Molecular dynamics test of the Brownian description of Na+ motion in water

International Nuclear Information System (INIS)

Wilson, M.A.; Pohorille, A.; Pratt, L.R.

1985-01-01

The autocorrelation function of the velocity of an infinitely dilute Na + ion in aqueous solution, and the autocorrelation function of the force exerted on a stationary Na + under the same conditions are evaluated by molecular dynamics calculations. The results are used to test the accuracy of Brownian motion assumptions which are basic to hydrodynamic models of ion dynamics in solution. The self-diffusion coefficient of the Na + ion predicted by Brownian motion theory is (0.65 +- 0.1) x 10 -5 cm 2 /s. This value is about 60% greater than the one obtained for the proper dynamics of the finite mass ion, (0.4 +- 0.1) x 10 -5 cm 2 /s. The numerically correct velocity autocorrelation function is nonexponential, and the autocorrelation of the force on the stationary ion does not decay faster than the ion velocity autocorrelation function. Motivated by previous hydrodynamic modeling of friction kernels, we examine the approximation in which the memory function for the velocity autocorrelation function is identified with the autocorrelation function of the force on the stationary ion. The overall agreement between this approximation for the velocity autocorrelation function and the numerically correct answer is quite good

Electron transfer in keV Li+-Na*(3p) collisions: Pt.2. Molecular basis model

International Nuclear Information System (INIS)

Machholm, M.; Courbin, C.

1996-01-01

The velocity dependence of state-to-state integral cross sections for electron transfer and excitation in Li + -Na(3s, 3p) collisions is studied in the 0.05-0.3 au velocity range using the impact parameter semi-classical method and a 28-state molecular orbital basis model including a common translation factor. The initial orbital alignment dependence of electron transfer is in fair agreement with recent experiments and with atomic orbital model calculations. The main electron transfer channel from Na*(3p) is to the Li*(2p) states. The integral cross sections from an aligned or oriented Na*(3p) state to an aligned or oriented Li*(2p) state and vice versa and the corresponding alignment and orientation parameters are presented as a function of the impact velocity. (author)

Molecular dynamics of polarizable point dipole models for molten NaI. Comparison with first principles simulations

Directory of Open Access Journals (Sweden)

Trullàs J.

2011-05-01

Full Text Available Molecular dynamics simulations of molten NaI at 995 K have been carried out using polarizable ion models based on rigid ion pair potentials to which the anion induced dipole polarization is added. The polarization is added in such a way that point dipoles are induced on the anions by both local electric field and deformation short-range damping interactions that oppose the electrically induced dipole moments. The structure and self-diffusion results are compared with those obtained by Galamba and Costa Cabral using first principles Hellmann-Feynman molecular dynamics simulations and using classical molecular dynamics of a shell model which allows only the iodide polarization

Molecular dynamics simulations of the three-layer hydrate of Na-montmorillonite

International Nuclear Information System (INIS)

Holmboe, Michael; Bourg, Ian C.

2012-01-01

Document available in extended abstract form only. In many nuclear waste repositories concepts, compacted and smectite-rich bentonite clay is considered as an engineered transport barrier surrounding the canisters holding the nuclear waste. One of the requirements in the safety assessment of these repositories is to predict the transport rate of radionuclides as well as the overall hydraulic conductivity through the bentonite barrier. Kozaki and co-workers have obtained important information from diffusion experiments in bentonite on the mechanisms that control solute transport by studying the temperature-dependence of apparent diffusivity for solutes such as Na + , Cs + and Sr 2+ . Their results showed that the apparent diffusivity follows an Arrhenius relation (ln D a ∝ -E A /RT) with distinct activation energies of diffusion (E A ) for certain montmorillonite compactions, ionic strengths, and types of interlayer cation (Na + vs. Ca 2+ ). Their results suggest that solutes follow different diffusion pathways in compacted montmorillonite at different experimental conditions. In order to identify these transport pathways in compacted montmorillonite one needs independent knowledge of the relative abundance of the different types of interlayer nano-pores, i.e. the different coexisting hydration states (1W-3W), and of the molecular-scale EA for solute diffusion on the external basal surfaces of montmorillonite particles and in the interlayer nano-pores. The latter property can be obtained using molecular dynamics (MD) simulations, an important tool in the characterization of clays and clay minerals that yields detailed atomistic insights into the structural, dynamical and thermodynamic properties of many different geochemically relevant systems. In particular, MD simulations yield insight into the behavior of individual atoms, where most experimental methods only would probe the average behavior of large numbers of atoms or molecules. Thus, by simulating systems of

Ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi

International Nuclear Information System (INIS)

Wadt, W.R.; Hay, P.J.

1985-01-01

A consistent set of ab initio effective core potentials (ECP) has been generated for the main group elements from Na to Bi using the procedure originally developed by Kahn. The ECP's are derived from all-electron numerical Hartree--Fock atomic wave functions and fit to analytical representations for use in molecular calculations. For Rb to Bi the ECP's are generated from the relativistic Hartree--Fock atomic wave functions of Cowan which incorporate the Darwin and mass--velocity terms. Energy-optimized valence basis sets of (3s3p) primitive Gaussians are presented for use with the ECP's. Comparisons between all-electron and valence-electron ECP calculations are presented for NaF, NaCl, Cl 2 , Cl 2 - , Br 2 , Br 2 - , and Xe 2 + . The results show that the average errors introduced by the ECP's are generally only a few percent

Dermatose responsiva à biotina em cão Dermatosis responsive to Biotin in a dog

OpenAIRE

Sandra Prudente Nogueira; Márcio Antonio Brunetto; Juliana Toloi Jeremias; Márcia de Oliveira Sampaio Gomes; Eliana Teshima; Aulus Cavalieri Carciofi

2010-01-01

Os transtornos da pele e dos pelos são parte importante na prática clínica de pequenos animais. Numerosos fatores nutricionais afetam a homeostase, a qualidade e o aspecto da pelagem. As vitaminas do complexo B incluem compostos hidrossolúveis necessários como coenzimas em diversas funções celulares envolvidas no metabolismo energético e na síntese tecidual. A biotina, em especial, é necessária nas reações de carboxilação, participando da síntese de ácidos graxos, aminoácidos e purinas pelo t...

Molecular dynamics simulations of the effect of NaCl-doping on the calcination characteristics in desulfurization processes

Energy Technology Data Exchange (ETDEWEB)

Murakami, T.; Kurita, N.; Naruse, I. [Toyohashi University of Technology, Toyohashi (Japan)

2003-03-01

Desulfurization performance of wasted seashells was found to be over twice as high as that of limestone, which was currently used as a desulfurizer in fluidized bed coal combustors. NaCl-doping into limestone was also found to be effective in improving the desulfurization efficiency. From X-ray diffraction (XRD) analyses of calcined seashell, limestone and NaCl-doped limestone, on the other hand, not only the calcined seashell but also the NaCl-doped limestone had strong peaks of CaO crystal, and those two materials also had high desulfurization activity. This improvement was hypothesized to be due to NaCl causing a change in the crystal structure of CaO. In order to elucidate the effect of NaCl addition on the CaO crystal structure in the incineration of CaCO{sub 3} the change of structures was simulated by means of molecular dynamics simulations of CaO. In the simulation one molecule of NaCl was exchanged into one molecule of CaO. A pair correlation functions and the distances between Ca and O atoms, which were obtained by the simulations, were compared with those from the crystal CaO. NaCl-doping affected the crystalization temperature of CaO. The crystallization temperature increased due to adding a little bit of NaCl. From the result of the pair correlation functions obtained in NaCl-doped CaO, the difference of the potential energy of NaCl from that of CaO seemed to contribute to the crystallization of the bulk of CaO. The simulation and experimental results obtained suggested that NaCl-doping contributed to crystallizing the CaO molecules.

[Comparison of manual and automated (MagNA Pure) nucleic acid isolation methods in molecular diagnosis of HIV infections].

Science.gov (United States)

Alp, Alpaslan; Us, Dürdal; Hasçelik, Gülşen

2004-01-01

Rapid quantitative molecular methods are very important for the diagnosis of human immunodeficiency virus (HIV) infections, assessment of prognosis and follow up. The purpose of this study was to compare and evaluate the performances of conventional manual extraction method and automated MagNA Pure system, for the nucleic acid isolation step which is the first and most important step in molecular diagnosis of HIV infections. Plasma samples of 35 patients in which anti-HIV antibodies were found as positive by microparticule enzyme immunoassay and confirmed by immunoblotting method, were included in the study. The nucleic acids obtained simultaneously by manual isolation kit (Cobas Amplicor, HIV-1 Monitor Test, version 1.5, Roche Diagnostics) and automated system (MagNA Pure LC Total Nucleic Acid Isolation Kit, Roche Diagnostics), were amplified and detected in Cobas Amplicor (Roche Diagnostics) instrument. Twenty three of 35 samples (65.7%) were found to be positive, and 9 (25.7%) were negative by both of the methods. The agreement between the methods were detected as 91.4%, for qualitative results. Viral RNA copies detected by manual and MagNA Pure isolation methods were found between 76.0-7.590.000 (mean: 487.143) and 113.0-20.300.0000 (mean: 2.174.097) copies/ml, respectively. When both of the overall and individual results were evaluated, the number of RNA copies obtained with automatized system, were found higher than the manual method (p<0.05). Three samples which had low numbers of nucleic acids (113, 773, 857, respectively) with MagNA Pure, yielded negative results with manual method. In conclusion, the automatized MagNA Pure system was found to be a reliable, rapid and practical method for the isolation of HIV-RNA.

Concentrações salivares, sanguíneas e plasmáticas de Óxido Nítrico em pacientes com Doença Periodontal antes e depois do tratamento periodontal não cirúrgico

OpenAIRE

Leonardo Raphael Zuardi

2012-01-01

O Óxido Nítrico (NO) faz parte de uma família de radicais livres que está envolvida em várias funções do organismo como controle cardiovascular, homeostase, formação óssea, neurotransmissão e funções imunológicas. Tem sido descrito que o NO atuaria na resposta de defesa do hospedeiro frente à infecção dos tecidos orais. Por outro lado, tem sido descrito também que quantidades excessivas de NO podem contribuir para a destruição tecidual na periodontite. Além destes aspectos muito importantes n...

Marcadores moleculares na predição do sexo em plantas de mamoeiro Molecular markers for sex identification in papaya

Directory of Open Access Journals (Sweden)

Eder Jorge de Oliveira

2007-12-01

Full Text Available O objetivo deste trabalho foi validar marcadores moleculares, previamente identificados como ligados ao sexo do mamoeiro, para utilização na seleção indireta em genótipos comerciais. Foram analisadas duas variedades do grupo Solo e dois híbridos do grupo Formosa, com utilização de 20 plantas por genótipo, quatro marcadores do tipo SCAR (Sequence Characterized Amplified Region e um RAPD (Random Amplified Polymorphic DNA. O RAPD BC210 permitiu a identificação de todas as plantas femininas e hermafroditas, o que revela grande potencial para ser usado na seleção assistida em alguns dos genótipos mais cultivados no Brasil. Os marcadores do tipo SCAR não permitiram a identificação correta do sexo dos genótipos, pois detectou-se a presença de falso-positivos e falso-negativos nas análises.The objective of this work was the validation of previous discovered sex related molecular markers of papaya, aiming at the indirect selection of Brazilian commercial genotypes. Two varieties of the Solo group and two hybrids of the Formosa group (20 plants for genotype, four SCAR (Sequence Characterized Amplified Region and one RAPD (Random Amplified Polymorphic DNA markers were used. All hermaphrodite and female plants were correctly predicted by RAPD BC210, showing its high potential for marker assisted selection in important commercial genotypes used in Brazil. The SCAR markers did not show the true sex identification of these genotypes, revealing the presence of false positives and negatives in the analyses.

Effect of thyroid status on the development of the different molecular forms of Na+,K+-ATPase in rat brain.

Science.gov (United States)

Atterwill, C K; Reid, J; Athayde, C M

1985-05-01

The effect of thyroid status on the postnatal development of the two molecular forms of Na+,K+-ATPase, distinguished kinetically on the basis of their ouabain sensitivity, was examined in rat brain. Hypothyroidism induced by PTU from day 1 postnatally significantly reduced the Na+,K+-ATPase activity in cerebellum (22-30 days) but not forebrain, whereas hyperthyroidism (T4 treatment from day 1) had no effect. The hypothyroidism-induced reduction in cerebellum was reflected by a 20-45% reduction in the activity of the alpha(+) form of Na+,K+-ATPase (high ouabain affinity) against control brains compared to a 60-70% reduction in the activity of the alpha form (low ouabain affinity). These results show that neonatally induced hypothyroidism leads to a selectively greater impairment of the ontogenesis of the activity of cerebellar alpha form of Na+,K+-ATPase. This may possibly reflect a retarded development of a selective cerebellar cell population containing predominantly the alpha form of the enzyme.

Molecular dynamics investigation of Na+ in Na2Ni2TeO6

International Nuclear Information System (INIS)

Sau, Kartik; Kumar, P. Padma

2014-01-01

An inter-atomic potential for Na 2 Ni 2 TeO 6 in the Parrinello- Rahman-Vashishta (PRV) model is parameterized empirically. The potential reproduces variety of structural and transport properties of that material in good agreement with recent experimental results. The study provides fresh insights on the migration channels and mechanism of Na + in the system

Urinary electrolyte monitoring in critically ill patients: a preliminary observational study

OpenAIRE

Maciel, Alexandre Toledo; Park, Marcelo; Macedo, Etienne

2012-01-01

OBJETIVO: Sobreviventes e não sobreviventes da unidade de terapia intensiva apresentam perfis ácido-básicos distintos. A regulação renal de eletrólitos urinários e a diferença de íons fortes urinários têm papéis principais na homeostase ácido- básica. O objetivo deste estudo foi avaliar a potencial utilidade da mensuração diária dos eletrólitos urinários na monitorização ácido-básica e da função renal. MÉTODOS: Foram registrados, prospectivamente e diariamente, parâmetros ácido-básicos plasmá...

Marcadores moleculares derivados de sequências expressas do genoma café potencialmente envolvidas na resistência à ferrugem

Directory of Open Access Journals (Sweden)

Samuel Mazzinghy Alvarenga

2011-08-01

Full Text Available O objetivo deste trabalho foi identificar marcadores moleculares relacionados à resistência do cafeeiro (Coffea arabica à ferrugem (Hemileia vastatrix. Foram identificadas sequências de DNA potencialmente envolvidas na resistência do cafeeiro a doenças, por meio de análise "in silico", a partir das informações geradas pelo Projeto Brasileiro do Genoma Café. A partir das sequências mineradas, foram desenhados 59 pares de iniciadores para amplificá-las. Os 59 iniciadores foram testados em 12 cafeeiros resistentes e 12 susceptíveis a H. vastatrix. Vinte e sete iniciadores resultaram em bandas únicas e bem definidas, enquanto um deles amplificou fragmento de DNA em todos os cafeeiros resistentes, mas não nos suscetíveis. Esse marcador molecular polimórfico amplificou uma região do DNA que corresponde a uma janela aberta de leitura parcial do genoma de C. arabica que codifica uma proteína de resistência a doenças. O marcador CARF 005 é capaz de diferenciar os cafeeiros analisados em resistentes e susceptíveis a H. vastatrix.

Levitation effect in zeolites: Quasielastic neutron scattering and molecular dynamics study of pentane isomers in zeolite NaY.

Science.gov (United States)

Borah, Bhaskar J; Jobic, H; Yashonath, S

2010-04-14

We report the quasielastic neutron scattering (QENS) and molecular dynamics (MD) investigations into diffusion of pentane isomers in zeolite NaY. The molecular cross section perpendicular to the long molecular axis varies for the three isomers while the mass and the isomer-zeolite interaction remains essentially unchanged. Both QENS and MD results show that the branched isomers neopentane and isopentane have higher self-diffusivities as compared with n-pentane at 300 K in NaY zeolite. This result provides direct experimental evidence for the existence of nonmonotonic, anomalous dependence of self-diffusivity on molecular diameter known as the levitation effect. The energetic barrier at the bottleneck derived from MD simulations exists for n-pentane which lies in the linear regime while no such barrier is seen for neopentane which is located clearly in the anomalous regime. Activation energy is in the order E(a)(n-pentane)>E(a)(isopentane)>E(a)(neopentane) consistent with the predictions of the levitation effect. In the liquid phase, it is seen that D(n-pentane)>D(isopentane)>D(neopentane) and E(a)(n-pentane)

Laser-induced ionization of Na vapor

International Nuclear Information System (INIS)

Wu, R.C.Y.; Judge, D.L.; Roussel, F.; Carre, B.; Breger, P.; Spiess, G.

1982-01-01

The production of Na 2 + ions by off-resonant laser excitation in the 5800-6200A region mainly results from two-photon absorption by the Na 2 molecule to highly excited gerade states followed by (a) direct ionization by absorbing a third photon or (b) coupling to the molecular Na 2 D 1 PIμ Rydberg state which is subsequently ionized by absorbing a third photon. This mechanism, i.e., a two-photon resonance three photon ionization process, explains a recent experimental observation of Roussel et al. It is suggested that the very same mechanism is also responsible for a similar observation reported by Polak-Dingels et al in their work using two crossed Na beams. In the latter two studies the laser-induced associative ionization processes were reported to be responsible for producing the Na 2 + ion. From the ratio of molecular to atomic concentration in the crossed beam experiment of Polak-Dingels et al we estimate that the cross section for producing Na 2 + through laser-induced associative ionization is at least four orders of magnitude smaller than ionization through the two-photon resonance three photon ionization process in Na 2 molecules

Infrared thermography to evaluate the training horse thermoregulation

OpenAIRE

Moura, Daniella J. de; Maia, Ana Paula de A; Vercellino, Rimena do A; Medeiros, Brenda B. L; Sarubbi, Juliana; Griska, Paulo R

2011-01-01

O estresse térmico em equinos aciona mecanismos termorregulatórios, como mudanças no fluxo sanguíneo periférico, para a manutenção da homeostase corporal. A termografia infravermelha permite detectar estas alterações, sendo uma ferramenta útil para avaliar o estresse em animais. Assim, o objetivo deste estudo foi avaliar o uso da termografia infravermelha na termorregulação de equino em condição de treinamento. Foi utilizado um cavalo anglo-árabe, exercitado uma vez ao dia. Foram captadas ima...

The thermodynamic characteristics of vaporization in the NaI-PrI3 system

Science.gov (United States)

Motalov, V. B.; Kudin, L. S.; Markus, T.

2009-05-01

The vaporization of the NaI-PrI3 quasi-binary system was studied by high-temperature mass spectrometry over the whole concentration range. At 623-994 K, saturated vapor contained not only (NaI) n and (PrI3) n molecules ( n = 1, 2) and Na+(NaI) n ( n = 0-4) and I-(PrI3) n ( n = 1-2) ions but also mixed molecular and ionic associates recorded for the first time (NaPrI4, Na2PrI5, NaPrI{3/+}, Na2PrI{4/+}, Na3PrI{5/+}, Na4PrI{6/+}, NaPrI{5/-}, and NaPr2I{8/-}). The partial vapor pressures of molecules were calculated, and the equilibrium constants of the dissociation of neutral and charged associates were measured. The enthalpies of molecular and ion-molecular reactions were determined, and the enthalpies of formation of gaseous molecules and ions were obtained.

Distinctly Different Glass Transition Behaviors of Trehalose Mixed with Na2HPO 4 or NaH 2PO 4: Evidence for its Molecular Origin.

Science.gov (United States)

Weng, Lindong; Elliott, Gloria D

2015-07-01

The present study is aimed at understanding how the interactions between sugar molecules and phosphate ions affect the glass transition temperature of their mixtures, and the implications for pharmaceutical formulations. The glass transition temperature (Tg) and the α-relaxation temperature (Tα) of dehydrated trehalose/sodium phosphate mixtures (monobasic or dibasic) were determined by differential scanning calorimetry and dynamic mechanical analysis, respectively. Molecular dynamics simulations were also conducted to investigate the microscopic interactions between sugar molecules and phosphate ions. The hydrogen-bonding characteristics and the self-aggregation features of these mixtures were quantified and compared. Thermal analysis measurements demonstrated that the addition of NaH2PO4 decreased both the glass transition temperature and the α-relaxation temperature of the dehydrated trehalose/NaH2PO4 mixture compared to trehalose alone while both Tg and Tα were increased by adding Na2HPO4 to pure trehalose. The hydrogen-bonding interactions between trehalose and HPO4(2-) were found to be stronger than both the trehalose-trehalose hydrogen bonds and those formed between trehalose and H2PO4(-). The HPO4(2-) ions also aggregated into smaller clusters than H2PO4(-) ions. The trehalose/Na2HPO4 mixture yielded a higher T g than pure trehalose because marginally self-aggregated HPO4(2-) ions established a strengthened hydrogen-bonding network with trehalose molecules. In contrast H2PO4(-) ions served only as plasticizers, resulting in a lower Tg of the mixtures than trehalose alone, creating large-sized ionic pockets, weakening interactions, and disrupting the original hydrogen-bonding network amongst trehalose molecules.

Na,K-ATPase: a molecular target for Leptospira interrogans endotoxin

Directory of Open Access Journals (Sweden)

Younes-Ibrahim M.

1997-01-01

Full Text Available On the basis of our report that a glycolipoprotein fraction (GLP extracted from Leptospira interrogans contains a potent inhibitor of renal Na,K-ATPase, we proposed that GLP-induced inhibition of Na,K-ATPase might be the primary cellular defect in the physiopathology of leptospirosis. The present study was designed to test this hypothesis by determining whether or not 1 GLP inhibits all the isoforms of Na,K-ATPase which are expressed in the tissues affected by leptospirosis, 2 Na,K-ATPase from leptospirosis-resistant species, such as the rat, is sensitive to GLP, 3 GLP inhibits Na,K-ATPase from intact cells, and 4 GLP inhibits ouabain-sensitive H,K-ATPase. The results indicate that in the rabbit, a leptospirosis-sensitive species, GLP inhibits with similar efficiency (apparent IC50: 120-220 µg protein GLP/ml all isoforms of Na,K-ATPase known to be expressed in target tissues for the disease. Na,K-ATPase from rat kidney displays a sensitivity to GLP similar to that of the rabbit kidney enzyme (apparent IC50: 25-80 and 50-150 µg protein GLP/ml for rat and rabbit, respectively, indicating that resistance to the disease does not result from the resistance of Na,K-ATPase to GLP. GLP also reduces ouabain-sensitive rubidium uptake in rat thick ascending limbs (pmol mm-1 min-1 ± SEM; control: 23.8 ± 1.8; GLP, 88 µg protein/ml: 8.2 ± 0.9, demonstrating that it is active in intact cells. Finally, GLP had no demonstrable effect on renal H,K-ATPase activity, even on the ouabain-sensitive form, indicating that the active principle of GLP is more specific for Na,K-ATPase than ouabain itself. Although the hypothesis remains to be demonstrated in vivo, the present findings are compatible with the putative role of GLP-induced inhibition of Na,K-ATPase as an initial mechanism in the physiopathology of leptospirosis

Molecular bond formation in Na* + N2 energy transfer: Crossed beam study of atomic alignment and orientation

International Nuclear Information System (INIS)

Reiland, W.; Jamieson, G.; Tittes, U.; Hertel, I.V.

1982-01-01

We report the first full analysis of collisionally induced atomic alignment and orientation for a molecular collision process. In an experiment with crossed supersonic beams of N 2 and laser excited Na(3 2 Psub(3/2)) we have studied the dependence of angular and energy resolved differential quenching cross sections as a function of the linear and circular polarization of the exciting laser light. The ansisotropies observed in the linear polarization data range up to 2:1 when corrected for electron and nuclear spin relaxation. The maximum effect is found at small scattering angles and intermediate energy transfer where the cross section is also largest. The atomic alignment angle most favourable for quenching relates to the scattering angle and can be understood in a model picture in such a way that the (NaN 2 )* molecular system is formed at internuclear distances as low as R = 10a 0 . The circular asymmetry is small but with significant structure and is attributed to interaction on different potential surfaces at R > 10a 0 . Full analysis of the four measurable parameter is given in terms of the density matrix in a frame with z-axis perpendicular to collision plane which allows a clear understanding of the properties of atomic reflection symmetry and coherence of the scattering process. (orig.)

Glucose-homeostase bij diabetes mellitus

NARCIS (Netherlands)

Oosten, Hessel Rienk

1988-01-01

In dit proefschrift worden enige aspecten van de glucosehomeostase bij type I (insuline afhankelijke) diabetes mellitus behandeld. Deze aspecten betreffen onder meer: het effect van verschillende glucosespiegels op de glucosebehoefte bij lage (±10 mE/m²/min) en verhoogde (30 mE/m²/min)

The human Na+-glucose cotransporter is a molecular water pump

DEFF Research Database (Denmark)

Meinild, A; Klaerke, D A; Loo, D D

1998-01-01

1. The human Na+-glucose cotransporter (hSGLT1) was expressed in Xenopus laevis oocytes. The transport activity, given by the Na+ current, was monitored as a clamp current and the concomitant flux of water followed optically as the change in oocyte volume. 2. When glucose was added to the bathing...... solution there was an abrupt increase in clamp current and an immediate swelling of the oocyte. The transmembrane transport of two Na+ ions and one sugar molecule was coupled, within the protein itself, to the influx of 210 water molecules. 3. This stoichiometry was constant and independent of the external...... parameters: Na+ concentrations, sugar concentrations, transmembrane voltages, temperature and osmotic gradients. 4. The cotransport of water occurred in the presence of adverse osmotic gradients. In accordance with the Gibbs equation, energy was transferred within the protein from the downhill fluxes of Na...

Na/K Pump and Beyond: Na/K-ATPase as a Modulator of Apoptosis and Autophagy

Directory of Open Access Journals (Sweden)

Cassiano Felippe Gonçalves-de-Albuquerque

2017-04-01

Full Text Available Lung cancer is a leading cause of global cancer deaths. Na/K-ATPase has been studied as a target for cancer treatment. Cardiotonic steroids (CS trigger intracellular signalling upon binding to Na/K-ATPase. Normal lung and tumour cells frequently express different pump isoforms. Thus, Na/K-ATPase is a powerful target for lung cancer treatment. Drugs targeting Na/K-ATPase may induce apoptosis and autophagy in transformed cells. We argue that Na/K-ATPase has a role as a potential target in chemotherapy in lung cancer treatment. We discuss the effects of Na/K-ATPase ligands and molecular pathways inducing deleterious effects on lung cancer cells, especially those leading to apoptosis and autophagy.

Na/K Pump and Beyond: Na/K-ATPase as a Modulator of Apoptosis and Autophagy.

Science.gov (United States)

Felippe Gonçalves-de-Albuquerque, Cassiano; Ribeiro Silva, Adriana; Ignácio da Silva, Camila; Caire Castro-Faria-Neto, Hugo; Burth, Patrícia

2017-04-21

Lung cancer is a leading cause of global cancer deaths. Na/K-ATPase has been studied as a target for cancer treatment. Cardiotonic steroids (CS) trigger intracellular signalling upon binding to Na/K-ATPase. Normal lung and tumour cells frequently express different pump isoforms. Thus, Na/K-ATPase is a powerful target for lung cancer treatment. Drugs targeting Na/K-ATPase may induce apoptosis and autophagy in transformed cells. We argue that Na/K-ATPase has a role as a potential target in chemotherapy in lung cancer treatment. We discuss the effects of Na/K-ATPase ligands and molecular pathways inducing deleterious effects on lung cancer cells, especially those leading to apoptosis and autophagy.

Suppression of Na interstitials in Na-F codoped ZnO

Science.gov (United States)

Huo, Wenxing; Mei, Zengxia; Tang, Aihua; Liang, Huili; Du, Xiaolong

2018-04-01

Controlling the formation of interstitial Na (Nai) self-compensating defects has been a long-term physics problem for effective Na doping in ZnO. Herein, we present an experimental approach to the suppression of Nai defects in ZnO via Na and F codoping under an oxygen-rich condition during the molecular beam epitaxy growth process. It is found that the incorporation of such large numbers of Na and F dopants (˜1020 cm-3) does not cause an obvious influence on the lattice parameters. Hall-effect measurements demonstrate that F doping efficiently raises the Fermi level (EF) of ZnO films, which is expected to make the formation energy of Nai and NaZn increase and decrease, respectively. Most of the Na atoms occupy the substitutional Zn sites, and the formation of Nai is suppressed consequently. Secondary ion mass spectrometry measurements reveal that F and Na atoms are tightly bonded together due to their strong Coulomb interaction. The enhanced deep level emission (DLE) in ZnO:Na-F is ascribed to the considerable amount of isolated Zn vacancy (VZn) defects induced by the elevated EF and the formation of neutral (" separators="| FO + - Na Zn - ) 0 complexes. On the other hand, formation of (" separators="| FO + - VZn 2 - ) - complexes in ZnO:F exhausts most of the isolated Zn vacancies, leading to the disappearance of the DLE band.

Molecular composition of vapor in the NaF-ZrF4 system

International Nuclear Information System (INIS)

Korenev, Yu.M.; Sidorov, L.N.; Rykov, A.N.; Novoselova, A.V.

1980-01-01

The NaF-ZrF 4 system is studied. It is established that Na 2 ZrF 6 , NaZrF 5 , (NaZrF 5 ) 2 , NaZr 2 F 9 complex molecules are present in the saturated vapor alongside with pure components. Partial pressures of all vapor components are determined. The values of partial pressure and evaporation heat have been used to calculate the vapor composition above the system; T-x and P-T projections of the phase diagram of the NaF-ZrF 4 system are plotted

Specialized functional diversity and interactions of the Na,K-ATPase

Directory of Open Access Journals (Sweden)

Igor I. Krivoi

2016-05-01

Full Text Available Na,K-ATPase is a protein ubiquitously expressed in the plasma membrane of all animal cells and vitally essential for their functions. A specialized functional diversity of the Na,K-ATPase isozymes is provided by molecular heterogeneity, distinct subcellular localizations and functional interactions with molecular environment. Studies over the last decades clearly demonstrated complex and isoform-specific reciprocal functional interactions between the Na,K-ATPase and neighboring proteins and lipids. These interactions are enabled by a spatially restricted ion homeostasis, direct protein-protein/lipid interactions and protein kinase signaling pathways. In addition to its ‘classical’ function in ion translocation, the Na,K-ATPase is now considered as one of the most important signaling molecules in neuronal, epithelial, skeletal, cardiac and vascular tissues. Accordingly, the Na,K-ATPase forms specialized sub-cellular multimolecular microdomains which act as receptors to circulating endogenous cardiotonic steroids triggering a number of signaling pathways. Changes in these endogenous cardiotonic steroid levels and initiated signaling responses have significant adaptive values for tissues and whole organisms under numerous physiological and pathophysiological conditions. This review discusses recent progress in the studies of functional interactions between the Na,K-ATPase and molecular microenvironment, the Na,K-ATPase-dependent signaling pathways and their significance for diversity of cell function.

Glutamate Water Gates in the Ion Binding Pocket of Na(+) Bound Na(+), K(+)-ATPase

DEFF Research Database (Denmark)

Han, Minwoo; Kopec, Wojciech; Solov'yov, Ilia A

2017-01-01

III is always protonated. Glutamic acid residues in the three binding sites act as water gates, and their deprotonation triggers water entry to the binding sites. From DFT calculations of Na(+) binding energies, we conclude that three protons in the binding site are needed to effectively bind Na......The dynamically changing protonation states of the six acidic amino acid residues in the ion binding pocket of the Na(+), K(+) -ATPase (NKA) during the ion transport cycle are proposed to drive ion binding, release and possibly determine Na(+) or K(+) selectivity. We use molecular dynamics (MD......(+) from water and four are needed to release them in the next step. Protonation of Asp926 in site III will induce Na(+) release, and Glu327, Glu954 and Glu779 are all likely to be protonated in the Na(+) bound occluded conformation. Our data provides key insights into the role of protons in the Na...

Structural Analysis of Molten NaNO3 by Molecular Dynamics Simulation

Science.gov (United States)

Tahara, Shuta; Toyama, Hiroshi; Shimakura, Hironori; Fukami, Takanori

2017-08-01

MD simulation for molten NaNO3 has been performed by using the Born-Mayer-Huggins-type potentials. The new structural features of molten NaNO3 are investigated by several analytical methods. The coordination-number and bond-angle distributions are similar to those of simple molten salts such as NaCl except for the variation caused by the different size of the anion and cation. Na+ ions are attracted toward O- ions, and get separated from N+ ions by Coulomb interactions. The distribution of the dihedral angle between NO3 - plannar ionic molecules has also been investigated.

