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1.
Biomol NMR Assign ; 14(2): 329-333, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32770392

RESUMO

The ongoing pandemic caused by the Betacoronavirus SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2) demonstrates the urgent need of coordinated and rapid research towards inhibitors of the COVID-19 lung disease. The covid19-nmr consortium seeks to support drug development by providing publicly accessible NMR data on the viral RNA elements and proteins. The SARS-CoV-2 genome encodes for approximately 30 proteins, among them are the 16 so-called non-structural proteins (Nsps) of the replication/transcription complex. The 217-kDa large Nsp3 spans one polypeptide chain, but comprises multiple independent, yet functionally related domains including the viral papain-like protease. The Nsp3e sub-moiety contains a putative nucleic acid-binding domain (NAB) with so far unknown function and consensus target sequences, which are conceived to be both viral and host RNAs and DNAs, as well as protein-protein interactions. Its NMR-suitable size renders it an attractive object to study, both for understanding the SARS-CoV-2 architecture and drugability besides the classical virus' proteases. We here report the near-complete NMR backbone chemical shifts of the putative Nsp3e NAB that reveal the secondary structure and compactness of the domain, and provide a basis for NMR-based investigations towards understanding and interfering with RNA- and small-molecule-binding by Nsp3e.


Assuntos
Betacoronavirus/metabolismo , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Isótopos de Nitrogênio/química , Ácidos Nucleicos/metabolismo , Espectroscopia de Prótons por Ressonância Magnética , Proteínas não Estruturais Virais/química , Ligação Proteica , Domínios Proteicos
2.
Biomol NMR Assign ; 14(2): 339-346, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32803496

RESUMO

The SARS-CoV-2 genome encodes for approximately 30 proteins. Within the international project COVID19-NMR, we distribute the spectroscopic analysis of the viral proteins and RNA. Here, we report NMR chemical shift assignments for the protein Nsp3b, a domain of Nsp3. The 217-kDa large Nsp3 protein contains multiple structurally independent, yet functionally related domains including the viral papain-like protease and Nsp3b, a macrodomain (MD). In general, the MDs of SARS-CoV and MERS-CoV were suggested to play a key role in viral replication by modulating the immune response of the host. The MDs are structurally conserved. They most likely remove ADP-ribose, a common posttranslational modification, from protein side chains. This de-ADP ribosylating function has potentially evolved to protect the virus from the anti-viral ADP-ribosylation catalyzed by poly-ADP-ribose polymerases (PARPs), which in turn are triggered by pathogen-associated sensing of the host immune system. This renders the SARS-CoV-2 Nsp3b a highly relevant drug target in the viral replication process. We here report the near-complete NMR backbone resonance assignment (1H, 13C, 15N) of the putative Nsp3b MD in its apo form and in complex with ADP-ribose. Furthermore, we derive the secondary structure of Nsp3b in solution. In addition, 15N-relaxation data suggest an ordered, rigid core of the MD structure. These data will provide a basis for NMR investigations targeted at obtaining small-molecule inhibitors interfering with the catalytic activity of Nsp3b.


Assuntos
Adenosina Difosfato Ribose/metabolismo , Apoproteínas/química , Betacoronavirus/metabolismo , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Isótopos de Nitrogênio/química , Espectroscopia de Prótons por Ressonância Magnética , Proteínas não Estruturais Virais/química , Sequência de Aminoácidos , Apoproteínas/metabolismo , Domínios Proteicos , Estrutura Secundária de Proteína , Proteínas não Estruturais Virais/metabolismo
3.
PLoS Biol ; 18(6): e3000728, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32516311

RESUMO

The development of multicellularity is a key evolutionary transition allowing for differentiation of physiological functions across a cell population that confers survival benefits; among unicellular bacteria, this can lead to complex developmental behaviors and the formation of higher-order community structures. Herein, we demonstrate that in the social δ-proteobacterium Myxococcus xanthus, the secretion of a novel biosurfactant polysaccharide (BPS) is spatially modulated within communities, mediating swarm migration as well as the formation of multicellular swarm biofilms and fruiting bodies. BPS is a type IV pilus (T4P)-inhibited acidic polymer built of randomly acetylated ß-linked tetrasaccharide repeats. Both BPS and exopolysaccharide (EPS) are produced by dedicated Wzx/Wzy-dependent polysaccharide-assembly pathways distinct from that responsible for spore-coat assembly. While EPS is preferentially produced at the lower-density swarm periphery, BPS production is favored in the higher-density swarm interior; this is consistent with the former being known to stimulate T4P retraction needed for community expansion and a function for the latter in promoting initial cell dispersal. Together, these data reveal the central role of secreted polysaccharides in the intricate behaviors coordinating bacterial multicellularity.


