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1.
Anticancer Res ; 40(7): 3831-3837, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32620622

RESUMO

BACKGROUND/AIM: The ketogenic diet has recently gained interest as potential adjuvant therapy for cancer. Many researchers have endeavored to support this claim in vitro. One common model utilizes treatment with exogenous acetoacetate in lithium salt form (LiAcAc). We aimed to determine whether the effects of treatment with LiAcAc on cell viability, as reported in the literature, accurately reflect the influence of acetoacetate. MATERIALS AND METHODS: Breast cancer and normal cell lines were treated with acetoacetate, in lithium and sodium salt forms, and cell viability was assessed. RESULTS: The effect of LiAcAc on cells was mediated by Li ions. Our results showed that the cytotoxic effects of LiAcAc treatment were significantly similar to those caused by LiCl, and also treatment with NaAcAc did not cause any significant cytotoxic effect. CONCLUSION: Treatment of cells with LiAcAc is not a convincing in vitro model for studying ketogenic diet. These findings are highly important for interpreting previously published results, and for designing new experiments to study the ketogenic diet in vitro.


Assuntos
Acetoacetatos/farmacologia , Neoplasias da Mama/tratamento farmacológico , Compostos de Lítio/farmacologia , Lítio/farmacologia , Acetoacetatos/química , Trifosfato de Adenosina/metabolismo , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Cátions Monovalentes/química , Cátions Monovalentes/farmacologia , Processos de Crescimento Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Humanos , Lítio/química , Cloreto de Lítio/química , Cloreto de Lítio/farmacologia , Compostos de Lítio/química , Células MCF-7
2.
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
3.
PLoS One ; 15(3): e0230327, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32150746

RESUMO

Sodium Calcium exchanger (NCX) proteins utilize the electrochemical gradient of Na+ to generate Ca2+ efflux (forward mode) or influx (reverse mode). In mammals, there are three unique NCX encoding genes-NCX1, NCX2, and NCX3, that comprise the SLC8A family, and mRNA from all three exchangers is expressed in hippocampal pyramidal cells. Furthermore, mutant ncx2-/- and ncx3-/- mice have each been shown to exhibit altered long-term potentiation (LTP) in the hippocampal CA1 region due to delayed Ca2+ clearance after depolarization that alters synaptic transmission. In addition to the role of NCX at the synapse of hippocampal subfields required for LTP, the three NCX isoforms have also been shown to localize to the dendrite of hippocampal pyramidal cells. In the case of NCX1, it has been shown to localize throughout the basal and apical dendrite of CA1 neurons where it helps compartmentalize Ca2+ between dendritic shafts and spines. Given the role for NCX and calcium in synaptic plasticity, the capacity of NCX splice-forms to influence backpropagating action potentials has clear consequences for the induction of spike-timing dependent synaptic plasticity (STDP). To explore this, we examined the effect of NCX localization, density, and allosteric activation on forward and back propagating signals and, next employed a STDP paradigm to monitor the effect of NCX on plasticity using back propagating action potentials paired with EPSPs. From our simulation studies we identified a role for the sodium calcium exchange current in normalizing STDP, and demonstrate that NCX is required at the postsynaptic site for this response. We also screened other mechanisms in our model and identified a role for the Ca2+ activated K+ current at the postsynapse in producing STDP responses. Together, our data reveal opposing roles for the Na+/Ca2+ exchanger current and the Ca2+ activated K+ current in setting STDP.


Assuntos
Região CA1 Hipocampal/fisiologia , Modelos Neurológicos , Plasticidade Neuronal/fisiologia , Células Piramidais/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Potenciais de Ação/fisiologia , Animais , Região CA1 Hipocampal/citologia , Cálcio/metabolismo , Cátions Bivalentes/metabolismo , Cátions Monovalentes/metabolismo , Simulação por Computador , Modelos Animais , Potássio/metabolismo , Ratos , Sódio/metabolismo
4.
Am J Physiol Lung Cell Mol Physiol ; 318(5): L931-L942, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32130033