Modeling the sorption dynamics of NaH using a reactive force field

International Nuclear Information System (INIS)

Ojwang, J. G. O.; Santen, Rutger van; Kramer, Gert Jan; Duin, Adri C. T. van; Goddard, William A. III

2008-01-01

We have parametrized a reactive force field for NaH, ReaxFF NaH , against a training set of ab initio derived data. To ascertain that ReaxFF NaH is properly parametrized, a comparison between ab initio heats of formation of small representative NaH clusters with ReaxFF NaH was done. The results and trend of ReaxFF NaH are found to be consistent with ab initio values. Further validation includes comparing the equations of state of condensed phases of Na and NaH as calculated from ab initio and ReaxFF NaH . There is a good match between the two results, showing that ReaxFF NaH is correctly parametrized by the ab initio training set. ReaxFF NaH has been used to study the dynamics of hydrogen desorption in NaH particles. We find that ReaxFF NaH properly describes the surface molecular hydrogen charge transfer during the abstraction process. Results on heat of desorption versus cluster size shows that there is a strong dependence on the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. To gain more insight into the structural transformations of NaH during thermal decomposition, we performed a heating run in a molecular dynamics simulation. These runs exhibit a series of drops in potential energy, associated with cluster fragmentation and desorption of molecular hydrogen. This is consistent with experimental evidence that NaH dissociates at its melting point into smaller fragments

The effect of prophylactic dose of a low molecular weight heparin on skin wound healing of rats Efeito da dose profilática de heparina de baixo peso molecular na cicatrização de feridas na pele de ratos

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Ozdamar Fuad Oken

2009-12-01

Full Text Available PURPOSE: To investigate the effect of prophylactic dose of a low molecular weight heparin, enoxaparin, on skin wound healing of rats. METHODS: Forty rats were used for the study. Rats were randomly assigned to two equal groups. Experimental group received prophylactic dose of enoxaparin. Physiologic saline was administered to the control group. Parameters of wound healing of experimental and control groups were compared. For comparison of the groups in terms of fibrosis, vascularization, inflammation, epithelization, and tensile strength test (Newton. Mann-Whitney-U test was used because variables were categorical data (fibrosis, vascularization, inflammation and epithelization. Differences between groups were analyzed with independent samples t-test (tensile strength. Significance was set at pOBJETIVO: Investigar o efeito de dose profilática da heparina de baixo peso molecular, enoxaparina, na cicatrização de feridas na pele de ratos. MÉTODOS: Quarenta ratos foram utilizados para o estudo. Ratos foram distribuídos aleatoriamente a dois grupos iguais. O grupo experimental recebeu profilática de enoxaparina. Solução salina fisiologica foi administrada ao grupo controle. Foram comparados parâmetros de cicatrização dos grupos experimental e controle.Os grupos foram comparados em termos de fibrose, vascularização, inflamação, epitelização e força tensil (teste de Newton. Foi realizado o teste de Mann-Whitney-U para variáveis com dados categóricos (fibrose, cicatrização, inflamação e epitelização. Diferenças entre os grupos foram analisadas como amostras independentes pelo t-teste (força tensil. Significância foi fixada para p < 0,05. RESULTADOS: A ferida do grupo experimental apresentou força tensil diminuída significativamente (p < 0,001, o exame histopatológico revelou um significativo (p < 0,001 retardo na epitelização e diminuição na fibrose, cicatrização, inflamação (p < 0,001 no grupo experimental

Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

Science.gov (United States)

Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

2015-04-30

We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees

Distinct interactions of Na+ and Ca2+ ions with the selectivity filter of the bacterial sodium channel NaVAb

International Nuclear Information System (INIS)

Ke, Song; Zangerl, Eva-Maria; Stary-Weinzinger, Anna

2013-01-01

Highlights: ► Ca 2+ translocates slowly in the filter, due to lack of “loose” knock-on mechanism. ► Identification of a high affinity binding site in Na V Ab selectivity filter. ► Changes of EEEE locus triggered by electrostatic interactions with Ca 2+ ions. -- Abstract: Rapid and selective ion transport is essential for the generation and regulation of electrical signaling pathways in living organisms. In this study, we use molecular dynamics simulations and free energy calculations to investigate how the bacterial sodium channel Na V Ab (Arcobacter butzleri) differentiates between Na + and Ca 2+ ions. Multiple nanosecond molecular dynamics simulations revealed distinct binding patterns for these two cations in the selectivity filter and suggested a high affinity calcium binding site formed by backbone atoms of residues Leu-176 and Thr-175 (S CEN ) in the sodium channel selectivity filter

Aplicaciones de la biología molecular en el aparato locomotor (proteína morfogenética ósea)

OpenAIRE

Carrillo Mateos, Juan Pablo; Carrillo Rivas, Belén

2000-01-01

La biología molecular constituye actualmente la base de la investigación biomédica. Gracias a la moderna técnica de transcripción inversa es posible obtener in Vitro proteínas humanas en gran cantidad. Un ejemplo de ello es la proteína morfogenética ósea recombinante humana (rhBMP), utilizada hasta ahora en forma experimental debido la disparidad de resultados observados en animales de experimentación y en humanos. Existen aún preguntas importantes que se deben responder antes de poder usar e...

Na+/K+-ATPase α-subunit in swimming crab Portunus trituberculatus: molecular cloning, characterization, and expression under low salinity stress

Science.gov (United States)

Han, Xiaolin; Liu, Ping; Gao, Baoquan; Wang, Haofeng; Duan, Yafei; Xu, Wenfei; Chen, Ping

2015-07-01

Na+/K+-ATPases are membrane-associated enzymes responsible for the active transport of Na+ and K+ ions across cell membranes, generating chemical and electrical gradients. These enzymes' α-subunit provides catalytic function, binding and hydrolyzing ATP, and itself becoming phosphorylated during the transport cycle. In this study, Na+/K+-ATPase α-subunit cDNA was cloned from gill tissue of the swimming crab Portunus trituberculatus by reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA end methods. Analysis of the nucleotide sequence revealed that the cDNA had a full-length of 3 833 base pairs (bp), with an open reading frame of 3 120 bp, 5' untranslated region (UTR) of 317 bp, and 3' UTR of 396 bp. The sequence encoded a 1 039 amino acid protein with a predicted molecular weight of 115.57 kDa and with estimated pI of 5.21. It was predicted here to possess all expected features of Na+/K+-ATPase members, including eight transmembrane domains, putative ATP-binding site, and phosphorylation site. Comparison of amino acid sequences showed that the P. trituberculatus α-subunit possessed an overall identity of 75%-99% to that of other organisms. Phylogenetic analysis revealed that this α-subunit was in the same category as those of crustaceans. Quantitative real-time RT-PCR analysis indicated that this α-subunit's transcript were most highly expressed in gill and lowest in muscle. RT-PCR analysis also revealed that α-subunit expression in crab gill decreased after 2 and 6 h, but increased after 12, 24, 48, and 72 h. In addition, α-subunit expression in hepatopancreas of crab decreased after 2-72 h. These facts indicated that the crab's Na+/K+-ATPase α-subunit was potentially involved in the observed acute response to low salinity stress.

Molecular-beam scattering

International Nuclear Information System (INIS)

Vernon, M.F.

1983-07-01

The molecular-beam technique has been used in three different experimental arrangements to study a wide range of inter-atomic and molecular forces. Chapter 1 reports results of a low-energy (0.2 kcal/mole) elastic-scattering study of the He-Ar pair potential. The purpose of the study was to accurately characterize the shape of the potential in the well region, by scattering slow He atoms produced by expanding a mixture of He in N 2 from a cooled nozzle. Chapter 2 contains measurements of the vibrational predissociation spectra and product translational energy for clusters of water, benzene, and ammonia. The experiments show that most of the product energy remains in the internal molecular motions. Chapter 3 presents measurements of the reaction Na + HCl → NaCl + H at collision energies of 5.38 and 19.4 kcal/mole. This is the first study to resolve both scattering angle and velocity for the reaction of a short lived (16 nsec) electronic excited state. Descriptions are given of computer programs written to analyze molecular-beam expansions to extract information characterizing their velocity distributions, and to calculate accurate laboratory elastic-scattering differential cross sections accounting for the finite apparatus resolution. Experimental results which attempted to determine the efficiency of optically pumping the Li(2 2 P/sub 3/2/) and Na(3 2 P/sub 3/2/) excited states are given. A simple three-level model for predicting the steady-state fraction of atoms in the excited state is included

Alterações moleculares no Mieloma Múltiplo Molecular abnormalities in Multiple Myeloma

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Esteban Braggio

2007-03-01

Full Text Available Nos últimos anos tem acontecido uma revolução no conhecimento dos mecanismos moleculares envolvidos na patogênese do mieloma múltiplo, principalmente devido à incorporação de técnicas de citogenética molecular (hibridização in situ fluorescente - FISH e biologia molecular (Reação em cadeia da polimerase - PCR, hibridização genômica comparativa baseada em microarranjos - aCGH e microarranjos de RNA. Estas técnicas permitem estudar as células em interfase e detectar alterações cromossômicas crípticas, superando assim problemas metodológicos relacionados à análise por citogenética convencional. Por outro lado, a complexidade metodológica relacionada com a realização das técnicas de FISH e biologia molecular tem impossibilitado que sejam amplamente utilizadas na rotina laboratorial. Este trabalho tem como objetivo fazer uma revisão das principais vias moleculares alteradas no mieloma múltiplo, o seu valor prognóstico e a sua utilização na estratificação dos pacientes em diferentes grupos de risco. São detalhadas diferentes abordagens metodológicas e uma ênfase especial é dada em relação à importância da análise se restringir exclusivamente às células plasmocitárias. Por último, discutimos uma série de prioridades e estratégias de estudo na rotina laboratorial.In recent years, we have seen an explosion in knowledge on genetic and cytogenetic mechanisms involved in the pathogenesis of multiple myeloma, mainly due to the incorporation of molecular tools in its study (fluorescence in situ hybridization - FISH, Real time PCR and RNA microarrays. These tools have enabled the study of cells in interphase and to detect cryptic chromosomal abnormalities, replacing cytogenetic techniques. The technical complexities associated with the performance of these tests, however, have limited their widespread applicability in routine clinical practice. The aim of this work is to review the present status of our

Metal cluster fission: jellium model and Molecular dynamics simulations

DEFF Research Database (Denmark)

Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Ilia

2004-01-01

Fission of doubly charged sodium clusters is studied using the open-shell two-center deformed jellium model approximation and it ab initio molecular dynamic approach accounting for all electrons in the system. Results of calculations of fission reactions Na_10^2+ --> Na_7^+ + Na_3^+ and Na_18...

Characterisation of Zygosaccharomyces rouxii Na+/H+ antiporters

Czech Academy of Sciences Publication Activity Database

Přibylová, Lenka; Papoušková, Klára; Sychrová, Hana; de Montigny, J.

2007-01-01

Roč. 274, Suppl.1 (2007), s. 127-127 ISSN 1742-464X. [FEBS Congress Molecular Machines /32./. 07.07.2007-12.07.2007, Vienna] R&D Projects: GA ČR(CZ) GA204/05/0028 Institutional research plan: CEZ:AV0Z50110509 Keywords : cpo1 * Zygosaccharomyces rouxii * Na+/H+ antiporters * salt tolerance Subject RIV: EB - Genetics ; Molecular Biology

Molecular dynamics study of structure and vibrational spectra at zwitterionoic lipid/aqueous KCl, NaCl, and CaCl2 solution interfaces

Science.gov (United States)

Ishiyama, Tatsuya; Shirai, Shinnosuke; Okumura, Tomoaki; Morita, Akihiro

2018-06-01

Molecular dynamics (MD) simulations of KCl, NaCl, and CaCl2 solution/dipalmytoylphosphatidylcholine lipid interfaces were performed to analyze heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectra in relation to the interfacial water structure. The present MD simulation well reproduces the experimental spectra and elucidates a specific cation effect on the interfacial structure. The K+, Na+, and Ca2+ cation species penetrate in the lipid layer more than the anions in this order, due to the electrostatic interaction with negative polar groups of lipid, and the electric double layer between the cations and anions cancels the intrinsic orientation of water at the water/lipid interface. These mechanisms explain the HD-VSFG spectrum of the water/lipid interface and its spectral perturbation by adding the ions. The lipid monolayer reverses the order of surface preference of the cations at the solution/lipid interface from that at the solution/air interface.

Inorganic-Organic Coating via Molecular Layer Deposition Enables Long Life Sodium Metal Anode.

Science.gov (United States)

Zhao, Yang; Goncharova, Lyudmila V; Zhang, Qian; Kaghazchi, Payam; Sun, Qian; Lushington, Andrew; Wang, Biqiong; Li, Ruying; Sun, Xueliang

2017-09-13

Metallic Na anode is considered as a promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to its high specific capacity, and low potential. However, the unstable solid electrolyte interphase layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we first demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as a protective layer for metallic Na anode. By protecting Na anode with controllable alucone layer, the dendrites and mossy Na formation have been effectively suppressed and the lifetime has been significantly improved. Moreover, the molecular layer deposition alucone coating shows better performances than the atomic layer deposition Al 2 O 3 coating. The novel design of molecular layer deposition protected Na metal anode may bring in new opportunities to the realization of the next-generation high energy-density NIBs and NMBs.

Biologia, conhecimento e consciência: articulações possíveis na construção da aprendizagem = Biology, knowledge and consciousness: possible links in learning construction = Biología, conocimiento y conciencia: posibles conexiones en la construcción del aprendizaje

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Flach, Pâmela Ziliotto Sant'Anna

2016-01-01

Full Text Available Neste trabalho apresenta-se uma discussão acerca das contribuições da neurobiologia e da epistemologia genética aos processos de construção do conhecimento e da consciência. Discute-se, também, como tais processos se relacionam com os mecanismos de conservação da homeostase dos organismos. Para isso, debruçou-se sobre obras de António Damásio e Jean Piaget na tentativa de compreender as articulações entre organismo e sujeito epistêmico como protagonistas dos atos de manter-se vivo, conhecer e tomar consciência. Seja no âmbito orgânico ou no cognitivo, a manutenção da vida passa pela interação constante e permanente entre organismo e meio. Concebe-se essa interação como fonte de sempre novos desequilíbrios que abrem espaço para novas experiências que, por sua vez, geram novos desenvolvimentos afetivos ou cognitivos. Com isso, são possibilitadas novas aprendizagens, escolares ou não, que concorrem para a sobrevivência em todos os níveis da vida humana

Protein kinase A (PKA) phosphorylation of Na+/K+-ATPase opens intracellular C-terminal water pathway leading to third Na+-binding site in molecular dynamics simulations

DEFF Research Database (Denmark)

Poulsen, Hanne; Nissen, Poul; Mouritsen, Ole G.

2012-01-01

-atom Molecular Dynamics (MD) simulations to investigate the structural consequences of phosphorylating the Na+/K+- ATPase (NKA) residue S936, which is the best characterized phosphorylation site in NKA, targeted in vivo by Protein Kinase A (PKA) (1-3). The MD simulations suggest that S936 phosphorylation opens......Phosphorylation is one of the major mechanisms for posttranscriptional modification of proteins. The addition of a compact, negatively charged moiety to a protein can significantly change its function and localization by affecting its structure and interaction network. We have used all...... a C-terminal hydrated pathway leading to D926, a transmembrane residue proposed to form part of the third sodium ion-binding site (4). Simulations of a S936E mutant form, for which only subtle effects are observed when expressed in Xenopus oocytes and studied with electrophysiology, does not mimic...

Goniotalamina : atividade antitumoral e anti-inflamatória

OpenAIRE

Débora Barbosa Vendramini Costa

2012-01-01

Resumo: A carcinogênese é um processo longo, multi-etapas, onde células normais progressivamente adquirem um fenótipo neoplásico. Sua origem é favorecida por fatores genéticos, exposição à carcinógenos químicos, infecções crônicas e incorporação de mutações em genes envolvidos com a regulação da homeostase celular. O crescente entendimento da biologia tumoral tem fornecido alvos moleculares para a triagem orientada de quimioterápicos e de agentes quimiopreventivos, geralmente de origem natura...

Sistema imunitário: Parte I. Fundamentos da imunidade inata com ênfase nos mecanismos moleculares e celulares da resposta inflamatória Immune system: Part I. Fundamentals of innate immunity with emphasis on molecular and cellular mechanisms of inflammatory response

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Wilson de Melo Cruvinel

2010-08-01

Full Text Available O sistema imunológico é constituído por uma intrincada rede de órgãos, células e moléculas, e tem por finalidade manter a homeostase do organismo, combatendo as agressões em geral. A imunidade inata atua em conjunto com a imunidade adaptativa e caracteriza-se pela rápida resposta à agressão, independentemente de estímulo prévio, sendo a primeira linha de defesa do organismo. Seus mecanismos compreendem barreiras físicas, químicas e biológicas, componentes celulares e moléculas solúveis. A primeira defesa do organismo frente a um dano tecidual envolve diversas etapas intimamente integradas e constituídas pelos diferentes componentes desse sistema. A presente revisão tem como objetivo resgatar os fundamentos dessa resposta, que apresenta elevada complexidade e é constituída por diversos componentes articulados que convergem para a elaboração da resposta imune adaptativa. Destacamos algumas etapas: reconhecimento molecular dos agentes agressores; ativação de vias bioquímicas intracelulares que resultam em modificações vasculares e teciduais; produção de uma miríade de mediadores com efeitos locais e sistêmicos no âmbito da ativação e proliferação celulares, síntese de novos produtos envolvidos na quimioatração e migração de células especializadas na destruição e remoção do agente agressor, e finalmente a recuperação tecidual com o restabelecimento funcional do tecido ou órgão.The immune system consists of an intricate network of organs, cells, and molecules responsible for maintaining the body's homeostasis and responding to aggression in general. Innate immunity operates in conjunction with adaptive immunity and is characterized by rapid response to aggression, regardless of previous stimulus, being the organism first line of defense. Its mechanisms include physical, chemical and biological barriers, cellular components, as well as soluble molecules. The organism first line of defense against

Efeitos da administração in vivo do ácido fitânico sobre parâmetros de homeostase redox em cerebelo de ratos jovens

OpenAIRE

Clarissa Günther Borges

2015-01-01

O ácido fitânico (Fit) é um ácido graxo saturado de cadeia ramificada que se acumula em diversas doenças peroxissomais, como na síndrome de Zellweger (SZ) e particularmente na doença de Refsum (DR). Essas doenças podem ocorrer devido a defeitos na biogênese do peroxissomo ou em alguma proteína peroxisomal envolvida na β ou α-oxidação de ácidos graxos. Os pacientes afetados geralmente apresentam disfunções neurológicas, incluindo anormalidades cerebelares. Considerando que a patogênese das alt...

Multichannel modeling and two-photon coherent transfer paths in NaK

Science.gov (United States)

Schulze, T. A.; Temelkov, I. I.; Gempel, M. W.; Hartmann, T.; Knöckel, H.; Ospelkaus, S.; Tiemann, E.

2013-08-01

We explore possible pathways for the creation of ultracold polar NaK molecules in their absolute electronic and rovibrational ground state starting from ultracold Feshbach molecules. In particular, we present a multichannel analysis of the electronic ground and K(4p)+Na(3s) excited-state manifold of NaK, analyze the spin character of both the Feshbach molecular state and the electronically excited intermediate states and discuss possible coherent two-photon transfer paths from Feshbach molecules to rovibronic ground-state molecules. The theoretical study is complemented by the demonstration of stimulated Raman adiabatic passage from the X1Σ+(v=0) state to the a3Σ+ manifold on a molecular beam experiment.

Na, K-ATPase as signaling transducer

OpenAIRE

Li, Juan

2007-01-01

It is now generally agreed that Na,K-ATPase (NKA), in addition to its role in the maintenance of Na+ and K+ gradients across the cell membrane, is a signal transducer. Our group has identified a novel signaling pathway where NKA interact with IP3R to form a signaling microdomain. Ouabain, a specific ligand of NKA, activates this pathway, triggers slow Ca2+ oscillations and activates NF-κB. In current study, the molecular mechanisms and some important downstream effects of NK...

Mechanism of μ-conotoxin PIIIA binding to the voltage-gated Na+ channel NaV1.4.

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Rong Chen

Full Text Available Several subtypes of voltage-gated Na+ (NaV channels are important targets for pain management. μ-Conotoxins isolated from venoms of cone snails are potent and specific blockers of different NaV channel isoforms. The inhibitory effect of μ-conotoxins on NaV channels has been examined extensively, but the mechanism of toxin specificity has not been understood in detail. Here the known structure of μ-conotoxin PIIIA and a model of the skeletal muscle channel NaV1.4 are used to elucidate elements that contribute to the structural basis of μ-conotoxin binding and specificity. The model of NaV1.4 is constructed based on the crystal structure of the bacterial NaV channel, NaVAb. Six different binding modes, in which the side chain of each of the basic residues carried by the toxin protrudes into the selectivity filter of NaV1.4, are examined in atomic detail using molecular dynamics simulations with explicit solvent. The dissociation constants (Kd computed for two selected binding modes in which Lys9 or Arg14 from the toxin protrudes into the filter of the channel are within 2 fold; both values in close proximity to those determined from dose response data for the block of NaV currents. To explore the mechanism of PIIIA specificity, a double mutant of NaV1.4 mimicking NaV channels resistant to μ-conotoxins and tetrodotoxin is constructed and the binding of PIIIA to this mutant channel examined. The double mutation causes the affinity of PIIIA to reduce by two orders of magnitude.

Rescue of Na+ affinity in aspartate 928 mutants of Na+,K+-ATPase by secondary mutation of glutamate 314.

Science.gov (United States)

Holm, Rikke; Einholm, Anja P; Andersen, Jens P; Vilsen, Bente

2015-04-10

The Na(+),K(+)-ATPase binds Na(+) at three transport sites denoted I, II, and III, of which site III is Na(+)-specific and suggested to be the first occupied in the cooperative binding process activating phosphorylation from ATP. Here we demonstrate that the asparagine substitution of the aspartate associated with site III found in patients with rapid-onset dystonia parkinsonism or alternating hemiplegia of childhood causes a dramatic reduction of Na(+) affinity in the α1-, α2-, and α3-isoforms of Na(+),K(+)-ATPase, whereas other substitutions of this aspartate are much less disruptive. This is likely due to interference by the amide function of the asparagine side chain with Na(+)-coordinating residues in site III. Remarkably, the Na(+) affinity of site III aspartate to asparagine and alanine mutants is rescued by second-site mutation of a glutamate in the extracellular part of the fourth transmembrane helix, distant to site III. This gain-of-function mutation works without recovery of the lost cooperativity and selectivity of Na(+) binding and does not affect the E1-E2 conformational equilibrium or the maximum phosphorylation rate. Hence, the rescue of Na(+) affinity is likely intrinsic to the Na(+) binding pocket, and the underlying mechanism could be a tightening of Na(+) binding at Na(+) site II, possibly via movement of transmembrane helix four. The second-site mutation also improves Na(+),K(+) pump function in intact cells. Rescue of Na(+) affinity and Na(+) and K(+) transport by second-site mutation is unique in the history of Na(+),K(+)-ATPase and points to new possibilities for treatment of neurological patients carrying Na(+),K(+)-ATPase mutations. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Interplay between structure and transport properties of molten salt mixtures of ZnCl2-NaCl-KCl: A molecular dynamics study.

Science.gov (United States)

Manga, Venkateswara Rao; Swinteck, Nichlas; Bringuier, Stefan; Lucas, Pierre; Deymier, Pierre; Muralidharan, Krishna

2016-03-07

Molten mixtures of network-forming covalently bonded ZnCl2 and network-modifying ionically bonded NaCl and KCl salts are investigated as high-temperature heat transfer fluids for concentrating solar power plants. Specifically, using molecular dynamics simulations, the interplay between the extent of the network structure, composition, and the transport properties (viscosity, thermal conductivity, and diffusion) of ZnCl2-NaCl-KCl molten salts is characterized. The Stokes-Einstein/Eyring relationship is found to break down in these network-forming liquids at high concentrations of ZnCl2 (>63 mol. %), while the Eyring relationship is seen with increasing KCl concentration. Further, the network modification due to the addition of K ions leads to formation of non-bridging terminal Cl ions, which in turn lead to a positive temperature dependence of thermal conductivity in these melts. This new understanding of transport in these ternary liquids enables the identification of appropriate concentrations of the network formers and network modifiers to design heat transfer fluids with desired transport properties for concentrating solar power plants.

K+ congeners that do not compromise Na+ activation of the Na+,K+-ATPase: hydration of the ion binding cavity likely controls ion selectivity.

Science.gov (United States)

Mahmmoud, Yasser A; Kopec, Wojciech; Khandelia, Himanshu

2015-02-06

The Na(+),K(+)-ATPase is essential for ionic homeostasis in animal cells. The dephosphoenzyme contains Na(+) selective inward facing sites, whereas the phosphoenzyme contains K(+) selective outward facing sites. Under normal physiological conditions, K(+) inhibits cytoplasmic Na(+) activation of the enzyme. Acetamidinium (Acet(+)) and formamidinium (Form(+)) have been shown to permeate the pump through the outward facing sites. Here, we show that these cations, unlike K(+), are unable to enter the inward facing sites in the dephosphorylated enzyme. Consistently, the organic cations exhibited little to no antagonism to cytoplasmic Na(+) activation. Na(+),K(+)-ATPase structures revealed a previously undescribed rotamer transition of the hydroxymethyl side chain of the absolutely conserved Thr(772) of the α-subunit. The side chain contributes its hydroxyl to Na(+) in site I in the E1 form and rotates to contribute its methyl group toward K(+) in the E2 form. Molecular dynamics simulations to the E1·AlF4 (-)·ADP·3Na(+) structure indicated that 1) bound organic cations differentially distorted the ion binding sites, 2) the hydroxymethyl of Thr(772) rotates to stabilize bound Form(+) through water molecules, and 3) the rotamer transition is mediated by water traffic into the ion binding cavity. Accordingly, dehydration induced by osmotic stress enhanced the interaction of the congeners with the outward facing sites and profoundly modified the organization of membrane domains of the α-subunit. These results assign a catalytic role for water in pump function, and shed light on a backbone-independent but a conformation-dependent switch between H-bond and dispersion contact as part of the catalytic mechanism of the Na(+),K(+)-ATPase. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

alpha-Adducin mutations increase Na/K pump activity in renal cells by affecting constitutive endocytosis: implications for tubular Na reabsorption.

Science.gov (United States)

Torielli, Lucia; Tivodar, Simona; Montella, Rosa Chiara; Iacone, Roberto; Padoani, Gloria; Tarsini, Paolo; Russo, Ornella; Sarnataro, Daniela; Strazzullo, Pasquale; Ferrari, Patrizia; Bianchi, Giuseppe; Zurzolo, Chiara

2008-08-01

Genetic variation in alpha-adducin cytoskeletal protein is implicated in the polymerization and bundling of actin and alteration of the Na/K pump, resulting in abnormal renal sodium transport and hypertension in Milan hypertensive rats and humans. To investigate the molecular involvement of alpha-adducin in controlling Na/K pump activity, wild-type or mutated rat and human alpha-adducin forms were, respectively, transfected into several renal cell lines. Through multiple experimental approaches (microscopy, enzymatic assays, coimmunoprecipitation), we showed that rat and human mutated forms increased Na/K pump activity and the number of pump units; moreover, both variants coimmunoprecipitate with Na/K pump. The increased Na/K pump activity was not due to changes in its basolateral localization, but to an alteration of Na/K pump residential time on the plasma membrane. Indeed, both rat and human mutated variants reduced constitutive Na/K pump endocytosis and similarly affected transferrin receptor trafficking and fluid-phase endocytosis. In fact, alpha-adducin was detected in clathrin-coated vesicles and coimmunoprecipitated with clathrin. These results indicate that adducin, besides its modulatory effects on actin cytoskeleton dynamics, might play a direct role in clathrin-dependent endocytosis. The constitutive reduction of the Na/K pump endocytic rate induced by mutated adducin variants may be relevant in Na-dependent hypertension.

Molecular methods to evaluate effects of feed additives and nutrients in poultry gut microflora Metodologias moleculares para avaliar efeitos de aditivos e nutrientes na microflora intestinal das aves

Directory of Open Access Journals (Sweden)

Edgar O. Oviedo-Rondón

2009-07-01

Full Text Available Intestines of each animal are the niche of a complex and dynamic ecosystem with important effects to the host. The members or final products of this ecosystem influence nutrient digestion, absorption, mucosa metabolism, general physiology, and local and systemic immunological responses of avian hosts. Better understanding of the avian gut microbial ecosystem may lead to improvements on poultry productivity, health, welfare, and reduction of food borne pathogens and the environmental impact of poultry production for a more sustainable industry. Molecular methods of microbial ecology are key tools to gain this knowledge. The objective of this presentation is to outline the basic concepts, applications, advantages, limitations, and evolution of these molecular methods used to study intestinal microbial ecology. The final goal is to stimulate their application in poultry applied research and development of new feed additives. Some practical examples in poultry research will be described to illustrate their relevance to advance in control methods for pathogens, avoid or manage disbiosis or subclinical intestinal diseases, reduce environmental impact, elucidate effects of nutrients in gut mucosa, microflora, and in general to improve poultry performance.O intestino de cada animal é o nicho de um ecossistema complexo e dinâmico com efeitos importantes para o hospedeiro. As comunidades microbianas componentes deste ecossistema e/ou os produtos finais do metabolismo influenciam a digestão e absorção de nutrientes, o metabolismo das mucosas, a fisiologia geral e as respostas imunitárias locais e gerais da ave hospedeira. A melhor compreensão do ecossistema microbiano do intestino das aves pode levar a melhorias na produtividade, saúde, bem estar, e redução de agente patogênicos dos alimentos e do impacto ambiental da produção avícola para uma indústria mais sustentável. Os métodos moleculares da ecologia microbiana são ferramentas chaves

Na(+)-D-glucose cotransporter in the kidney of Squalus acanthias: molecular identification and intrarenal distribution.

Science.gov (United States)

Althoff, Thorsten; Hentschel, Hartmut; Luig, Jutta; Schütz, Hendrike; Kasch, Myriam; Kinne, Rolf K-H

2006-04-01

Using primers against conserved regions of mammalian Na(+)-d-glucose cotransporters (SGLT), a cDNA was cloned from the kidney of spiny dogfish shark (Squalus acanthias). On the basis of comparison of amino acid sequence, membrane topology, and putative glycosylation and phosphorylation sites, the cDNA could be shown to belong to the family of sglt genes. Indeed, Na(+)-dependent d-glucose uptake could be demonstrated after expression of the gene in Xenopus laevis oocytes. In a dendrogram, the SGLT from shark kidney has a high homology to the mammalian SGLT2. Computer analysis revealed that the elasmobranch protein is most similar to the mammalian proteins in the transmembrane regions and contains already all the amino acids identified to be functionally important, suggesting early conservation during evolution. Extramembraneous loops show larger variations. This holds especially for loop 13, which has been implied as a phlorizin-binding domain. Antibodies were generated and the intrarenal distribution of the SGLT was studied in cryosections. In parallel, the nephron segments were identified by lectins. Positive immunoreactions were found in the proximal tubule in the early parts PIa and PIb and the late segment PIIb. The large PIIa segment of the proximal tubule showed no reaction. In contrast to the mammalian kidney also the late distal tubule, the collecting tubule, and the collecting duct showed immunoreactivity. The molecular information confirms previous vesicle studies in which a low affinity SGLT with a low stoichiometry has been observed and supports the notion of a similarity of the shark kidney SGLT to the mammalian SGLT2. Despite its presence in the late parts of the nephron, the absence of SGLT in the major part of the proximal tubule, the relatively low affinity, and in particular the low stoichiometry might explain the lack of a T(m) for d-glucose in the shark kidney.