Assuntos
Myxococcus xanthus/citologia , Myxococcus xanthus/metabolismo , Polissacarídeos Bacterianos/metabolismo , Acetilação , Vias Biossintéticas/genética , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Membrana Celular/metabolismo , Família Multigênica , Myxococcus xanthus/genética , Polissacarídeos Bacterianos/química , Espectroscopia de Prótons por Ressonância Magnética , Tensoativos/metabolismo
4.
Nat Commun ; 11(1): 3135, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32561713

RESUMO

It is commonly thought that when multiple carbon sources are available, bacteria metabolize them either sequentially (diauxic growth) or simultaneously (co-utilization). However, this view is mainly based on analyses in relatively simple laboratory settings. Here we show that a heterotrophic marine bacterium, Pseudoalteromonas haloplanktis, can use both strategies simultaneously when multiple possible nutrients are provided in the same growth experiment. The order of nutrient uptake is partially determined by the biomass yield that can be achieved when the same compounds are provided as single carbon sources. Using transcriptomics and time-resolved intracellular 1H-13C NMR, we reveal specific pathways for utilization of various amino acids. Finally, theoretical modelling indicates that this metabolic phenotype, combining diauxie and co-utilization of substrates, is compatible with a tight regulation that allows the modulation of assimilatory pathways.


Assuntos
Carbono/metabolismo , Processos Heterotróficos/fisiologia , Modelos Biológicos , Pseudoalteromonas/fisiologia , Biomassa , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Meios de Cultura/metabolismo , Cinética , Espectroscopia de Prótons por Ressonância Magnética
5.
PLoS One ; 15(5): e0232765, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32365099

RESUMO

The water-soluble fullerenols are novel carbon-based nanomaterials with unique properties, which afford them with wide agricultural applications. Iron (Fe) deficiency is the most common and widespread nutrition disorder affecting plants. Foliar Fe treatments of plants have been carried out with solutions devoid of fullerenol. In this study, the role of fullerenol [C60(OH)22-24] in alleviation of Fe deficiency in Cucumis sativus (a Strategy I plant) via foliar fertilization was investigated. Cucumber plants were grown hydroponically, either with (Fe) or in Fe-free (-Fe) nutrient solution. The following foliar spray treatments were applied: fullerenol at final concentrations of 1 (F1) and 10 (F10) mg L-1; Fe(II)SO4·7H2O; Fe(II)-EDTA (ethylenediaminetetraacetic acid); and Fe(II)-F1 and Fe(II)-F10. The best used compound was a combination of Fe(II)-sulfate with fullerenol, especially Fe-F1. The addition of fullerenol to Fe(II)-sulfate solutions significantly increased leaf-active Fe (extracted by an Fe(II) chelator) and re-greening at the site of application. The fullerenol-induced mutual influences did not appear when fullerenol was sprayed alone, suggesting a beneficial role of Fe(II)-fullerenol interactions in the penetration of Fe(II) in the leaves and re-greening under Fe-limited conditions. The results are of importance to enhancing the potential of foliar Fe fertilization as the commonly used strategy for ameliorating Fe deficiency and improving crop yield and quality.