RESUMO

The human airway is protected by an efficient innate defense mechanism that requires healthy secretion of airway surface liquid (ASL) to clear pathogens from the lungs. Most of the ASL in the upper airway is secreted by submucosal glands. In cystic fibrosis (CF), the function of airway submucosal glands is abnormal, and these abnormalities are attributed to anomalies in ion transport across the epithelia lining the different sections of the glands that function coordinately to produce the ASL. However, the ion transport properties of most of the anatomical regions of the gland have never been measured, and there is controversy regarding which segments express CFTR. This makes it difficult to determine the glandular abnormalities that may contribute to CF lung disease. Using a noninvasive, extracellular self-referencing ion-selective electrode technique, we characterized ion transport properties in all four segments of submucosal glands from wild-type and CFTR-/- swine. In wild-type airways, the serous acini, mucus tubules, and collecting ducts secrete Cl- and Na+ into the lumen in response to carbachol and forskolin stimulation. The ciliated duct also transports Cl- and Na+ but in the opposite direction, i.e., reabsorption from the ASL, which may contribute to lowering Na+ and Cl- activities in the secreted fluid. In CFTR-/- airways, the serous acini, collecting ducts, and ciliated ducts fail to transport ions after forskolin stimulation, resulting in the production of smaller volumes of ASL with normal Cl-, Na+, and K+ concentration.


Assuntos
Células Acinares/metabolismo , Cílios/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Fibrose Cística/metabolismo , Pulmão/metabolismo , Células Acinares/efeitos dos fármacos , Células Acinares/patologia , Animais , Carbacol/farmacologia , Cátions Monovalentes , Cloretos/metabolismo , Cílios/efeitos dos fármacos , Cílios/patologia , Colforsina/farmacologia , Fibrose Cística/genética , Fibrose Cística/patologia , Regulador de Condutância Transmembrana em Fibrose Cística/deficiência , Modelos Animais de Doenças , Técnicas Eletroquímicas , Eletrodos , Deleção de Genes , Expressão Gênica , Humanos , Transporte de Íons , Pulmão/efeitos dos fármacos , Pulmão/patologia , Potássio/metabolismo , Sódio/metabolismo , Suínos
5.
J Chem Theory Comput ; 16(1): 794-799, 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31809048

RESUMO

Ion permeation, selectivity, and the behavior of the K+ channel selectivity filter have been studied intensively in the previous two decades. The agreement among multiple approaches used to study ion flux in K+ channels suggests a consensus mechanism of ion permeation across the selectivity that has been put to the test in recent years with the proposal of an alternative way by which ions can cross the selectivity filter of K+ channels via direct Coulomb repulsion between contacting cations. Past experimental work by Zhou and MacKinnon (J. Mol. Biol. 2004, 338, 839) showed that mutation of the site S4 reduces the total occupancy of the selectivity filter to less than two ions on average by lowering the occupancy of the S2-S4 configuration without changing the S1-S3 configuration much, and this reduction of occupancy means that ion configurations different from the ones involved in the canonical mechanism are likely to be involved. At that time, calculations using complicated kinetic networks to relate occupancy to conduction did not provide deeper insight into the conduction mechanism. Here, to help solve this enigma, umbrella sampling simulations have been performed to evaluate the potential of mean force of two KcsA mutant channels where the S4 site is substituted. Our new results provide insights into the significance of threonine in this position, revealing the effect of substitution on the alternate mechanisms of conduction proposed, involving either water or vacant sites.


Assuntos
Proteínas de Bactérias/metabolismo , Canais de Potássio/metabolismo , Potássio/metabolismo , Streptomyces coelicolor/metabolismo , Proteínas de Bactérias/química , Sítios de Ligação , Cátions Monovalentes/metabolismo , Simulação por Computador , Cinética , Modelos Moleculares , Canais de Potássio/química , Conformação Proteica , Streptomyces coelicolor/química
6.
Food Chem ; 306: 125578, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31622835

RESUMO

Oleosomes are storage vehicles of TAGs in plant seeds. They are protected with a phospholipid-protein monolayer and extracted with alkaline aqueous media; however, pH adjustment intensifies the extraction process. Therefore, the aim of this work was to investigate the extraction mechanism of rapeseed oleosomes at pH 7 and at the presence of monovalent and divalent cations (Na+, K+, Mg2+, and Ca+2). The oleosome yield at pH 9.5 was 64 wt%, while the yield at pH 7 with H2O was just 43 wt.%. The presence of cations at pH 7, significantly enhanced the yield, with K+ giving the highest yield (64 wt.%). The cations affected the oleosome interface and their interactions. The presence of monovalent cations resulted in aggregation and minor coalescence, while divalent cations resulted in extensive coalescence. These results help to understand the interactions of oleosomes in their native matrix and design simple extraction processes at neutral conditions.


