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1.
Nat Commun ; 11(1): 4557, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917908

RESUMO

Why metalloenzymes often show dramatic changes in their catalytic activity when subjected to chemically similar but non-native metal substitutions is a long-standing puzzle. Here, we report on the catalytic roles of metal ions in a model metalloenzyme system, human carbonic anhydrase II (CA II). Through a comparative study on the intermediate states of the zinc-bound native CA II and non-native metal-substituted CA IIs, we demonstrate that the characteristic metal ion coordination geometries (tetrahedral for Zn2+, tetrahedral to octahedral conversion for Co2+, octahedral for Ni2+, and trigonal bipyramidal for Cu2+) directly modulate the catalytic efficacy. In addition, we reveal that the metal ions have a long-range (~10 Å) electrostatic effect on restructuring water network in the active site. Our study provides evidence that the metal ions in metalloenzymes have a crucial impact on the catalytic mechanism beyond their primary chemical properties.


Assuntos
Anidrases Carbônicas/química , Íons/química , Metaloproteínas/química , Metais/química , Sítios de Ligação , Anidrase Carbônica II/química , Anidrase Carbônica II/metabolismo , Anidrases Carbônicas/metabolismo , Catálise , Domínio Catalítico , Cobalto/química , Cobre/química , Cristalografia por Raios X , Humanos , Íons/metabolismo , Cinética , Metaloproteínas/metabolismo , Metais/metabolismo , Modelos Moleculares , Níquel/química , Conformação Proteica , Relação Estrutura-Atividade , Especificidade por Substrato , Zinco/química
2.
Nat Commun ; 11(1): 3818, 2020 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-32732937

RESUMO

The formation of peptide bonds by energetic processing of amino acids is an important step towards the formation of biologically relevant molecules. As amino acids are present in space, scenarios have been developed to identify the roots of life on Earth, either by processes occurring in outer space or on Earth itself. We study the formation of peptide bonds in single collisions of low-energy He2+ ions (α-particles) with loosely bound clusters of ß-alanine molecules at impact energies typical for solar wind. Experimental fragmentation mass spectra produced by collisions are compared with results of molecular dynamics simulations and an exhaustive exploration of potential energy surfaces. We show that peptide bonds are efficiently formed by water molecule emission, leading to the formation of up to tetrapeptide. The present results show that a plausible route to polypeptides formation in space is the collision of energetic ions with small clusters of amino acids.


Assuntos
Aminoácidos/química , Simulação de Dinâmica Molecular , Peptídeos/química , Termodinâmica , beta-Alanina/química , Dipeptídeos/síntese química , Dipeptídeos/química , Íons/química , Oligopeptídeos/síntese química , Oligopeptídeos/química , Peptídeos/síntese química , Espectrometria de Massas por Ionização por Electrospray/métodos , Água/química
3.
J Chromatogr A ; 1627: 461394, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823099

RESUMO

The early identification of unstable glass objects in museum collections is essential for their conservation, but as yet cannot be accomplished straightforwardly. Accordingly, this paper describes the development and validation of a simple protocol for quantitative determination of ions characteristic of the chemical decay of historic glass, using surface swabbing combined with ion-exchange chromatography. The establishment of a robust protocol is an important step in the development of an early warning system for the chemical deterioration of unstable glass. Using a model system, the protocol was validated for specificity, linearity, accuracy, precision, limits of detection, and limits of quantification for 10 anionic species (fluoride, acetate, formate, chloride, nitrite, bromide, nitrate, carbonate, sulfate and phosphate) and 6 cationic species (lithium, sodium, ammonium, potassium, magnesium and calcium). Good validation parameters (R2 > 0.995; RSD < 5%; Recovery 90-100%) were obtained for acetate, formate, nitrite, nitrate, phosphate, lithium, sodium, potassium, magnesium and calcium. Chloride (R2 = 0.934; RSD = 13.6%; recovery 71.4%) and carbonate (R2 = 0.993; RSD = 10.3%; recovery 120%) had poor validation parameters. Sulfate had low recovery (78.2%), but high reproducibility (RSD = 4.32%) with R2 = 0.997. Limits of quantification were below 1 mg/L for all analytes, which is satisfactory for the study of unstable glass in museum collections. The validated sampling protocol was trialled using artificially aged unstable glass fragments, which resulted in a high relative standard deviation (between 1 and 30%). The ability to achieve improved care of historic glass by application of the validated protocol in museum collections is discussed in the context of a pilot study undertaken at the Rijksmuseum, Amsterdam.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Vidro/química , Íons/análise , Cloretos/análise , Cromatografia por Troca Iônica , Fluoretos/análise , Íons/química , Limite de Detecção , Metais/análise , Metais/química , Museus , Nitratos/análise , Reprodutibilidade dos Testes , Propriedades de Superfície
4.
Ecotoxicol Environ Saf ; 204: 110977, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32739673