Assuntos
Cucumis sativus/metabolismo , Fulerenos/farmacologia , Ferro/deficiência , Folhas de Planta/metabolismo , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Clorofila/metabolismo , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/crescimento & desenvolvimento , Hidroponia , Tamanho da Partícula , Folhas de Planta/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Espectrofotometria Infravermelho , Eletricidade Estática
6.
J Chromatogr A ; 1621: 461081, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32349863

RESUMO

The chemical composition distribution (CCD) of three single site made ethylene/1-octene copolymers was investigated through offline-hyphenation of solvent gradient interaction chromatography (SGIC) with 1H NMR. Thus, a clear, non-linear correlation between SGIC elution time and chemical composition was found under the specific measurement conditions applied here. The application of 1H NMR as detection allowed to determine the CCD with unprecedented accuracy. 2D-LC of the copolymers revealed the correlation between CCD and molar mass distribution (MMD) in a quantitative manner. Furthermore, this approach allowed a comparison between the response behavior of an evaporative light scattering detector (ELSD, semi-quantitative, commonly applied in SGIC) and that of an infrared (IR) detector (quantitative, commonly applied in SEC). As a result, it could be shown that ELSD results are close to IR results for the system investigated here, in other words, the often-criticized semi-quantitative response behavior of the ELSD is affecting results in an acceptable manner.


Assuntos
Alcenos/análise , Cromatografia Líquida de Alta Pressão/métodos , Elastômeros/análise , Etilenos/análise , Polienos/análise , Calibragem , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Elastômeros/química , Peso Molecular , Espectroscopia de Prótons por Ressonância Magnética , Solventes/química , Temperatura , Fatores de Tempo
7.
Phys Chem Chem Phys ; 22(12): 6572-6583, 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-32159206

RESUMO

The outermost layer of the skin is the stratum corneum (SC), which is mainly comprised of solid proteins and lipids. Minor amounts of mobile proteins and lipids are crucial for the macroscopic properties of the SC, including softness, elasticity and barrier function. Still this minor number of mobile components are not well characterized in terms of structure or amount. Conventional quantitative direct polarization (Q-DP) 13C solid-state NMR gives signal amplitudes proportional to concentrations, but fails to quantify the SC mobile components because of spectral overlap with the overwhelming signals from the solids. Spectral editing with the INEPT scheme suppresses the signals from solids, but also modulates the amplitudes of the mobile components depending on their values of the transverse relaxation times T2, scalar couplings JCH, and number of covalently bound hydrogens nH. This study describes a quantitative INEPT (Q-INEPT) method relying on systematic variation of the INEPT timing variables to estimate T2, JCH, nH, and amplitude for each of the resolved resonances from the mobile components. Q-INEPT is validated with a series of model systems containing molecules with different hydrophobicity and dynamics. For selected systems where Q-DP is applicable, the results of Q-INEPT and Q-DP are similar with respect to the linearity and uncertainty of the obtained molar ratios. Utilizing a reference compound with known concentration, we quantify the concentrations of mobile lipids and proteins within the mainly solid SC. By melting all lipids at high temperature, we obtain the total lipid concentration. These Q-INEPT results are the first steps towards a quantitative understanding of the relations between mobile component concentrations and SC macroscopic properties.


Assuntos
Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Epiderme/diagnóstico por imagem , Lipídeos/análise , Proteínas/análise , Humanos
8.
J Vis Exp ; (156)2020 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-32116307

RESUMO

Heteroarylation introduces heteroaryl fragments to organic molecules. Despite the numerous available reactions reported for arylation via transition metal catalysis, the literature on direct heteroarylation is scarce. The presence of heteroatoms such as nitrogen, sulfur and oxygen often make heteroarylation a challenging research field due to catalyst poisoning, product decomposition and the rest. This protocol details a highly efficient direct α-C(sp3) heteroarylation of ketones under microwave irradiation. Key factors for successful heteroarylation include the use of XPhos Palladacycle Gen. 4 Catalyst, excess base to suppress side reactions and the high temperature and pressure achieved in a sealed reaction vial under microwave irradiation. The heteroarylation compounds prepared by this method were fully characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR) and high-resolution mass spectrometry (HRMS). This methodology has several advantages over literature precedents including broad substrate scope, rapid reaction time, greener procedure and operational simplicity by eliminating the preparation of intermediates such as silyl enol ether. Possible applications for this protocol include, but are not limited to, diversity-oriented synthesis for the discovery of biologically active small molecules, domino synthesis for the preparation of natural products and ligand development for new transition metal catalytic systems.