Molecular Recognition Involving Anthraquinone Derivatives and Molecular Clips

Science.gov (United States)

Alaparthi, Madhubabu

In the past, we have demonstrated that 1,8-anthraquinone-18-crown-5 (1) and its heterocyclic derivatives act as luminescent hosts for a variety of cations of environmental and clinical concern. We report here a series of heteroatom-substituted macrocycles containing an anthraquinone moiety as a fluorescent signaling unit and a cyclic polyheteroether chain as the receptor. Sulfur, selenium, and tellurium derivatives of 1,8-anthraquinone-18-crown-5 (1) were synthesized by reacting sodium sulfide (Na2S), sodium selenide (Na2Se) and sodium telluride (Na2Te) with 1,8-bis(2-bromoethylethyleneoxy)anthracene - 9,10-dione in a 1:1 ratio (2,3, and 6). These sensors bind metal ions in a 1:1 ratio (7 and 8), and the optical properties of the new complexes were examined and the sulfur and selenium analogues show that selectivity for Pb(II) is markedly improved as compared to the oxygen analogue 1 which was competitive for Ca(II) ion. Selective reduction of 1 yields secondary alcohols where either one or both of the anthraquinone carbonyl groups has been reduced ( 15 and 9). A new mechanism for the fluorescence detection of metal cations in solution is introduced involving a unique keto-enol tautomerization. Reduction of 1 yields the doubly reduced secondary alcohol, 9. 9 acts as a chemodosimeter for Al(III) ion producing a strong blue emission due to the formation of the anthracene fluorophore, 10, via dehydration of the internal secondary alcohol in DMSO/aqueous solution. The enol form is not the most thermodynamically stable form under these conditions however, and slowly converts to the keto form 11.. Currently we are focusing on cucurbituril derivatives, also described as molecular clips due to their folded geometry used as molecular recognition hosts. We first investigated the synthesis and characterization of aromatic methoxy/catechol terminated cucurbituril units that act as hosts for small solvent molecules, such as CH2Cl2, CH3CN, DMF, and MeOH, through dual pi...H-C T

Tuning of the Na,K-ATPase by the beta subunit

DEFF Research Database (Denmark)

Hilbers, Florian; Kopec, Wojciech; Isaksen, Toke Jost

2016-01-01

The vital gradients of Na(+) and K(+) across the plasma membrane of animal cells are maintained by the Na,K-ATPase, an αβ enzyme complex, whose α subunit carries out the ion transport and ATP hydrolysis. The specific roles of the β subunit isoforms are less clear, though β2 is essential for motor...... to the cerebellar Na(+) and K(+) gradients....... physiology in mammals. Here, we show that compared to β1 and β3, β2 stabilizes the Na(+)-occluded E1P state relative to the outward-open E2P state, and that the effect is mediated by its transmembrane domain. Molecular dynamics simulations further demonstrate that the tilt angle of the β transmembrane helix...

A molecular switch between the outer and the inner vestibule of the voltage-gated Na+ channel

International Nuclear Information System (INIS)

Zarrabi, T.

2010-01-01

conformational change of the inner vestibule generates the IUS state. In order to explain the involvement of both the outer and the inner vestibule in ultra-slow inactivation, we proposed a model in which the mutation K1237E produces a conformational change of the outer vestibule which is transmitted to the internal vestibule through the DIV- S6 segment. The resulting conformational change of the internal vestibule gives rise to the extremely stable IUS state. If this molecular mechanism holds true, then mutations at the location of interaction between the selectivity filter and the adjacent S6 segment should substantially modulate the ultra-slow inactivated state. A homology model of the voltage-gated Na+ channel, based on the crystal structure of the KcsA channel places the domain IV-S6 segment in close proximity to the domain III P-loop (containing the site 1237 which is essential for the generation of IUS). In order to search for experimental evidence for an interaction site between the domain III P-loop and the internal vestibule we generated serial alanine and cysteine replacements of amino acids of the domain DIV- S6 segment in the background of the mutation K1237E. We find that mutations only at the site 1575 substantially decrease the likelihood of entry into IUS or significantly accelerate recovery from IUS, suggesting that this residue represents an interaction site between the domain III p-loop and the domain IV- S6 segment. For the first time these functional data confirm a molecular model in which the turn of the domain III P-loop is in close relationship with the domain IV- S6 segment at the level of I1575. (author) [de

Distinct pH dependencies of Na+/K+ selectivity at the two faces of Na,K-ATPase.

Science.gov (United States)

Cornelius, Flemming; Tsunekawa, Naoki; Toyoshima, Chikashi

2018-02-09

The sodium pump (Na,K-ATPase) in animal cells is vital for actively maintaining ATP hydrolysis-powered Na + and K + electrochemical gradients across the cell membrane. These ion gradients drive co- and countertransport and are critical for establishing the membrane potential. It has been an enigma how Na,K-ATPase discriminates between Na + and K + , despite the pumped ion on each side being at a lower concentration than the other ion. Recent crystal structures of analogs of the intermediate conformations E2·Pi·2K + and Na + -bound E1∼P·ADP suggest that the dimensions of the respective binding sites in Na,K-ATPase are crucial in determining its selectivity. Here, we found that the selectivity at each membrane face is pH-dependent and that this dependence is unique for each face. Most notable was a strong increase in the specific affinity for K + at the extracellular face ( i.e. E2 conformation) as the pH is lowered from 7.5 to 5. We also observed a smaller increase in affinity for K + on the cytoplasmic side (E1 conformation), which reduced the selectivity for Na + Theoretical analysis of the p K a values of ion-coordinating acidic amino acid residues suggested that the face-specific pH dependences and Na + /K + selectivities may arise from the protonation or ionization of key residues. The increase in K + selectivity at low pH on the cytoplasmic face, for instance, appeared to be associated with Asp 808 protonation. We conclude that changes in the ionization state of coordinating residues in Na,K-ATPase could contribute to altering face-specific ion selectivity. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Separation of molecular hydrogen isotope mixtures using zeolite NaX-3M

International Nuclear Information System (INIS)

Polevoj, A.S.; Yudin, I.P.

1984-01-01

The components of transfer unit height (TUH) at separation of the H 2 -D 2 mixture using zeolite NaX-3M in the countercurrent column are determined. It is shown that the interphase isotopic exchange in the column is limited by gaseous diffusion in sorbent primary pores. On the basis of the TUH dependence the value of the hydrogen diffusion coefficient in primary pores of NaX-3M zeolite equal at 77 K and 87.3 K, respectively, approximately 1.09x10 -15 and approximately 1.69x10 -15 m 2 /s is calculated

Nonadiabatic ionic--covalent transitions. Exponential-linear model for the charge exchange and neutralization reactions Na+H arrow-right-left Na++H-

International Nuclear Information System (INIS)

Errea, L.F.; Mendez, L.; Mo, O.; Riera, A.

1986-01-01

A previous study of charge exchange processes taking place through ionic--covalent transitions is extended to the case of Na+H and Na + +H - collisions. A five-state molecular expansion, with the inclusion of two-electron translation factors, is employed to calculate the charge exchange and neutralization cross sections. Transitions at the first two pseudocrossings between the energy curves, practically determine the cross sections in the energy range 0.16--5 keV amu -1 . We also show that the widely used multichannel Landau--Zener theory is totally inadequate, to treat these transitions

Molecular simulation of thermodynamic and transport properties for the H{sub 2}O+NaCl system

Energy Technology Data Exchange (ETDEWEB)

Orozco, Gustavo A.; Jiang, Hao; Panagiotopoulos, Athanassios Z., E-mail: azp@princeton.edu [Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Moultos, Othonas A.; Economou, Ioannis G. [Chemical Engineering Program, Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar)

2014-12-21

Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H{sub 2}O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration.

General and specific lipid-protein interactions in Na,K-ATPase.

Science.gov (United States)

Cornelius, F; Habeck, M; Kanai, R; Toyoshima, C; Karlish, S J D

2015-09-01

The molecular activity of Na,K-ATPase and other P2 ATPases like Ca(2+)-ATPase is influenced by the lipid environment via both general (physical) and specific (chemical) interactions. Whereas the general effects of bilayer structure on membrane protein function are fairly well described and understood, the importance of the specific interactions has only been realized within the last decade due particularly to the growing field of membrane protein crystallization, which has shed new light on the molecular details of specific lipid-protein interactions. It is a remarkable observation that specific lipid-protein interactions seem to be evolutionarily conserved, and conformations of specifically bound lipids at the lipid-protein surface within the membrane are similar in crystal structures determined with different techniques and sources of the protein, despite the rather weak lipid-protein interaction energy. Studies of purified detergent-soluble recombinant αβ or αβFXYD Na,K-ATPase complexes reveal three separate functional effects of phospholipids and cholesterol with characteristic structural selectivity. The observations suggest that these three effects are exerted at separate binding sites for phophatidylserine/cholesterol (stabilizing), polyunsaturated phosphatidylethanolamine (stimulatory), and saturated PC or sphingomyelin/cholesterol (inhibitory), which may be located within three lipid-binding pockets identified in recent crystal structures of Na,K-ATPase. The findings point to a central role of direct and specific interactions of different phospholipids and cholesterol in determining both stability and molecular activity of Na,K-ATPase and possible implications for physiological regulation by membrane lipid composition. This article is part of a special issue titled "Lipid-Protein Interactions." Copyright © 2015 Elsevier B.V. All rights reserved.

Mechanism of potassium ion uptake by the Na+/K+-ATPase

Science.gov (United States)

Castillo, Juan P.; Rui, Huan; Basilio, Daniel; Das, Avisek; Roux, Benoît; Latorre, Ramon; Bezanilla, Francisco; Holmgren, Miguel

2015-07-01

The Na+/K+-ATPase restores sodium (Na+) and potassium (K+) electrochemical gradients dissipated by action potentials and ion-coupled transport processes. As ions are transported, they become transiently trapped between intracellular and extracellular gates. Once the external gate opens, three Na+ ions are released, followed by the binding and occlusion of two K+ ions. While the mechanisms of Na+ release have been well characterized by the study of transient Na+ currents, smaller and faster transient currents mediated by external K+ have been more difficult to study. Here we show that external K+ ions travelling to their binding sites sense only a small fraction of the electric field as they rapidly and simultaneously become occluded. Consistent with these results, molecular dynamics simulations of a pump model show a wide water-filled access channel connecting the binding site to the external solution. These results suggest a mechanism of K+ gating different from that of Na+ occlusion.

Functional interaction of nicotinic acetylcholine receptors and Na+/K+ ATPase from Locusta migratoria manilensis (Meyen).

Science.gov (United States)

Bao, Haibo; Sun, Huahua; Xiao, Youxin; Zhang, Yixi; Wang, Xin; Xu, Xiaoyong; Liu, Zewen; Fang, Jichao; Li, Zhong

2015-03-06

Associated proteins are important for the correct functioning of nicotinic acetylcholine receptors (nAChRs). In the present study, a neonicotinoid-agarose affinity column was used to isolate related proteins from a solubilized membrane preparation from the nervous system of Locusta migratoria manilensis (Meyen). 1530 peptides were identified and most of them were involved in the membranous structure, molecular interaction and cellular communication. Among these peptides, Na(+)/K(+) ATPase had the highest MASCOT score and were involved in the molecular interaction, which suggested that Na(+)/K(+) ATPase and nAChRs might have strong and stable interactions in insect central nervous system. In the present study, functional interactions between nAChRs and Na(+)/K(+) ATPase were examined by heterologous expression in Xenopus oocytes. The results showed that the activated nAChRs increased pump currents of Na(+)/K(+) ATPase, which did not require current flow through open nAChRs. In turn, Na(+)/K(+) ATPase significantly increased agonist sensitivities of nAChRs in a pump activity-independent manner and reduced the maximum current (Imax) of nAChRs. These findings provide novel insights concerning the functional interactions between insect nAChRs and Na(+)/K(+) ATPase.

Clues to NaCN formation

Science.gov (United States)

Quintana-Lacaci, G.; Cernicharo, J.; Velilla Prieto, L.; Agúndez, M.; Castro-Carrizo, A.; Fonfría, J. P.; Massalkhi, S.; Pardo, J. R.

2017-11-01

Context. ALMA is providing us essential information on where certain molecules form. Observing where these molecules emission arises from, the physical conditions of the gas, and how this relates with the presence of other species allows us to understand the formation of many species, and to significantly improve our knowledge of the chemistry that occurs in the space. Aims: We studied the molecular distribution of NaCN around IRC +10216, a molecule detected previously, but whose origin is not clear. High angular resolution maps allow us to model the abundance distribution of this molecule and check suggested formation paths. Methods: We modeled the emission of NaCN assuming local thermal equilibrium (LTE) conditions. These profiles were fitted to azimuthal averaged intensity profiles to obtain an abundance distribution of NaCN. Results: We found that the presence of NaCN seems compatible with the presence of CN, probably as a result of the photodissociation of HCN, in the inner layers of the ejecta of IRC +10216. However, similar as for CH3CN, current photochemical models fail to reproduce this CN reservoir. We also found that the abundance peak of NaCN appears at a radius of 3 × 1015 cm, approximately where the abundance of NaCl, suggested to be the parent species, starts to decay. However, the abundance ratio shows that the NaCl abundance is lower than that obtained for NaCN. We expect that the LTE assumption might result in NaCN abundances higher than the real ones. Updated photochemical models, collisional rates, and reaction rates are essential to determine the possible paths of the NaCN formation. Based on observations carried out with ALMA and the IRAM 30 m Telescope. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. IRAM is supported by INSU/CNRS (France

Hydrothermal Synthesis and Electrochemical Performance of Manganese Oxide (Na-OMS-2) Nanorods.

Science.gov (United States)

Zhang, Qing; Xu, Shan; Zheng, Hao; Luo, Zhaohui; Liu, Kang; Wang, Wei; Li, Guohua; Wang, Shiquan; Liu, Jianwen; Feng, Chuanqi

2017-02-01

Sodium octahedral molecular sieve nanorods (Na-OMS-2) were prepared through a facile hydrothermal method. The effects of reaction temperature and duration on particle sizes of the products were investigated. The electrochemical performance of samples was studied by constant current charge–discharge tests as cathode material for Li-ion batteries (LIBs). The initial discharge capacity of Na-OMS-2 is 123.4 mAh g−1 and the capacity retention was 123.9 mAh g−1 after 100 cycles. The result demonstrates that Na-OMS-2 cathode material behaves a good cycling stability.

Dinâmica molecular ab initio:aplicações ao estudo de propriedades electrónicas de sistemas moleculares

OpenAIRE

Martiniano, Hugo Filipe de Mesquita Costa, 1978-

2013-01-01

Tese de doutoramento, Química (Química-Física), Universidade de Lisboa, Faculdade de Ciências, 2013 O método da dinâmica molecular ab initio exibe vantagens significativas para o estudo da estrutura e propriedades electrónicas de sistemas moleculares complexos. No entanto, uma das suas desvantagens é o elevado custo computacional, quando comparado com os métodos de dinâmica molecular clássicos. Um dos modos de resolver este problema é adoptar uma abordagem sequencial, na qual a dinâmica é ...

Análise do transcriptoma do estágio invasivo de Fasciola hepatica e sua contribuição na compreensão dos mecanismos moleculares envolvidos no processo de infecção

OpenAIRE

Martín Pablo Cancela Sehabiague

2010-01-01

Fasciola hepatica é um trematódeo parasita e o agente causador da fasciolose. Esta zoonose causa perdas importantes na produção agropecuária e tem uma crescente incidência na saúde dos seres humanos, principalmente em países em desenvolvimento. Mesmo que existem drogas fasciolicidas, estas não evitam a reinfecção e o surgimento de resistência e, portanto são necessárias novas estratégias de controle. A compreensão dos mecanismos moleculares que envolvem a relação parasito-hospedeiro e os proc...

Na+/H+ exchange activity in the plasma membrane of Arabidopsis.

Science.gov (United States)

Qiu, Quan-Sheng; Barkla, Bronwyn J; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S

2003-06-01

In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt.

Interaction of molecular oxygen with single wall nanotubes: Role of surfactant contamination

International Nuclear Information System (INIS)

Larciprete, R.; Goldoni, A.; Lizzit, S.

2003-01-01

The interaction of molecular oxygen with single wall nanotubes in the form of a commercial bucky paper was investigated by high resolution photoemission spectroscopy. Sodium contamination was found in the sample, which was completely removed only after prolonged heating at 1250 K. The C 1s core level spectrum measured on the sample annealed to 1020 K dramatically changed upon exposure to molecular oxygen. On the contrary, when exposing the Na-free SWNTs to several KL of O 2 , the sample remained oxygen free and no modification in the C 1s core level was observed. Therefore the observed sensitivity of the sample to O 2 was due to a Na mediated oxidation, determining a charge transfer from the C tubes to the Na-O complex

Perinatal Na+ Overload Programs Raised Renal Proximal Na+ Transport and Enalapril-Sensitive Alterations of Ang II Signaling Pathways during Adulthood

Science.gov (United States)

Cabral, Edjair V.; Vieira-Filho, Leucio D.; Silva, Paulo A.; Nascimento, Williams S.; Aires, Regina S.; Oliveira, Fabiana S. T.; Luzardo, Ricardo; Vieyra, Adalberto; Paixão, Ana D. O.

2012-01-01

Background High Na+ intake is a reality in nowadays and is frequently accompanied by renal and cardiovascular alterations. In this study, renal mechanisms underlying perinatal Na+ overload-programmed alterations in Na+ transporters and the renin/angiotensin system (RAS) were investigated, together with effects of short-term treatment with enalapril in terms of reprogramming molecular alterations in kidney. Methodology/Principal Findings Male adult Wistar rats were obtained from dams maintained throughout pregnancy and lactation on a standard diet and drinking water (control) or 0.17 M NaCl (saline group). Enalapril (100 mg/l), an angiotensin converting enzyme inhibitor, was administered for three weeks after weaning. Ninety day old offspring from dams that drank saline presented with proximal tubules exhibiting increased (Na++K+)ATPase expression and activity. Ouabain-insensitive Na+-ATPase activity remained unchanged but its response to angiotensin II (Ang II) was lost. PKC, PKA, renal thiobarbituric acid reactive substances (TBARS), macrophage infiltration and collagen deposition markedly increased, and AT2 receptor expression decreased while AT1 expression was unaltered. Early treatment with enalapril reduced expression and activity of (Na++K+)ATPase, partially recovered the response of Na+-ATPase to Ang II, and reduced PKC and PKA activities independently of whether offspring were exposed to high perinatal Na+ or not. In addition, treatment with enalapril per se reduced AT2 receptor expression, and increased TBARS, macrophage infiltration and collagen deposition. The perinatally Na+-overloaded offspring presented high numbers of Ang II-positive cortical cells, and significantly lower circulating Ang I, indicating that programming/reprogramming impacted systemic and local RAS. Conclusions/Significance Maternal Na+ overload programmed alterations in renal Na+ transporters and in its regulation, as well as severe structural lesions in adult offspring. Enalapril

Phenylethynyl-butyltellurium inhibits the sulfhydryl enzyme Na+, K+ -ATPase: an effect dependent on the tellurium atom.

Science.gov (United States)

Quines, Caroline B; Rosa, Suzan G; Neto, José S S; Zeni, Gilson; Nogueira, Cristina W

2013-11-01

Organotellurium compounds are known for their toxicological effects. These effects may be associated with the chemical structure of these compounds and the oxidation state of the tellurium atom. In this context, 2-phenylethynyl-butyltellurium (PEBT) inhibits the activity of the sulfhydryl enzyme, δ-aminolevulinate dehydratase. The present study investigated on the importance of the tellurium atom in the PEBT ability to oxidize mono- and dithiols of low molecular weight and sulfhydryl enzymes in vitro. PEBT, at high micromolar concentrations, oxidized dithiothreitol (DTT) and inhibited cerebral Na(+), K(+)-ATPase activity, but did not alter the lactate dehydrogenase activity. The inhibition of cerebral Na(+), K(+)-ATPase activity was completely restored by DTT. By contrast, 2-phenylethynyl-butyl, a molecule without the tellurium atom, neither oxidized DTT nor altered the Na(+), K(+)-ATPase activity. In conclusion, the tellurium atom of PEBT is crucial for the catalytic oxidation of sulfhydryl groups from thiols of low molecular weight and from Na(+), K(+)-ATPase.

Rotational dynamics of propylene inside Na-Y zeolite cages

Indian Academy of Sciences (India)

We report here the quasielastic neutron scattering (QENS) studies on the dynamics of propylene inside Na-Y zeolite using triple axis spectrometer (TAS) at Dhruva reactor, Trombay. Molecular dynamics (MD) simulations performed on the system had shown that the rotational motion involves energy larger than that involved ...

Parametri za procena na kvalitetot na polietilenska i na polipropilenska ambalaza i na gumeni zatvoraci nameneti za farmacevtski preparati

Directory of Open Access Journals (Sweden)

Liljana Ugrinova

2002-03-01

Full Text Available Napraven e pregled na parametrite za procena na kvalitetot na polietilenska i na polipropilenska ambalaza i na gumeni zatvoraci nameneti za farmacevtski preparati. Za procena na kvalitetot na ispituvaniot materijal bea izvrseni fizicki, hemiski i bioloski ispituvanja spored postapkite dadeni vo Ph. Eur., DIN i spored DIN ISO standardite. Baranjata za kvalitet na ovoj vid ambalaza propisani spored Ph. Eur., DIN i DIN ISO standardite se razlikuvaat vo odnos na predvidenite parametri za fizicki, za hemiski i za bioloski ispituvanja. Isto taka, propisani se i razlicni granici na dozvoleno otstapuvanje na oddelni parametri.

Regulation of renal function and structure by the signaling Na/K-ATPase.

Science.gov (United States)

Xie, Jeffrey X; Li, Xin; Xie, Zijian

2013-12-01

The Na/K-ATPase as an essential ion pump was discovered more than 50 years ago (Skou (1989) Biochim. Biophys. Acta 1000, 439-446; Feraille and Doucet (2001) Physiol. Rev. 81, 345-418). The signaling function of Na/K-ATPase has been gradually appreciated over the last 20 years, first from the studies of regulatory effects of ouabain on cardiac cell growth. Several reviews on this topic have been written during the last few years (Schoner and Scheiner-Bobis (2007) Am. J. Physiol. Cell. Physiol. 293, C509-C536; Xie and Cai (2003) Mol. Interv. 3, 157 - 168; Bagrov et al. (2009) Pharmacol. Rev. 61, 9-38; Tian and Xie (2008) Physiology 23, 205-211; Fontana et al. (2013) FEBS J. 280, 5450-5455; Blanco and Wallace (2013) Am. J. Physiol. Renal Physiol. 305, F797-F812). This article will focus on the molecular mechanism of Na/K-ATPase-mediated signal transduction and its potential regulatory role in renal physiology and diseases. © 2013 International Union of Biochemistry and Molecular Biology.

Nonadiabatic ionic--covalent transitions. Exponential-linear model for the charge exchange and neutralization reactions Na+H arrow-right-left Na/sup +/+H/sup -/

Energy Technology Data Exchange (ETDEWEB)

Errea, L.F.; Mendez, L.; Mo, O.; Riera, A.

1986-01-01

A previous study of charge exchange processes taking place through ionic--covalent transitions is extended to the case of Na+H and Na/sup +/+H/sup -/ collisions. A five-state molecular expansion, with the inclusion of two-electron translation factors, is employed to calculate the charge exchange and neutralization cross sections. Transitions at the first two pseudocrossings between the energy curves, practically determine the cross sections in the energy range 0.16--5 keV amu/sup -1/. We also show that the widely used multichannel Landau--Zener theory is totally inadequate, to treat these transitions.

Selectivity analyses of γ-benzylidene digoxin derivatives to different Na,K-ATPase α isoforms: a molecular docking approach.

Science.gov (United States)

Pessôa, Marco T C; Alves, Silmara L G; Taranto, Alex G; Villar, José A F P; Blanco, Gustavo; Barbosa, Leandro A

2018-12-01

Digoxin and other cardiotonic steroids (CTS) exert their effect by inhibiting Na,K-ATPase (NKA) activity. CTS bind to the various NKA isoforms that are expressed in different cell types, which gives CTS their narrow therapeutic index. We have synthesised a series of digoxin derivatives (γ-Benzylidene digoxin derivatives) with substitutions in the lactone ring (including non-oxygen and ether groups), to obtain CTS with better NKA isoform specificity. Some of these derivatives show some NKA isoform selective effects, with BD-3, BD-8, and BD-13 increasing NKA α2 activity, BD-5 inhibiting NKA α1 and NKA α3, BD-10 reducing NKA α1, but stimulating NKA α2 and α3; and BD-14, BD-15, and BD-16 enhancing NKA α3 activity. A molecular-docking approach favoured NKA isoform specific interactions for the compounds that supported their observed activity. These results show that BD compounds are a new type of CTS with the capacity to target NKA activity in an isoform-specific manner.

Conformational Dynamics on the Extracellular Side of LeuT Controlled by Na+ and K+ Ions and the Protonation State of Glu(290)

DEFF Research Database (Denmark)

Khelashvili, George; Schmidt, Solveig Gaarde; Shi, Lei

2016-01-01

Na+ ions and substrate have left, and the transporter prepares for a new cycle. We compare the results with the consequences of binding Na+ in the same apo system. Analysis of >50-μs atomistic molecular dynamics and enhanced sampling trajectories of constructs with Glu290, either charged or neutral......Ions play key mechanistic roles in the gating dynamics of neurotransmitter:sodium symporters (NSSs). In recent microsecond scale molecular dynamics simulations of a complete model of the dopamine transporter, a NSS protein, we observed a partitioning of K+ ions from the intracellular side toward...... the unoccupied Na2 site of dopamine transporter following the release of the Na2-bound Na+. Here we evaluate with computational simulations and experimental measurements of ion affinities under corresponding conditions, the consequences of K+ binding in the Na2 site of LeuT, a bacterial homolog of NSS, when both...

Hofmeister effect on thermo-responsive poly(propylene oxide): Role of polymer molecular weight and concentration.

Science.gov (United States)

Moghaddam, Saeed Zajforoushan; Thormann, Esben

2016-03-01

Although a vast amount of research has been dedicated to investigate the Hofmeister effect on the stability of polymer solutions, a clear understanding of the role of polymer properties in this phenomenon is still missing. Here, the Hofmeister effect of NaCl (destabilizing) and NaSCN (stabilizing) salts on aqueous solutions of poly(propylene oxide) (PPO) is studied. Four different molecular weights of PPO were investigated, to determine how the variation in the polymer coil size affects the Hofmeister effect. The investigation was further conducted for different PPO concentrations, in order to understand the effect of inter-chain interactions on the response to addition of salt. The temperature-driven phase separation of the solutions was monitored by differential scanning calorimetry, which provides the precise value of the phase separation temperature, as well as the enthalpy change accompanied with the transition. It was observed that increasing the molecular weight weakens the effect of the both salts, which is interpreted in terms of a scaling law between the molecular weight and the accessible surface area of the polymers. Increasing the PPO concentration further diminished the NaCl effect, but amplified the NaSCN effect. This difference is attributed to an electrostatic stabilization mechanism in the case of NaSCN. Copyright © 2015 Elsevier Inc. All rights reserved.

Na+/H+ Exchange Activity in the Plasma Membrane of Arabidopsis1

Science.gov (United States)

Qiu, Quan-Sheng; Barkla, Bronwyn J.; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S.

2003-01-01

In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt. PMID:12805632

Molecular alignment effect on the photoassociation process via a pump-dump scheme

Science.gov (United States)

Wang, Bin-Bin; Han, Yong-Chang; Cong, Shu-Lin

2015-09-01

The photoassociation processes via the pump-dump scheme for the heternuclear (Na + H → NaH) and the homonuclear (Na + Na → Na2) molecular systems are studied, respectively, using the time-dependent quantum wavepacket method. For both systems, the initial atom pair in the continuum of the ground electronic state (X1Σ+) is associated into the molecule in the bound states of the excited state (A1Σ+) by the pump pulse. Then driven by a time-delayed dumping pulse, the prepared excited-state molecule can be transferred to the bound states of the ground electronic state. It is found that the pump process can induce a superposition of the rovibrational levels |v, j> on the excited state, which can lead to the field-free alignment of the excited-state molecule. The molecular alignment can affect the dumping process by varying the effective coupling intensity between the two electronic states or by varying the population transfer pathways. As a result, the final population transferred to the bound states of the ground electronic state varies periodically with the delay time of the dumping pulse.

Ankyrin-B coordinates the Na/K ATPase, Na/Ca exchanger, and InsP3 receptor in a cardiac T-tubule/SR microdomain.

Directory of Open Access Journals (Sweden)

2005-12-01

Full Text Available We report identification of an ankyrin-B-based macromolecular complex of Na/K ATPase (alpha 1 and alpha 2 isoforms, Na/Ca exchanger 1, and InsP3 receptor that is localized in cardiomyocyte T-tubules in discrete microdomains distinct from classic dihydropyridine receptor/ryanodine receptor "dyads." E1425G mutation of ankyrin-B, which causes human cardiac arrhythmia, also blocks binding of ankyrin-B to all three components of the complex. The ankyrin-B complex is markedly reduced in adult ankyrin-B(+/- cardiomyocytes, which may explain elevated [Ca2+]i transients in these cells. Thus, loss of the ankyrin-B complex provides a molecular basis for cardiac arrhythmia in humans and mice. T-tubule-associated ankyrin-B, Na/Ca exchanger, and Na/K ATPase are not present in skeletal muscle, where ankyrin-B is expressed at 10-fold lower levels than in heart. Ankyrin-B also is not abundantly expressed in smooth muscle. We propose that the ankyrin-B-based complex is a specialized adaptation of cardiomyocytes with a role for cytosolic Ca2+ modulation.

Aspects of gene structure and functional regulation of the isozymes of Na,K-ATPase

DEFF Research Database (Denmark)

Jorgensen, P.L.

2001-01-01

genomes, the genes of four alpha-subunit and at least three beta-subunit isoforms of Na,K-ATPase are identified and two gamma-subunits are expressed in kidney. The isoforms combine in a number of Na,K-ATPase isozymes that are expressed in a tissue and cell specific manner. Models of the molecular...... mechanism of regulation of these isozymes have become more reliable due to progress in understanding the three-dimensional protein structure and conformational transitions mediating transfer of energy from the P-domain to intramembrane Na+ and K+ binding sites....

Connecting the molecular scale to the continuum scale for diffusion processes in smectite-rich porous media.

Science.gov (United States)

Bourg, Ian C; Sposito, Garrison

2010-03-15

In this paper, we address the manner in which the continuum-scale diffusive properties of smectite-rich porous media arise from their molecular- and pore-scale features. Our starting point is a successful model of the continuum-scale apparent diffusion coefficient for water tracers and cations, which decomposes it as a sum of pore-scale terms describing diffusion in macropore and interlayer "compartments." We then apply molecular dynamics (MD) simulations to determine molecular-scale diffusion coefficients D(interlayer) of water tracers and representative cations (Na(+), Cs(+), Sr(2+)) in Na-smectite interlayers. We find that a remarkably simple expression relates D(interlayer) to the pore-scale parameter δ(nanopore) ≤ 1, a constrictivity factor that accounts for the lower mobility in interlayers as compared to macropores: δ(nanopore) = D(interlayer)/D(0), where D(0) is the diffusion coefficient in bulk liquid water. Using this scaling expression, we can accurately predict the apparent diffusion coefficients of tracers H(2)0, Na(+), Sr(2+), and Cs(+) in compacted Na-smectite-rich materials.

Načrtovan porod na domu

OpenAIRE

Todorović, Tamara; Takač, Iztok

2017-01-01

Izhodišča: Porod na domu je sicer star toliko kot človeštvo, pa vendar v veliki večini srednje in visoko razvitih držav prevladuje mnenje, da so zaradi nepredvidljivosti zapletov porodnišnice najbolj varno okolje za rojevanje. Kljub temu obstaja peščica držav, v katerih je porod na domu integriran v sistem zdravstvenega varstva (npr. Nizozemska, Velika Britanija, Kanada). Pri porodih na domu ločimo nenačrtovane in načrtovane porode na domu, slednje pa lahko nadalje razdelimo še na porode s sp...

Tuning of the Na,K-ATPase by the beta subunit

Science.gov (United States)

Hilbers, Florian; Kopec, Wojciech; Isaksen, Toke Jost; Holm, Thomas Hellesøe; Lykke-Hartmann, Karin; Nissen, Poul; Khandelia, Himanshu; Poulsen, Hanne

2016-02-01

The vital gradients of Na+ and K+ across the plasma membrane of animal cells are maintained by the Na,K-ATPase, an αβ enzyme complex, whose α subunit carries out the ion transport and ATP hydrolysis. The specific roles of the β subunit isoforms are less clear, though β2 is essential for motor physiology in mammals. Here, we show that compared to β1 and β3, β2 stabilizes the Na+-occluded E1P state relative to the outward-open E2P state, and that the effect is mediated by its transmembrane domain. Molecular dynamics simulations further demonstrate that the tilt angle of the β transmembrane helix correlates with its functional effect, suggesting that the relative orientation of β modulates ion binding at the α subunit. β2 is primarily expressed in granule neurons and glomeruli in the cerebellum, and we propose that its unique functional characteristics are important to respond appropriately to the cerebellar Na+ and K+ gradients.