RESUMO

Indirect oxidation induced by reactive free radicals, such as hydroxyl radical (HO), sulfate radical (SO4-) and carbonate radical (CO3-), plays an important or even crucial role in the degradation of micropollutants. Thus, the coadjutant degradation of phenacetin (PNT) by HO, SO4- and CO3-, as well as the synergistic effect of O2 on HO and HO2 were studied through mechanism, kinetics and toxicity evaluation. The results showed that the degradation of PNT was mainly caused by radical adduct formation (RAF) reaction (69% for Г, the same as below) and H atom transfer (HAT) reaction (31%) of HO. For the two inorganic anionic radicals, SO4- initiated PNT degradation by sequential radical addition-elimination (SRAE; 55%), HAT (28%) and single electron transfer (SET; 17%) reactions, while only by HAT reaction for CO3-. The total initial reaction rate constants of PNT by three radicals were in the order: SO4- > HO > CO3-. The kinetics of PNT degradation simulated by Kintecus program showed that UV/persulfate could degrade target compound more effectively than UV/H2O2 in ultrapure water. In the subsequent reaction of PNT with O2, HO and HO2, the formation of mono/di/tri-hydroxyl substitutions and unsaturated aldehydes/ketones/alcohols were confirmed. The results of toxicity assessment showed that the acute and chronic toxicity of most products to fish increased and to daphnia decreased, and acute toxicity to green algae decreased while chronic toxicity increased.


Assuntos
Carbonatos/toxicidade , Peróxido de Hidrogênio/toxicidade , Fenacetina/toxicidade , Sulfatos/toxicidade , Testes de Toxicidade Aguda , Testes de Toxicidade Crônica , Animais , Carbonatos/química , Clorófitas/efeitos dos fármacos , Daphnia/efeitos dos fármacos , Peixes , Peróxido de Hidrogênio/química , Íons/química , Íons/toxicidade , Cinética , Modelos Químicos , Oxigênio/química , Fenacetina/química , Sulfatos/química , Água/química
5.
Proc Natl Acad Sci U S A ; 117(26): 14667-14675, 2020 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-32532923

RESUMO

Many natural materials possess built-in structural variation, endowing them with superior performance. However, it is challenging to realize programmable structural variation in self-assembled synthetic materials since self-assembly processes usually generate uniform and ordered structures. Here, we report the formation of asymmetric microribbons composed of directionally self-assembled two-dimensional nanoflakes in a polymeric matrix during three-dimensional direct-ink printing. The printed ribbons with embedded structural variations show site-specific variance in their mechanical properties. Remarkably, the ribbons can spontaneously transform into ultrastretchable springs with controllable helical architecture upon stimulation. Such springs also exhibit superior nanoscale transport behavior as nanofluidic ionic conductors under even ultralarge tensile strains (>1,000%). Furthermore, to show possible real-world uses of such materials, we demonstrate in vivo neural recording and stimulation using such springs in a bullfrog animal model. Thus, such springs can be used as neural electrodes compatible with soft and dynamic biological tissues.