Assuntos
Cetonas/síntese química , Metais/química , Micro-Ondas , Elementos de Transição/química , Compostos Inorgânicos de Carbono/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Catálise , Cromatografia , Cetonas/química , Paládio/química , Espectroscopia de Prótons por Ressonância Magnética , Compostos de Silício/química , Temperatura
9.
Biochemistry ; 59(7): 901-910, 2020 02 25.
Artigo em Inglês | MEDLINE | ID: mdl-32022556

RESUMO

Hydrogen tunneling in enzymatic C-H activation requires a dynamical sampling among ground-state enzyme-substrate (E-S) conformations, which transiently generates a tunneling-ready state (TRS). The TRS is characterized by a hydrogen donor-acceptor distance (DAD) of 2.7 Å, ∼0.5 Å shorter than the dominant DAD of optimized ground states. Recently, a high-resolution, 13C electron-nuclear double-resonance (ENDOR) approach was developed to characterize the ground-state structure of the complex of the linoleic acid (LA) substrate with soybean lipoxygenase (SLO). The resulting enzyme-substrate model revealed two ground-state conformers with different distances between the target C11 of LA and the catalytically active cofactor [Fe(III)-OH]: the active conformer "a", with a van der Waals DAD of 3.1 Å between C11 and metal-bound hydroxide, and an inactive conformer "b", with a distance that is almost 1 Å longer. Herein, the structure of the E-S complex is examined for a series of six variants in which subtle structural modifications of SLO have been introduced either at a hydrophobic side chain near the bound substrate or at a remote residue within a protein network whose flexibility influences hydrogen transfer. A remarkable correlation is found between the ENDOR-derived population of the active ground-state conformer a and the kinetically derived differential enthalpic barrier for D versus H transfer, ΔEa, with the latter increasing as the fraction of conformer a decreases. As proposed, ΔEa provides a "ruler" for the DAD within the TRS. ENDOR measurements further corroborate the previous identification of a dynamical network coupling the buried active site of SLO to the surface. This study shows that subtle imperfections within the initial ground-state structures of E-S complexes are accompanied by compromised geometries at the TRS.


Assuntos
Ácido Linoleico/química , Lipoxigenase/química , Soja/enzimologia , Isótopos de Carbono/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Hidrogênio/química , Lipoxigenase/genética , Mutação , Conformação Proteica
10.
Chemphyschem ; 21(3): 251-256, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31922367

RESUMO

The promise of hyperpolarized glucose as a non-radioactive imaging agent capable of reporting on multiple metabolic routes has led to recent advances in its dissolution-DNP (dDNP) driven polarization using UV-light induced radicals and trityl radicals at high field (6.7 T) and 1.1 K. However, most preclinical dDNP polarizers operate at the field of 3.35 T and 1.4-1.5 K. Minute amounts of Gd3+ complexes have shown large improvements in solid-state polarization, which can be translated to improved hyperpolarization in solution. However, this Gd3+ effect seems to depend on magnetic field strength, metal ion concentration, and sample formulation. The effect of varying Gd3+ concentrations at 3.35 T has been described for 13 C-labeled pyruvic acid and acetate. However, it has not been studied for other compounds at this field. The results presented here suggest that Gd3+ doping can lead to various concentration and temperature dependent effects on the polarization of [13 C6 ,2 H7 ]glucose, not necessarily similar to the effects observed in pyruvic acid or acetate in size or direction. The maximal polarization for [13 C6 ,2 H7 ]glucose appears to be at a Gd3+ concentration of 2 mM, when irradiating for more than 2 h at the negative maximum of the DNP intensity profile. Surprisingly, for shorter irradiation times, higher polarization levels were determined at 1.50 K compared to 1.45 K, at a [Gd3+ ]=1.3 mM. This was explained by the build-up time constant and maximum at these temperatures.