Investigations on the interactions of diclofenac sodium with HSA and ctDNA using molecular modeling and multispectroscopic methods

Science.gov (United States)

Cui, Yanrui; Hao, Erjun; Hui, Guangquan; Guo, Wei; Cui, Fengling

2013-06-01

A tentative study on interaction of diclofenac sodium (DF-Na) with human serum albumin (HSA) and calf thymus DNA (ctDNA) was conducted by using multi-spectroscopic and molecular modeling techniques under simulative physiological conditions. The results of spectroscopic measurements suggested that the quenching mechanisms were static quenching. Three-dimensional fluorescence spectroscopy clearly demonstrated the occurrence of conformational changes of HSA with addition of DF-Na. In addition, competitive studies with ethidium bromide (EB) have shown that DF-Na can bind to ctDNA relatively strong via groove binding. Based on the values of thermodynamic parameters and the results of molecular modeling, it was confirmed that hydrophobic forces and hydrogen bond were the mainly binding forces in DF-Na-HSA and DF-Na-DNA systems. The binding distance between DF-Na and HSA was also determined using the theory of the Förster energy transference.

Experimental investigation of the EPR parameters and molecular orbital bonding coefficients for VO{sup 2+} ion in NaH{sub 2}PO{sub 4}·2H{sub 2}O single crystals

Energy Technology Data Exchange (ETDEWEB)

Kalfaoğlu, Emel [Ondokuz Mayıs University, Faculty of Sciences, Department of Physics, 55139 Kurupelit-Samsun (Turkey); Karabulut, Bünyamin, E-mail: bbulut@omu.edu.tr [Ondokuz Mayıs University, Faculty of Engineering, Department of Computer Engineering, 55139 Kurupelit-Samsun (Turkey)

2016-09-15

Electron paramagnetic resonance (EPR) spectra of VO{sup 2+} ions in NaH{sub 2}PO{sub 4}·2H{sub 2}O single crystal have been studied. The spin-Hamiltonian parameters and molecular orbital bonding coefficients were calculated. The angular variation of the EPR spectra shows two different VO{sup 2+} complexes. These are located in different chemical environment and each environment contains four magnetically inequivalent VO{sup 2+} sites. The crystal field around VO{sup 2+} ion is approximately axially symmetric since a strong V=O bond distorts the crystal lattice. Spin Hamiltonian parameters and molecular orbital bonding coefficients were calculated from the EPR data and the nature of bonding in the complex was discussed together.

Thermal Inactivation Kinetics and Secondary Structure Change of a Low Molecular Weight Halostable Exoglucanase from a Marine Aspergillus niger at High Salinities.

Science.gov (United States)

Xue, Dong-Sheng; Liang, Long-Yuan; Lin, Dong-Qiang; Yao, Shan-Jing

2017-11-01

Two kinds of exoglucanase were purified from a marine Aspergillus niger. Catalytic ability of halophilic exoglucanase with a lower molecular weight and secondary structure change was analyzed at different salinities. Activity of the low molecular weight exoglucanase in 10% NaCl solution (w/v) was 1.69-fold higher of that in NaCl-free solution. Half-life time in 10% NaCl solution (w/v) was over 1.27-fold longer of that in NaCl-free solution. Free energy change of the low molecular weight exoglucanase denaturation, △G, in 10% NaCl solution (w/v) was 0.54 kJ/mol more than that in NaCl-free solution. Melt point in 10% NaCl solution (w/v), 52.01 °C, was 4.21 °C higher than that in NaCl-free solution, 47.80 °C. K m value, 0.179 mg/ml in 10% NaCl solution (w/v) was less 0.044 mg/ml than that, 0.224 mg/ml, in NaCl-free solution. High salinity made content of α-helix increased. Secondary structure change caused by high salinities improved exoglucanase thermostability and catalysis activity. The halophilic exoglucanase from a marine A. niger was valuable for hydrolyzing cellulose at high salinities.

Optical Pumping of Molecular Gases

Science.gov (United States)

1976-04-01

ser emission ott a The typical experimental apparatus is shown i.- Fig. *series of green and yellow molecular B-X’-basnd transi- 2. For B-bantd optical...with A, at 0. 473 pim and that Na2 may operate as a flash -lamp -pumped laser X,... at 0. 54 umn the Doppler widths are AwD - 12.42 source with buffer

A sol-gel based molecular imprint incorporating carbon dots for fluorometric determination of nicotinic acid

International Nuclear Information System (INIS)

Zuo, Pengli; Gao, Junfa; Liu, Jianha; Zhao, Mingming; Zhao, Jiahong; Peng, Jun; Zuo, Pengjian; He, Hua

2016-01-01

We are introducing functionalized carbon dots (C-dots) coated with a shell of molecularly imprinted sol-gel as a new tool in molecular imprint-based detection. Specifically, an imprint recognizing nicotinic acid (NA) was prepared in two steps. The first involves pyrolytic decomposition of citric acid in the presence of aminopropyltriethoxysilane to yield triethoxysilyl-modified C-dots with a typical size of 2.8 ± 1.1 nm. These are then polycondensed in the presence of tetraethoxysilane and NA at room temperature to give spherical silica nanoparticles (SiNPs) with a typical size of ∼300 nm and containing C-dots and NA in the silica matrix. NA was then removed by extraction. The resulting SiNPs are well permeable to NA, photostable, display strong blue luminescence and can bind NA fairly selectively. The fluorometric detection scheme is based on the finding that increasing concentrations of NA quench the fluorescence of the C-dots in the SiNPs. NA can be determined by this method in the 0.5 to 10.5 μM concentration range, with a 12.6 nM detection limit. The composite was successfully utilized as a fluorescent probe for the determination of NA in spiked human urine samples. The method is believed to have a wider scope in being applicable to other analytes that are capable of quenching the fluorescence of C-dots. (author)

Hydrothermal synthesis, structure and photocatalytic properties of La/Bi co-doped NaTaO3

International Nuclear Information System (INIS)

Lan, Nguyen Thi; Huan, Bui Doan; Anh, Trinh Xuan; Chinh, Huynh Dang; Phan, Le Gia; Hoang, Luc Huy; Hong, Le Van

2016-01-01

La/Bi co-doped NaTaO 3 nanomaterials for photocatalytic applications have been successfully synthesized by hydrothermal method at low temperature. The obtained materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and UV-Vis molecular absorption spectroscopy. The results showed that the particle sizes of La/Bi co-doped NaTaO 3 were smaller than that of the pure NaTaO 3 . La/Bi co-doping has extended optical absorption in the visible light region and then successfully increased photocatalytic activity of the La/Bi-codoped NaTaO 3 that were evaluated by degradation of methylene blue (MB). (author)

Comparative molecular-orbital and atomic-orbital study of electron transfer and excitation in He++Na(3s) collisions at energies of 0.05 to 20 keV/amu

International Nuclear Information System (INIS)

Fritsch, W.; Kimura, M.; Lane, N.F.

1990-01-01

Electron transfer and excitation in 0.05- to 20-keV/amu He + +Na(3s) collisions is studied theoretically within the close-coupling method with two-electron molecular- and atomic-orbital expansion basis sets. Results agree with the trend of other information on this system. Remaining discrepancies that are larger than those in similar contemporary studies of one-electron systems are discussed with reference to the convergence of this two-electron study. Results for the integral alignment parameter A 20 are also presented as a guideline for future experimental study

Alteration in DNA structure, molecular responses and Na+ -K+ -ATPase activities in the gill of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) in response to sub-lethal verapamil.

Science.gov (United States)

Ajima, Malachy N O; Pandey, Pramod K; Kumar, Kundan; Poojary, Nalini

2018-01-01

The ecotoxicological consequences of residues from pharmaceutical drugs on aquatic biota have necessitated the development of sensitive and reliable techniques to assess the impact of these xenobiotics on aquatic organisms. This study investigated the alteration in DNA structure, molecular responses and the activities of Na + -K + -ATPase and antioxidant enzymes in the gill of Nile tilapia, Oreochromis niloticus, exposed to long-term effects at the concentrations (0.14, 0.28 and 0.57mgL -1 ) of verapamil in static renewal system for 15, 30, 45 and 60 days. Evaluation of DNA structure, using single cell gel electrophoresis, revealed certain degree of DNA damages in the gill in a time and concentration-dependent relationship. Transcription of mRNA of superoxide dismutase (sod), catalase (cat) and heat shock protein (hsp70) genes in the gill of the fish showed the genes were up-regulated. Na + -K + -ATPase activity was inhibited in a concentration and time dependent manner. The indices of oxidative stress biomarkers (lipid peroxidation and carbonyl protein) as well as superoxide dismutase, glutathione peroxidase, glutathione-S-transferase were elevated in the treated fish in comparison to the control. Further, the level of reduced glutathione and catalase activity were inhibited at 0.28mgL -1 after day 30. Long-term exposure to sub-lethal concentration of verapamil can cause DNA damages, molecular effects and oxidative stress in O. niloticus. The biomarkers analysed can be used as early warning signals in environmental biomonitoring and assessment of drug contamination in aquatic ecosystem. Copyright © 2017 Elsevier Inc. All rights reserved.

Molecular beam study of the a 3Σ+ state of NaK up to the dissociation limit

Science.gov (United States)

Temelkov, I.; Knöckel, H.; Pashov, A.; Tiemann, E.

2015-03-01

We provide spectroscopic data for the a 3Σ+ state of the 23Na39K molecule. The experiment is done in an ultrasonic beam apparatus, starting from the ground state X 1Σ+and driving the population to the a 3Σ+ state, using a Λ scheme with fixed pump and scanning dump laser. The signals are observed as dips of the total fluorescence. The intermediate level is chosen to be strongly perturbed by the B 1Π/c 3Σ+ states mixing to overcome the singlet-triplet transfer prohibition. We observed highly resolved hyperfine spectra of various rovibrational levels of the a 3Σ+state from va=2 up to the highest vibrational levels for rotational quantum numbers Na=4 ,6 ,8 . By the typical experimental linewidth of 17 MHz, the vibrational dependence of the hyperfine splitting is clearly revealed for NaK. The absolute frequency measurements of the vibrational levels are used for improvement of the a 3Σ+ potential curve and of the derived scattering length of all natural isotope combinations. Applying the Λ scheme in the reverse direction can provide a pathway for efficient transfer of ultracold 23Na39K molecules from the Na(3 s )+K(4 s ) asymptote to the lowest levels of the ground state. We show spectra that couple the absolute ground state vX=0 ,J =0 with an appropriate intermediate state for direct realization of the reverse path. The refined theoretical model of the coupled excited states of the Na(3 s )+K(4 p ) asymptote allows predictions of efficient paths for 23Na40K ; one example is calculated.

Conformational changes of the cytoplasmic part of Na+/K+-ATPase induced by the ligand binding

Czech Academy of Sciences Publication Activity Database

Kubala, Martin; Gryčová, Lenka; Lánský, Zdeněk; Otyepka, M.

2007-01-01

Roč. 274, Suppl.1 (2007), s. 127-127 ISSN 1742-464X. [FEBS Congress Molecular Machines /32./. 07.07.2007-12.07.2007, Vienna] R&D Projects: GA ČR(CZ) GA203/07/0564 Institutional research plan: CEZ:AV0Z50110509 Keywords : cpo1 * Na+/K+- ATPase * molecular dynamic simulations * fluorescence quenching Subject RIV: BO - Biophysics

Media optimization for elevated molecular weight and mass production of pigment-free pullulan.

Science.gov (United States)

Yu, Xiaoliu; Wang, Yulei; Wei, Gongyuan; Dong, Yingying

2012-07-01

In this study, an Aureobasidium pullulans SZU 1001 mutant, deficient in pigment production, was screened by complex UV and γ-ray mutagenesis. Medium composition optimization for increased pullulan molecular weight and production was conducted using this mutant. Six nutrients: yeast extract, (NH4)2SO4, K2HPO4, NaCl, MgSO4·7H2O and CaCl2 were detected within pullulan production in flasks. It is shown that NaCl and K2HPO4 have significant influences on molecular weight of pullulan, while yeast extract and (NH4)2SO4 significantly affect pullulan yield. To achieve a higher molecular weight and more efficient pullulan production, a response surface methodology approach was introduced to predict an optimal nutrient combination. A molecular weight of 5.74 × 10(6) and pullulan yield on glucose of 51.30% were obtained under batch pullulan fermentation with the optimized media, which increased molecular weight and pullulan production by 97.25% and 11.04%, respectively compared with the control media. Copyright © 2012 Elsevier Ltd. All rights reserved.

Molecular dynamics simulations of cluster fission and fusion processes

DEFF Research Database (Denmark)

Lyalin, Andrey G.; Obolensky, Oleg I.; Solov'yov, Ilia

2004-01-01

Results of molecular dynamics simulations of fission reactions Na_10^2+ --> Na_7^+ +Na_3^+ and Na_18^2+ --> 2Na_9^+ are presented. The dependence of the fission barriers on the isomer structure of the parent cluster is analyzed. It is demonstrated that the energy necessary for removing homothetic...... separation of the daughter fragments begins and/or forming a "neck" between the separating fragments. A novel algorithm for modeling the cluster growth process is described. This approach is based on dynamic search for the most stable cluster isomers and allows one to find the optimized cluster geometries...... groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. The importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual...

Separation of molecular hydrogen isotope mixtures on zeolite NaX-3M

International Nuclear Information System (INIS)

Polevoj, A.S.; Yudin, I.P.

1984-01-01

The transfer unito height (TUH) have been determined at separation of the H 2 -D 2 mixture using zeolite NaX-3M depending on temperature and linear gas flow rate in the column. Experimentally the TUH value has been determined by the method of stepped variation of the concentration of one of the separated components at the entrance into the column and measurement of the substance front wash-out at the outlet. The results of determining TUH in the column of 10 mm diameter filled by the zeolite immobile layer with granules of 2-3 mm size show that with increasing the temperature from 77 K to 87.3 K TUH decreases while at constant temperature it increases with the growth of linear gas flow rate. The mentioned above circumstances testify to the essential contribution to the TUH value of the hydrogen diffusion process in the sorbent grain. The given TUH absolute values indicate the high rate of interphase isotope exchange at separation of the H 2 -D 2 mixture using NaX-3M zeolite

NaCl islands decorated with 2D or 3D 3,4,9,10-perylene-tetracarboxylic-dianhydride nanostructures

International Nuclear Information System (INIS)

Sun Xiaonan; Silly, Fabien

2010-01-01

The formation of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) nanostrutures on Au(1 1 1)-(22x√(3)) covered with NaCl islands has been studied using scanning tunneling microscopy (STM). Atomically resolved STM images show that NaCl grows as (1 0 0)-terminated layers on Au(1 1 1)-(22x√(3)). Local atomic hexagonal packing has also been observed in the NaCl(1 0 0) layer. At submonolayer NaCl coverage, PTCDA forms two-dimensional islands on the Au(1 1 1) surface and nucleate preferentially at the NaCl island step edges. When the Au surface is fully covered with NaCl layers, PTCDA molecules form three-dimensional molecular clusters decorating the step edges of NaCl layers.

NaCl islands decorated with 2D or 3D 3,4,9,10-perylene-tetracarboxylic-dianhydride nanostructures

Energy Technology Data Exchange (ETDEWEB)

Sun Xiaonan [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen (Netherlands); Silly, Fabien, E-mail: Fabien.silly@cea.fr [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen (Netherlands); CEA, IRAMIS, SPCSI, Nanostructures and Organic Semiconductors Laboratory, F-91191 Gif-sur-Yvette (France); UPMC, IPCM, UMR CNRS 7201, 4 place Jussieu, F-75005 Paris (France)

2010-01-15

The formation of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) nanostrutures on Au(1 1 1)-(22x{radical}(3)) covered with NaCl islands has been studied using scanning tunneling microscopy (STM). Atomically resolved STM images show that NaCl grows as (1 0 0)-terminated layers on Au(1 1 1)-(22x{radical}(3)). Local atomic hexagonal packing has also been observed in the NaCl(1 0 0) layer. At submonolayer NaCl coverage, PTCDA forms two-dimensional islands on the Au(1 1 1) surface and nucleate preferentially at the NaCl island step edges. When the Au surface is fully covered with NaCl layers, PTCDA molecules form three-dimensional molecular clusters decorating the step edges of NaCl layers.

Steroid-like compounds in Chinese medicines promote blood circulation via inhibition of Na+/K+ -ATPase.

Science.gov (United States)

Chen, Ronald J Y; Chung, Tse-yu; Li, Feng-yin; Yang, Wei-hung; Jinn, Tzyy-rong; Tzen, Jason T C

2010-06-01

To examine if steroid-like compounds found in many Chinese medicinal products conventionally used for the promotion of blood circulation may act as active components via the same molecular mechanism triggered by cardiac glycosides, such as ouabain. The inhibitory potency of ouabain and the identified steroid-like compounds on Na(+)/K(+)-ATPase activity was examined and compared. Molecular modeling was exhibited for the docking of these compounds to Na(+)/K(+)-ATPase. All the examined steroid-like compounds displayed more or less inhibition on Na(+)/K(+)-ATPase, with bufalin (structurally almost equivalent to ouabain) exhibiting significantly higher inhibitory potency than the others. In the pentacyclic triterpenoids examined, ursolic acid and oleanolic acid were moderate inhibitors of Na(+)/K(+)-ATPase, and their inhibitory potency was comparable to that of ginsenoside Rh2. The relatively high inhibitory potency of ursolic acid or oleanolic acid was due to the formation of a hydrogen bond between its carboxyl group and the Ile322 residue in the deep cavity close to two K(+) binding sites of Na(+)/K(+)-ATPase. Moreover, the drastic difference observed in the inhibitory potency of ouabain, bufalin, ginsenoside Rh2, and pentacyclic triterpenoids is ascribed mainly to the number of hydrogen bonds and partially to the strength of hydrophobic interaction between the compounds and residues around the deep cavity of Na(+)/K(+)-ATPase. Steroid-like compounds seem to contribute to therapeutic effects of many cardioactive Chinese medicinal products. Chinese herbs, such as Prunella vulgaris L, rich in ursolic acid, oleanolic acid and their glycoside derivatives may be adequate sources for cardiac therapy via effective inhibition on Na(+)/K(+)-ATPase.

Gastronomia Molecular: Desconstruindo 20 anos de Uma Tendência

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Joana Pellerano

2013-06-01

Full Text Available A gastronomia molecular gera interesse e controvérsia desde que foi criada, em 1992, nos workshops de Erice, na Itália. Da curiosidade dos cientistas Nicholas Kurti e Hervé This, que desenvolveram a disciplina, à aplicação prática encontrada por chefs de todo o mundo, a gastronomia molecular é perseguida por parecer ser mais complicada do que realmente é: o estudo meticuloso dos alimentos. O objetivo desse artigo é descrever o seu surgimento e o que trouxe ao cenário contemporâneo enquanto tendência gastronômica. Para tanto, foi realizada uma revisão bibliográfica em livros e citações na imprensa estrangeira, o que permitiu descrever os motivos para que essa forma de cozinhar cause tanta polêmica.

Carbon dioxide sorption in a nanoporous octahedral molecular sieve

Science.gov (United States)

Williamson, Izaak; Nelson, Eric B.; Li, Lan

2015-08-01

We have performed first-principles density functional theory calculations, incorporated with van der Waals interactions, to study CO2 adsorption and diffusion in nanoporous solid—OMS-2 (Octahedral Molecular Sieve). We found the charge, type, and mobility of a cation, accommodated in a porous OMS-2 material for structural stability, can affect not only the OMS-2 structural features but also CO2 sorption performance. This paper targets K+, Na+, and Ba2+ cations. First-principles energetics and electronic structure calculations indicate that Ba2+ has the strongest interaction with the OMS-2 porous surface due to valence electrons donation to the OMS-2 and molecular orbital hybridization. However, the Ba-doped OMS-2 has the worst CO2 uptake capacity. We also found evidence of sorption hysteresis in the K- and Na-doped OMS-2 materials.

MOLECULAR CLOUD CHEMISTRY AND THE IMPORTANCE OF DIELECTRONIC RECOMBINATION

International Nuclear Information System (INIS)

Bryans, P.; Kreckel, H.; Savin, D. W.; Roueff, E.; Wakelam, V.

2009-01-01

Dielectronic recombination (DR) of singly charged ions is a reaction pathway that is commonly neglected in chemical models of molecular clouds. In this study we include state-of-the-art DR data for He + , C + , N + , O + , Na + , and Mg + in chemical models used to simulate dense molecular clouds, protostars, and diffuse molecular clouds. We also update the radiative recombination (RR) rate coefficients for H + , He + , C + , N + , O + , Na + , and Mg + to the current state-of-the-art values. The new RR data have little effect on the models. However, the inclusion of DR results in significant differences in gas-grain models of dense, cold molecular clouds for the evolution of a number of surface and gas-phase species. We find differences of a factor of 2 in the abundance for 74 of the 655 species at times of 10 4 -10 6 yr in this model when we include DR. Of these 74 species, 16 have at least a factor of 10 difference in abundance. We find the largest differences for species formed on the surface of dust grains. These differences are due primarily to the addition of C + DR, which increases the neutral C abundance, thereby enhancing the accretion of C onto dust. These results may be important for the warm-up phase of molecular clouds when surface species are desorbed into the gas phase. We also note that no reliable state-of-the-art RR or DR data exist for Si + , P + , S + , Cl + , and Fe + . Modern calculations for these ions are needed to better constrain molecular cloud models.

The Na+/H+ exchanger controls deoxycholic acid-induced apoptosis by a H+-activated, Na+-dependent ionic shift in esophageal cells.

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Aaron Goldman

Full Text Available Apoptosis resistance is a hallmark of cancer cells. Typically, bile acids induce apoptosis. However during gastrointestinal (GI tumorigenesis the cancer cells develop resistance to bile acid-induced cell death. To understand how bile acids induce apoptosis resistance we first need to identify the molecular pathways that initiate apoptosis in response to bile acid exposure. In this study we examined the mechanism of deoxycholic acid (DCA-induced apoptosis, specifically the role of Na(+/H(+ exchanger (NHE and Na(+ influx in esophageal cells. In vitro studies revealed that the exposure of esophageal cells (JH-EsoAd1, CP-A to DCA (0.2 mM-0.5 mM caused lysosomal membrane perturbation and transient cytoplasmic acidification. Fluorescence microscopy in conjunction with atomic absorption spectrophotometry demonstrated that this effect on lysosomes correlated with influx of Na(+, subsequent loss of intracellular K(+, an increase of Ca(2+ and apoptosis. However, ethylisopropyl-amiloride (EIPA, a selective inhibitor of NHE, prevented Na(+, K(+ and Ca(2+ changes and caspase 3/7 activation induced by DCA. Ouabain and amphotericin B, two drugs that increase intracellular Na(+ levels, induced similar changes as DCA (ion imbalance, caspase3/7 activation. On the contrary, DCA-induced cell death was inhibited by medium with low a Na(+ concentrations. In the same experiments, we exposed rat ileum ex-vivo to DCA with or without EIPA. Severe tissue damage and caspase-3 activation was observed after DCA treatment, but EIPA almost fully prevented this response. In summary, NHE-mediated Na(+ influx is a critical step leading to DCA-induced apoptosis. Cells tolerate acidification but evade DCA-induced apoptosis if NHE is inhibited. Our data suggests that suppression of NHE by endogenous or exogenous inhibitors may lead to apoptosis resistance during GI tumorigenesis.

Photoaffinity labelling of a small protein component of a purified (Na+-K+)ATPase

International Nuclear Information System (INIS)

Rogers, T.B.; Lazdunski, M.

1979-01-01

Studies have been carried out on the photoaffinity labelling of the (Na + -K + )ATPase from the electric organ of Electrophorus electricus. The aims were to see if different photoaffinity labels of the ouabain binding site, are capable of labelling a small protein component and to know if there is a small protein component, in addition to the major protein chains with molecular weights in the regions of 100 000 and 50 000, which is present in other purified (Na + -K + )ATPase preparations. (Auth.)

Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry.

Science.gov (United States)

Zhu, Wandi; Varga, Zoltan; Silva, Jonathan R

2016-01-01

Very recently, voltage-clamp fluorometry (VCF) protocols have been developed to observe the membrane proteins responsible for carrying the ventricular ionic currents that form the action potential (AP), including those carried by the cardiac Na(+) channel, NaV1.5, the L-type Ca(2+) channel, CaV1.2, the Na(+)/K(+) ATPase, and the rapid and slow components of the delayed rectifier, KV11.1 and KV7.1. This development is significant, because VCF enables simultaneous observation of ionic current kinetics with conformational changes occurring within specific channel domains. The ability gained from VCF, to connect nanoscale molecular movement to ion channel function has revealed how the voltage-sensing domains (VSDs) control ion flux through channel pores, mechanisms of post-translational regulation and the molecular pathology of inherited mutations. In the future, we expect that this data will be of great use for the creation of multi-scale computational AP models that explicitly represent ion channel conformations, connecting molecular, cell and tissue electrophysiology. Here, we review the VCF protocol, recent results, and discuss potential future developments, including potential use of these experimental findings to create novel computational models. Copyright © 2015 Elsevier Ltd. All rights reserved.

Isolation, crystallization and crystal structure determination of bovine kidney Na(+),K(+)-ATPase.

Science.gov (United States)

Gregersen, Jonas Lindholt; Mattle, Daniel; Fedosova, Natalya U; Nissen, Poul; Reinhard, Linda

2016-04-01

Na(+),K(+)-ATPase is responsible for the transport of Na(+) and K(+) across the plasma membrane in animal cells, thereby sustaining vital electrochemical gradients that energize channels and secondary transporters. The crystal structure of Na(+),K(+)-ATPase has previously been elucidated using the enzyme from native sources such as porcine kidney and shark rectal gland. Here, the isolation, crystallization and first structure determination of bovine kidney Na(+),K(+)-ATPase in a high-affinity E2-BeF3(-)-ouabain complex with bound magnesium are described. Crystals belonging to the orthorhombic space group C2221 with one molecule in the asymmetric unit exhibited anisotropic diffraction to a resolution of 3.7 Å with full completeness to a resolution of 4.2 Å. The structure was determined by molecular replacement, revealing unbiased electron-density features for bound BeF3(-), ouabain and Mg(2+) ions.

Molecular determinants of voltage-gated sodium channel regulation by the Nedd4/Nedd4-like proteins

DEFF Research Database (Denmark)

Rougier, Jean-Sébastien; van Bemmelen, Miguel X; Bruce, M Christine

2004-01-01

-ubiquitin ligases of the Nedd4 family. We recently reported that cardiac Na(v)1.5 is regulated by Nedd4-2. In this study, we further investigated the molecular determinants of regulation of Na(v) proteins. When expressed in HEK-293 cells and studied using whole cell voltage clamping, the neuronal Na(v)1.2 and Na...... that Nedd4-dependent ubiquitination of Na(v) channels may represent a general mechanism regulating the excitability of neurons and myocytes via modulation of channel density at the plasma membrane....

Separation of the genera in the subtribe Cassiinae (Leguminosae: Caesalpinioidae using molecular markers Separação dos gêneros na subtribo Cassiinae (Leguminosae: Caesalpinioidae utilizando marcadores moleculares

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Laxmikanta Acharya

2011-03-01

Full Text Available Random amplified polymorphic DNA (RAPD, Inter simple sequence repeat (ISSR and Amplified fragment length polymorphism (AFLP markers were used to verify the segregation of the genus Cassia L. senso lato into three distinct genera namely Chamaecrista Moench., Senna P. Mill. and Cassia L. sensostricto Eighteen representatives of the three taxa were characterized using the molecular markers. 25 RAPD, six ISSR primers and six AFLP primer combinations resulted in the amplification of 612, 115 and 622 bands (loci respectively. Most of the loci are found to be polymorphic, showing high degrees of genetic diversity among the different taxa studied. The dendrogram constructed on the basis of the RAPD, ISSR and AFLP data using SHAN clustering, divided Cassia L. senso lato. into three different clusters as Chamaecrista Moench. Senna P. Mill. and Cassia L. senso stricto High bootstrap value revealed that all the clusters were stable and robust. It was observed from the present investigation that these genera have their identity at molecular level, which supports the elevation of the genus Cassia L. senso lato to the level of subtribe Cassiinae and segregation into three distinct genera instead of intrageneric categories.Técnicas de Random amplified polymorphic DNA (RAPD, Inter simple sequence repeat (ISSR e Amplified Fragment Length Polymorphism markers (AFLP foram utilizadas para verificar a segregação do gênero Cassia L. senso lato em três diferentes gêneros, Chamaecrista Moench., Senna P. Mill. e Cassia L. senso stricto Dezoito representantes dos três táxons foram caracterizados com o uso de marcadores moleculares: 25 RAPD, seis iniciadores ("primers" ISSR e seis AFLP combinações de iniciadores, resultando na amplificação de 612, 115 e 622 bandas (loci, respectivamente. A maioria dos loci apresentou-se como polimórfico, mostrando um alto grau de diversidade genética entre os táxons estudados. O dendrograma construído com base nos dados de

A construção social de gênero na Biologia: preconceitos e obstáculos na biologia molecular Social construction of gender in biology: prejudice and barriers in molecular biology

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Neide Mayumi Osada

2006-12-01

Full Text Available Este paper tem como objetivo analisar a presença de homens e mulheres nas ciências biológicas a partir do Projeto Genoma Fapesp (PGF. Baseado nos estudos sociais das ciências e nos estudos de gênero em ciências, pretende-se, portanto, entender as principais razões que levam ao avanço mais lento na carreira das mulheres pesquisadoras, analisar como ocorre a participação das mulheres na construção das ciências e, por fim, avaliar os principais obstáculos por elas enfrentados.This paper analyses the presence of women and men in Biological Sciences, specifically at the Fapesp Genome Project. Considering the Social Studies of Sciences and Gender Studies, this article highlights the barrier and prejudices women face in their scientific carrier and show how this reproduces a situation in which men advance faster than women.

Expression of Insoluble Influenza Neuraminidase Type 1 (NA1 Protein in Tobacco

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Teen Lee Pua

2012-12-01

Full Text Available The avian influenza virus, particularly H5N1 strain, is highly virulent to poultry and mankind. Several expression systems, like yeast, baculovirus and mammalian cells, have been adopted to produce vaccine candidate for this lethal disease. The present research aimed at developing a recombinant vaccine candidate, neuraminidase type 1 (NA1, for the Malaysia isolate of H5N1 in Nicotiana benthamiana. The NA1 gene was fused directly in-frame in cowpea mosaic virus (CPMV-based pEAQ-HT vector with C-terminal polyhistidine-tag incorporated to ease the subsequent purification step. The expression of the NA1 gene in tobacco was confirmed at RNA and protein levels at 6 days post-infiltration (Dpi. From the insoluble fraction of the protein, a recombinant glycosylated NA1 protein with a molecular weight of ~56 kDa was immunogenically detected by a specific anti-NA polyclonal antibody. We report for the first time the insolubility of the plant-made NA1 protein where a native sequence was used for its expression. This study signifies the necessity of the use of optimised sequences for expression work and provides great opportunity for the exploration of plant-manufactured NA1 protein as vaccine candidate.

Substrate-Na{sup +} complex formation: Coupling mechanism for {gamma}-aminobutyrate symporters

Energy Technology Data Exchange (ETDEWEB)

Pallo, Anna; Simon, Agnes [Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences (Hungary); Bencsura, Akos [Department of Theoretical Chemistry, Institute of Structural Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest (Hungary); Heja, Laszlo [Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences (Hungary); Kardos, Julianna, E-mail: jkardos@chemres.hu [Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences (Hungary)

2009-07-24

Crystal structures of transmembrane transport proteins belonging to the important families of neurotransmitter-sodium symporters reveal how they transport neurotransmitters across membranes. Substrate-induced structural conformations of gated neurotransmitter-sodium symporters have been in the focus of research, however, a key question concerning the mechanism of Na{sup +} ion coupling remained unanswered. Homology models of human glial transporter subtypes of the major inhibitory neurotransmitter {gamma}-aminobutyric acid were built. In accordance with selectivity data for subtype 2 vs. 3, docking and molecular dynamics calculations suggest similar orthosteric substrate (inhibitor) conformations and binding crevices but distinguishable allosteric Zn{sup 2+} ion binding motifs. Considering the occluded conformational states of glial human {gamma}-aminobutyric acid transporter subtypes, we found major semi-extended and minor ring-like conformations of zwitterionic {gamma}-aminobutyric acid in complex with Na{sup +} ion. The existence of the minor ring-like conformation of {gamma}-aminobutyric acid in complex with Na{sup +} ion may be attributed to the strengthening of the intramolecular H-bond by the electrostatic effect of Na{sup +} ion. Coupling substrate uptake into cells with the thermodynamically favorable Na{sup +} ion movement through substrate-Na{sup +} ion complex formation may be a mechanistic principle featuring transmembrane neurotransmitter-sodium symporter proteins.