Assuntos
Neuroestimuladores Implantáveis , Microtecnologia/instrumentação , Nanoestruturas , Impressão Tridimensional , Animais , Anuros , Elasticidade , Grafite/química , Íons/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Neurofisiologia/instrumentação , Nervo Isquiático/fisiologia
6.
Nat Commun ; 11(1): 3024, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32541684

RESUMO

The canonical mechanistic model explaining potassium channel gating is of a conformational change that alternately dilates and constricts a collar-like intracellular entrance to the pore. It is based on the premise that K+ ions maintain a complete hydration shell while passing between the transmembrane cavity and cytosol, which must be accommodated. To put the canonical model to the test, we locked the conformation of a Kir K+ channel to prevent widening of the narrow collar. Unexpectedly, conduction was unimpaired in the locked channels. In parallel, we employed all-atom molecular dynamics to simulate K+ ions moving along the conduction pathway between the lower cavity and cytosol. During simulations, the constriction did not significantly widen. Instead, transient loss of some water molecules facilitated K+ permeation through the collar. The low free energy barrier to partial dehydration in the absence of conformational change indicates Kir channels are not gated by the canonical mechanism.


Assuntos
Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Potássio/metabolismo , Citosol/química , Citosol/metabolismo , Condutividade Elétrica , Impedância Elétrica , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/química , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/genética , Humanos , Transporte de Íons , Íons/química , Íons/metabolismo , Simulação de Dinâmica Molecular , Potássio/química , Conformação Proteica , Água/metabolismo
7.
Nat Commun ; 11(1): 3186, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32581242

RESUMO

Mass spectrometry based metabolomics is a widely used approach in biomedical research. However, current methods coupling mass spectrometry with chromatography are time-consuming and not suitable for high-throughput analysis of thousands of samples. An alternative approach is flow-injection mass spectrometry (FI-MS) in which samples are directly injected to the ionization source. Here, we show that the sensitivity of Orbitrap FI-MS metabolomics methods is limited by ion competition effect. We describe an approach for overcoming this effect by analyzing the distribution of ion m/z values and computationally determining a series of optimal scan ranges. This enables reproducible detection of ~9,000 and ~10,000 m/z features in metabolomics and lipidomics analysis of serum samples, respectively, with a sample scan time of ~15 s and duty time of ~30 s; a ~50% increase versus current spectral-stitching FI-MS. This approach facilitates high-throughput metabolomics for a variety of applications, including biomarker discovery and functional genomics screens.


Assuntos
Análise de Injeção de Fluxo/métodos , Espectrometria de Massas/métodos , Metabolômica/métodos , Linhagem Celular Tumoral , Análise de Injeção de Fluxo/normas , Ensaios de Triagem em Larga Escala , Humanos , Íons/química , Lipidômica/métodos , Espectrometria de Massas/normas , Metabolômica/normas , Soro/química , Soro/metabolismo
8.
Food Chem ; 331: 127208, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32554309

RESUMO

In this work, we have developed a simple, fast and visual Hg2+ detection strategy based on distance as readout on paper chip by the Hg2+-mediated formation of G-quadruplex-hemin DNAzymes. In the presence of Hg2+, the two oligonucleotides hybridize to form G-quadruplex DNA by T-Hg2+-T base pair, which was able to bind hemin to form the catalytically active G-quadruplex-hemin DNAzymes. Once DNAzymes were added to react with the precipitated 3,3,5,5-tetramethyl benzidine (TMB) immobilized on the sample area, a visible color band was produced, and the formed length was positively correlated with the concentration of Hg2+. This biosensor is capable of selectively detecting mercuric ions with good reproducibility and satisfactory dynamic range. The limit of detection was low to 0.23 nM. Therefore, this strategy not only provides a visual and quick screen of Hg2+, but also shows a promising future in monitoring analysis of other metal ions in POC diagnostic field.