Assuntos
Gadolínio/química , Glucose/química , Isótopos de Carbono , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Deutério , Ácido Pirúvico/química
11.
J Chromatogr A ; 1609: 460438, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31447207

RESUMO

Plants are an important source of natural iridoids. This study demonstrates for the first time the acetylcholinesterase (AChE) inhibitory activity of iridoids belonging to the class of antirrhinosides. As iridoids distinguish the chemical composition of most species of the Plantaginaceae family, the active AChE inhibitors were investigated in the hydro-alcoholic extract of Anarrhinum pubescens Fresen. High-performance thin-layer chromatography (HPTLC) in combination with the AChE inhibition assay is a time and material saving methodology, and thus was employed to directly point to the individual enzyme inhibitors occurring in the plant. The effect-directed screening successfully discovered three active metabolites. These were characterized as antirrhinoside-derived iridoids. Two of these are here reported as newly isolated natural compounds. Identification of the two new metabolites was based on analysis of their collected spectroscopic data (HRMS, 1D and 2D NMR). Their structures were elucidated to be 6-O-, 6'-O-di-trans-cinnamoyl-antirrhinoside (1) and 5-O-, 6-O-difoliamenthoyl-antirrhinoside (3), while the previously known compound 6-O-foliamenthoyl-(6'-O-cinnamoyl)-antirrhinoside (2) was assigned by extensive analysis of its HRMS and HRMS/MS data. The activity of the isolated compounds was referred to the known AChE inhibitor rivastigmine, i.e. their activity were calculated and expressed as values equivalently to rivastigmine. This neuroprotective potential of iridoids mediated through AChE inhibition promote them to compete as natural curatives for neurodegenerative disorders like Alzheimer's disease.


Assuntos
Acetilcolinesterase/análise , Cromatografia em Camada Delgada/métodos , Ensaios Enzimáticos/métodos , Glucosídeos Iridoides/isolamento & purificação , Plantaginaceae/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Inibidores da Colinesterase/análise , Inibidores da Colinesterase/farmacologia , Fluorescência , Glucosídeos Iridoides/farmacologia , Metaboloma , Espectroscopia de Prótons por Ressonância Magnética
13.
J Chromatogr A ; 1611: 460604, 2020 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-31676090

RESUMO

From the analytical chemistry point-of-view, an ideal sample preparation method should be simple, rapid, automatic, selective, precise, exhaustive, reproducible and protect the analyte-of-interest from degradation. In this study, a novel sample preparation method, named pressurized matrix solid-phase dispersion (p-MSPD) extraction was developed for simultaneously extracting, separating, purifying, isolating, and analyzing endogenous components in a solid sample matrix. Etlingera elatior, a traditional medicinal plant known as the torch ginger, was applied as a sample matrix to evaluate the p-MSPD process. The entire extraction, separation, isolation, fractionation and detection were performed automatically with a commercial LC-MS system. The novel method was satisfactorily applied for the preparation of real samples without optimization, which had the ability to selectively isolate pure compounds from the solid sample matrix for further NMR analysis. Therefore, the method is recommended for quality control of traditional medicines, research efforts when sample amounts are limited, and laboratories that have ordinary LC-MS instrumentation.


Assuntos
Cromatografia Líquida/métodos , Espectrometria de Massas/métodos , Compostos Fitoquímicos/isolamento & purificação , Extração em Fase Sólida/métodos , Zingiberaceae/química , Automação , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Fracionamento Químico , Compostos Fitoquímicos/química , Espectroscopia de Prótons por Ressonância Magnética
14.
J Chromatogr A ; 1609: 460435, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31515075

RESUMO

Azolla imbricata (Roxb.) Nakai is used as a traditional Chinese medicine. However, very limited information is available on its effective components. Traditional procedures for discovering natural bioactive compounds, especially for minor ones, are usually time-consuming and labor-intensive. Therefore, an efficient approach using ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS) combined with multicomponent knockout and bioactivity evaluation was developed to obtain more information about the bioactive constituents in A. imbricata. A total of 93 compounds were identified or tentatively identified, including five major components knocked out by semi-preparative HPLC and 88 minor components in the extract with the major components' knockout. These compounds involved chlorogenic acid derivatives, flavonoids, cinnamoyltyrosine derivatives, cinnamic acid derivatives, fatty acids and their derivatives, coumarins, lignans, and chromones. Eighty-two compounds have not been previously reported in the literature for this species, including a new flavanol derivative named brainin D. Among them, 64 compounds, including brainin D, exhibited antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl radical (DPPH)-UHPLC-MS as guidance. The new antioxidant, brainin D, was concomitantly isolated and unequivocally identified by spectroscopic methods, and it showed good DPPH radical activity with an IC50 value of 9.3 ±â€¯0.6 µg/mL. In conclusion, the proposed combination approach can be used for systematic identification of minor constituents and guided isolation of new compounds from natural sources with high efficiency. The comprehensive understanding of the minor constituents and antioxidants in A. imbricata lays the foundation for further rational utilization of this medicinal herb.