Influence of Extractant and Soil Type on Molecular Characteristics of Humic Substances From Two Brazilian Soils

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Dick Deborah Pinheiro

1999-01-01

Full Text Available In a previous study it was observed that humic substances (HS extracted with NaOH solution and with Na4P2O7 solution presented different molecular weights, and also that the extracted HS yield by each method varied between an Oxisol and a Mollisol from South Brazil. In the present study, we further investigated the organic matter in these soils by characterizing HS extracted with 0.5 mol L-1 NaOH and with neutral 0.15 mol L-1 Na4P2O7 solutions from the above mentioned samples, using elemental analysis and nuclear magnetic ressonance spectroscopy (liquid state ¹H- and 13C-NMR, and by relating the molecular differences to the extraction method and soil type. HS extracted with pyrophosphate were more humified, showing a higher aromaticity and higher carboxylic content. The NaOH-extracted HS were more aliphatic and contained a higher O-alkyl proportion, which is indicative of a less humified nature than the pyrophosphate-extracted HS.

Preparation and Characterization of High Silica Molecular Sieve from Rice Husk

International Nuclear Information System (INIS)

Hnaung Hnaung Win; Tin Tin Aye; Kyaw Myo Naing; Nyunt Wynn

2008-03-01

A mordenite type of hight silica molecular sieve with a formula composition Na32 (ALO2)32 (SiO2)176 192H2O having a high molar ratio of SiO2 /Al2O3 (5.4) with a percent yield of 98.76% has been prepared from synthesized zeolite NaY and glycolato silicate on the basis of hydrothermal condition.Zeolicate NaY and glycolato silicate were synthesized by using 98.34% purified silica which was extracted from rice husk.The characterizations with XRD, FT-IR, EDXRF,TG-DTA and SEM techniques were studied.

The initial stages of NaCl dissolution: Ion or ion pair solvation?

Science.gov (United States)

Klimes, Jiri; Michaelides, Angelos

2009-03-01

The interaction of water with rock salt (NaCl) is important in a wide variety of natural processes and human activities. A lot is known about NaCl dissolution at the macroscopic level but we do not yet have a detailed atomic scale picture of how salt crystals dissolve. Here we report an extensive series of density functional theory, forcefield and molecular dynamics studies of water clusters at flat and defective NaCl surfaces and NaCl clusters. The focus is on answering seemingly elementary questions such as how many water molecules are needed before it becomes favorable to extract an ion or a pair of ions from the crystal or the cluster. It turns out, however, that the answers to these questions are not so straightforward: below a certain number of water molecules (˜ 12) solvation of individual ions is less costly and above this number solvation of ion pairs is favored. These results reveal a hitherto unknown complexity in the NaCl dissolution process born out of a subtle interplay between water-water and water-ion interactions.

DNA fingerprinting of sugarcane for detecting molecular evidence of somaclonal variation

International Nuclear Information System (INIS)

Ramos Leal, M.; Canales, E.; Michel, R.; Coto, O.; Cornide, M.T.

1998-01-01

Molecular characterisation of eight sugarcane mutants which tolerate 1% NaCl, was performed by means of restriction fragment length polymorphism (RFLP) analysis at the genomic level, using a group of molecular probes for ribosomal DNAs and two others, Δ-pyrroline-5-carboxylate reductase (ΔP5CR) and ATPase, probably related to salinity stress tolerance. Results showed the molecular evidence of genetic changes in comparison to the susceptible donor variety and the possible presence of more that one mechanism to tolerate salt stress. (author)

Identification of CW two-photon transitions in Na2 and NaK

International Nuclear Information System (INIS)

Morgan, G.P.

1983-01-01

This thesis reports on the two-photon visible excitation spectra of sodium and potassium vapors. In the past, similar work has been performed on sodium and many atomic two-photon transitions have been characterized. However, many extra signals exist which do not possess the ground, 3S, state hyperfine splitting. These extra transitions are due to the sodium dimer Na 2 . 79 such transitions, from 5800A - 6500A, which lie within the resolution of the apparatus have been studied. The molecules are excited with a lowpower narrow band counterpropagating cw dye laser beam and two-photon fluorescence. The fluorescence intensities of many of these transitions are greater than the 3S to 5S and 3S to 4D atomic signals, where the 3P enhancing state lies 300 cm -1 from resonance. By comparing the number density of the atomic with any molecular ground state and also the two-photon transition rates to excited states, the intermediate enhancing state for a two-photon transition in Na 2 can be predicted to be less than 1 cm -1 from resonance with the two-photon transition. This observation, along with published Dunham coefficients, is used to identify the states involved in the two-photon transitions

Suppression of NaNO3 crystal nucleation by glycerol: micro-Raman observation on the efflorescence process of mixed glycerol/NaNO3/water droplets.

Science.gov (United States)

Yu, Jun-Ying; Zhang, Yun; Zeng, Guang; Zheng, Chuan-Ming; Liu, Yong; Zhang, Yun-Hong

2012-02-09

Although the hygroscopicity of a NaNO(3)/water microdroplet and a polyalcohol/water microdroplet, two of the most important aerosols in atmosphere, has been widely studied, little is known about the relationship between the hygroscopic behavior of mixed NaNO(3)/polyalcohol/water droplets and their structures on the molecular level. In this study, the hygroscopicity of mixed glycerol/NaNO(3)/water droplets deposited on a hydrophobic substrate was studied by micro-Raman spectroscopy with organic-to-inorganic molar ratios (OIRs) of 0.5, 1, and 2. In the mixed glycerol/NaNO(3)/water droplets, glycerol molecules tended to combine with Na(+) and NO(3)(-) ions by electrostatic interaction and hydrogen bonding, respectively. On the basis of the analyses of the changes of symmetric stretching (v(s)-CH(2)), asymmetric stretching (v(a)-CH(2)), their area ratio (Av(a)-CH(2)/Av(s)-CH(2)) of glycerol, and symmetric stretching band of NO(3)(-) (ν(1)-NO(3)(-)) with relative humidity (RH), it was found that the conformation of glycerol was transformed from αα mainly to γγ and partly to αγ with a decreasing RH in the mixed droplets, contrary to the case in the glycerol/water droplet. In addition, the glycerol with γγ and αγ conformation had strong interaction with Na(+) and NO(3)(-) respectively, which suppressed the formation of contact of ions and delayed the efflorescence relative humidity (ERH) for the mixed droplets compared to the NaNO(3)/water droplet. © 2012 American Chemical Society

Na-no-body : De l’oubli du corps sensible en nanomédecine

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Noury, Mathieu

2016-09-01

Full Text Available This article presents the ethical reflexion of a recent art project, Na-no-body, presented at the Montreal gallery Espace Projet in the context of the exposition Art + Bioéthique. Na-no-body is the result of a collaborative work between the artist Stephanie Coleman and the sociologist Mathieu Noury. The aim of this project was to open an ethical dialogue on nanomedicine and its relationship with the body. To do so, the article examines specifically the notion of “personalized medicine” promoted by nanomedicine. This article proposes that, far from developing an approach reintegrating the person and the personal experience of illness at the heart of the care relationship, nanomedicine brings a simple molecular and technical response to caring. It is argued that two major themes constitute the core of this notion: 1 a molecular conception of personalization, and 2 a technical conception of personalization.

Development of a pilot molecular distillation unit; Desenvolvimento de unidade de destilacao molecular nacional e aplicacao na avaliacao de petroleos extrapesados

Energy Technology Data Exchange (ETDEWEB)

Rocha, Erica Roberta Lovo da; Maciel, Maria Regina Wolf; Maciel Filho, Rubens; Batistella, Cesar Benedito [Universidade Estadual de Campinas (UNICAMP), SP (Brazil); Medina, Lilian Carmem [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)

2008-07-01

Due to the importance and the need in studies with heavy and extra heavy petroleums and their residues, it was designed and built up by the oil research group of LOPCA/LDPS/FEQ/UNICAMP, in partnership with the Laboratory of Valuation Processes of CENPES / PETROBRAS, a pilot plant of falling film molecular distiller (national prototype), where some specific operational facilities were introduced. This project resulted in a suitable system for distillation of products of high molecular weight and thermally sensitive, without degradation of them. This work aims the achievement of distillate fractions of atmospheric residue 400 deg C+, using the new molecular distillation equipment. The experiments were carried out according to factorial design to assess the significant process variables in the molecular distillation prototype. The results showed that the evaporator temperature has high influence on the process and the feed flow rate has minimum influence, as it is desired. Additionally, the equipment showed easy handing operation, high operational stability and results varying around 1%. (author)

Ab initio interionic potentials for NaCl by multiple lattice inversion

International Nuclear Information System (INIS)

Zhang Shuo; Chen Nanxian

2002-01-01

Based on the Chen-Moebius lattice inversion and a series of pseudopotential total-energy curves, a different method is presented to derive the ab initio interionic pair potentials for B1-type ionic crystals. Comparing with the experimental data, the static properties of B1- and B2-type NaCl are well reproduced by the interionic potentials. Moreover, the phase stability of B1-NaCl has been described by the energy minimizations from the global deformed and disturbed states. The molecular-dynamics simulations for the molten NaCl indicate that the calculated mean-square displacements, radial distribution function, and diffusion coefficients gain good agreements with the experimental results. It can be concluded that the inversion pair potentials are valid over a wide range of interionic separations for describing the structural properties of B1-type ionic crystals

Total serum vitamin C concentration in pregnant women: implications for a healthy pregnancy Concentração total de vitamina C na gestante: implicações para uma gestação saudável

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Garba Ibrahim Hassan

2006-09-01

Full Text Available OBJECTIVES: total serum vitamin C (L-ascorbic acid concentration was measured in 90 pregnant women, 30 in each trimester (age range 18-35 years and a control group of age-matched non-pregnant women. METHODS: total serum vitamin C concentration was measured using the 2.4-dinitrophenylhydrazine method which involves the conversion of vitamin C to dehydroascorbic acid in the presence of copper (II ions and subsequent measurement of the resulting bis-hydrazone at 540nm. RESULTS: the total vitamin C concentration in the first trimester was 2.55 ± 0.82 mg/dl and 2.32 ± 0.40 mg/dl and 0.77 ± 0.10 mg/dl in the second and third trimesters respectively. Relative to serum total vitamin C concentration in the controls (3.15 ± 0.13 mg/dl these values are significantly lower (p OBJETIVOS: a concentração sérica total de vitamina C (ácido 1-ascórbico foi medida em 90 mulheres grávidas sendo 30 em cada trimestre (idade de 18-35 anos e um grupo controle, pareado por idade, de mulheres não grávidas. MÉTODOS: a concentração sérica total de vitamina C foi medida usando o método 2.4-dinitrofenilhidrazina que envolve a conversão de vitama C a ácido dehidroascorbico na presença de íons cobre II e, em seguida, medindo a resultante bi-hidrazona em 540 nm. RESULTADOS: a concentração total de vitamina C no primeiro semestre foi de 2.55 ± 0,13 mg/dL e de 2,32 ± 0,40 mg/dL e 0,77 ± 0,10 mg/dL no segundo e terceiro trimestres, respectivamente. Estes valores são significativamente mais baixos do que nos controles (3,15 ± 0,13 mg/dL(p<0,05. CONCLUSÕES: reduzida concentração de vitamina C sérica na gestação pode indicar a sua utilização para retirar o excesso de espécies oxigênio-reativas e manter a homeostase normal. Assim, recomenda-se a suplementação de vitamina C na gestação para aumentar o seu baixo nível no organismo e previnir a predisposição para o baixo peso ao nascer, parto prematuro e pré-eclâmpsia, condições associadas

Na+-stimulated ATPase of alkaliphilic halotolerant cyanobacterium Aphanothece halophytica translocates Na+ into proteoliposomes via Na+ uniport mechanism

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Soontharapirakkul Kanteera

2010-08-01

Full Text Available Abstract Background When cells are exposed to high salinity conditions, they develop a mechanism to extrude excess Na+ from cells to maintain the cytoplasmic Na+ concentration. Until now, the ATPase involved in Na+ transport in cyanobacteria has not been characterized. Here, the characterization of ATPase and its role in Na+ transport of alkaliphilic halotolerant Aphanothece halophytica were investigated to understand the survival mechanism of A. halophytica under high salinity conditions. Results The purified enzyme catalyzed the hydrolysis of ATP in the presence of Na+ but not K+, Li+ and Ca2+. The apparent Km values for Na+ and ATP were 2.0 and 1.2 mM, respectively. The enzyme is likely the F1F0-ATPase based on the usual subunit pattern and the protection against N,N'-dicyclohexylcarbodiimide inhibition of ATPase activity by Na+ in a pH-dependent manner. Proteoliposomes reconstituted with the purified enzyme could take up Na+ upon the addition of ATP. The apparent Km values for this uptake were 3.3 and 0.5 mM for Na+ and ATP, respectively. The mechanism of Na+ transport mediated by Na+-stimulated ATPase in A. halophytica was revealed. Using acridine orange as a probe, alkalization of the lumen of proteoliposomes reconstituted with Na+-stimulated ATPase was observed upon the addition of ATP with Na+ but not with K+, Li+ and Ca2+. The Na+- and ATP-dependent alkalization of the proteoliposome lumen was stimulated by carbonyl cyanide m - chlorophenylhydrazone (CCCP but was inhibited by a permeant anion nitrate. The proteoliposomes showed both ATPase activity and ATP-dependent Na+ uptake activity. The uptake of Na+ was enhanced by CCCP and nitrate. On the other hand, both CCCP and nitrate were shown to dissipate the preformed electric potential generated by Na+-stimulated ATPase of the proteoliposomes. Conclusion The data demonstrate that Na+-stimulated ATPase from A. halophytica, a likely member of F-type ATPase, functions as an electrogenic Na

Ciguatoxins Evoke Potent CGRP Release by Activation of Voltage-Gated Sodium Channel Subtypes NaV1.9, NaV1.7 and NaV1.1

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Filip Touska

2017-08-01

Full Text Available Ciguatoxins (CTXs are marine toxins that cause ciguatera fish poisoning, a debilitating disease dominated by sensory and neurological disturbances that include cold allodynia and various painful symptoms as well as long-lasting pruritus. Although CTXs are known as the most potent mammalian sodium channel activator toxins, the etiology of many of its neurosensory symptoms remains unresolved. We recently described that local application of 1 nM Pacific Ciguatoxin-1 (P-CTX-1 into the skin of human subjects induces a long-lasting, painful axon reflex flare and that CTXs are particularly effective in releasing calcitonin-gene related peptide (CGRP from nerve terminals. In this study, we used mouse and rat skin preparations and enzyme-linked immunosorbent assays (ELISA to study the molecular mechanism by which P-CTX-1 induces CGRP release. We show that P-CTX-1 induces CGRP release more effectively in mouse as compared to rat skin, exhibiting EC50 concentrations in the low nanomolar range. P-CTX-1-induced CGRP release from skin is dependent on extracellular calcium and sodium, but independent from the activation of various thermosensory transient receptor potential (TRP ion channels. In contrast, lidocaine and tetrodotoxin (TTX reduce CGRP release by 53–75%, with the remaining fraction involving L-type and T-type voltage-gated calcium channels (VGCC. Using transgenic mice, we revealed that the TTX-resistant voltage-gated sodium channel (VGSC NaV1.9, but not NaV1.8 or NaV1.7 alone and the combined activation of the TTX-sensitive VGSC subtypes NaV1.7 and NaV1.1 carry the largest part of the P-CTX-1-caused CGRP release of 42% and 34%, respectively. Given the contribution of CGRP to nociceptive and itch sensing pathways, our findings contribute to a better understanding of sensory symptoms of acute and chronic ciguatera that may help in the identification of potential therapeutics.

Ciguatoxins Evoke Potent CGRP Release by Activation of Voltage-Gated Sodium Channel Subtypes NaV1.9, NaV1.7 and NaV1.1

Science.gov (United States)

Touska, Filip; Sattler, Simon; Malsch, Philipp; Lewis, Richard J.; Zimmermann, Katharina

2017-01-01

Ciguatoxins (CTXs) are marine toxins that cause ciguatera fish poisoning, a debilitating disease dominated by sensory and neurological disturbances that include cold allodynia and various painful symptoms as well as long-lasting pruritus. Although CTXs are known as the most potent mammalian sodium channel activator toxins, the etiology of many of its neurosensory symptoms remains unresolved. We recently described that local application of 1 nM Pacific Ciguatoxin-1 (P-CTX-1) into the skin of human subjects induces a long-lasting, painful axon reflex flare and that CTXs are particularly effective in releasing calcitonin-gene related peptide (CGRP) from nerve terminals. In this study, we used mouse and rat skin preparations and enzyme-linked immunosorbent assays (ELISA) to study the molecular mechanism by which P-CTX-1 induces CGRP release. We show that P-CTX-1 induces CGRP release more effectively in mouse as compared to rat skin, exhibiting EC50 concentrations in the low nanomolar range. P-CTX-1-induced CGRP release from skin is dependent on extracellular calcium and sodium, but independent from the activation of various thermosensory transient receptor potential (TRP) ion channels. In contrast, lidocaine and tetrodotoxin (TTX) reduce CGRP release by 53–75%, with the remaining fraction involving L-type and T-type voltage-gated calcium channels (VGCC). Using transgenic mice, we revealed that the TTX-resistant voltage-gated sodium channel (VGSC) NaV1.9, but not NaV1.8 or NaV1.7 alone and the combined activation of the TTX-sensitive VGSC subtypes NaV1.7 and NaV1.1 carry the largest part of the P-CTX-1-caused CGRP release of 42% and 34%, respectively. Given the contribution of CGRP to nociceptive and itch sensing pathways, our findings contribute to a better understanding of sensory symptoms of acute and chronic ciguatera that may help in the identification of potential therapeutics. PMID:28867800

Polarization dependence of Na* + Na* associative ionization revisited

NARCIS (Netherlands)

Meijer, H.A.J.; Meulen, H.P. v.d.; Morgenstern, R.; Hertel, I.V.; Meyer, E.; Witte, R.

1986-01-01

The dependence of the associative ionization process Na 3 2P3/2 + Na 3 2P3/2 → Na2+ + e- on the polarization of the laser light used for Na excitation was independently investigated in Utrecht and Berlin. The purpose of this paper is to clarify discrepancies between two other earlier experimental

Protonation of key acidic residues is critical for the K⁺-selectivity of the Na/K pump.

Science.gov (United States)

Yu, Haibo; Ratheal, Ian M; Artigas, Pablo; Roux, Benoît

2011-09-11

The sodium-potassium (Na/K) pump is a P-type ATPase that generates Na(+) and K(+) concentration gradients across the cell membrane. For each hydrolyzed ATP molecule, the pump extrudes three Na(+) and imports two K(+) by alternating between outward- and inward-facing conformations that preferentially bind K(+) or Na(+), respectively. Remarkably, the selective K(+) and Na(+) binding sites share several residues, and how the pump is able to achieve the selectivity required for the functional cycle is unclear. Here, free energy-perturbation molecular dynamics (FEP/MD) simulations based on the crystal structures of the Na/K pump in a K(+)-loaded state (E2·P(i)) reveal that protonation of the high-field acidic side chains involved in the binding sites is crucial to achieving the proper K(+) selectivity. This prediction is tested with electrophysiological experiments showing that the selectivity of the E2P state for K(+) over Na(+) is affected by extracellular pH.

Cardiac glycoside activities link Na(+)/K(+) ATPase ion-transport to breast cancer cell migration via correlative SAR.

Science.gov (United States)

Magpusao, Anniefer N; Omolloh, George; Johnson, Joshua; Gascón, José; Peczuh, Mark W; Fenteany, Gabriel

2015-02-20

The cardiac glycosides ouabain and digitoxin, established Na(+)/K(+) ATPase inhibitors, were found to inhibit MDA-MB-231 breast cancer cell migration through an unbiased chemical genetics screen for cell motility. The Na(+)/K(+) ATPase acts both as an ion-transporter and as a receptor for cardiac glycosides. To delineate which function is related to breast cancer cell migration, structure-activity relationship (SAR) profiles of cardiac glycosides were established at the cellular (cell migration inhibition), molecular (Na(+)/K(+) ATPase inhibition), and atomic (computational docking) levels. The SAR of cardiac glycosides and their analogs revealed a similar profile, a decrease in potency when the parent cardiac glycoside structure was modified, for each activity investigated. Since assays were done at the cellular, molecular, and atomic levels, correlation of SAR profiles across these multiple assays established links between cellular activity and specific protein-small molecule interactions. The observed antimigratory effects in breast cancer cells are directly related to the inhibition of Na(+)/K(+) transport. Specifically, the orientation of cardiac glycosides at the putative cation permeation path formed by transmembrane helices αM1-M6 correlates with the Na(+) pump activity and cell migration. Other Na(+)/K(+) ATPase inhibitors that are structurally distinct from cardiac glycosides also exhibit antimigratory activity, corroborating the conclusion that the antiport function of Na(+)/K(+) ATPase and not the receptor function is important for supporting the motility of MDA-MB-231 breast cancer cells. Correlative SAR can establish new relationships between specific biochemical functions and higher-level cellular processes, particularly for proteins with multiple functions and small molecules with unknown or various modes of action.

Na-ion batteries based on the inorganic BN nanocluster anodes: DFT studies.

Science.gov (United States)

Nejati, K; Hosseinian, A; Bekhradnia, A; Vessally, E; Edjlali, L

2017-06-01

It has been recently indicated that the Li-ion batteries may be replaced by Na-ion batteries because of their low safety, high cost, and low-temperature performance, and lack of the Li mineral reserves. Here, using density functional theory calculations, we studied the potential application of B 12 N 12 nanoclusters as anode in Na-ion batteries. Our calculations indicate that the adsorption energy of Na + and Na are about -23.4 and -1.4kcal/mol, respectively, and the pristine BN cage to improve suffers from a low cell voltage (∼0.92V) as an anode in Na-ion batteries. We presented a strategy to increase the cell voltage and performance of Na-ion batteries. We showed that encapsulation of different halides (X=F - , Cl - , or Br - ) into BN cage significantly increases the cell voltage. By increasing the atomic number of X, the Gibbs free energy change of cell becomes more negative and the cell voltage is increased up to 3.93V. The results are discussed based on the structural, energetic, frontier molecular orbital, charge transfer and electronic properties and compared with the performance of other nanostructured anodes. Copyright © 2017 Elsevier Inc. All rights reserved.

On the coupling between molecular diffusion and solvation shell exchange

DEFF Research Database (Denmark)

Møller, Klaus Braagaard; Rey, Rossend; Masia, Marco

2005-01-01

The connection between diffusion and solvent exchanges between first and second solvation shells is studied by means of molecular dynamics simulations and analytic calculations, with detailed illustrations for water exchange for the Li+ and Na+ ions, and for liquid argon. First, two methods...

Double rotation NMR studies of zeolites and aluminophosphate molecular sieves

Energy Technology Data Exchange (ETDEWEB)

Jelinek, Raz [Univ. of California, Berkeley, CA (United States)

1993-07-01

Goal is to study the organization and structures of guest atoms and molecules and their reactions on internal surfaces within pores of zeolites and aluminophosphate molecular sieves. ²⁷Al and ²³Na double rotation NMR (DOR) is used since it removes the anisotropic broadening in NMR spectra of quadrupolar nuclei, thus increasing resolution. This work concentrates on probing aluminum framework atoms in aluminophosphate molecular sieves and sodium extra framework cations in porous aluminosilicates. In aluminophosphates, ordering and electronic environments of the framework ²⁷Al nuclei are modified upon adsorption of water molecules within the channels; a relation is sought between the sieve channel topology and the organization of adsorbed water, as well as the interaction between the Al nuclei and the water molecules. Extra framework Na⁺ cations are directly involved in adsorption processes and reactions in zeolite cavities.

Genética Molecular das Epidermólises Bolhosas Molecular Genetics of Epidermolysis Bullosa

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Hiram Larangeira de Almeida Jr

2002-10-01

Full Text Available O estudo das alterações moleculares das epidermólises bolhosas tem contribuído para que se compreenda melhor essas enfermidades. Na epidermólise bolhosa simples a maioria dos casos está associada com alteração nas citoqueratinas basais 5 (gen KRT5 e 14 (gen KRT14, o que modifica o citoesqueleto na camada basal da epiderme, levando à degeneração dessa camada, formando bolha intra-epidérmica. Mutações na plectina (gen PLEC1, componente da placa interna do hemidesmossoma, levam também à clivagem intra-epidérmica. Na epidermólise bolhosa juncional vários gens estão envolvidos, em decorrência da complexidade da zona da membrana basal, todos levando ao descolamento dos queratinócitos basais na lâmina lúcida, pela disfunção da aderência entre esses e a lâmina densa. Alterações na laminina 5 (gens LAMA3, LAMB3 e LAMC2, integrina alfa6beta4 (gens ITGA6 e ITGB4 e colágeno XVII (gen COL17A1 foram descritas. Por fim, na epidermólise bolhosa distrófica apenas um gen está mutado, alterando o colágeno VII (gen COL7A1, principal componente das fibrilas ancorantes, produzindo clivagem abaixo da lâmina densa, variando fenotipicamente de acordo com a conseqüência da mutação. Outra aplicação importante dessas informações refere-se ao diagnóstico pré-natal, com a perspectiva no futuro da terapia gênica.New data regarding the molecular aspects of the heterogeneous group of epidermolysis bullosa has brought some important information about its pathogenesis. In epidermolysis bullosa simplex the majority of mutations are localized in the genes of the basal cytokeratin 5 (gene KRT5 and 14 (gene KRT14, cytolysis at this layer with intraepidermal blister is seen under light microscopy. Mutations of plectin (gene PLEC1, a protein found in the inner hemidesmosomal plaque, leads also to intraepidermal blisters. In junctional epidermolysis bullosa many proteins from the basal membrane zone are involved, such as laminin 5 (genes

Pseudo-ternary phase diagram in the Na2O-Na2O2-NaOH system

International Nuclear Information System (INIS)

Saito, Jun-ichi; Tendo, Masayuki; Aoto, Kazumi

1997-10-01

Generally, the phase diagrams are always used to understand the present state of compounds at certain temperature. In order to understand the corrosion behavior of structural material for FBR by main sodium compounds (Na 2 O, Na 2 O 2 and NaOH), it is very important to comprehend the phase diagrams of their compounds. However, only Na 2 O-NaOH pseudo-binary phase diagram had been investigated previously in this system. There is no study of other pseudo-binary or ternary phase diagrams in the Na 2 O-Na 2 O 2 -NaOH system. In this study, in order to clarify the present states of their compounds at certain temperatures, the pseudo-binary and ternary phase diagrams in the Na 2 O-Na 2 O 2 -NaOH system were prepared. A series of thermal analyses with binary and ternary component system has been carried out using the differential scanning calorimetry (DSC). The liquidus temperature and ternary eutectic temperatures were confirmed by these measurements. The beneficial indications for constructing phase diagrams were obtained from these experiments. On the basis of these results, the interaction parameters between compounds which were utilized for the Thermo-Calc calculation were optimized. Thermo-Calc is one of thermodynamic calculation software. Consequently the accurate pseudo-binary and ternary phase diagrams were indicated using the optimized parameters. (author)

Naïve Induced Pluripotent Stem Cells Generated From β-Thalassemia Fibroblasts Allow Efficient Gene Correction With CRISPR/Cas9.

Science.gov (United States)

Yang, Yuanyuan; Zhang, Xiaobai; Yi, Li; Hou, Zhenzhen; Chen, Jiayu; Kou, Xiaochen; Zhao, Yanhong; Wang, Hong; Sun, Xiao-Fang; Jiang, Cizhong; Wang, Yixuan; Gao, Shaorong

2016-01-01

Conventional primed human embryonic stem cells and induced pluripotent stem cells (iPSCs) exhibit molecular and biological characteristics distinct from pluripotent stem cells in the naïve state. Although naïve pluripotent stem cells show much higher levels of self-renewal ability and multidifferentiation capacity, it is unknown whether naïve iPSCs can be generated directly from patient somatic cells and will be superior to primed iPSCs. In the present study, we used an established 5i/L/FA system to directly reprogram fibroblasts of a patient with β-thalassemia into transgene-free naïve iPSCs with molecular signatures of ground-state pluripotency. Furthermore, these naïve iPSCs can efficiently produce cross-species chimeras. Importantly, using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 nuclease genome editing system, these naïve iPSCs exhibit significantly improved gene-correction efficiencies compared with the corresponding primed iPSCs. Furthermore, human naïve iPSCs could be directly generated from noninvasively collected urinary cells, which are easily acquired and thus represent an excellent cell resource for further clinical trials. Therefore, our findings demonstrate the feasibility and superiority of using patient-specific iPSCs in the naïve state for disease modeling, gene editing, and future clinical therapy. In the present study, transgene-free naïve induced pluripotent stem cells (iPSCs) directly converted from the fibroblasts of a patient with β-thalassemia in a defined culture system were generated. These naïve iPSCs, which show ground-state pluripotency, exhibited significantly improved single-cell cloning ability, recovery capacity, and gene-targeting efficiency compared with conventional primed iPSCs. These results provide an improved strategy for personalized treatment of genetic diseases such as β-thalassemia. ©AlphaMed Press.

FXYD5: Na+/ K+-ATPase Regulator in Health and Disease.

Directory of Open Access Journals (Sweden)

Irina eLubarski Gotliv

2016-03-01

Full Text Available FXYD5 (Dysadherin, RIC is a single span type I membrane protein that plays multiple roles in regulation of cellular functions. It is expressed in a variety of epithelial tissues and acts as an auxiliary subunit of the Na+/ K+-ATPase. During the past decade, a correlation between enhanced expression of FXYD5 and tumor progression has been established for various tumor types. In this review, current knowledge on FXYD5 is discussed, including experimental data on the functional effects of FXYD5 on the Na+/ K+-ATPase. FXYD5 modulates cellular junctions, influences chemokine production, and affects cell adhesion. The accumulated data may provide a basis for understanding the molecular mechanisms underlying FXYD5 mediated phenotypes.

Neurological disease mutations compromise a C-terminal ion pathway in the Na(+)/K(+)-ATPas

DEFF Research Database (Denmark)

Poulsen, Hanne; Khandelia, Himanshu; Morth, Jens Preben

2010-01-01

severe neurological diseases. This novel model for ion transport by the Na(+)/K(+)-ATPase is established by electrophysiological studies of C-terminal mutations in familial hemiplegic migraine 2 (FHM2) and is further substantiated by molecular dynamics simulations. A similar ion regulation is likely...

Neurological disease mutations compromise a C-terminal ion pathway in the Na(+)/K(+)-ATPase

DEFF Research Database (Denmark)

Poulsen, Hanne; Khandelia, Himanshu; Morth, J Preben

2010-01-01

severe neurological diseases. This novel model for ion transport by the Na(+)/K(+)-ATPase is established by electrophysiological studies of C-terminal mutations in familial hemiplegic migraine 2 (FHM2) and is further substantiated by molecular dynamics simulations. A similar ion regulation is likely...

Over-expression of Arabidopsis DnaJ (Hsp40) contributes to NaCl ...

African Journals Online (AJOL)

Over-expression of Arabidopsis DnaJ (Hsp40) contributes to NaCl-stress tolerance. Z Zhichang, Z Wanrong, Y Jinping, Z Jianjun, LZL Xufeng, Y Yang. Abstract. DnaJ (Hsp40), a heat shock protein, is a molecular chaperones responsive to various environmental stress. To analyze the protective role of DnaJ, we obtained ...

Spectroscopy of Na-18: Bridging the two-proton radioactivity of Mg-19

Czech Academy of Sciences Publication Activity Database

Assie, M.; de Oliveira Santos, F.; Achouri, L.; Angelique, J. C.; Borcea, C.; Borcea, R.; Caceres, L.; Chudoba, V.; Pang, D. Y.; Ducoin, D.; Fallot, M.; Kamalou, O.; Kiener, J.; Lam, Y.; Lefevre, A.; Lotay, G.; Mrázek, Jaromír; Perrot, L.; Sánchez, A.; Rotaru, F.