Assuntos
Técnicas Biossensoriais/métodos , Quadruplex G , Mercúrio/análise , Colorimetria , Íons/química , Limite de Detecção , Microfluídica , Papel , Sistemas Automatizados de Assistência Junto ao Leito , Reprodutibilidade dos Testes
9.
Chemosphere ; 256: 127124, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32450354

RESUMO

In the present work, talc (a low-cost clay) encapsulated salts alginate (TAL) beads were synthesized by cross-linking with lanthanum ion and tested for phosphate adsorption. Multiple methods were applied for the characterization of composites. The combined effect of talc and lanthanum improved phosphate removal performance of TAL beads. Factors such as talc content, La3+ concentration, adsorbent dosage, pH, co-existing ions (Cl-, NO3- and SO42-) were studied in batch experiments. The optimized TAL-7 beads exhibited satisfactory selectivity towards phosphate in the coexistence of competing anions and could remain efficient phosphate removal in the pH range of 4-6. The phosphate removal efficiency reached to 95% with a maximum uptake of 16.4 mg P/g obtained at the optimal pH 4. Further experiments suggested that Langmuir isotherm model and the pseudo-second-order kinetic model could well describe the phosphate adsorption process of TAL-7 beads. Moreover, TAL-7 beads exhibited superior phosphate fixation performance in the long-term experiment. The results from adsorption experiment and characterization analysis demonstrated that TAL-7 beads could be a cost-effective and promising biosorbent for phosphate adsorption and fixation in the aqueous environment.


Assuntos
Alginatos/química , Hidrogéis/química , Lantânio/química , Fosfatos/análise , Talco/química , Poluentes Químicos da Água/análise , Adsorção , Ânions , Concentração de Íons de Hidrogênio , Íons/química , Cinética , Fosfatos/química , Água/química , Poluentes Químicos da Água/química , Purificação da Água/métodos
10.
Food Chem ; 324: 126887, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32339788

RESUMO

Epigenetic regulation and salt ions play essential roles in senescence control, but the underlying regulatory mechanism of senescence has not been thoroughly revealed in broccoli postharvest buds. Here, we found 200 mmol·L-1 NaCl, 400 mmol·L-1 KCl, 40 mmol·L-1 CaCl2 and 0.5 µmol·L-1 Trichostatin-A (TSA, a histone deacetylase inhibitor) delayed the bud senescence. They resulted in significantly inhibiting the malondialdehyde (MDA) content, and dramatically promoting the contents of superoxide dismutase (SOD), peroxidase (POD) and Chlorophyll. Furthermore, the expression of PHEOPHYTINASE (PPH) and NONYELLOWING (NYE1), but not SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), were remarkably repressed by salt ions and TSA. Interestingly, HISTONE DEACETYLASE 9 (HDA9) and CATION/Ca2+ EXCHANGER 1 (CCX1) were down-regulated by NaCl, CaCl2 and TSA. Further assays demonstrated that HDA9 could not interact with CCX1 promoter. It suggested that CCX1 along with HDA9 were involved in inhibiting the senescence of broccoli buds, and regulated aging by indirect interaction.


Assuntos
Antioxidantes/metabolismo , Brassica/metabolismo , Regulação para Baixo/efeitos dos fármacos , Histona Desacetilases/metabolismo , Proteínas de Plantas/metabolismo , Sais/farmacologia , Sequência de Aminoácidos , Antiporters/química , Antiporters/genética , Antiporters/metabolismo , Brassica/química , Brassica/classificação , Cloreto de Cálcio/química , Cloreto de Cálcio/farmacologia , Clorofila/metabolismo , Flores/química , Flores/metabolismo , Ácidos Hidroxâmicos/química , Ácidos Hidroxâmicos/farmacologia , Íons/química , Filogenia , Sais/química , Alinhamento de Sequência
11.
Chemistry ; 26(41): 8875-8878, 2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32237247

RESUMO

The nickel(II)-mediated self-assembly of a multimeric DNA binder is described. The binder is composed of two metal-chelating peptides derived from a bZIP transcription factor (brHis2 ) and one short AT-hook domain equipped with two bipyridine ligands (HkBpy2 ). These peptides reversibly assemble in the presence of NiII ions at selected DNA sequences of 13 base pairs.