Assuntos
Brassica/química , Cálcio/química , Magnésio/química , Extratos Vegetais/química , Potássio/química , Sódio/química , Cátions Bivalentes/química , Cátions Monovalentes/química , Concentração de Íons de Hidrogênio , Gotículas Lipídicas , Sementes/química , Água
7.
Phys Rev Lett ; 123(21): 218101, 2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31809131

RESUMO

We develop an iterated map model to describe the bifurcations and complex dynamics caused by the feedback between voltage and intracellular Ca^{2+} and Na^{+} concentrations in paced ventricular myocytes. Voltage and Ca^{2+} can form either a positive or a negative feedback loop, while voltage and Na^{+} form a negative feedback loop. Under certain diseased conditions, when the feedback between voltage and Ca^{2+} is positive, Hopf bifurcations occur, leading to periodic oscillatory behaviors. When this feedback is negative, period-doubling bifurcation routes to alternans and chaos occur.


Assuntos
Cálcio/metabolismo , Modelos Cardiovasculares , Miócitos Cardíacos/metabolismo , Sódio/metabolismo , Relógios Biológicos , Cátions Bivalentes/metabolismo , Cátions Monovalentes/metabolismo , Membrana Celular/metabolismo , Polaridade Celular , Retroalimentação Fisiológica , Ventrículos do Coração/citologia , Ventrículos do Coração/metabolismo , Potenciais da Membrana , Miócitos Cardíacos/citologia , Trocador de Sódio e Cálcio/metabolismo
8.
Biochemistry (Mosc) ; 84(11): 1280-1295, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31760918

RESUMO

Maintenance of non-equilibrium Na+ and K+ distribution between cytoplasm and extracellular medium suggests existence of sensors responding with conformational transitions to the changes of these monovalent cations' intracellular concentration. Molecular nature of monovalent cation sensors has been established in Na,K-ATPase, G-protein-coupled receptors, and heat shock proteins structural studies. Recently, it was found that changes in Na+ and K+ intracellular concentration are the key factors in the transcription and translation control, respectively. In this review, we summarize results of these studies and discuss physiological and pathophysiological significance of Na+i,K+i-dependent gene expression regulation mechanism.


Assuntos
Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Sódio/metabolismo , Animais , Cátions Monovalentes/química , Citoplasma/metabolismo , Proteínas de Choque Térmico/metabolismo , Potássio/química , Biossíntese de Proteínas , Sódio/química , Transcrição Genética
9.
Proc Natl Acad Sci U S A ; 116(42): 21022-21030, 2019 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-31570624

RESUMO

RNA molecules cannot fold in the absence of counterions. Experiments are typically performed in the presence of monovalent and divalent cations. How to treat the impact of a solution containing a mixture of both ion types on RNA folding has remained a challenging problem for decades. By exploiting the large concentration difference between divalent and monovalent ions used in experiments, we develop a theory based on the reference interaction site model (RISM), which allows us to treat divalent cations explicitly while keeping the implicit screening effect due to monovalent ions. Our theory captures both the inner shell and outer shell coordination of divalent cations to phosphate groups, which we demonstrate is crucial for an accurate calculation of RNA folding thermodynamics. The RISM theory for ion-phosphate interactions when combined with simulations based on a transferable coarse-grained model allows us to predict accurately the folding of several RNA molecules in a mixture containing monovalent and divalent ions. The calculated folding free energies and ion-preferential coefficients for RNA molecules (pseudoknots, a fragment of the rRNA, and the aptamer domain of the adenine riboswitch) are in excellent agreement with experiments over a wide range of monovalent and divalent ion concentrations. Because the theory is general, it can be readily used to investigate ion and sequence effects on DNA properties.