Assuntos
Antioxidantes/isolamento & purificação , Bioensaio/métodos , Cromatografia Líquida/métodos , Polypodiaceae/química , Espectrometria de Massas em Tandem/métodos , Antioxidantes/análise , Compostos de Bifenilo/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Ácido Clorogênico/análise , Cinamatos/análise , Ácidos Graxos/análise , Flavonoides/análise , Picratos/química , Extratos Vegetais/química , Espectroscopia de Prótons por Ressonância Magnética
15.
J Chromatogr A ; 1609: 460514, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31561969

RESUMO

Quantitative structure - retention relationships analysis was applied to investigate the molecular retention mechanism of proteinogenic and non-proteinogenic amino acids on the amino acid- and peptide-silica stationary phases. Twelve stationary phases with chemically bonded amino acids of different types (glycine, alanine, phenylalanine, leucine, methionine, aspartic acid, and N-(9-Fluorenylmethoxycarbonyl)-O-tert-butyl-l-tyrosine) and chains lengths (amino acid, dipeptide, and tripeptide) were tested. In order to compare chromatographic properties of the prepared materials with the conventional columns, the amino-bonded phases (laboratory-prepared and commercial one) were also studied. For each of analyte, the molecular descriptors were calculated using quantum mechanics method. The QSRR models were determined using 13 molecular descriptors mainly related to the surface area, hydrophobicity, polarity, ion-exchange and hydrogen bonding capabilities of the analytes. Finally, the prediction potency of the molecular modeling descriptors-based models was also independently studied for the tested stationary phases using 15 training set and 6 test set of amino acids.


Assuntos
Aminoácidos/química , Cromatografia Líquida/métodos , Peptídeos/química , Dióxido de Silício/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Concentração de Íons de Hidrogênio , Análise de Regressão
16.
Magn Reson Chem ; 58(2): 198-203, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31692051

RESUMO

The exquisitely cytotoxic macrolides, satratoxins G and H, have been reisolated from a solvent extract of a rice culture inoculated with Stachybotrys chartarum to be used as high-purity reference compounds for analytical analyses. Extensive chromatographic separation realized the compounds that were fully recharacterized in two solvents by 1D- and 2D-NMR spectroscopy, revealing some discrepancies in the nuclear magnetic resonance (NMR) data as compared with the previously reported values found in the literature. Detailed spectra are provided in order to aid future identification and dereplication.


Assuntos
Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Espectroscopia de Prótons por Ressonância Magnética/métodos , Tricotecenos/química , Oryza/microbiologia , Stachybotrys/metabolismo
17.
Int J Biol Macromol ; 144: 143-150, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31843606

RESUMO

Herein we describe the interaction of starch, urea, and melamine (C3N6H6) in composite materials for use as controlled-release plant fertilizer. Slow-release fertilizers are important in minimizing nutrient losses due to run-off, leaching, and other factors. Urea is an effective plasticizer for starch and is an important nitrogen fertilizer throughout the world. Melamine also has high nitrogen content and could be combined with urea-starch composites to provide enhanced controlled-release fertilizer. This study reports the structural interaction and the performance gain of melamine addition to starch-urea composites. Composites were characterized by spectroscopic techniques (FT-Raman and 13C NMR) detailing the interaction between melamine, urea, and starch. These interactions helped facilitate extrusion processing by lowering viscosity and processing temperatures suggesting an enhanced starch plasticizing effect of starch-urea-melamine composites. Further research into the co-plasticization of starch by urea and melamine could be exploited for improved controlled-release fertilizer products. Further research into the co-plasticization of starch by urea and melamine could be exploited for improved controlled-release fertilizer products.