Assuntos
Complexos de Coordenação/química , DNA/química , Níquel/química , Peptídeos/química , Fatores de Transcrição/química , Complexos de Coordenação/síntese química , Íons/química , Ligantes
12.
Proc Natl Acad Sci U S A ; 117(18): 9832-9839, 2020 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-32317383

RESUMO

G-quadruplex, assembled from a square array of guanine (G) molecules, is an important structure with crucial biological roles in vivo but also a versatile template for ordered functional materials. Although the understanding of G-quadruplex structures is the focus of numerous studies, little is known regarding the control of G-quartet stacking modes and the spontaneous orientation of G-quadruplex fibrils. Here, the effects of different metal ions and their concentrations on stacking modes of G-quartets are elucidated. Monovalent cations (typically K+) facilitate the formation of G-quadruplex hydrogels with both heteropolar and homopolar stacking modes, showing weak mechanical strength. In contrast, divalent metal ions (Ca2+, Sr2+, and Ba2+) at given concentrations can control G-quartet stacking modes and increase the mechanical rigidity of the resulting hydrogels through ionic bridge effects between divalent ions and borate. We show that for Ca2+ and Ba2+ at suitable concentrations, the assembly of G-quadruplexes results in the establishment of a mesoscopic chirality of the fibrils with a regular left-handed twist. Finally, we report the discovery of nematic tactoids self-assembled from G-quadruplex fibrils characterized by homeotropic fibril alignment with respect to the interface. We use the Frank-Oseen elastic energy and the Rapini-Papoular anisotropic surface energy to rationalize two different configurations of the tactoids. These results deepen our understanding of G-quadruplex structures and G-quadruplex fibrils, paving the way for their use in self-assembly and biomaterials.


Assuntos
DNA/química , Quadruplex G , Guanina/química , Hidrogéis/química , Anisotropia , Cátions Bivalentes/química , Cátions Monovalentes/química , DNA/ultraestrutura , Metabolismo Energético/efeitos dos fármacos , Líquidos Iônicos/química , Íons/química , Metais/química , Conformação de Ácido Nucleico/efeitos dos fármacos , Propriedades de Superfície
13.
BMC Bioinformatics ; 21(1): 118, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32192433

RESUMO

BACKGROUND: mRNA interaction with other mRNAs and other signaling molecules determine different biological pathways and functions. Gene co-expression network analysis methods have been widely used to identify correlation patterns between genes in various biological contexts (e.g., cancer, mouse genetics, yeast genetics). A challenge remains to identify an optimal partition of the networks where the individual modules (clusters) are neither too small to make any general inferences, nor too large to be biologically interpretable. Clustering thresholds for identification of modules are not systematically determined and depend on user-settable parameters requiring optimization. The absence of systematic threshold determination may result in suboptimal module identification and a large number of unassigned features. RESULTS: In this study, we propose a new pipeline to perform gene co-expression network analysis. The proposed pipeline employs WGCNA, a software widely used to perform different aspects of gene co-expression network analysis, and Modularity Maximization algorithm, to analyze novel RNA-Seq data to understand the effects of low-dose 56Fe ion irradiation on the formation of hepatocellular carcinoma in mice. The network results, along with experimental validation, show that using WGCNA combined with Modularity Maximization, provides a more biologically interpretable network in our dataset, than that obtainable using WGCNA alone. The proposed pipeline showed better performance than the existing clustering algorithm in WGCNA, and identified a module that was biologically validated by a mitochondrial complex I assay. CONCLUSIONS: We present a pipeline that can reduce the problem of parameter selection that occurs with the existing algorithm in WGCNA, for applicable RNA-Seq datasets. This may assist in the future discovery of novel mRNA interactions, and elucidation of their potential downstream molecular effects.