Assuntos
Cátions Bivalentes/metabolismo , Cátions Monovalentes/metabolismo , Dobramento de RNA/fisiologia , RNA/metabolismo , Íons/metabolismo , Termodinâmica
10.
Pharmacol Rev ; 71(4): 571-595, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31551350

RESUMO

Endogenous ions play important roles in the function and pharmacology of G-protein coupled receptors (GPCRs). Historically the evidence for ionic modulation of GPCR function dates to 1973 with studies of opioid receptors, where it was demonstrated that physiologic concentrations of sodium allosterically attenuated agonist binding. This Na+-selective effect was distinct from effects of other monovalent and divalent cations, with the latter usually counteracting sodium's negative allosteric modulation of binding. Since then, numerous studies documenting the effects of mono- and divalent ions on GPCR function have been published. While ions can act selectively and nonselectively at many sites in different receptors, the discovery of the conserved sodium ion site in class A GPCR structures in 2012 revealed the unique nature of Na+ site, which has emerged as a near-universal site for allosteric modulation of class A GPCR structure and function. In this review, we synthesize and highlight recent advances in the functional, biophysical, and structural characterization of ions bound to GPCRs. Taken together, these findings provide a molecular understanding of the unique roles of Na+ and other ions as GPCR allosteric modulators. We will also discuss how this knowledge can be applied to the redesign of receptors and ligand probes for desired functional and pharmacological profiles. SIGNIFICANCE STATEMENT: The function and pharmacology of GPCRs strongly depend on the presence of mono and divalent ions in experimental assays and in living organisms. Recent insights into the molecular mechanism of this ion-dependent allosterism from structural, biophysical, biochemical, and computational studies provide quantitative understandings of the pharmacological effects of drugs in vitro and in vivo and open new avenues for the rational design of chemical probes and drug candidates with improved properties.


Assuntos
Receptores Acoplados a Proteínas-G/antagonistas & inibidores , Receptores Acoplados a Proteínas-G/metabolismo , Sódio/metabolismo , Sítio Alostérico , Ânions/química , Ânions/metabolismo , Sítios de Ligação , Cátions Bivalentes/química , Cátions Bivalentes/metabolismo , Cátions Monovalentes/química , Cátions Monovalentes/metabolismo , Cloretos/química , Cloretos/metabolismo , Cristalografia por Raios X , Humanos , Ligantes , Conformação Proteica , Receptores Acoplados a Proteínas-G/química , Sódio/química , Relação Estrutura-Atividade , Zinco/química , Zinco/metabolismo
11.
Chem Commun (Camb) ; 55(80): 12004-12007, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31503273

RESUMO

Single-stranded DNA designed G-quadruplexes, modified with lipophilic 12-carbon spacers and cholesterol to span lipid membranes, were developed as smart transmembrane channels for selective and switchable potassium ion (K+) transport across membranes.


Assuntos
DNA de Cadeia Simples/química , Quadruplex G , Potássio/química , Lipossomas Unilamelares/química , 1,2-Dipalmitoilfosfatidilcolina/química , Materiais Biomiméticos , Cátions Monovalentes , Gramicidina/química , Concentração de Íons de Hidrogênio , Transporte de Íons , Cinética , Valinomicina/química
12.
Molecules ; 24(16)2019 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-31426565

RESUMO

A series of ditopic ion pair receptors equipped with 4-nitrophenylurea and 1-aza-18-crown-6-ether linked by ortho-(1), meta-(2), and para-(3) substituted benzoic acid were readily synthesized in three steps from commercially available materials. The binding properties of these regioisomeric receptors were determined using UV-vis and 1H NMR spectroscopy in MeCN and in the solid state by single-crystal X-ray diffraction crystallography. The solution studies revealed that, apart from carboxylates, all the anions tested formed stronger complexes in the presence of sodium cations. Receptors 2 and 3 were found to interact with ion pairs with remarkably higher affinity than ortho-substituted 1. 1H NMR titration experiments showed that both urea NH protons interacted with anions with comparable strength in the case of receptors 2 and 3, but only one of the NHs was effective in anion binding in the case of receptor 1. X-ray analysis of the crystal structure of receptor 1 and 1·NaPF6 complex showed that binding was hampered due to the formation of an intramolecular hydrogen bond. Analysis of the crystal structures of 2·NaBr and 3·NaBr complexes revealed that proper mutual orientation of binding domains was responsible for the improved binding of the sodium salts.