Assuntos
Fertilizantes/análise , Plastificantes/química , Amido/química , Triazinas/química , Ureia/química , Varredura Diferencial de Calorimetria , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Análise Espectral Raman , Amido/ultraestrutura , Difração de Raios X
18.
Molecules ; 24(23)2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31816870

RESUMO

Leaves of Ilex aquifolium L. have been used for their therapeutic properties. In previous studies, components contained in the leaves were first isolated by various chromatographic techniques. Then, quantitation of oleanolic and ursolic acids, which are responsible for the biological and therapeutic activities of the plant, was performed by HPLC, HPTLC, and somewhat by GC-MS. Our objective was to develop a simple method that allows the identification of compounds contained in the leaves of Corsican I. aquifolium and to quantify ursolic and oleanolic acids. Leaves were successively extracted with hexane and dichloromethane. The extracts were chromatographed on silica gel and the fractions of column chromatography submitted to 13C-NMR analysis, following a computerized method developed in the laboratory. 13C-NMR allowed the identification of various triterpenes including ursolic acid and oleanolic acid. Quantitation of both acids was achieved, for the first time, by 1H-NMR after validation of the method (accuracy, precision, linearity, limit of detection and limit of quantitation). Ursolic and oleanolic acids accounted for 55.3% and 20.8% of the dichloromethane extract, respectively. This represents 1.3% and 0.5% of the mass of dried leaves. 1H-NMR spectroscopy appeared as a powerful tool for a rapid quantitation of biologically active compounds from I. aquifolium.


Assuntos
Ilex/química , Ácido Oleanólico/isolamento & purificação , Triterpenos/isolamento & purificação , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Cromatografia Gasosa-Espectrometria de Massas , Ácido Oleanólico/química , Extratos Vegetais/química , Folhas de Planta/química , Espectroscopia de Prótons por Ressonância Magnética , Triterpenos/química
19.
Molecules ; 24(24)2019 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-31817301

RESUMO

The fungal strain Alternaria alternata JS0515 was isolated from Vitex rotundifolia (beach vitex). Twelve secondary metabolites, including one new altenusin derivative (1), were isolated. The isolated metabolites included seven known altenusin derivatives (2-8), two isochromanones (9, 10), one perylenequinone (11), and one benzocycloalkanone (12). Their structures were determined via 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), and computational electronic circular dichroism (ECD) analysis. Compounds 3 and 11 increased pyruvate dehydrogenase (PDH) activity in AD-293 human embryonic kidney cells and significantly inhibited PDH phosphorylation. The IC50 values of 3 and 11 were 32.58 and 27.82 µM, respectively.


Assuntos
Alternaria/isolamento & purificação , Alternaria/metabolismo , Endófitos/isolamento & purificação , Endófitos/metabolismo , Complexo Piruvato Desidrogenase/metabolismo , Metabolismo Secundário , Vitex/microbiologia , Alternaria/enzimologia , Bioensaio , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Endófitos/enzimologia , Espectroscopia de Prótons por Ressonância Magnética
20.
Acta Bioeng Biomech ; 21(3): 39-47, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31798027

RESUMO

PURPOSE: Poly(L-lactide-co-glycolide-co-trimethylene carbonate) rods with risperidone and 17-ß-estradiol were sterilized by electron beam irradiation. The aim of the study was to assess electron beam irradiation impact on terpolymer composition, chain microstructure, glass transition temperature, molecular weight and the morphological features of rods. METHODS: Hot melt extrusion in the formulation of rods was applied. Sterilization of the rods was performed by electron beam in an electron beam accelerator (10 MeV, 360 mA, 25 kGy). The following methods in the development of rods were applied: nuclear magnetic resonance, differential scanning calorimetry, gel permeation chromatography and scanning electron microscopy. RESULTS: Sterilization influenced only glass transition temperature in blind rods and rods with risperidone. As for the other parameters, no significant changes were observed as far as a sterilization effect is concerned. However, some changes were noted after introducing drug substances and after extrusion. CONCLUSIONS: Electron beam irradiation of rods with risperidone and rods with 17-ß-estradiol is an adequate method for sterilizing implantable drug delivery systems.


Assuntos
Elétrons , Estradiol/farmacologia , Próteses e Implantes , Risperidona/farmacologia , Esterilização , Varredura Diferencial de Calorimetria , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Sistemas de Liberação de Medicamentos , Peso Molecular , Polímeros/química , Espectroscopia de Prótons por Ressonância Magnética , Temperatura
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