Assuntos
Ferro/química , Fígado/metabolismo , Software , Algoritmos , Animais , Perfilação da Expressão Gênica/métodos , Redes Reguladoras de Genes/genética , Íons/química , Ferro/toxicidade , Fígado/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , RNA-Seq
14.
Proc Natl Acad Sci U S A ; 117(11): 5861-5872, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32123101

RESUMO

The cytoskeletal protein actin polymerizes into filaments that are essential for the mechanical stability of mammalian cells. In vitro experiments showed that direct interactions between actin filaments and lipid bilayers are possible and that the net charge of the bilayer as well as the presence of divalent ions in the buffer play an important role. In vivo, colocalization of actin filaments and divalent ions are suppressed, and cells rely on linker proteins to connect the plasma membrane to the actin network. Little is known, however, about why this is the case and what microscopic interactions are important. A deeper understanding is highly beneficial, first, to obtain understanding in the biological design of cells and, second, as a possible basis for the building of artificial cortices for the stabilization of synthetic cells. Here, we report the results of coarse-grained molecular dynamics simulations of monomeric and filamentous actin in the vicinity of differently charged lipid bilayers. We observe that charges on the lipid head groups strongly determine the ability of actin to adsorb to the bilayer. The inclusion of divalent ions leads to a reversal of the binding affinity. Our in silico results are validated experimentally by reconstitution assays with actin on lipid bilayer membranes and provide a molecular-level understanding of the actin-membrane interaction.


Assuntos
Citoesqueleto de Actina/química , Citoesqueleto de Actina/metabolismo , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , Actinas/química , Células Artificiais , Membrana Celular/química , Membrana Celular/metabolismo , Fenômenos Químicos , Biologia Computacional , Simulação por Computador , Citoesqueleto/química , Citoesqueleto/metabolismo , Íons/química , Íons/metabolismo , Modelos Moleculares , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica , Eletricidade Estática
15.
Chemosphere ; 252: 126485, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32222516

RESUMO

Degradation of benzenesulfonic acid (BSA), the simplest aromatic sulfonic acid with extreme industrial importantance, by sonochemically generated hydroxyl radical (OH) have been thoroughly investigated. A reasonable reduction (∼50%) in the total organic carbon (TOC) was achieved only after prolonged irradiation (∼275 min, 350 kHz) of ultrasound, although a short irradiation of less than an hour is enough to degrade significant amount of BSA. The degradation efficiency of ultrasound has been reduced in lower and extremely higher frequencies, and upon increasing the pH. An irregular, but continuous, release of sulfate ions was also observed. Further, the release of protons upon the oxidation of BSA consistently reduces the experimental pH to nearly 2. High resolution mass spectrometric (HRMS) analyses reveals the formation of a number of aromatic intermediates, including three mono (Ia-c) and two di (IIa&b) hydroxylated BSA derivatives as the key products in the initial stages of the reaction. Pulse radiolysis studies revealed the generation of hydroxycyclohexadienyl-type radicals, characterized by absorption bands at 320 nm (k2 = (7.16 ± 0.04) × 109 M-1 s-1) and 380 nm, as the immediate intermediates of the reaction. The mechanism(s) leading to the degradation of BSA under sonolytic irradiation conditions along with the effect of various factors, such as the ultrasound frequency and reaction pH, have been explained in detail. The valuable mechanistic aspects obtained from our pulse radiolysis and HRMS studies are essential for the proper implementation of sonochemical techniques into real water purification process and, thus, receives extreme environmental relevance.