2012-01-01

Roč. 712, č. 3 (2012), s. 198-202 ISSN 0370-2693 Grant - others:European Commission(XE) RII3-CT-2004-506065 Institutional support: RVO:61389005 Keywords : two-proton radioactivity * resonant elastic scattering * (19)mg * Na-18 * Ne-17 Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 4.569, year: 2012

Tribological behavior of in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films

International Nuclear Information System (INIS)

Guo Yanbao; Wang Deguo; Liu Shuhai

2010-01-01

Multilayer polyelectrolyte films containing silver ions were obtained by molecular deposition method on a glass plate or a quartz substrate. The in situ Ag nanoparticles were synthesized in the multilayer polyelectrolyte films which were put into fresh NaBH 4 aqueous solution. The structure and surface morphology of composite molecular deposition films were observed by UV-vis spectrophotometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tribological characteristic was investigated by AFM and micro-tribometer. It was found that the in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have lower coefficient of friction and higher anti-wear life than pure polyelectrolyte molecular deposition films.

Vacancy profile in reverse osmosis membranes studied by positron annihilation lifetime measurements and molecular dynamics simulations

International Nuclear Information System (INIS)

Shimazu, A; Shintani, T; Hirose, M; Goto, H; Suzuki, R; Kobayashi, Y

2013-01-01

The positron annihilation technique using a slow positron beam can be used for the study of the vacancy profiles in typical reverse osmosis (RO) membranes. In this study, the vacancy profile in the polyamide membrane that exhibits a high permselectivity between ions and water was studied using the positron annihilation technique and molecular dynamics simulations. Ortho-positronium (o-Ps) lifetimes in the surface region of the membranes were evaluated by using a slow positron beam. The diffusion behavior of Na + and water in the polyamides was simulated by molecular dynamics (MD) methods using the TSUBAME2 supercomputer at the Tokyo Institute of Technology and discussed with the vacancy profile probed by the o-Ps. The results suggested that the large hydration size of Na + compared to the vacancy size in the polyamides contributes to the increased diffusivity selectivity of water/Na + that is related to the NaCl desalination performance of the membrane. Both the hydration size of the ions and the vacancy size appeared to be significant parameters to discuss the diffusivity selectivity of water/ions in typical polyamide membranes.

A study of the excited 1Σ+sub(g) states in Na2

International Nuclear Information System (INIS)

Taylor, A.J.; Jones, K.M.; Schawlow, A.L.

1981-01-01

Using the technique of two-step polarization labeling spectroscopy seven excited 1 Σ + sub(g) states in Na 2 have been found. Molecular constants are derived from a Dunham expansion. Tentative assignments are made to the 3p + 3p, 3s + nd and 3s + ns atomic asymptotes. (orig.)

Extracellular Na+ levels regulate formation and activity of the NaX/alpha1-Na+/K+-ATPase complex in neuronal cells.

Directory of Open Access Journals (Sweden)

Emmanuelle eBerret

2014-12-01

Full Text Available MnPO neurons play a critical role in hydromineral homeostasis regulation by acting as sensors of extracellular sodium concentration ([Na+]out. The mechanism underlying Na+-sensing involves Na+-flow through the NaX channel, directly regulated by the Na+/K+-ATPase α1-isoform which controls Na+-influx by modulating channel permeability. Together, these two partners form a complex involved in the regulation of intracellular sodium ([Na+]in. Here we aim to determine whether environmental changes in Na+ could actively modulate the NaX/Na+/K+-ATPase complex activity.We investigated the complex activity using patch-clamp recordings from rat MnPO neurons and Neuro2a cells. When the rats were fed with a high-salt-diet, or the [Na+] in the culture medium was increased, the activity of the complex was up-regulated. In contrast, drop in environmental [Na+] decreased the activity of the complex. Interestingly under hypernatremic condition, the colocalization rate and protein level of both partners were up-regulated. Under hyponatremic condition, only NaX protein expression was increased and the level of NaX/Na+/K+-ATPase remained unaltered. This unbalance between NaX and Na+/K+-ATPase pump proportion would induce a bigger portion of Na+/K+-ATPase-control-free NaX channel. Thus we suggest that hypernatremic environment increases NaX/Na+/K+-ATPase α1-isoform activity by increasing the number of both partners and their colocalization rate, whereas hyponatremic environment down-regulates complex activity via a decrease in the relative number of NaX channels controlled by the pump.

Stem cells. m6A mRNA methylation facilitates resolution of naïve pluripotency toward differentiation.

Science.gov (United States)

Geula, Shay; Moshitch-Moshkovitz, Sharon; Dominissini, Dan; Mansour, Abed AlFatah; Kol, Nitzan; Salmon-Divon, Mali; Hershkovitz, Vera; Peer, Eyal; Mor, Nofar; Manor, Yair S; Ben-Haim, Moshe Shay; Eyal, Eran; Yunger, Sharon; Pinto, Yishay; Jaitin, Diego Adhemar; Viukov, Sergey; Rais, Yoach; Krupalnik, Vladislav; Chomsky, Elad; Zerbib, Mirie; Maza, Itay; Rechavi, Yoav; Massarwa, Rada; Hanna, Suhair; Amit, Ido; Levanon, Erez Y; Amariglio, Ninette; Stern-Ginossar, Noam; Novershtern, Noa; Rechavi, Gideon; Hanna, Jacob H

2015-02-27

Naïve and primed pluripotent states retain distinct molecular properties, yet limited knowledge exists on how their state transitions are regulated. Here, we identify Mettl3, an N(6)-methyladenosine (m(6)A) transferase, as a regulator for terminating murine naïve pluripotency. Mettl3 knockout preimplantation epiblasts and naïve embryonic stem cells are depleted for m(6)A in mRNAs, yet are viable. However, they fail to adequately terminate their naïve state and, subsequently, undergo aberrant and restricted lineage priming at the postimplantation stage, which leads to early embryonic lethality. m(6)A predominantly and directly reduces mRNA stability, including that of key naïve pluripotency-promoting transcripts. This study highlights a critical role for an mRNA epigenetic modification in vivo and identifies regulatory modules that functionally influence naïve and primed pluripotency in an opposing manner. Copyright © 2015, American Association for the Advancement of Science.

A Study of the Distribution of Sodium Cations in the Zeolites NaX, NaY and ZnNaY Using Carbon Monoxide Adsorption and 23Na NMR Techniques

Science.gov (United States)

Seidel, A.; Boddenberg, B.

1995-03-01

The zeolites NaX, NaY, Zn(55)NaY, and Zn(74)NaY were investigated by means of carbon monoxide adsorption and with static and magic angle spinning (MAS) 23Na NMR spectroscopy. The Na+ distribution between the sodalite (ß)- and supercages of the fully hydrated zeolites NaX and NaY were found to agree with XRD results. In the hydrated zinc-exchanged zeolites the Na+ ions almost exclusively populate the ß-cages. The adsorption isotherms of CO in the dehydrated zeolites were analyzed quantitatively to yield the concentrations of Na+ residing in the supercages. The measured static and MAS 23Na NMR spectra were analyzed by comparing their widths and shapes with simulated central transition patterns and yield, inter alia, the concentrations of Na+ associated with the spectrum components. Arguments are put forward that 23Na NMR of dehydrated zeolites is well suited to distinguish Na+ cations in highly symmetric environments and mobile Na+ species from others located on general positions, but further resolution is hardly feasible.

HCO3(-)-coupled Na+ influx is a major determinant of Na+ turnover and Na+/K+ pump activity in rat hepatocytes

International Nuclear Information System (INIS)

Fitz, J.G.; Lidofsky, S.D.; Weisiger, R.A.; Xie, M.H.; Cochran, M.; Grotmol, T.; Scharschmidt, B.F.

1991-01-01

Recent studies in hepatocytes indicate that Na(+)-coupled HCO3- transport contributes importantly to regulation of intracellular pH and membrane HCO3- transport. However, the direction of net coupled Na+ and HCO3- movement and the effect of HCO3- on Na+ turnover and Na+/K+ pump activity are not known. In these studies, the effect of HCO3- on Na+ influx and turnover were measured in primary rat hepatocyte cultures with 22Na+, and [Na+]i was measured in single hepatocytes using the Na(+)-sensitive fluorochrome SBFI. Na+/K+ pump activity was measured in intact perfused rat liver and hepatocyte monolayers as Na(+)-dependent or ouabain-suppressible 86Rb uptake, and was measured in single hepatocytes as the effect of transient pump inhibition by removal of extracellular K+ on membrane potential difference (PD) and [Na+]i. In hepatocyte monolayers, HCO3- increased 22Na+ entry and turnover rates by 50-65%, without measurably altering 22Na+ pool size or cell volume, and HCO3- also increased Na+/K+ pump activity by 70%. In single cells, exposure to HCO3- produced an abrupt and sustained rise in [Na+]i from approximately 8 to 12 mM. Na+/K+ pump activity assessed in single cells by PD excursions during transient K+ removal increased congruent to 2.5-fold in the presence of HCO3-, and the rise in [Na+]i produced by inhibition of the Na+/K+ pump was similarly increased congruent to 2.5-fold in the presence of HCO3-. In intact perfused rat liver, HCO3- increased both Na+/K+ pump activity and O2 consumption. These findings indicate that, in hepatocytes, net coupled Na+ and HCO3- movement is inward and represents a major determinant of Na+ influx and Na+/K+ pump activity. About half of hepatic Na+/K+ pump activity appears dedicated to recycling Na+ entering in conjunction with HCO3- to maintain [Na+]i within the physiologic range

Comparable investigation of the molecular size distribution and the amount of humic substances isolated from ONKALO, Olkiluoto, 2011

International Nuclear Information System (INIS)

Luste, S.; Maekelae, J.; Manninen, P.

2012-06-01

The humic substances (HS) at groundwater from ONKALO, Olkiluoto were studied in order to determine the apparent molecular size distribution and the amount of humic substances. Humic substances were isolated from the water sample using DAX-8 resin and eluted with 0.1 M NaOH. The molecular size distribution was defined using high performance size exclusion chromatography (HPSEC) and ultraviolet (UV) and refractive index (RI) detector. In the SEC calibration (polystyrene sulfonate) sodium salts (PSS) were employed. Different eluents (NaNO 3 , Na-acetate and asetonitrile) with phosphate buffer and distinct ionic strengths were studied in order to optimize the determination method. The amount of humic substances was determined using total organic carbon (TOC) measurements. The results were compared with the previous ones in order to find out the variation of different methods (HPSEC) and to follow up the HS quantity (TOC). The method developed during the study is considered to be suitable for the HS molecular size distribution follow up, although the method development is suggested to be continued. (orig.)

Comparable investigation of the molecular size distribution and the amount of humic substances isolated from ONKALO, Olkiluoto, 2011

Energy Technology Data Exchange (ETDEWEB)

Luste, S.; Maekelae, J.; Manninen, P. [Ramboll Finland Oy, Espoo (Finland)

2012-06-15

The humic substances (HS) at groundwater from ONKALO, Olkiluoto were studied in order to determine the apparent molecular size distribution and the amount of humic substances. Humic substances were isolated from the water sample using DAX-8 resin and eluted with 0.1 M NaOH. The molecular size distribution was defined using high performance size exclusion chromatography (HPSEC) and ultraviolet (UV) and refractive index (RI) detector. In the SEC calibration (polystyrene sulfonate) sodium salts (PSS) were employed. Different eluents (NaNO{sub 3}, Na-acetate and asetonitrile) with phosphate buffer and distinct ionic strengths were studied in order to optimize the determination method. The amount of humic substances was determined using total organic carbon (TOC) measurements. The results were compared with the previous ones in order to find out the variation of different methods (HPSEC) and to follow up the HS quantity (TOC). The method developed during the study is considered to be suitable for the HS molecular size distribution follow up, although the method development is suggested to be continued. (orig.)

The effect of Na vapor on the Na content of chondrules

Science.gov (United States)

Lewis, R. Dean; Lofgren, Gary E.; Franzen, Hugo F.; Windom, Kenneth E.

1993-01-01

Chondrules contain higher concentrations of volatiles (Na) than expected for melt droplets in the solar nebula. Recent studies have proposed that chondrules may have formed under non-canonical nebular conditions such as in particle/gas-rich clumps. Such chondrule formation areas may have contained significant Na vapor. To test the hypothesis of whether a Na-rich vapor would minimize Na volatilization reaction rates in a chondrule analog and maintain the Na value of the melt, experiments were designed where a Na-rich vapor could be maintained around the sample. A starting material with a melting point lower that typical chondrules was required to keep the logistics of working with Na volatilization from NaCl within the realm of feasibility. The Knippa basalt, a MgO-rich alkali olivine basalt with a melting temperature of 1325 +/- 5 C and a Na2O content of 3.05 wt%, was used as the chondrule analog. Experiments were conducted in a 1 atm, gas-mixing furnace with the fO2 controlled by a CO/CO2 gas mixture and fixed at the I-W buffer curve. To determine the extent of Na loss from the sample, initial experiments were conducted at high temperatures (1300 C - 1350 C) for duration of up to 72 h without a Na-rich vapor present. Almost all (up to 98%) Na was volatilized in runs of 72 h. Subsequent trials were conducted at 1330 C for 16 h in the presence of a Na-rich vapor, supplied by a NaCl-filled crucible placed in the bottom of the furnace. Succeeding Knudsen cell weight-loss mass-spectrometry analysis of NaCl determined the P(sub Na) for these experimental conditions to be in the 10(exp -6) atm range. This value is considered high for nebula conditions but is still plausible for non-canonical environments. In these trials the Na2O content of the glass was maintained or in some cases increased; Na2O values ranged from 2.62% wt to 4.37% wt. The Na content of chondrules may be controlled by the Na vapor pressure in the chondrule formation region. Most heating events capable

Induced pluripotent stem cells derived from rabbits exhibit some characteristics of naïve pluripotency

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Pierre Osteil

2013-05-01

Not much is known about the molecular and functional features of pluripotent stem cells (PSCs in rabbits. To address this, we derived and characterized 2 types of rabbit PSCs from the same breed of New Zealand White rabbits: 4 lines of embryonic stem cells (rbESCs, and 3 lines of induced PSCs (rbiPSCs that were obtained by reprogramming adult skin fibroblasts. All cell lines required fibroblast growth factor 2 for their growth and proliferation. All rbESC lines showed molecular and functional properties typically associated with primed pluripotency. The cell cycle of rbESCs had a prolonged G1 phase and a DNA damage checkpoint before entry into the S phase, which are the 2 features typically associated with the somatic cell cycle. In contrast, the rbiPSC lines exhibited some characteristics of naïve pluripotency, including resistance to single-cell dissociation by trypsin, robust activity of the distal enhancer of the mouse Oct4 gene, and expression of naïve pluripotency-specific genes, as defined in rodents. According to gene expression profiles, rbiPSCs were closer to the rabbit inner cell mass (ICM than rbESCs. Furthermore, rbiPSCs were capable of colonizing the ICM after aggregation with morulas. Therefore, we propose that rbiPSCs self-renew in an intermediate state between naïve and primed pluripotency, which represents a key step toward the generation of bona fide naïve PSC lines in rabbits.

Induced pluripotent stem cells derived from rabbits exhibit some characteristics of naïve pluripotency

Science.gov (United States)

Osteil, Pierre; Tapponnier, Yann; Markossian, Suzy; Godet, Murielle; Schmaltz-Panneau, Barbara; Jouneau, Luc; Cabau, Cédric; Joly, Thierry; Blachère, Thierry; Gócza, Elen; Bernat, Agnieszka; Yerle, Martine; Acloque, Hervé; Hidot, Sullivan; Bosze, Zsuzsanna; Duranthon, Véronique; Savatier, Pierre; Afanassieff, Marielle

2013-01-01

Summary Not much is known about the molecular and functional features of pluripotent stem cells (PSCs) in rabbits. To address this, we derived and characterized 2 types of rabbit PSCs from the same breed of New Zealand White rabbits: 4 lines of embryonic stem cells (rbESCs), and 3 lines of induced PSCs (rbiPSCs) that were obtained by reprogramming adult skin fibroblasts. All cell lines required fibroblast growth factor 2 for their growth and proliferation. All rbESC lines showed molecular and functional properties typically associated with primed pluripotency. The cell cycle of rbESCs had a prolonged G1 phase and a DNA damage checkpoint before entry into the S phase, which are the 2 features typically associated with the somatic cell cycle. In contrast, the rbiPSC lines exhibited some characteristics of naïve pluripotency, including resistance to single-cell dissociation by trypsin, robust activity of the distal enhancer of the mouse Oct4 gene, and expression of naïve pluripotency-specific genes, as defined in rodents. According to gene expression profiles, rbiPSCs were closer to the rabbit inner cell mass (ICM) than rbESCs. Furthermore, rbiPSCs were capable of colonizing the ICM after aggregation with morulas. Therefore, we propose that rbiPSCs self-renew in an intermediate state between naïve and primed pluripotency, which represents a key step toward the generation of bona fide naïve PSC lines in rabbits. PMID:23789112

Effects of dilute aqueous NaCl solution on caffeine aggregation

Energy Technology Data Exchange (ETDEWEB)

Sharma, Bhanita; Paul, Sandip, E-mail: sandipp@iitg.ernet.in [Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam (India)

2013-11-21

The effect of salt concentration on association properties of caffeine molecule was investigated by employing molecular dynamics simulations in isothermal-isobaric ensemble of eight caffeine molecules in pure water and three different salt (NaCl) concentrations, at 300 K temperature and 1 atm pressure. The concentration of caffeine was taken almost at the solubility limit. With increasing salt concentration, we observe enhancement of first peak height and appearance of a second peak in the caffeine-caffeine distribution function. Furthermore, our calculated solvent accessible area values and cluster structure analyses suggest formation of higher order caffeine cluster on addition of salt. The calculated hydrogen bond properties reveal that there is a modest decrease in the average number of water-caffeine hydrogen bonds on addition of NaCl salt. Also observed are: (i) decrease in probability of salt contact ion pair as well as decrease in the solvent separated ion pair formation with increasing salt concentration, (ii) a modest second shell collapse in the water structure, and (iii) dehydration of hydrophobic atomic sites of caffeine on addition of NaCl.

Effects of dilute aqueous NaCl solution on caffeine aggregation

International Nuclear Information System (INIS)

Sharma, Bhanita; Paul, Sandip

2013-01-01

The effect of salt concentration on association properties of caffeine molecule was investigated by employing molecular dynamics simulations in isothermal-isobaric ensemble of eight caffeine molecules in pure water and three different salt (NaCl) concentrations, at 300 K temperature and 1 atm pressure. The concentration of caffeine was taken almost at the solubility limit. With increasing salt concentration, we observe enhancement of first peak height and appearance of a second peak in the caffeine-caffeine distribution function. Furthermore, our calculated solvent accessible area values and cluster structure analyses suggest formation of higher order caffeine cluster on addition of salt. The calculated hydrogen bond properties reveal that there is a modest decrease in the average number of water-caffeine hydrogen bonds on addition of NaCl salt. Also observed are: (i) decrease in probability of salt contact ion pair as well as decrease in the solvent separated ion pair formation with increasing salt concentration, (ii) a modest second shell collapse in the water structure, and (iii) dehydration of hydrophobic atomic sites of caffeine on addition of NaCl

Biologia molecular do câncer cervical Molecular biology of cervical cancer

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Waldemar Augusto Rivoire

2006-01-01

Full Text Available A carcinogênese é um processo de múltiplas etapas. Alterações no equilíbrio citogenético ocorrem na transformação do epitélio normal a câncer cervical. Numerosos estudos apoiam a hipótese de que a infecção por HPV está associada com o desenvolvimento de alterações malignas e pré-malignas do trato genital inferior. Neste trabalho são apresentadas as bases para a compreensão da oncogênese cervical. O ciclo celular é controlado por proto-oncogenes e genes supressores. Quando ocorrem mutações, proto-oncogenes tornam-se oncogenes, que são carcinogênicos e causam multiplicação celular excessiva. A perda da ação de genes supressores funcionais pode levar a célula ao crescimento inadequado. O ciclo celular também pode ser alterado pela ação de vírus, entre eles o HPV (Human Papiloma Virus, de especial interesse na oncogênese cervical. Os tipos de HPV 16 e 18 são os de maior interesse, freqüentemente associados a câncer cervical e anal. O conhecimento das bases moleculares que estão envolvidas na oncogênese cervical tem sido possível devido a utilização de técnicas avançadas de biologia molecular. A associação destas técnicas aos métodos diagnósticos clássicos, poderão levar a uma melhor avaliação das neoplasias cervicais e auxiliar no desenvolvimento de novas terapias, talvez menos invasivas e mais efetivas.Carcinogenesis involves several steps. Disorders of the cytogenetic balance occur during the evolution from normal epithelium to cervical cancer. Several studies support the hypothesis that the Human Papiloma Virus (HPV infection is associated to development of premalignant and malignant lesions of cervical cancer. In this review we show the basis to understand cervical oncogenesis. The cell cycle is controlled by protooncogenes and supressive genes. This orchestrated cell cycle can be affected by virus such as HPV. Of special interest in the cervical carcinogenesis are the HPV subtypes 16 and 18

Molecular sites for the positive allosteric modulation of glycine receptors by endocannabinoids.

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Gonzalo E Yévenes

Full Text Available Glycine receptors (GlyRs are transmitter-gated anion channels of the Cys-loop superfamily which mediate synaptic inhibition at spinal and selected supraspinal sites. Although they serve pivotal functions in motor control and sensory processing, they have yet to be exploited as drug targets partly because of hitherto limited possibilities for allosteric control. Endocannabinoids (ECs have recently been characterized as direct allosteric GlyR modulators, but the underlying molecular sites have remained unknown. Here, we show that chemically neutral ECs (e.g. anandamide, AEA are positive modulators of α(1, α(2 and α(3 GlyRs, whereas acidic ECs (e.g. N-arachidonoyl-glycine; NA-Gly potentiate α(1 GlyRs but inhibit α(2 and α(3. This subunit-specificity allowed us to identify the underlying molecular sites through analysis of chimeric and mutant receptors. We found that alanine 52 in extracellular loop 2, glycine 254 in transmembrane (TM region 2 and intracellular lysine 385 determine the positive modulation of α(1 GlyRs by NA-Gly. Successive substitution of non-conserved extracellular and TM residues in α(2 converted NA-Gly-mediated inhibition into potentiation. Conversely, mutation of the conserved lysine within the intracellular loop between TM3 and TM4 attenuated NA-Gly-mediated potentiation of α(1 GlyRs, without affecting inhibition of α(2 and α(3. Notably, this mutation reduced modulation by AEA of all three GlyRs. These results define molecular sites for allosteric control of GlyRs by ECs and reveal an unrecognized function for the TM3-4 intracellular loop in the allosteric modulation of Cys-loop ion channels. The identification of these sites may help to understand the physiological role of this modulation and facilitate the development of novel therapeutic approaches to diseases such as spasticity, startle disease and possibly chronic pain.

Na/K pump inactivation, subsarcolemmal Na measurements, and cytoplasmic ion turnover kinetics contradict restricted Na spaces in murine cardiac myocytes.

Science.gov (United States)

Lu, Fang-Min; Hilgemann, Donald W

2017-07-03

Decades ago, it was proposed that Na transport in cardiac myocytes is modulated by large changes in cytoplasmic Na concentration within restricted subsarcolemmal spaces. Here, we probe this hypothesis for Na/K pumps by generating constitutive transsarcolemmal Na flux with the Na channel opener veratridine in whole-cell patch-clamp recordings. Using 25 mM Na in the patch pipette, pump currents decay strongly during continuous activation by extracellular K (τ, ∼2 s). In contradiction to depletion hypotheses, the decay becomes stronger when pump currents are decreased by hyperpolarization. Na channel currents are nearly unchanged by pump activity in these conditions, and conversely, continuous Na currents up to 0.5 nA in magnitude have negligible effects on pump currents. These outcomes are even more pronounced using 50 mM Li as a cytoplasmic Na congener. Thus, the Na/K pump current decay reflects mostly an inactivation mechanism that immobilizes Na/K pump charge movements, not cytoplasmic Na depletion. When channel currents are increased beyond 1 nA, models with unrestricted subsarcolemmal diffusion accurately predict current decay (τ ∼15 s) and reversal potential shifts observed for Na, Li, and K currents through Na channels opened by veratridine, as well as for Na, K, Cs, Li, and Cl currents recorded in nystatin-permeabilized myocytes. Ion concentrations in the pipette tip (i.e., access conductance) track without appreciable delay the current changes caused by sarcolemmal ion flux. Importantly, cytoplasmic mixing volumes, calculated from current decay kinetics, increase and decrease as expected with osmolarity changes (τ >30 s). Na/K pump current run-down over 20 min reflects a failure of pumps to recover from inactivation. Simulations reveal that pump inactivation coupled with Na-activated recovery enhances the rapidity and effectivity of Na homeostasis in cardiac myocytes. In conclusion, an autoregulatory mechanism enhances cardiac Na/K pump activity when

Molecular dynamics simulations of a lithium/sodium carbonate mixture.

Science.gov (United States)

Ottochian, Alistar; Ricca, Chiara; Labat, Frederic; Adamo, Carlo

2016-03-01

The diffusion and ionic conductivity of Li x Na1-x CO3 salt mixtures were studied by means of Molecular Dynamics (MD) simulations, using the Janssen and Tissen model (Janssen and Tissen, Mol Simul 5:83-98; 1990). These salts have received particular attention due to their central role in fuel cells technology, and reliable numerical methods that could perform as important interpretative tool of experimental data are thus required but still lacking. The chosen computational model nicely reproduces the main structural behaviour of the pure Li2CO3, Na2CO3 and K2CO3 carbonates, but also of their Li/K and Li/Na mixtures. However, it fails to accurately describe dynamic properties such as activation energies of diffusion and conduction processes, outlining the need to develop more accurate models for the simulation of molten salt carbonates.

A comparative molecular dynamics study of diffusion of n-decane ...

Indian Academy of Sciences (India)

Administrator

Abstract. Molecular dynamics simulations are reported on the structure and dynamics of n-decane and. 3-methylpentane in zeolite NaY. We have calculated several properties such as the center of mass-center of mass rdf, the end-end distance distribution, bond angle distribution and dihedral angle distribution. We.

Mechanism of Na,K-ATPase decline during sheep red cell maturation

International Nuclear Information System (INIS)

Grafova, E.; Blostein, R.

1987-01-01

Na,K-ATPase of immature and mature sheep red cells of both the high-K + and low-K + genotypes as well as cells of both types matured in vitro was detected using polyclonal antiserum to sheep kidney Na,K-ATPase. Following SDS-PAGE and immunoblotting, the major reactive component was the ∼ 100 kDa catalytic α subunit. A less prominent band migrating as a sharper, lower molecular weight (50 kDa) component than the kidney Na,K-ATPase β subunit is apparent in reticulocytes but not mature cells. Membranes from both genotypes showed identical immunologically reactive peptides, except for the lower intensity of the α subunit in the mature cells of the low- compared to high-K + sheep. Following culture of both types, moderate reduction in reactivity was apparent. Immunologically reactive α subunit as well as the 50 kDa species were detected in membranous material shed into the culture medium. This material was functionally inactive (lack of both [ 3 H] ouabain binding and Na + -dependent phosphorylation of Na,K-ATPase). The existence in reticulocytes of an intracellular pool of ouabain binding sites is evidenced in appearance of extra sites following rapid ATP depletion and also after addition of chloroquine. Taken together, these findings are consistent with a maturation-associated decrease of sodium pumps by a process of membrane recycling, processing and, to some extent, exocytosis

Scanning probe methods applied to molecular electronics

Energy Technology Data Exchange (ETDEWEB)

Pavlicek, Niko

2013-08-01

Scanning probe methods on insulating films offer a rich toolbox to study electronic, structural and spin properties of individual molecules. This work discusses three issues in the field of molecular and organic electronics. An STM head to be operated in high magnetic fields has been designed and built up. The STM head is very compact and rigid relying on a robust coarse approach mechanism. This will facilitate investigations of the spin properties of individual molecules in the future. Combined STM/AFM studies revealed a reversible molecular switch based on two stable configurations of DBTH molecules on ultrathin NaCl films. AFM experiments visualize the molecular structure in both states. Our experiments allowed to unambiguously determine the pathway of the switch. Finally, tunneling into and out of the frontier molecular orbitals of pentacene molecules has been investigated on different insulating films. These experiments show that the local symmetry of initial and final electron wave function are decisive for the ratio between elastic and vibration-assisted tunneling. The results can be generalized to electron transport in organic materials.

Na+/Ca2+ exchange and Na+/K+-ATPase in the heart

Science.gov (United States)

Shattock, Michael J; Ottolia, Michela; Bers, Donald M; Blaustein, Mordecai P; Boguslavskyi, Andrii; Bossuyt, Julie; Bridge, John H B; Chen-Izu, Ye; Clancy, Colleen E; Edwards, Andrew; Goldhaber, Joshua; Kaplan, Jack; Lingrel, Jerry B; Pavlovic, Davor; Philipson, Kenneth; Sipido, Karin R; Xie, Zi-Jian

2015-01-01

This paper is the third in a series of reviews published in this issue resulting from the University of California Davis Cardiovascular Symposium 2014: Systems approach to understanding cardiac excitation–contraction coupling and arrhythmias: Na+ channel and Na+ transport. The goal of the symposium was to bring together experts in the field to discuss points of consensus and controversy on the topic of sodium in the heart. The present review focuses on cardiac Na+/Ca2+ exchange (NCX) and Na+/K+-ATPase (NKA). While the relevance of Ca2+ homeostasis in cardiac function has been extensively investigated, the role of Na+ regulation in shaping heart function is often overlooked. Small changes in the cytoplasmic Na+ content have multiple effects on the heart by influencing intracellular Ca2+ and pH levels thereby modulating heart contractility. Therefore it is essential for heart cells to maintain Na+ homeostasis. Among the proteins that accomplish this task are the Na+/Ca2+ exchanger (NCX) and the Na+/K+ pump (NKA). By transporting three Na+ ions into the cytoplasm in exchange for one Ca2+ moved out, NCX is one of the main Na+ influx mechanisms in cardiomyocytes. Acting in the opposite direction, NKA moves Na+ ions from the cytoplasm to the extracellular space against their gradient by utilizing the energy released from ATP hydrolysis. A fine balance between these two processes controls the net amount of intracellular Na+ and aberrations in either of these two systems can have a large impact on cardiac contractility. Due to the relevant role of these two proteins in Na+ homeostasis, the emphasis of this review is on recent developments regarding the cardiac Na+/Ca2+ exchanger (NCX1) and Na+/K+ pump and the controversies that still persist in the field. PMID:25772291

Oxintomodulina e obesidade Oxyntomodulin and obesity

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Gustavo Duarte Pimentel

2009-10-01

Full Text Available Desde o descobrimento da leptina, avanços consideráveis foram obtidos na caracterização dos mecanismos hipotalâmicos do controle da ingestão alimentar e, atualmente, a oxintomodulina é reconhecida como um regulador da homeostase energética. O presente artigo de revisão enfoca algumas das mais relevantes inter-relações do hormônio oxintomodulina com o apetite, a homeostase energética e aspectos de seu papel na bioquímica e fisiologia nutricional. A oxintomodulina é um peptídeo intestinal anorexígeno produzido pelas células L do intestino. Recentes estudos têm demonstrado que em longo prazo a administração de oxintomodulina reduz a ingestão alimentar e o ganho de peso. Pesquisas em humanos têm verificado que o seu uso reduz o consumo energértico em 25%. Portanto, a oxintomodulina representa uma potente terapia anti-obesidade. Entretanto, o mecanismo de ação da oxintomodulina ainda é desconhecido. Atuais evidências sugerem que tem ação via receptor do peptídeo semelhante ao glucagon 1. Além disso, a literatura mostra que, juntamente com a adoção de hábitos saudáveis e a mudança do estilo de vida, a oxintomodulina pode proporcionar menor avanço da obesidade.Since the discovery of leptin, great advances occurred in the characterization of hypothalamic mechanisms involved in the control of food intake and oxyntomodulin is currently recognized as a homeostasis energy regulator. This review discusses the most important interrelationships between the hormone oxyntomodulin and appetite, energy homeostasis and aspects of its role in nutritional biochemistry and physiology. Oxyntomodulin is an anorexigenic peptide produced by the L cells of the small intestine. Recent studies have shown that long-term use of oxyntomodulin in rats leads to reduced food intake and weight gain. Studies in humans have demonstrated that its administration reduces food intake by 25%. Therefore, oxyntomodulin represents a potent anti

Comparable investigation of the molecular size distribution and the amount of humic substances isolated from ONKALO, Olkiluoto, 2010

International Nuclear Information System (INIS)

Vilhunen, S.; Manninen, P.