Assuntos
Ânions/química , Benzoatos/química , Carbanilidas/química , Éteres de Coroa/química , Receptores Artificiais/química , Sódio/química , Cátions Monovalentes , Cristalografia por Raios X , Ligação de Hidrogênio , Cinética , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Prótons , Receptores Artificiais/síntese química , Estereoisomerismo
13.
Nature ; 572(7770): 488-492, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31367042

RESUMO

Cation-chloride cotransporters (CCCs) mediate the electroneutral transport of chloride, potassium and/or sodium across the membrane. They have critical roles in regulating cell volume, controlling ion absorption and secretion across epithelia, and maintaining intracellular chloride homeostasis. These transporters are primary targets for some of the most commonly prescribed drugs. Here we determined the cryo-electron microscopy structure of the Na-K-Cl cotransporter NKCC1, an extensively studied member of the CCC family, from Danio rerio. The structure defines the architecture of this protein family and reveals how cytosolic and transmembrane domains are strategically positioned for communication. Structural analyses, functional characterizations and computational studies reveal the ion-translocation pathway, ion-binding sites and key residues for transport activity. These results provide insights into ion selectivity, coupling and translocation, and establish a framework for understanding the physiological functions of CCCs and interpreting disease-related mutations.


Assuntos
Microscopia Crioeletrônica , Membro 2 da Família 12 de Carreador de Soluto/metabolismo , Membro 2 da Família 12 de Carreador de Soluto/ultraestrutura , Peixe-Zebra , Sequência de Aminoácidos , Animais , Sítios de Ligação , Cátions Monovalentes/metabolismo , Cloretos/metabolismo , Citosol/metabolismo , Síndrome de Gitelman/genética , Humanos , Transporte de Íons , Modelos Moleculares , Simulação de Dinâmica Molecular , Potássio/metabolismo , Domínios Proteicos , Sódio/metabolismo , Membro 2 da Família 12 de Carreador de Soluto/química , Membro 2 da Família 12 de Carreador de Soluto/genética , Peixe-Zebra/genética
14.
Chemistry ; 25(66): 15030-15035, 2019 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-31365771

RESUMO

Intracellular CuI is controlled by the transcriptional regulator CueR, which effectively discriminates between monovalent and divalent metal ions. It is intriguing that HgII does not activate transcription, as bis-thiolate metal sites exhibit high affinity for HgII . Here the binding of HgII to CueR and a truncated variant, ΔC7-CueR, without the last 7 amino acids at the C-terminus including a conserved CCHH motif is explored. ESI-MS demonstrates that up to two HgII bind to CueR, while ΔC7-CueR accommodates only one HgII . 199m Hg PAC and UV absorption spectroscopy indicate HgS2 structure at both the functional and the CCHH metal site. However, at sub-equimolar concentrations of HgII at pH 8.0, the metal binding site displays an equilibrium between HgS2 and HgS3 , involving cysteines from both sites. We hypothesize that the C-terminal CCHH motif provides auxiliary ligands that coordinate to HgII and thereby prevents activation of transcription.


Assuntos
Cisteína/química , Proteínas de Escherichia coli/química , Mercúrio/química , Transativadores/química , Sequência de Aminoácidos , Sítios de Ligação , Cátions Bivalentes/química , Cátions Monovalentes/química , Cobre/química , Cisteína/metabolismo , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Ligantes , Mercúrio/metabolismo , Alinhamento de Sequência , Transativadores/genética , Transativadores/metabolismo , Ativação Transcricional
15.
Methods Cell Biol ; 153: 151-168, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31395377

RESUMO

Aldosterone-sensitive distal nephron (ASDN) including the distal convoluted tubule (DCT), connecting tubule (CNT) and collecting duct (CD) plays an important role in the regulation of hormone-dependent Na+ reabsorption and dietary K+-intake dependent K+ excretion. The major Na+ transporters in the ASDN are thiazide-sensitive Na-Cl cotransporter (NCC), epithelial Na+ channel (ENaC), pendrin/Na+-dependent Cl--bicarbonate exchanger (NDCBE). Whereas major K+ channels in the ASDN are Kir4.1 and Kir5.1 in the basolateral membrane; and Kir1.1 (ROMK) and Ca2+ activated big conductance K+ channel (BK) in the apical membrane. Although a variety of in vitro cell lines of the ASDN is available and these cell models have been employed for studying Na+ and K+ channels, the biophysical properties and the regulation of Na+ and K+ channels in vitro cell models may not be able to recapitulate those in vivo conditions. Thus, the studies performed in the native ASDN are essential for providing highly physiological relevant information and for understanding the Na+ and K+ transport in the ASDN. Here we provide a detailed methodology describing how to perform the electrophysiological measurement in the native DCT, CNT and cortical collecting duct (CCD).