Assuntos
Benzenossulfonatos/química , Poluentes Químicos da Água/química , Radical Hidroxila/química , Íons/química , Cinética , Espectrometria de Massas , Oxirredução , Sonicação , Água/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
16.
Chemistry ; 26(39): 8511-8517, 2020 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-32196774

RESUMO

A nanopore-based CuII -sensing system is reported that allows for an ultrasensitive and selective detection of CuII with the possibility for a broad range of applications, for example in medical diagnostics. A fluorescent ATCUN-like peptide 5/6-FAM-Dap-ß-Ala-His is employed to selectively bind CuII ions in the presence of NiII and ZnII and was crafted into ion track-etched nanopores. Upon CuII binding the fluorescence of the peptide sensor is quenched, permitting the detection of CuII in solution. The ion transport characteristics of peptide-modified nanopore are shown to be extremely sensitive and selective towards CuII allowing to sense femtomolar CuII concentrations in human urine mimics. Washing with EDTA fully restores the CuII -binding properties of the sensor, enabling multiple repetitive measurements. The robustness of the system clearly has the potential to be further developed into an easy-to-use, lab-on-chip CuII -sensing device, which will be of great importance for bedside diagnosis and monitor of CuII levels in patients with copper-dysfunctional homeostasis.


Assuntos
Cobre/análise , Íons/química , Peptídeos/química , Cobre/química , Cobre/metabolismo , Fluorescência , Humanos , Peptídeos/metabolismo
17.
Phys Chem Chem Phys ; 22(10): 5584-5596, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32107511

RESUMO

The identity of metal ions surrounding DNA is key to its biological function and materials applications. In this work, we compare atomistic molecular dynamics simulations of double strand DNA (dsDNA) with four alkaline earth metal ions (Mg2+, Ca2+, Sr2+, and Ba2+) to elucidate the physical interactions that govern DNA-ion binding. Simulations accurately model the ion-phosphate distance of Mg2+ and reproduce ion counting experiments for Ca2+, Sr2+, and Ba2+. Our analysis shows that alkaline earth metal ions prefer to bind at the phosphate backbone compared to the major groove and negligible binding occurs in the minor groove. Larger alkaline earth metal ions with variable first solvation shells (Ca2+, Sr2+, and Ba2+) show both direct and indirect binding, where indirect binding increases with ion size. Mg2+ does not fit this trend because the strength of its first solvation shell predicts indirect binding only. Ions bound to the phosphate backbone form fewer contacts per ion compared to the major groove. Within the major groove, metal ions preferentially bind to guanine-cystosine base pairs and form simultaneous contacts with the N7 and O6 atoms of guanine. Overall, we find that the interplay among ion size, DNA-ion interaction, and the size and flexibility of the first solvation shell are key to predicting how alkaline earth metal ions interact with DNA.


Assuntos
DNA/química , Íons/química , Metais Alcalinoterrosos/química , Metais/química , Simulação de Dinâmica Molecular , Água/química
18.
Cell Physiol Biochem ; 54(2): 180-194, 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32068980

RESUMO

BACKGROUND/AIMS: Still in 1999 the first hints were published for the pharmacoresistant Cav2.3 calcium channel to be involved in the generation of epileptic seizures, as transcripts of alpha1E (Cav2.3) and alpha1G (Cav3.1) are changed in the brain of genetic absence epilepsy rats from Strasbourg (GAERS). Consecutively, the seizure susceptibility of mice lacking Cav2.3 was analyzed in great detail by using 4-aminopyridine, pentylene-tetrazol, N-methyl-D-aspartate and kainic acid to induce experimentally convulsive seizures. Further, γ-hydroxybutyrolactone was used for the induction of non-convulsive absence seizures. For all substances tested, Cav2.3-competent mice differed from their knockout counterparts in the sense that for convulsive seizures the deletion of the pharmacoresistant channel was beneficial for the outcome during experimentally induced seizures [1]. The antiepileptic drug lamotrigine reduces seizure activity in Cav2.3-competent but increases it in Cav2.3-deficient mice. In vivo, Cav2.3 must be under tight control by endogenous trace metal cations (Zn2+ and Cu2+). The dyshomeostasis of either of them, especially of Cu2+, may alter the regulation of Cav2.3 severely and its activity for Ca2+ conductance, and thus may change hippocampal and neocortical signaling to hypo- or hyperexcitation. METHODS: To investigate by telemetric EEG recordings the mechanism of generating hyperexcitation by kainate, mice were tested for their sensitivity of changes in neuronal (intracerebroventricular) concentrations of the trace metal cation Zn2+. As the blood-brain barrier limits the distribution of bioavailable Zn2+ or Cu2+ into the brain, we administered micromolar Zn2+ ions intracerebroventricularly in the presence of 1 mM histidine as carrier and compared the effects on behavior and EEG activity in both genotypes. RESULTS: Kainate seizures are more severe in Cav2.3-competent mice than in KO mice and histidine lessens seizure severity in competent but not in Cav2.3-deficient mice. Surprisingly, Zn2+ plus histidine resembles the kainate only control with more seizure severity in Cav2.3-competent than in deficient mice. CONCLUSION: Cav2.3 represents one important Zn2+-sensitive target, which is useful for modulating convulsive seizures.