2010-11-01

The humic substances at groundwater from Onkalo, Olkiluoto were studied in order to determine the molecular size distribution and the amount of humic substances. Humic substances were isolated from the water sample using DAX-8 resin and eluted with 0.1 M NaOH. The molecular size distribution was defined using high performance size exclusion chromatography (HPSEC) and ultraviolet (UV) or reflactive index (RI) detector. Two calibration standard sets (poly(styrene sulfonate) sodium salt (PSS) or polyethylene glycol (PEG) standards) with distinct structures as well as two eluents (0.05 M NaNO3 or 0.01 M Na-acetate) were studied and the results were compared with the previous ones. The calibration standards and eluents were found to have major effect on the measured parameters. The amount of humic substances was determined using total organic carbon (TOC) measurements. (orig.)

Altered Na+ transport after an intracellular alpha-subunit deletion reveals strict external sequential release of Na+ from the Na/K pump.

Science.gov (United States)

Yaragatupalli, Siddhartha; Olivera, J Fernando; Gatto, Craig; Artigas, Pablo

2009-09-08

The Na/K pump actively exports 3 Na(+) in exchange for 2 K(+) across the plasmalemma of animal cells. As in other P-type ATPases, pump function is more effective when the relative affinity for transported ions is altered as the ion binding sites alternate between opposite sides of the membrane. Deletion of the five C-terminal residues from the alpha-subunit diminishes internal Na(+) (Na(i)(+)) affinity approximately 25-fold [Morth et al. (2007) Nature 450:1043-1049]. Because external Na(+) (Na(o)(+)) binding is voltage-dependent, we studied the reactions involving this process by using two-electrode and inside-out patch voltage clamp in normal and truncated (DeltaKESYY) Xenopus-alpha1 pumps expressed in oocytes. We observed that DeltaKESYY (i) decreased both Na(o)(+) and Na(i)(+) apparent affinities in the absence of K(o)(+), and (ii) did not affect apparent Na(o)(+) affinity at high K(o)(+). These results support a model of strict sequential external release of Na(+) ions, where the Na(+)-exclusive site releases Na(+) before the sites shared with K(+) and the DeltaKESYY deletion only reduces Na(o)(+) affinity at the shared sites. Moreover, at nonsaturating K(o)(+), DeltaKESYY induced an inward flow of Na(+) through Na/K pumps at negative potentials. Guanidinium(+) can also permeate truncated pumps, whereas N-methyl-D-glucamine cannot. Because guanidinium(o)(+) can also traverse normal Na/K pumps in the absence of both Na(o)(+) and K(o)(+) and can also inhibit Na/K pump currents in a Na(+)-like voltage-dependent manner, we conclude that the normal pathway transited by the first externally released Na(+) is large enough to accommodate guanidinium(+).

Neutron activation analysis of trace metallic elements eluted from molecular sieves in the dehydration process of safflower oil

International Nuclear Information System (INIS)

Takasago, Masahisa; Kobayashi, Koichi; Taru, Yasunori; Takaoka, Kyo

1992-01-01

Dissolved water in safflower oil affects the autoxidation of this oil significantly. Molecular sieves were used to remove the dissolved water from the oil. This method is much simpler than that of distillation, and dissolved water can be removed to the same extent as that by distillation. But, due to the elution of many kinds of trace metallic elements in the oil dehydrated with molecular sieves, these elements were analyzed by neutron activation analysis. For a data comparison trace amounts of metallic elements in the oil dehydrated by distillation were also analyzed. Since the intensity of the γ ray-photoelectric peak of nuclide 28 Al was largest among the detected elements, this element was analyzed quantitatively and the other elements qualitatively. In safflower oil dehydrated with molecular sieves, 14 kinds of the elements (I, Br, Al, Mg, Si, V, Cl, Nd, Ta, Cr, Sb, Cs, Co, Na) were detected. Also, I, Br, Cl, Cr, Ta, Sb, and Al elements were detected in the oil dehydrated by distillation. The intensity of the photoelectric peak of nuclide except 28 Al was essentially the same as that in the oil dehydrated by distillation, but the intensity of 28 Al in the oil with molecular sieves was about 28 times stronger than that in distillation oil. In the molecular sieves, 19 impure elements in addition to the original constituents (Na, K, Al, si, O) were detected. It was Al, Na, Si, Nd, Cs, and Co along with impure elements may possibly have been eluted in the oil. Al element in safflower oil dehydrated with molecular sieves was analyzed quantitatively. 0.91 ppm of Al was detected in safflower oil. The eluted amount of Al in safflower oil dehydrated by distillation was 0.032 ppm. A larger amount of Al element was thus eluted into the oil dehydrated with molecular sieves than by distillation. (author)

Molecular dynamics study of the vaporization of an ionic drop.

Science.gov (United States)

Galamba, N

2010-09-28

The melting of a microcrystal in vacuum and subsequent vaporization of a drop of NaCl were studied through molecular dynamics simulations with the Born-Mayer-Huggins-Tosi-Fumi rigid-ion effective potential. The vaporization was studied for a single isochor at increasing temperatures until the drop completely vaporized, and gaseous NaCl formed. Examination of the vapor composition shows that the vapor of the ionic drop and gaseous NaCl are composed of neutral species, the most abundant of which, ranging from simple NaCl monomers (ion pairs) to nonlinear polymers, (Na(n)Cl(n))(n=2-4). The enthalpies of sublimation, vaporization, and dissociation of the different vapor species are found to be in reasonable agreement with available experimental data. The decrease of the enthalpy of vaporization of the vapor species, with the radius of the drop decrease, accounts for a larger fraction of trimers and tetramers than that inferred from experiments. Further, the rhombic dimer is significantly more abundant than its linear isomer although the latter increases with the temperature. The present results suggest that both trimers and linear dimers may be important to explain the vapor pressure of molten NaCl at temperatures above 1500 K.

Ultrasound degradation of xanthan polymer in aqueous solution: Its scission mechanism and the effect of NaCl incorporation.

Science.gov (United States)

Saleh, H M; Annuar, M S M; Simarani, K

2017-11-01

Degradation of xanthan polymer in aqueous solution by ultrasonic irradiation was investigated. The effects of selected variables i.e. sonication intensity, irradiation time, concentration of xanthan gum and molar concentration of NaCl in solution were studied. Combined approach of full factorial design and conventional one-factor-at-a-time was applied to obtain optimum degradation at sonication power intensity of 11.5Wcm -2 , irradiation time 120min and 0.1gL -1 xanthan in a salt-free solution. Molecular weight reduction of xanthan gum under sonication was described by an exponential decay function with higher rate constant for polymer degradation in the salt free solution. The limiting molecular weight where fragments no longer undergo scission was determined from the function. The incorporation of NaCl in xanthan solution resulted in a lower limiting molecular weight. The ultrasound-mediated degradation of aqueous xanthan polymer chain agreed with a random scission model. Side chain of xanthan polymer is proposed to be the primary site of scission action. Copyright © 2017 Elsevier B.V. All rights reserved.

Impacto dos nutrientes na saúde óssea: novas tendências Nutrients impact on bone health: new trends

Directory of Open Access Journals (Sweden)

Glaucia Queiroz Morais

2007-07-01

Full Text Available A nutrição é fator importante modificável no desenvolvimento/manutenção da massa óssea (MO e prevenção da osteoporose. Esta é uma doença caracterizada por decréscimo na massa esquelética e elevação da suscetibilidade a fraturas. O desenvolvimento do pico de massa óssea (PMO é ainda o maior determinante dessa condição. Por isso, alterações com a idade sinalizam a importância da manutenção de nutrição adequada durante o desenvolvimento desse pico. Indivíduos que atingiram elevado PMO terão, na idade adulta, baixo risco de desenvolver doenças osteometabólicas com o envelhecimento. Os efeitos dos nutrientes sobre as estruturas esqueléticas são intensos e amplos; alguns, há anos, são consistentemente relacionados com a saúde óssea, como o cálcio, fósforo e vitamina D. Entretanto, outros nutrientes vêm sendo sugeridos como essenciais para o metabolismo ósseo normal: proteínas, lipídeos, potássio, vitaminas K e A e cloreto de sódio. A influência das interações entre tais fatores nutricionais, meio ambiente, estilo de vida e hereditariedade auxiliarão na compreensão da complexidade do desenvolvimento da osteoporose e subseqüentes fraturas. Em adição, déficit energético pode acarretar redução da MO, em face dos distúrbios endócrino-metabólicos desencadeados pela privação alimentar. Esta revisão objetiva elucidar o impacto dos nutrientes e ingestão calórica sobre o osso, em diferentes estágios da vida, descrevendo possíveis interações entre nutrientes e como estas poderiam afetar a homeostase óssea e mineral.Nutrition is an important factor in bone mass development/maintenance and in osteoporosis prevention. This disease is characterized by decreased skeletal mass and increased susceptibility to fractures. The greatest determinant of this condition is the peak bone mass (PBM. Hence, alterations over time indicate the importance of maintaining adequate nutrition during the development of

Generation of a High Resistance in vitro Blood-Brain-Barrier Model and Investigations of Brain-to-Blood Glutamate Efflux

DEFF Research Database (Denmark)

Helms, Hans Christian

Blod-hjernebarrieren (blood-brain barrier, BBB) opretholder den generelle homeostase i hjernens væsker. BBB kan også spille en rolle i homeostasen for den eksitatoriske aminosyre, L-glutamat. In vitro modeller kan være effektive værktøjer til at få mekanistiske informationer om transcellulær...

AVALIAÇÃO DO POTENCIAL TERAPÊUTICO DE BACCHARIS DRACUNCULIFOLIA E PEUMUS BOLDUS NO PROCESSO FIBROSANTE HEPÁTICO

Directory of Open Access Journals (Sweden)

Caio Mateus da Silva

2017-03-01

Full Text Available As doenças do fígado são consideradas um problema de saúde mundial e ainda terapias eficientes não foram desenvolvidas para a maioria dessas patologias. Mais especificamente, a fibrose hepática é característica comum do início de várias das anomalias no órgão. Dentro desse contexto, a busca por novos fármacos é necessária e o uso de plantas medicinais tem ganhado destaque. Neste trabalho, foi avaliado os efeitos dos extratos de Baccharis dracunculifolia e Peumus boldus em culturas de células hepáticas estreladas LX-2 em relação as alterações na morfologia dos filamentos de actina do citoesqueleto e no núcleo celular em ensaios de microscopia e na avaliação do padrão de expressão de genes relacionados à processos de apoptose e marcadores clássicos da fibrose hepática. Nos resultados, para as concentrações testadas o extrato de P. boldus altera o perfil de expressão de genes relacionados a apoptose causando maior estresse celular e quebrando a homeostase celular quando observados os filamentos de actina. Enquanto que a planta B. dracunculifolia apresentou uma grande melhora na reorganização do citoesqueleto e diminuição do estresse celular.

Molecular dynamics study of the vaporization of an ionic drop

Science.gov (United States)

Galamba, N.

2010-09-01

The melting of a microcrystal in vacuum and subsequent vaporization of a drop of NaCl were studied through molecular dynamics simulations with the Born-Mayer-Huggins-Tosi-Fumi rigid-ion effective potential. The vaporization was studied for a single isochor at increasing temperatures until the drop completely vaporized, and gaseous NaCl formed. Examination of the vapor composition shows that the vapor of the ionic drop and gaseous NaCl are composed of neutral species, the most abundant of which, ranging from simple NaCl monomers (ion pairs) to nonlinear polymers, (NanCln)n=2-4. The enthalpies of sublimation, vaporization, and dissociation of the different vapor species are found to be in reasonable agreement with available experimental data. The decrease of the enthalpy of vaporization of the vapor species, with the radius of the drop decrease, accounts for a larger fraction of trimers and tetramers than that inferred from experiments. Further, the rhombic dimer is significantly more abundant than its linear isomer although the latter increases with the temperature. The present results suggest that both trimers and linear dimers may be important to explain the vapor pressure of molten NaCl at temperatures above 1500 K.

The Na(+) cycle in Acetobacterium woodii: identification and characterization of a Na(+) translocating F(1)F(0)-ATPase with a mixed oligomer of 8 and 16 kDa proteolipids.

Science.gov (United States)

Müller, V; Aufurth, S; Rahlfs, S

2001-05-01

The homoacetogenic bacterium Acetobacterium woodii relies on a sodium ion current across its cytoplasmic membrane for energy-dependent reactions. The sodium ion potential is established by a yet to be identified primary, electrogenic pump connected to the Wood-Ljungdahl pathway. Reactions possibly involved in Na(+) export are discussed. The electrochemical sodium ion potential generated is used to drive endergonic reactions such as flagellar rotation and ATP synthesis. Biochemical and molecular data identified the Na(+)-ATPase of A. woodii as a typical member of the F(1)F(0) class of ATPases. Its catalytic properties and the hypothetical sodium ion binding site in subunit c are discussed. The encoding genes were cloned and, surprisingly, the atp operon was shown to contain multiple copies of genes encoding subunit c. Two copies encode identical 8 kDa proteolipids, and a third copy arose by duplication and subsequent fusion of two genes. Furthermore, the duplicated subunit c does not contain the ion binding site in hair pin two. Biochemical and molecular data revealed that all three copies of subunit c constitute a mixed oligomer. The evolution of the structure and function of subunit c in ATPases from eucarya, bacteria, and archaea is discussed.

Structual Dynamics and Function of the Na+/H+ Exchanger 1

DEFF Research Database (Denmark)

Hendus-Altenburger, Ruth

Na+/H+ Exchangers (SLC9As) are of pivotal importance in several physiological processes, and their dysfunction is linked to the pathogenesis of several diseases. The Na+/H+ Exchanger 1 (NHE1) is ubiquitously expressed at the plasma membrane. It contains two domains, the transmembrane ion...... translocation domain and a large cytoplasmic regulatory domain. Despite its physiological and pathophysiological importance, high resolution structural data of NHE1 is missing, and even though several binding partners and phosphorylation sites of the NHE1 regulatory domain are known and many more suggested......, the molecular structures and mechanisms underlying NHE1 regulation and function are still incompletely understood. In this work, in silico analysis revealed two structured and two intrinsically disordered regions in the regulatory domain. A divide-and-conquer approach was used to identify subdomains...

Active transport of Na+ by reconstituted Na,K-ATPase

International Nuclear Information System (INIS)

Boldyrev, A.A.; Svinukhova, I.A.

1987-01-01

The ability of ATP, CTP, ITP, GTP, and UTP to support ouabain-sensitive accumulation of Na + by proteoliposomes with a reconstituted Na/K-pump was investigated. At a low [Na + ]/[K + ] ratio in the medium (20 mM/50 mM), a correlation is observed between the proton-accepting capacity of the nucleotide and its effectiveness as a substrate of active transport. To test the hypothesis of the importance of the presence of a negative charge in the 1-position of the purine (3-pyrimidine) base of the nucleotide for mutual transitions between the Na- and K-conformations of Na,K-ATPase they used two analogs of ATP: N 1 -hydroxy-ATP, possessing proton acceptor capacity, and N 1 -methoxy-ATP, in the molecule of which the negative charge is quenched by a methyl group. The first substrate supports active accumulation of Na + in proteoliposomes at the same rate as ATP, whereas the second substrate is relatively ineffective

Investigation on U - O - Na, Pu - O - Na and U,Pu - O - Na phase diagrams

International Nuclear Information System (INIS)

Pillon, S.

1989-03-01

The thermochemical interaction between the nuclear fuel (uranium and plutonium mixed oxides) and the sodium has been investigated and particularly the three phase diagrams: U - O - Na; Pu - O - Na; U,Pu - O - Na. High temperature neutron diffraction, microcalorimetry and powder X-ray diffraction were used for the characterization of the compounds synthetized. This study allowed to complete the knowledge about each of these diagrams and to measure some physical and thermal properties on the compounds. The limits on the modelization of the fuel-sodium interaction are discussed from the results of the UO 2 - Na reaction [fr

Cross sections and coherence terms for associative ionization of two differently excited Na(3p) atoms

International Nuclear Information System (INIS)

Meijer, H.A.J.; Pelgrim, T.J.C.; Heideman, H.G.M.; Morgenstern, R.; Andersen, N.

1988-01-01

The associative ionization process in thermal Na(3p)-Na(3p) encounters has been studied in a series of crossed-beam experiments where the light polarization of the two laser beams preparing the excited atoms before collision was varied independently. It is shown how in this way maximum possible information for our geometry is extracted about the dependence of the ion formation process on the shape and spatial orientation of the electron clouds of the two approaching atoms, including all coherence terms. The experimental findings are discussed in the light of recent theoretical results for the states of the Na 2 molecule. It is concluded that just a few of the possible geometrical approaches are favourable for molecular-ion formation. (orig.)

Multicomponent diffusion in molten salt NaF-ZrF{sub 4}: Dynamical correlations and Maxwell–Stefan diffusivities

Energy Technology Data Exchange (ETDEWEB)

Baig, Mohammad Saad, E-mail: saad110baig@gmail.com; Chakraborty, Brahmananda; Ramaniah, Lavanya M. [High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai-85 (India)

2016-05-23

NaF-ZrF{sub 4} is used as a waste incinerator and as a coolant in Generation IV reactors.Structural and dynamical properties of molten NaF-ZrF{sub 4} system were studied along with Onsagercoefficients and Maxwell–Stefan (MS) Diffusivities applying Green–Kubo formalism and molecular dynamics (MD) simulations. The zirconium ions are found to be 8 fold coordinated with fluoride ions for all temperatures and concentrations. All the diffusive flux correlations show back-scattering. Even though the MS diffusivities are expected to depend very lightly on the composition because of decoupling of thermodynamic factor, the diffusivity Đ{sub Na-F} shows interesting behavior with the increase in concentration of ZrF{sub 4}. This is because of network formation in NaF-ZrF{sub 4}. Positive entropy constraints have been plotted to authenticate negative diffusivities observed.

Supercooling of aqueous NaCl and KCl solutions under acoustic levitation.

Science.gov (United States)

Lü, Y J; Wei, B

2006-10-14

The supercooling capability of aqueous NaCl and KCl solutions is investigated at containerless state by using acoustic levitation method. The supercooling of water is obviously enhanced by the alkali metal ions and increases linearly with the augmentation of concentrations. Furthermore, the supercooling depends on the nature of ions and is 2-3 K larger for NaCl solution than that for KCl solution in the present concentration range: Molecular dynamics simulations are performed to reveal the intrinsic correlation between supercoolability and microstructure. The translational and orientational order parameters are applied to quantitatively demonstrate the effect of ionic concentration on the hydrogen-bond network and ice melting point. The disrupted hydrogen-bond structure determines essentially the concentration dependence of supercooling. On the other hand, the introduced acoustic pressure suppresses the increase of supercooling by promoting the growth and coalescence of microbubbles, the effective nucleation catalysts, in water. However, the dissolved ions can weaken this effect, and moreover the degree varies with the ion type. This results in the different supercoolability for NaCl and KCl solutions under the acoustic levitation conditions.

Measurement of exchangeable sodium: 22Na or 24Na

International Nuclear Information System (INIS)

Smith, T.; Edmonds, C.J.

1987-01-01

A case is made for the use of 22 Na in low activities in preference to 24 Na for routine diagnostic estimation of exchangeable sodium, and is based chiefly on considerations of availability, cost and radiation dosimetry. A method in which only 37 kBq (1 μCi) 22 Na is administered orally is shown to be sufficiently accurate and to possess distinct advantages in terms of cost and convenience with a committed radiation dose no greater than that for a measurement using 24 Na. (author)

Identification of a 3rd Na+ Binding Site of the Glycine Transporter, GlyT2.

Directory of Open Access Journals (Sweden)

Nandhitha Subramanian

Full Text Available The Na+/Cl- dependent glycine transporters GlyT1 and GlyT2 regulate synaptic glycine concentrations. Glycine transport by GlyT2 is coupled to the co-transport of three Na+ ions, whereas transport by GlyT1 is coupled to the co-transport of only two Na+ ions. These differences in ion-flux coupling determine their respective concentrating capacities and have a direct bearing on their functional roles in synaptic transmission. The crystal structures of the closely related bacterial Na+-dependent leucine transporter, LeuTAa, and the Drosophila dopamine transporter, dDAT, have allowed prediction of two Na+ binding sites in GlyT2, but the physical location of the third Na+ site in GlyT2 is unknown. A bacterial betaine transporter, BetP, has also been crystallized and shows structural similarity to LeuTAa. Although betaine transport by BetP is coupled to the co-transport of two Na+ ions, the first Na+ site is not conserved between BetP and LeuTAa, the so called Na1' site. We hypothesized that the third Na+ binding site (Na3 site of GlyT2 corresponds to the BetP Na1' binding site. To identify the Na3 binding site of GlyT2, we performed molecular dynamics (MD simulations. Surprisingly, a Na+ placed at the location consistent with the Na1' site of BetP spontaneously dissociated from its initial location and bound instead to a novel Na3 site. Using a combination of MD simulations of a comparative model of GlyT2 together with an analysis of the functional properties of wild type and mutant GlyTs we have identified an electrostatically favorable novel third Na+ binding site in GlyT2 formed by Trp263 and Met276 in TM3, Ala481 in TM6 and Glu648 in TM10.

Atualidades proteômicas na sepse Proteomic updates on sepsis

Directory of Open Access Journals (Sweden)

Rodrigo Siqueira-Batista

2012-06-01

Full Text Available A ampliação do conhecimento das técnicas de análise proteômica tem permitido maior compreensão das bases moleculares relacionadas à identificação de vias de sinalização celular, de proteínas modificadoras, de modificações pós-traducionais, além de caracterizar marcadores biológicos específicos. Desta feita, a documentação de determinadas proteínas expressas na sepse constitui uma promissora abordagem para elucidação dos aspectos fisiopatológicos, diagnósticos, terapêuticos e prognósticos dessa condição, com a finalidade de aplicação na prática clínica. Embora os resultados sejam ainda preliminares, a proteômica poderá oferecer bons subsídios para o melhor manejo dos pacientes sépticos. Dessa feita, o objetivo do presente artigo é apresentar uma breve revisão das aplicações dos estudos proteômicos na sepse.The increased knowledge regarding proteomic analysis techniques has allowed for better understanding of the molecular bases related to the identification of cell signaling, modifying protein, and post-translational modification pathways, in addition to the characterization of specific biological markers. Thus, documenting certain proteins expressed in sepsis is a promising approach to elucidate pathophysiological, diagnostic, therapeutic, and prognostic aspects in this condition with a purpose of applying them to clinical practice. Although the studies are still preliminary, proteomics may offer good benefits for the better management of septic patients. Thus, this article aims to introduce a short review of the applications of proteomic studies to sepsis.

Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers.

Science.gov (United States)

Rodríguez-Dorado, Rosalía; Carro, Antonia M; Chianella, Iva; Karim, Kal; Concheiro, Angel; Lorenzo, Rosa A; Piletsky, Sergey; Alvarez-Lorenzo, Carmen

2016-09-01

Polymers for recovery/removal of the antimicrobial agent oxytetracycline (OTC) from aqueous media were developed with use of computational design and molecular imprinting. 2-Hydroxyethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and mixtures of the two were chosen according to their predicted affinity for OTC and evaluated as functional monomers in molecularly imprinted polymers and nonimprinted polymers. Two levels of AMPS were tested. After bulk polymerization, the polymers were crushed into particles (200-1000 μm). Pressurized liquid extraction was implemented for template removal with a low amount of methanol (less than 20 mL in each extraction) and a few extractions (12-18 for each polymer) in a short period (20 min per extraction). Particle size distribution, microporous structure, and capacity to rebind OTC from aqueous media were evaluated. Adsorption isotherms obtained from OTC solutions (30-110 mg L(-1)) revealed that the polymers prepared with AMPS had the highest affinity for OTC. The uptake capacity depended on the ionic strength as follows: purified water > saline solution (0.9 % NaCl) > seawater (3.5 % NaCl). Polymer particles containing AMPS as a functional monomer showed a remarkable ability to clean water contaminated with OTC. The usefulness of the stationary phase developed for molecularly imprinted solid-phase extraction was also demonstrated. Graphical Abstract Selection of functional monomers by molecular modeling renders polymer networks suitable for removal of pollutants from contaminated aqueous environments, under either dynamic or static conditions.

Mechanism of Na,K-ATPase decline during sheep red cell maturation

Energy Technology Data Exchange (ETDEWEB)

Grafova, E.; Blostein, R.

1987-05-01

Na,K-ATPase of immature and mature sheep red cells of both the high-K/sup +/ and low-K/sup +/ genotypes as well as cells of both types matured in vitro was detected using polyclonal antiserum to sheep kidney Na,K-ATPase. Following SDS-PAGE and immunoblotting, the major reactive component was the approx. 100 kDa catalytic ..cap alpha.. subunit. A less prominent band migrating as a sharper, lower molecular weight (50 kDa) component than the kidney Na,K-ATPase ..beta.. subunit is apparent in reticulocytes but not mature cells. Membranes from both genotypes showed identical immunologically reactive peptides, except for the lower intensity of the ..cap alpha.. subunit in the mature cells of the low- compared to high-K/sup +/ sheep. Following culture of both types, moderate reduction in reactivity was apparent. Immunologically reactive ..cap alpha.. subunit as well as the 50 kDa species were detected in membranous material shed into the culture medium. This material was functionally inactive (lack of both (/sup 3/H) ouabain binding and Na/sup +/-dependent phosphorylation of Na,K-ATPase). The existence in reticulocytes of an intracellular pool of ouabain binding sites is evidenced in appearance of extra sites following rapid ATP depletion and also after addition of chloroquine. Taken together, these findings are consistent with a maturation-associated decrease of sodium pumps by a process of membrane recycling, processing and, to some extent, exocytosis.

Produção da proteína recombinante anexina V humana em cultivos de Escherichia coli em batelada alimentada

OpenAIRE

Marder, Laura Schirmbeck

2013-01-01

A Anexina V é uma proteína humana endógena dependente de Ca+2, com peso molecular de 35,8 kDa, amplamente distribuída intracelularmente em altas concentrações na placenta e em concentrações mais baixas nas células endoteliais, renais, miocárdicas, epiteliais, esqueléticas musculares, eritrócitos, plaquetas e monócitos. Apresenta como principal característica a capacidade de se ligar à fosfatidilserina, um fosfolipídeo presente na camada interna da bicamada lipídica, que durante a apoptose cel...

OGLAŠEVANJE NA DRUŽBENIH OMREŽJIH NA PRIMERU FACEBOOKA

OpenAIRE

Novak, Martina

2012-01-01

V diplomskem delu obravnavamo družbene medije kot novo priložnost za promocijo in oglaševanje podjetij. Spoznali smo družbena omrežja na splošno in nekaj teh, ki jih uporabljamo tudi v Sloveniji na kratko predstavili. Podrobneje smo se osredotočili na družbeno omrežje Facebook, predvsem na samo spletno stran, njen izgled in storitve, ki jih ponuja uporabnikom. V nalogi je podrobneje opisan Facebook kot orodje za uporabo oglaševanja. Spoznali smo brezplačne in plačljive načine promocije in ogl...

Molecular Simulation Study of Montmorillonite in Contact with Variably Wet Supercritical Carbon Dioxide

KAUST Repository

Kadoura, Ahmad Salim; Nair, Arun Kumar Narayanan; Sun, Shuyu

2017-01-01

We perform grand canonical Monte Carlo simulations to study the detailed molecular mechanism of intercalation behavior of CO2 in Na-, Ca-, and Mg- montmorillonite exposed to variably hydrated supercritical CO2 at 323.15 K and 90 bar, The simulations

A Chimeric NaV1.8 Channel Expression System Based on HEK293T Cell Line

Directory of Open Access Journals (Sweden)

Xi Zhou

2018-04-01

Full Text Available Among the nine voltage-gated sodium channel (NaV subtypes, NaV1.8 is an attractive therapeutic target for pain. The heterologous expression of recombinant NaV1.8 currents is of particular importance for its electrophysiological and pharmacological studies. However, NaV1.8 expresses no or low-level functional currents when transiently transfected into non-neuronal cell lines. The present study aims to explore the molecular determinants limiting its functional expression and accordingly establish a functional NaV1.8 expression system. We conducted screening analysis of the NaV1.8 intracellular loops by constructing NaV chimeric channels and confirmed that the NaV1.8 C-terminus was the only limiting factor. Replacing this sequence with that of NaV1.4, NaV1.5, or NaV1.7 constructed functional channels (NaV1.8/1.4L5, NaV1.8/1.5L5, and NaV1.8/1.7L5, respectively, which expressed high-level NaV1.8-like currents in HEK293T cells. The chimeric channel NaV1.8/1.7L5 displayed much faster inactivation of its macroscopic currents than NaV1.8/1.4L5 and NaV1.8/1.5L5, and it was the most similar to wild-type NaV1.8 expressed in ND7/23 cells. Its currents were very stable during repetitive depolarizations, while its repriming kinetic was different from wild-type NaV1.8. Most importantly, NaV1.8/1.7L5 pharmacologically resembled wild-type NaV1.8 as revealed by testing their susceptibility to two NaV1.8 selective antagonists, APETx-2 and MrVIB. NaV chimeras study showed that at least the domain 2 and domain 4 of NaV1.8 were involved in binding with APETx-2. Our study provided new insights into the function of NaV1.8 intracellular loops, as well as a reliable and convenient expression system which could be useful in NaV1.8 studies.

Nuclear spin phonon relaxation by Raman process in Na{sub 3}H(SO{sub 4}){sub 2} single crystals with the electric-quadrupole-type interaction using {sup 1}H and {sup 23}Na NMR

Energy Technology Data Exchange (ETDEWEB)

Lim, Ae Ran [Department of Science Education, Jeonju University, Jeonju 560-759, Chonbuk (Korea, Republic of)], E-mail: aeranlim@hanmail.net; Shin, Chang Woo [Solid State Analysis Team, Korea Basic Science Institute, Daegu 702-701 (Korea, Republic of)

2008-11-30

Successive phase transitions in a Na{sub 3}H(SO{sub 4}){sub 2} single crystal were found at 296, 513, and 533 K. To investigate the mechanism of the phase transition at 296 K, the {sup 1}H and {sup 23}Na spin-lattice relaxation time and the spin-spin relaxation time of Na{sub 3}H(SO{sub 4}){sub 2} were measured near the phase transition temperature using a FT NMR spectrometer. The spin-lattice relaxation time, T{sub 1}, for {sup 1}H in Na{sub 3}H(SO{sub 4}){sub 2} crystals exhibits a minimum below T{sub C1} (=296 K) indicating the presence of distinct molecular motion governed by the Bloembergen-Purcell-Pound (BPP) theory. Although the results for the {sup 1}H and {sup 23}Na relaxation times provide no evidence of the phase transition at T{sub C1}, the separation of the {sup 23}Na resonance lines changes abruptly at T{sub C1}. The phase transition at 296 K produces a change in the separation of the Na resonance line that is associated with a change in the atomic positions in the vicinity of the Na ions. Also, the nuclear spin-lattice relaxation process in Na{sub 3}H(SO{sub 4}){sub 2} crystals with the electric-quadrupole-type interaction proceed via Raman process. These results are compared with those obtained for other M{sub 3}H(SO{sub 4}){sub 2} (M=K, Rb, and Cs) crystals, which have similar hydrogen-bonded structures.

Epidemiologia molecular de papilomavírus bovino identificados em sarcoides equinos

OpenAIRE

Brígida Kussumoto de Alcântara

2013-01-01

Em equinos os sarcoides são considerados tumores fibroblásticos de pele mais comuns e raramente apresentam regressão espontânea. Os papilomavírus bovino (BPV) tipos 1 e 2 estão envolvidos na etiologia dos sarcoides e, provavelmente, o BPV13 descrito recentemente também pode apresentar participação na etiopatogenia destes tumores. O objetivo do presente estudo foi definir a epidemiologia molecular do BPV em uma coleção de 20 espécimes de sarcoide equino de 15 animais provenientes de quatro reg...

Na+,K+-ATPase Na+ affinity in rat skeletal muscle fiber types

DEFF Research Database (Denmark)

Kristensen, Michael; Juel, Carsten

2010-01-01

Previous studies in expression systems have found different ion activation of the Na(+)/K(+)-ATPase isozymes, which suggest that different muscles have different ion affinities. The rate of ATP hydrolysis was used to quantify Na(+),K(+)-ATPase activity, and the Na(+) affinity of Na(+),K(+)-ATPase...

Effects of electric fields on membrane-bound Na, K-ATPase. Progress report, 1 July 1989-30 June 1990

Energy Technology Data Exchange (ETDEWEB)

Tsong, T.Y.

1990-06-30

We continued to work on effects of oscillating electric fields on membrane functions, in particular the electric activation of Na, K-ATPase, and to develop theory of electro-conformational coupling. We believe transmembrane electric fields are involved in the regulation of the internal activity of a cell and also in the cell-to-cell communications. An in depth study of Na, K-ATPase will provide useful information concerning the molecular design of a cell to sense and to transmit signals.

