace. Thus, a transition point, corresponding to the MP of AKD wax, was observed when plotting the GC signal of methanol vs. the temperature. The results showed that the method has a good measurement precision (RSD < 0.68%) and accuracy (the relative differences were < 7.16%, compared to a reference method). The present method is simple, accurate and particularly suitable to be used in the batch sample testing. This new measurement concept can be also adopted to many related applications.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Gasosa , Etilenos/química , Cetonas/química , Temperatura de Transição , Ceras/química , Técnicas de Química Analítica/instrumentação , Reprodutibilidade dos Testes
18.
Spectrochim Acta A Mol Biomol Spectrosc ; 211: 166-177, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30537628

RESUMO

In our previous work, we highlighted the thermodynamic and spectroscopic characteristics of the 1:1 charge transfer (CT) complexation of TCNE acceptor with various medically important drugs. Continuing that work, we further examine drugs that react with the TCNE acceptor via a 1:2 interaction. The examined drugs are atenolol, quinidine, cimetidine, reserpine, and levofloxacin. We aimed through this study to: i) make the spectrophotometric and thermodynamic data of the examined drugs, both initially and when reacted via a 1:2 M ratio with the TCNE acceptor, available to use in the determination or detection of these drugs in pharmaceuticals and other environments; and ii) compare the mode of interactions and the spectrophotometric and thermodynamic properties between drugs that react via a 1:1 or 1:2 ratio with the TCNE acceptor. To achieve these aims, the five examined drugs were reacted with TCNE in acetonitrile (MeCN) solvent at room temperature. Several thermodynamic and spectroscopic data were experimentally estimated using the van't Hoff and the Benesi-Hildebrand equations and discussed.


Assuntos
Etilenos/química , Nitrilos/química , Preparações Farmacêuticas/química , Acetonitrilos/química , Atenolol/química , Cimetidina/química , Levofloxacino/química , Quinidina/química , Reserpina/química , Solventes/química , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , Termodinâmica
19.
J Colloid Interface Sci ; 533: 207-215, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30165298

RESUMO

A novel gas storage and release system was developed for ethylene, an exogenous plant hormone that regulates fruit ripening and senescence. This system consists of a metal organic framework (MOF) core and an alginate-based shell. The MOF comprises a coordination complex of Al and [btc]3- ligands, which formed hexagonal structure (P63/mmc) with unit cell of 14.28 × 14.28 × 31.32 Å3, as revealed by the X-ray diffraction analysis. Ethylene absorption isotherm exhibited an absorption capacity of 41.0 cm3/g MOF at 25 °C and 101.3 kPa. After charging with ethylene, the MOFs are further entrapped in a close-knit bead formed with alginate-Fe(III) matrix, observed under a scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The alginate shell is degraded by exposing to 200 mM sodium citrate aqueous solution, triggering a continuous release of ethylene. With 20 mg of MOF, ethylene concentration reached 0.41-0.46 mg/L per mg MOF after 2.5 h. This is the first report regarding a controlled release of ethylene through degrading alginate-Fe(III) matrix rather than by changing the interfacial pore size of MOF under extreme conditions. This technology can enable precisely controlled and targeted applications of ethylene for food processing and agricultural applications.


Assuntos
Alumínio/química , Derivados de Benzeno/química , Etilenos/isolamento & purificação , Estruturas Metalorgânicas/química , Etilenos/química , Ligantes , Tamanho da Partícula , Propriedades de Superfície
20.
Phys Chem Chem Phys ; 21(7): 3637-3643, 2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30379159

RESUMO

DNA binding modes of the stereoisomeric rotamers of two dithenylethene derivatives (DTE1 and DTE2) representing candidate molecular photoswitches of great promise for photopharmacology and nanotechnology have been identified and characterized in terms of their binding energies and electronic circular dichroism (CD) responses. In the open form, two binding modes are identified namely minor-groove binding of the lowest-energy conformer with an anti-parallel arrangement of methyl groups and major-groove double-intercalation of the P-enantiomers of an intermediate-state rotamer. Only the latter binding mode is found to be enantiomerically selective and expected to have an overall negative linear dichroism (LD) as observed in the experiment for DTE1 (Angew. Chem., Int. Ed., 2013, 52, 4393). In the closed form, the most favorable binding mode is found to be minor groove binding. Also this binding mode is found to be enantiomerically selective and for DTE1, it is the M-enantiomer that binds the strongest, showing a positive theoretical signature CD band in the long wavelength region with origin in pyridinium ligands. The theoretical CD spectrum is found to be in good agreement with the experimental one, which provides an indirect evidence for a correct identification of the binding mode in the closed form.


Assuntos
Dicroísmo Circular , DNA/química , Etilenos/química , Simulação de Dinâmica Molecular
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