Assuntos
Canais de Cálcio Tipo R/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Convulsões/tratamento farmacológico , Zinco/uso terapêutico , Animais , Canais de Cálcio Tipo R/genética , Proteínas de Transporte de Cátions/genética , Eletroencefalografia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Histidina/farmacologia , Íons/química , Ácido Caínico/toxicidade , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Convulsões/induzido quimicamente , Convulsões/patologia , Índice de Gravidade de Doença , Zinco/farmacologia , Ácido gama-Aminobutírico/metabolismo
19.
J Agric Food Chem ; 68(10): 3163-3170, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32069043

RESUMO

The purpose of this work was to develop a facile strategy based on self-crosslinking between the core and wall materials in the coacervation system for effective procyanidins (PCs) encapsulation. The coacervates were constructed through the interaction of bioactive PCs, gelatin, and sodium alginate, followed by forming cationic bridge of sodium alginate-calcium ions to improve the stability of PCs. When the concentration of PCs and calcium ions were 6.25 and 0.24 mg/mL, respectively, the PC-loaded coacervates showed spherical shape with a size about 150 nm, and the microcapsulation efficiency and yield was 81.19 ± 1.47 and 87.86 ± 2.67%, respectively. The photothermal stability of PCs was effectively improved by embedding them in coacervates. The decrease of mitochondrial membrane potential in PC-12 cells induced by H2O2 was significantly inhibited by PC coacervates, demonstrating an improved protection effect of PCs after being encapsulated in coacervates.


Assuntos
Biflavonoides/química , Quelantes de Cálcio/química , Cálcio/química , Catequina/química , Extratos Vegetais/química , Proantocianidinas/química , Animais , Reagentes para Ligações Cruzadas/química , Estabilidade de Medicamentos , Íons/química , Células PC12 , Ratos , Sementes/química , Vitis
20.
Biochem Soc Trans ; 48(1): 317-326, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-32010951

RESUMO

Advances in sample preparation, ion sources and mass spectrometer technology have enabled the detection and characterisation of intact proteins. The challenges associated include an appropriately soft ionisation event, efficient transmission and detection of the often delicate macromolecules. Ambient ion sources, in particular, offer a wealth of strategies for analysis of proteins from solution environments, and directly from biological substrates. The last two decades have seen rapid development in this area. Innovations include liquid extraction surface analysis, desorption electrospray ionisation and nanospray desorption electrospray ionisation. Similarly, developments in native mass spectrometry allow protein-protein and protein-ligand complexes to be ionised and analysed. Identification and characterisation of these large ions involves a suite of hyphenated mass spectrometry techniques, often including the coupling of ion mobility spectrometry and fragmentation techniques. The latter include collision, electron and photon-induced methods, each with their own characteristics and benefits for intact protein identification. In this review, recent developments for in situ protein analysis are explored, with a focus on ion sources and tandem mass spectrometry techniques used for identification.


Assuntos
Proteínas/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Espectrometria de Massas em Tandem/métodos , Elétrons , Íons/química , Íons/efeitos da radiação , Fótons , Raios Ultravioleta
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