Assuntos
Canais Iônicos/metabolismo , Túbulos Renais Distais/metabolismo , Técnicas de Patch-Clamp/métodos , Potássio/metabolismo , Sódio/metabolismo , Aldosterona/metabolismo , Animais , Cátions Monovalentes/metabolismo , Camundongos , Microdissecção/instrumentação , Microdissecção/métodos , Técnicas de Patch-Clamp/instrumentação , Eliminação Renal/fisiologia , Reabsorção Renal/fisiologia
16.
RNA ; 25(11): 1532-1548, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31391217

RESUMO

RNA kissing complexes are essential for genomic RNA dimerization and regulation of gene expression, and their structures and stability are critical to their biological functions. In this work, we used our previously developed coarse-grained model with an implicit structure-based electrostatic potential to predict three-dimensional (3D) structures and stability of RNA kissing complexes in salt solutions. For extensive RNA kissing complexes, our model shows great reliability in predicting 3D structures from their sequences, and our additional predictions indicate that the model can capture the dependence of 3D structures of RNA kissing complexes on monovalent/divalent ion concentrations. Moreover, the comparisons with extensive experimental data show that the model can make reliable predictions on the stability for various RNA kissing complexes over wide ranges of monovalent/divalent ion concentrations. Notably, for RNA kissing complexes, our further analyses show the important contribution of coaxial stacking to the 3D structures and stronger stability than the corresponding kissing-interface duplexes at high salts. Furthermore, our comprehensive analyses for RNA kissing complexes reveal that the thermally folding pathway for a complex sequence is mainly determined by the relative stability of two possible folded states of kissing complex and extended duplex, which can be significantly modulated by its sequence.


Assuntos
Conformação de Ácido Nucleico , RNA/química , Sais/química , Cátions Bivalentes , Cátions Monovalentes , Soluções
17.
Am J Physiol Lung Cell Mol Physiol ; 317(4): L498-L509, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31389736

RESUMO

Muco-obstructive lung diseases (MOLDs), like cystic fibrosis and chronic obstructive pulmonary disease, affect a spectrum of subjects globally. In MOLDs, the airway mucus becomes hyperconcentrated, increasing osmotic and viscoelastic moduli and impairing mucus clearance. MOLD research requires relevant sources of healthy airway mucus for experimental manipulation and analysis. Mucus collected from endotracheal tubes (ETT) may represent such a source with benefits, e.g., in vivo production, over canonical sample types such as sputum or human bronchial epithelial (HBE) mucus. Ionic and biochemical compositions of ETT mucus from healthy human subjects were characterized and a stock of pooled ETT samples generated. Pooled ETT mucus exhibited concentration-dependent rheologic properties that agreed across spatial scales with reported individual ETT samples and HBE mucus. We suggest that the practical benefits compared with other sample types make ETT mucus potentially useful for MOLD research.


Assuntos
Muco/química , Potássio/análise , Reologia/métodos , Sódio/análise , Traqueia/química , Adulto , Idoso , Idoso de 80 Anos ou mais , Cátions Monovalentes , Feminino , Voluntários Saudáveis , Humanos , Intubação Intratraqueal , Masculino , Pessoa de Meia-Idade , Polissacarídeos/classificação , Polissacarídeos/isolamento & purificação , Potássio/metabolismo , Proteínas/classificação , Proteínas/isolamento & purificação , Sódio/metabolismo , Escarro/química , Traqueia/fisiologia
18.
Colloids Surf B Biointerfaces ; 183: 110335, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31394422

RESUMO

Au11(SG)7 gold nanoparticles (GNPs) were synthesized from HAuCl4 using thiol compounds containing an amino group to serve as both the reducing agent and the ligand. A three-dimensional network structure (…Au-SNH2→Mn+⟵H2NS-Au…) was formed after the Mn+ (Pb2+, Cd2+, Zn2+ and Ag+) coordinated the gold nanoparticles through the amino group in the thiol ligand, which promoted aurophilicity (…Au…Au…) and induced GNP aggregation and emission. The differences in coordination between the amino group and metal ions resulted in different emission wavelengths (Pb2+, Cd2+, Zn2+ and Ag+: λex = 365 nm˜370 nm, λem = 580, 645, 630 and 565 nm). Aggregation induced emission of amino thiol capped GNPs via coordination of Pb2+ or Cd2+ can be used as a fluorescent sensor of the both metal ions (λex = 365 nm, λem = 580/645 nm) and were used for living bioimaging in vivo and in vitro.


Assuntos
Técnicas Biossensoriais/métodos , Cádmio/química , Ouro/química , Chumbo/química , Nanopartículas Metálicas/química , Compostos de Sulfidrila/química , Cádmio/metabolismo , Cátions Bivalentes , Cátions Monovalentes , Linhagem Celular , Complexos de Coordenação/química , Complexos de Coordenação/metabolismo , Hepatócitos/metabolismo , Hepatócitos/ultraestrutura , Humanos , Chumbo/metabolismo , Ligantes , Nanopartículas Metálicas/ultraestrutura , Imagem Molecular/métodos , Imagem Óptica/métodos , Oxirredução , Prata/química , Prata/metabolismo , Zinco/química , Zinco/metabolismo
19.
Molecules ; 24(16)2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31405189

RESUMO

The influence of Li+, Na+ and Cs+ cations on the surface excess and structure of dodecyl sulfate (DS-) anions at the air-water interface was investigated with the vibrational sum-frequency generation (SFG) and surface tensiometry. Particularly, we have addressed the change in amplitude and frequency of the symmetric S-O stretching vibrations as a function of electrolyte and DS- concentration in the presence of Li+, Na+ and Cs+ cations. For the Li+ and Na+ ions, we show that the resonance frequency is shifted noticeably from 1055 cm-1 to 1063 cm-1 as a function of the surfactants' surfaces excess, which we attribute to the vibrational Stark effect within the static electric field at the air-water interface. For Cs+ ions the resonance frequency is independent of the surfactant concentration with the S-O stretching band centered at 1063 cm-1. This frequency is identical to the frequency at the maximum surface excess when Li+ and Na+ ions are present and points to the ion pair formation between the sulfate headgroup and Cs+ counterions, which reduces the local electric field. In addition, SFG experiments of the O-H stretching bands of interfacial H2O molecules are used in order to calculate the apparent double layer potential and the degree of dissociation between the surfactant head group and the investigated cations. The latter was found to be 12.0%, 10.4% and 7.7% for lithium dodecyl sulfate (LiDS), sodium dodecyl sulfate (SDS) and cesium dodecyl sulfate (CsDS) surfactants, which is in agreement with Collins 'rule of matching water affinities'.


Assuntos
Lítio/química , Dodecilsulfato de Sódio/química , Sódio/química , Tensoativos/química , Álcalis/química , Cátions Monovalentes/química
20.
J Am Soc Mass Spectrom ; 30(9): 1758-1767, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31286444

RESUMO

Gas-phase conformations of the sodium-cationized forms of the 2'-deoxycytidine and cytidine mononucleotides, [pdCyd+Na]+ and [pCyd+Na]+, are examined by infrared multiple photon dissociation action spectroscopy. Complimentary electronic structure calculations at the B3LYP/6-311+G(2d,2p)//B3LYP/6-311+G(d,p) level of theory provide candidate conformations and their respective predicted IR spectra for comparison across the IR fingerprint and hydrogen-stretching regions. Comparisons of the predicted IR spectra and the measured infrared multiple photon dissociation action spectra provide insight into the impact of sodium cationization on intrinsic mononucleotide structure. Further, comparison of present results with those reported for the sodium-cationized cytidine nucleoside analogues elucidates the impact of the phosphate moiety on gas-phase structure. Across the neutral, protonated, and sodium-cationized cytidine mononucleotides, a preference for stabilization of the phosphate moiety and nucleobase orientation is observed, although the details of this stabilization differ with the state of cationization. Several low-energy conformations of [pdCyd+Na]+ and [pCyd+Na]+ involving several different orientations of the phosphate moiety and sugar puckering modes are observed experimentally.


Assuntos
Citidina/química , DNA/química , RNA/química , Sódio/química , Espectrofotometria Infravermelho/métodos , Cátions Monovalentes/química , Citidina Monofosfato/química , Desoxicitidina Monofosfato/química , Gases/química , Conformação de Ácido Nucleico
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