Imaging of tumor viability in lung cancer. Initial results using 23Na-MRI

International Nuclear Information System (INIS)

Henzler, T.; Apfaltrer, P.; Haneder, S.; Schoenberg, S.O.; Fink, C.; Konstandin, S.; Schad, L.; Schmid-Bindert, G.; Manegold, C.; Wenz, F.

2012-01-01

23 Na-MRI has been proposed as a potential imaging biomarker for the assessment of tumor viability and the evaluation of therapy response but has not yet been evaluated in patients with lung cancer. We aimed to assess the feasibility of 23 Na-MRI in patients with lung cancer. Three patients with stage IV adenocarcinoma of the lung were examined on a clinical 3 Tesla MRI system (Magnetom TimTrio, Siemens Healthcare, Erlangen, Germany). Feasibility of 23 Na-MRI images was proven by comparison and fusion of 23 Na-MRI with 1 H-MR, CT and FDG-PET-CT images. 23 Na signal intensities (SI) of tumor and cerebrospinal fluid (CSF) of the spinal canal were measured and the SI ratio in tumor and CSF was calculated. One chemonaive patient was examined before and after the initiation of combination therapy (Carboplatin, Gemcitabin, Cetuximab). All 23 Na-MRI examinations were successfully completed and were of diagnostic quality. Fusion of 23 Na-MRI images with 1 H-MRI, CT and FDG-PET-CT was feasible in all patients and showed differences in solid and necrotic tumor areas. The mean tumor SI and the tumor/CSF SI ratio were 13.3 ± 1.8 x 103 and 0.83 ± 0.14, respectively. In necrotic tumors, as suggested by central non-FDG-avid areas, the mean tumor SI and the tumor/CSF ratio were 19.4 x 103 and 1.10, respectively. 23 Na-MRI is feasible in patients with lung cancer and could provide valuable functional molecular information regarding tumor viability, and potentially treatment response. (orig.)

Crystal structure of Na+, K(+)-ATPase in the Na(+)-bound state.

Science.gov (United States)

Nyblom, Maria; Poulsen, Hanne; Gourdon, Pontus; Reinhard, Linda; Andersson, Magnus; Lindahl, Erik; Fedosova, Natalya; Nissen, Poul

2013-10-04

The Na(+), K(+)-adenosine triphosphatase (ATPase) maintains the electrochemical gradients of Na(+) and K(+) across the plasma membrane--a prerequisite for electrical excitability and secondary transport. Hitherto, structural information has been limited to K(+)-bound or ouabain-blocked forms. We present the crystal structure of a Na(+)-bound Na(+), K(+)-ATPase as determined at 4.3 Å resolution. Compared with the K(+)-bound form, large conformational changes are observed in the α subunit whereas the β and γ subunit structures are maintained. The locations of the three Na(+) sites are indicated with the unique site III at the recently suggested IIIb, as further supported by electrophysiological studies on leak currents. Extracellular release of the third Na(+) from IIIb through IIIa, followed by exchange of Na(+) for K(+) at sites I and II, is suggested.

Ion pump as molecular ratchet and effects of noise: electric activation of cation pumping by Na,K-ATPase

Science.gov (United States)

Tsong, T. Y.; Xie, T. D.

2002-08-01

Na,K-ATPase is a universal ion pump of the biological cell. Under physiological conditions, it uses the γ-phosphorus bond energy of ATP during hydrolysis to pump 2 K+ inward and 3 Na+ outward; both being uphill transports. The experiment presented here demonstrates that the protein transporter can also use electric energy to fuel its pump activity. A theory of electroconformational coupling (TEC) is described and an experiment performed to verify several predictions of the model. Analysis based on the TEC model suggests that Na,K-ATPase is a Brownian ratchet. The enzyme harvests energy from the applied field by means of the field-induced conformational oscillation or fluctuation. However, high efficiency of energy transduction can only be achieved with an electric field of certain intensities, frequencies and waveforms. This property of the enzyme allows us to define an electric signal and differentiate it from electric noise on the basis of the analysis by the TEC model. Data show that electric noise alone does not induce pump activity. However, an appropriate power level of noise imposed on a signal can enhance the pump efficiency. The effect of noise on the signal transduction of Na,K-ATPase is reminiscent of the stochastic resonance phenomenon reported in other biological systems [3, 35]. The TEC model embodies many common features of enzymes and biological motors. It is potentially energy-efficient, much more so than models based on the ion-rectification mechanism.

Carbon monoxide induces cardiac arrhythmia via induction of the late Na+ current.

Science.gov (United States)

Dallas, Mark L; Yang, Zhaokang; Boyle, John P; Boycott, Hannah E; Scragg, Jason L; Milligan, Carol J; Elies, Jacobo; Duke, Adrian; Thireau, Jérôme; Reboul, Cyril; Richard, Sylvain; Bernus, Olivier; Steele, Derek S; Peers, Chris

2012-10-01

Clinical reports describe life-threatening cardiac arrhythmias after environmental exposure to carbon monoxide (CO) or accidental CO poisoning. Numerous case studies describe disruption of repolarization and prolongation of the QT interval, yet the mechanisms underlying CO-induced arrhythmias are unknown. To understand the cellular basis of CO-induced arrhythmias and to identify an effective therapeutic approach. Patch-clamp electrophysiology and confocal Ca(2+) and nitric oxide (NO) imaging in isolated ventricular myocytes was performed together with protein S-nitrosylation to investigate the effects of CO at the cellular and molecular levels, whereas telemetry was used to investigate effects of CO on electrocardiogram recordings in vivo. CO increased the sustained (late) component of the inward Na(+) current, resulting in prolongation of the action potential and the associated intracellular Ca(2+) transient. In more than 50% of myocytes these changes progressed to early after-depolarization-like arrhythmias. CO elevated NO levels in myocytes and caused S-nitrosylation of the Na(+) channel, Na(v)1.5. All proarrhythmic effects of CO were abolished by the NO synthase inhibitor l-NAME, and reversed by ranolazine, an inhibitor of the late Na(+) current. Ranolazine also corrected QT variability and arrhythmias induced by CO in vivo, as monitored by telemetry. Our data indicate that the proarrhythmic effects of CO arise from activation of NO synthase, leading to NO-mediated nitrosylation of Na(V)1.5 and to induction of the late Na(+) current. We also show that the antianginal drug ranolazine can abolish CO-induced early after-depolarizations, highlighting a novel approach to the treatment of CO-induced arrhythmias.

Structural study of Na2O-B2O3-SiO2 glasses from molecular simulations using a polarizable force field.

Science.gov (United States)

Pacaud, Fabien; Delaye, Jean-Marc; Charpentier, Thibault; Cormier, Laurent; Salanne, Mathieu

2017-10-28

Sodium borosilicate glasses Na 2 O-B 2 O 3 -SiO 2 (NBS) are complex systems from a structural point of view. Three main building units are present: tetrahedral SiO 4 and BO 4 (B IV ) and triangular BO 3 (B III ). One of the salient features of these compounds is the change of the B III /B IV ratio with the alkali concentration, which is very difficult to capture in force fields-based molecular dynamics simulations. In this work, we develop a polarizable force field that is able to reproduce the boron coordination and more generally the structure of several NBS systems in the glass and in the melt. The parameters of the potential are fitted from density functional theory calculations only, in contrast with the existing empirical potentials for NBS systems. This ensures a strong improvement on the transferability of the parameters from one composition to another. Using this new force field, the structure of NBS systems is validated against neutron diffraction and nuclear magnetic resonance experiments. A special focus is given to the distribution of B III /B IV with respect to the composition and the temperature.

A complete analysis of HA and NA genes of influenza A viruses.

LENUS (Irish Health Repository)

Shi, Weifeng

2010-12-01

More and more nucleotide sequences of type A influenza virus are available in public databases. Although these sequences have been the focus of many molecular epidemiological and phylogenetic analyses, most studies only deal with a few representative sequences. In this paper, we present a complete analysis of all Haemagglutinin (HA) and Neuraminidase (NA) gene sequences available to allow large scale analyses of the evolution and epidemiology of type A influenza.

Hofmeister effect on thermo-responsive poly(propylene oxide): Role of polymer molecular weight and concentration

DEFF Research Database (Denmark)

Moghaddam, Saeed Zajforoushan; Thormann, Esben

2016-01-01

) salts on aqueous solutions of poly(propylene oxide) (PPO) is studied. Four different molecular weights of PPO were investigated, to determine how the variation in the polymer coil size affects the Hofmeister effect. The investigation was further conducted for different PPO concentrations, in order...... with the transition. It was observed that increasing the molecular weight weakens the effect of the both salts, which is interpreted in terms of a scaling law between the molecular weight and the accessible surface area of the polymers. Increasing the PPO concentration further diminished the NaCl effect...

Direct interaction of beta-amyloid with Na,K-ATPase as a putative regulator of the enzyme function

Science.gov (United States)

Petrushanko, Irina Yu.; Mitkevich, Vladimir A.; Anashkina, Anastasia A.; Adzhubei, Alexei A.; Burnysheva, Ksenia M.; Lakunina, Valentina A.; Kamanina, Yulia V.; Dergousova, Elena A.; Lopina, Olga D.; Ogunshola, Omolara O.; Bogdanova, Anna Yu.; Makarov, Alexander A.

2016-06-01

By maintaining the Na+ and K+ transmembrane gradient mammalian Na,K-ATPase acts as a key regulator of neuronal electrotonic properties. Na,K-ATPase has an important role in synaptic transmission and memory formation. Accumulation of beta-amyloid (Aβ) at the early stages of Alzheimer’s disease is accompanied by reduction of Na,K-ATPase functional activity. The molecular mechanism behind this phenomenon is not known. Here we show that the monomeric Aβ(1-42) forms a tight (Kd of 3 μM), enthalpy-driven equimolar complex with α1β1 Na,K-ATPase. The complex formation results in dose-dependent inhibition of the enzyme hydrolytic activity. The binding site of Aβ(1-42) is localized in the “gap” between the alpha- and beta-subunits of Na,K-ATPase, disrupting the enzyme functionality by preventing the subunits from shifting towards each other. Interaction of Na,K-ATPase with exogenous Aβ(1-42) leads to a pronounced decrease of the enzyme transport and hydrolytic activity and Src-kinase activation in neuroblastoma cells SH-SY5Y. This interaction allows regulation of Na,K-ATPase activity by short-term increase of the Aβ(1-42) level. However prolonged increase of Aβ(1-42) level under pathological conditions could lead to chronical inhibition of Na,K-ATPase and disruption of neuronal function. Taken together, our data suggest the role of beta-amyloid as a novel physiological regulator of Na,K-ATPase.

Spectroscopic calculation of the excited electronic states with spin orbit effect of the molecule NaCs

International Nuclear Information System (INIS)

Bleik, S.; Korek, M.; Allouche, A.R.

2004-01-01

Full text.The existence of new experimental data on the alkali dimers has stimulated theoretical approaches, necessary to provide predictions accurate enough to be useful for interpretation and evenly for guidance of experiments. With the aim of improving the accuracy of predictions we will perform a theoretical study of the electronic structure of the molecule NaCs using a method mainly in the way by which core-valence effects are taken into account. To investigate the electronic structure of NaCs we will use the package CIPSI (Configuration Interaction by Perturbation of a multiconfiguration wave function Selected Interactively) of the Laboratoire de Physique Quantique (Toulouse, France). The atoms Na and Cs will be treated through non-empirical effective one electron core potentials of Durand and Barthelat type. Molecular orbitals for NaCs will be derived from Self Consistent field Calculations (SCF) and full valence Configuration Interaction (IC) calculations. A core-core interaction more elaborated than the usual approximation 1/R will be taken into account as the sum of an exponential repulsive term plus a long range dispersion term approximated by the well known London formula. Potential energy calculations will be performed for different molecular states, for numerous values of the inter-nuclear distance R in a wide range. Spectroscopic constants have been derived for the bound states with regular shape. A ro vibrational study have been performed for the ground states with a calculation of the rotational and centrifugal distortion constants. A calculation for the transition dipole moment and matrix elements have been done for the bound states

Structure and properties of sodium aluminosilicate glasses from molecular dynamics simulations

DEFF Research Database (Denmark)

Xiang, Ye; Du, Jincheng; Smedskjær, Morten Mattrup

2013-01-01

the recent Corning® Gorilla® Glass. In this paper, the structures of sodium aluminosilicate glasses with a wide range of Al/Na ratios (from 1.5 to 0.6) have been studied using classical molecular dynamics simulations in a system containing around 3000 atoms, with the aim to understand the structural role...

Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions

International Nuclear Information System (INIS)

Zong-Liang, Li; Huai-Zhi, Li; Yong, Ma; Guang-Ping, Zhang; Chuan-Kui, Wang

2010-01-01

A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H 2 O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H 2 O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H 2 O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H 2 O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Meltability in system of K2TaF7-NaF-NaCl-KCl

International Nuclear Information System (INIS)

Kartsev, V.E.; Kovalev, F.V.; Korshunov, B.G.

1975-01-01

Thermographic and visual-polythermal techniques were used to study the meltability in K 2 TaF 7 -NaF-NaCl-KCl system. The tetrahedron-forming sections NaF-NaCl-K 2 TaF 7 xKCl and NaF-K 2 TaF 7 xKCl-2K 2 TaF 7 xNaCl divide the concentration tetrahedron into three particular tetrahedra: NaF-K 2 TaF 7 xKCl-2K 2 TaF 7 xNaCl-K 2 TaF 7 , NaF-NaCl-K 2 TaF 7 xKCl-2K 2 TaF 7 xaCl, and NaF-NaCl-KCl-K 2 TaF 7 xKCl. Non-variant equilibrium points in all of the particular four-component systems have been determined

The Role of Concentration and Solvent Character in the Molecular Organization of Humic Acids

Directory of Open Access Journals (Sweden)

Martina Klučáková

2016-10-01

Full Text Available The molecular organization of humic acids in different aqueous solutions was studied over a wide concentration range (0.01–10 g·dm−3. Solutions of humic acids were prepared in three different media: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. Potentiometry, conductometry, densitometry, and high resolution ultrasound spectrometry were used in order to investigate conformational changes in the humic systems. The molecular organization of humic acids in the studied systems could be divided into three concentration ranges. The rearrangements were observed at concentrations of ~0.02 g·dm−3 and ~1 g·dm−3. The first “switch-over point” was connected with changes in the hydration shells of humic particles resulting in changes in their elasticity. The compressibility of water in the hydration shells is less than the compressibility of bulk water. The transfer of hydration water into bulk water increased the total compressibility of the solution, reducing the ultrasonic velocity. The aggregation of humic particles and the formation of rigid structures in systems with concentrations higher than 1 g·dm−3 was detected.

Systematic Study of Binding of μ-Conotoxins to the Sodium Channel NaV1.4

Directory of Open Access Journals (Sweden)

Somayeh Mahdavi

2014-12-01

Full Text Available Voltage-gated sodium channels (NaV are fundamental components of the nervous system. Their dysfunction is implicated in a number of neurological disorders, such as chronic pain, making them potential targets for the treatment of such disorders. The prominence of the NaV channels in the nervous system has been exploited by venomous animals for preying purposes, which have developed toxins that can block the NaV channels, thereby disabling their function. Because of their potency, such toxins could provide drug leads for the treatment of neurological disorders associated with NaV channels. However, most toxins lack selectivity for a given target NaV channel, and improving their selectivity profile among the NaV1 isoforms is essential for their development as drug leads. Computational methods will be very useful in the solution of such design problems, provided accurate models of the protein-ligand complex can be constructed. Using docking and molecular dynamics simulations, we have recently constructed a model for the NaV1.4-μ-conotoxin-GIIIA complex and validated it with the ample mutational data available for this complex. Here, we use the validated NaV1.4 model in a systematic study of binding other μ-conotoxins (PIIIA, KIIIA and BuIIIB to NaV1.4. The binding mode obtained for each complex is shown to be consistent with the available mutation data and binding constants. We compare the binding modes of PIIIA, KIIIA and BuIIIB to that of GIIIA and point out the similarities and differences among them. The detailed information about NaV1.4-μ-conotoxin interactions provided here will be useful in the design of new NaV channel blocking peptides.

Active transport of Na/sup +/ by reconstituted Na,K-ATPase

Energy Technology Data Exchange (ETDEWEB)

Boldyrev, A.A.; Svinukhova, I.A.

1987-02-20

The ability of ATP, CTP, ITP, GTP, and UTP to support ouabain-sensitive accumulation of Na/sup +/ by proteoliposomes with a reconstituted Na/K-pump was investigated. At a low (Na/sup +/)/(K/sup +/) ratio in the medium (20 mM/50 mM), a correlation is observed between the proton-accepting capacity of the nucleotide and its effectiveness as a substrate of active transport. To test the hypothesis of the importance of the presence of a negative charge in the 1-position of the purine (3-pyrimidine) base of the nucleotide for mutual transitions between the Na- and K-conformations of Na,K-ATPase they used two analogs of ATP: N/sub 1/-hydroxy-ATP, possessing proton acceptor capacity, and N/sub 1/-methoxy-ATP, in the molecule of which the negative charge is quenched by a methyl group. The first substrate supports active accumulation of Na/sup +/ in proteoliposomes at the same rate as ATP, whereas the second substrate is relatively ineffective.

Relationship between intracellular Na+ concentration and reduced Na+ affinity in Na+,K+-ATPase mutants causing neurological disease

DEFF Research Database (Denmark)

Toustrup-Jensen, Mads Schak; Einholm, Anja P.; Schack, Vivien

The neurological disorders familial hemiplegic migraine type 2 (FHM2), alternating hemiplegia of childhood (AHC), and rapid-onset dystonia parkinsonism (RDP) are caused by mutations of Na+,K+-ATPase α2 and α3 isoforms, expressed in glial and neuronal cells, respectively. Although these disorders......, addressing the question to what extent they cause a change of the intracellular Na+ and K+ concentrations ([Na+]i and [K+]i) in COS cells. C-terminal extension mutants generally showed dramatically reduced Na+ affinity without disturbance of K+ binding, as did other RDP mutants. No phosphorylation from ATP...

Repeated functional convergent effects of NaV1.7 on acid insensitivity in hibernating mammals.

Science.gov (United States)

Liu, Zhen; Wang, Wei; Zhang, Tong-Zuo; Li, Gong-Hua; He, Kai; Huang, Jing-Fei; Jiang, Xue-Long; Murphy, Robert W; Shi, Peng

2014-02-07

Hibernating mammals need to be insensitive to acid in order to cope with conditions of high CO2; however, the molecular basis of acid tolerance remains largely unknown. The African naked mole-rat (Heterocephalus glaber) and hibernating mammals share similar environments and physiological features. In the naked mole-rat, acid insensitivity has been shown to be conferred by the functional motif of the sodium ion channel NaV1.7. There is now an opportunity to evaluate acid insensitivity in other taxa. In this study, we tested for functional convergence of NaV1.7 in 71 species of mammals, including 22 species that hibernate. Our analyses revealed a functional convergence of amino acid sequences, which occurred at least six times independently in mammals that hibernate. Evolutionary analyses determined that the convergence results from both parallel and divergent evolution of residues in the functional motif. Our findings not only identify the functional molecules responsible for acid insensitivity in hibernating mammals, but also open new avenues to elucidate the molecular underpinnings of acid insensitivity in mammals.

MOŽNOSTI VSTOPA NA TUJE TRGE NA PRIMERU PODJETJA AWOODTURE

OpenAIRE

Orličnik, Urša

2014-01-01

Danes pojavljanje podjetja samo na domačem trgu ni več dovolj. Spremembe okolja, naraščanje konkurence ter hiter tehnološki napredek, silijo podjetja k nenehnemu prilagajanju in iskanju novih priložnosti tako na domačem kot tudi na tujem trgu. Internacionalizacija podjetja tako postaja vedno bolj pomemembna za preživetje podjetja. Internacionalizacija se v najširšem smislu nanaša na vse oblike mednarodnega ekonomskega sodelovanja. Je dinamičen proces, kateremu nujno sledi sprememba stanja...

Molecular dynamics simulations of the electrical double layer on smectite surfaces contacting concentrated mixed electrolyte (NaCl-CaCl2)

Energy Technology Data Exchange (ETDEWEB)

Bourg, I.C.; Sposito, G.

2011-04-01

We report new molecular dynamics results elucidating the structure of the electrical double layer (EDL) on smectite surfaces contacting mixed NaCl-CaCl{sup 2} electrolyte solutions in the range of concentrations relevant to pore waters in geologic repositories for CO{sub 2} or high-level radioactive waste (0.34-1.83 mol{sub c} dm{sup -3}). Our results confirm the existence of three distinct ion adsorption planes (0-, {beta}-, and d-planes), often assumed in EDL models, but with two important qualifications: (1) the location of the {beta}- and d-planes are independent of ionic strength or ion type and (2) 'indifferent electrolyte' ions can occupy all three planes. Charge inversion occurred in the diffuse ion swarm because of the affinity of the clay surface for CaCl{sup +} ion pairs. Therefore, at concentrations 0.34 mol{sub c} dm{sup -3}, properties arising from long-range electrostatics at interfaces (electrophoresis, electro-osmosis, co-ion exclusion, colloidal aggregation) will not be correctly predicted by most EDL models. Co-ion exclusion, typically neglected by surface speciation models, balanced a large part of the clay mineral structural charge in the more concentrated solutions. Water molecules and ions diffused relatively rapidly even in the first statistical water monolayer, contradicting reports of rigid 'ice-like' structures for water on clay mineral surfaces.

Corrosion control of copper in 3.5 wt.% NaCl Solution by Domperidone: Experimental and Theoretical Study

International Nuclear Information System (INIS)

Wang, Dan; Xiang, Bin; Liang, Yuanpeng; Song, Shan; Liu, Chao

2014-01-01

Highlights: • Domperidone has good inhibition effect for copper in 3.5 wt.% NaCl solution. • Domperidone acts as an anodic type inhibitor. • The SEM and AFM analyses support the weight loss, polarization, and EIS data. • Molecular dynamics (MD) method simulates the adsorption model of domperidone on Cu surface. • The adsorption of domperidone on copper surface obeys Langmuir adsorption isotherm. - Abstract: Inhibition of copper corrosion in 3.5 wt.% NaCl solution by domperidone was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental results revealed that domperidone was an anodic inhibitor with a maximum achievable inhibition efficiency of 94.2%. The results of SEM and AFM studies further confirmed the inhibition action of domperidone. Quantum chemical calculation and the molecular dynamics (MD) simulation showed that the domperidone molecule could be adsorbed on copper surface through the imidazolidinone ring, benzene ring and N atom of hexaheterocyclic. Adsorption of domperidone was found to follow the Langmuir adsorption isotherm

Molecular basis for interaction of Na⁺/K⁺-ATPase with other transporters in membrane microdomains of vascular smooth muscle cells

DEFF Research Database (Denmark)

Hansen, Anne Kirstine; Matchkov, Vladimir; Bouzinova, Elena

2008-01-01

Ouabain, a specific inhibitor of the Na+/K+-pump, has previously been shown to interfere with intercellular communication. We have recently demonstrated a mechanism of this action of ouabain (1). We have showed that gap junctions between vascular smooth muscle cells (SMCs) are regulated through...... an interaction between the Na+/K+-pump and the Na+/Ca2+-exchanger leading to an increase in the intracellular calcium concentration in discrete areas near the plasma membrane. This regulation suggests a close association of the proteins in microdomains. We have also suggested that this Na...

Infrared (1-12 μm) atomic and molecular emission signatures from energetic materials using laser-induced breakdown spectroscopy

Science.gov (United States)

Kumi Barimah, E.; Hömmerich, U.; Brown, E.; Yang, C. S.-C.; Trivedi, S. B.; Jin, F.; Wijewarnasuriya, P. S.; Samuels, A. C.; Snyder, A. P.

2013-05-01

Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique to detect the elemental composition of solids, liquids, and gases in real time. For example, recent advances in UV-VIS LIBS have shown great promise for applications in chemical, biological, and explosive sensing. The extension of conventional UVVIS LIBS to the near-IR (NIR), mid-IR (MIR) and long wave infrared (LWIR) regions (~1-12 μm) offers the potential to provide additional information due to IR atomic and molecular signatures. In this work, a Q-switched Nd: YAG laser operating at 1064 nm was employed as the excitation source and focused onto several chlorate and nitrate compounds including KClO3, NaClO3, KNO3, and NaNO3 to produce intense plasma at the target surface. IR LIBS studies on background air, KCl , and NaCl were also included for comparison. All potassium and sodium containing samples revealed narrow-band, atomic-like emissions assigned to transitions of neutral alkali-metal atoms in accordance with the NIST atomic spectra database. In addition, first evidence of broad-band molecular LIBS signatures from chlorate and nitrate compounds were observed at ~10 μm and ~7.3 μm, respectively. The observed molecular emissions showed strong correlation with FTIR absorption spectra of the investigated materials.

K+ Block Is the Mechanism of Functional Asymmetry in Bacterial Na(v Channels.

Directory of Open Access Journals (Sweden)

Van Ngo

2016-01-01

Full Text Available Crystal structures of several bacterial Na(v channels have been recently published and molecular dynamics simulations of ion permeation through these channels are consistent with many electrophysiological properties of eukaryotic channels. Bacterial Na(v channels have been characterized as functionally asymmetric, and the mechanism of this asymmetry has not been clearly understood. To address this question, we combined non-equilibrium simulation data with two-dimensional equilibrium unperturbed landscapes generated by umbrella sampling and Weighted Histogram Analysis Methods for multiple ions traversing the selectivity filter of bacterial Na(vAb channel. This approach provided new insight into the mechanism of selective ion permeation in bacterial Na(v channels. The non-equilibrium simulations indicate that two or three extracellular K+ ions can block the entrance to the selectivity filter of Na(vAb in the presence of applied forces in the inward direction, but not in the outward direction. The block state occurs in an unstable local minimum of the equilibrium unperturbed free-energy landscape of two K+ ions that can be 'locked' in place by modest applied forces. In contrast to K+, three Na+ ions move favorably through the selectivity filter together as a unit in a loose "knock-on" mechanism of permeation in both inward and outward directions, and there is no similar local minimum in the two-dimensional free-energy landscape of two Na+ ions for a block state. The useful work predicted by the non-equilibrium simulations that is required to break the K+ block is equivalent to large applied potentials experimentally measured for two bacterial Na(v channels to induce inward currents of K+ ions. These results illustrate how inclusion of non-equilibrium factors in the simulations can provide detailed information about mechanisms of ion selectivity that is missing from mechanisms derived from either crystal structures or equilibrium unperturbed free

Na/K pump inactivation, subsarcolemmal Na measurements, and cytoplasmic ion turnover kinetics contradict restricted Na spaces in murine cardiac myocytes

OpenAIRE

Lu, Fang-Min; Hilgemann, Donald W.

2017-01-01

The Na/K pump exports cytoplasmic Na ions while importing K ions, and its activity is thought to be affected by restricted intracellular Na diffusion in cardiac myocytes. Lu and Hilgemann find instead that the pump can enter an inactivated state and that inactivation can be relieved by cytoplasmic Na.

Computer modelling reveals new conformers of the ATP binding loop of Na+/K+-ATPase involved in the transphosphorylation process of the sodium pump.

Science.gov (United States)

Tejral, Gracian; Sopko, Bruno; Necas, Alois; Schoner, Wilhelm; Amler, Evzen

2017-01-01

Hydrolysis of ATP by Na + /K + -ATPase, a P-Type ATPase, catalyzing active Na + and K + transport through cellular membranes leads transiently to a phosphorylation of its catalytical α -subunit. Surprisingly, three-dimensional molecular structure analysis of P-type ATPases reveals that binding of ATP to the N-domain connected by a hinge to the P-domain is much too far away from the Asp 369 to allow the transfer of ATP's terminal phosphate to its aspartyl-phosphorylation site. In order to get information for how the transfer of the γ -phosphate group of ATP to the Asp 369 is achieved, analogous molecular modeling of the M 4 -M 5 loop of ATPase was performed using the crystal data of Na + /K + -ATPase of different species. Analogous molecular modeling of the cytoplasmic loop between Thr 338 and Ile 760 of the α 2 -subunit of Na + /K + -ATPase and the analysis of distances between the ATP binding site and phosphorylation site revealed the existence of two ATP binding sites in the open conformation; the first one close to Phe 475 in the N-domain, the other one close to Asp 369 in the P-domain. However, binding of Mg 2+ •ATP to any of these sites in the "open conformation" may not lead to phosphorylation of Asp 369 . Additional conformations of the cytoplasmic loop were found wobbling between "open conformation"  "semi-open conformation  "closed conformation" in the absence of 2Mg 2+ •ATP. The cytoplasmic loop's conformational change to the "semi-open conformation"-characterized by a hydrogen bond between Arg 543 and Asp 611 -triggers by binding of 2Mg 2+ •ATP to a single ATP site and conversion to the "closed conformation" the phosphorylation of Asp 369 in the P-domain, and hence the start of Na + /K + -activated ATP hydrolysis.

[Effect of adaptogenic preparations on Na+/H+-antiporter function in plasma membrane of corn root cells under salinity conditions].

Science.gov (United States)

Kovalenko, N O; Bilyk, Zh I; Palladina, T O

2014-01-01

Salinity is a hard stress factor for plant organisms which negative effect is caused chiefly by sodium toxic for plants. Plant cells try to remove Na+ from their cytoplasm outside and to vacuolar space by secondary active Na+/H+-antiporters. Their functions can be intensified by gene engineering methods however we try do it with the help of non-toxic bioactive preparations. A comparison of their effect on the plasma membrane of Na+/H+-antiporters was carried out on corn seedling roots of Zea mays L. exposed at 0.1 M NaCl. Before we have established that Methyure used by seed pretreating possesses a high salt protective ability as against Ivine. It was found that without NaCl exposition Na+/H+-antiporter activity in root plasma membrane was nearly unnoticeable but increased slightly with seedling age. Methyure and Ivine did not influence its activity in control root seedling. One day 0.1 M NaCl exposition evoked a considerable increasing of Na+/H+-antiporter activity and its gene expression but these effects disappeared at 10 day NaCl exposition. Methyure use reinforced Na+/H+-antiporter activity and prolonged it at NaCl exposition without effect on its gene expression whereas Ivine effects on these indexes were insignificant. Obtained results showed that the salt protective capability of Methyure is connected with plasma membrane Na+/H+-antiporter activation which is realized on molecular level.

Neutron activation analysis of trace metallic elements eluted from molecular sieves in the dehydration process of safflower oil

Energy Technology Data Exchange (ETDEWEB)

Takasago, Masahisa; Kobayashi, Koichi; Taru, Yasunori; Takaoka, Kyo (Musashi Inst. of Tech., Tokyo (Japan))

1992-11-01

Dissolved water in safflower oil affects the autoxidation of this oil significantly. Molecular sieves were used to remove the dissolved water from the oil. This method is much simpler than that of distillation, and dissolved water can be removed to the same extent as that by distillation. But, due to the elution of many kinds of trace metallic elements in the oil dehydrated with molecular sieves, these elements were analyzed by neutron activation analysis. For a data comparison trace amounts of metallic elements in the oil dehydrated by distillation were also analyzed. Since the intensity of the [gamma] ray-photoelectric peak of nuclide [sup 28]Al was largest among the detected elements, this element was analyzed quantitatively and the other elements qualitatively. In safflower oil dehydrated with molecular sieves, 14 kinds of the elements (I, Br, Al, Mg, Si, V, Cl, Nd, Ta, Cr, Sb, Cs, Co, Na) were detected. Also, I, Br, Cl, Cr, Ta, Sb, and Al elements were detected in the oil dehydrated by distillation. The intensity of the photoelectric peak of nuclide except [sup 28]Al was essentially the same as that in the oil dehydrated by distillation, but the intensity of [sup 28]Al in the oil with molecular sieves was about 28 times stronger than that in distillation oil. In the molecular sieves, 19 impure elements in addition to the original constituents (Na, K, Al, si, O) were detected. It was Al, Na, Si, Nd, Cs, and Co along with impure elements may possibly have been eluted in the oil. Al element in safflower oil dehydrated with molecular sieves was analyzed quantitatively. 0.91 ppm of Al was detected in safflower oil. The eluted amount of Al in safflower oil dehydrated by distillation was 0.032 ppm. A larger amount of Al element was thus eluted into the oil dehydrated with molecular sieves than by distillation. (author).

Molecular mechanisms underlying the regulation of brain-derived neurotrophic factor (BDNF) translation in dendrites

OpenAIRE

Pinheiro, Vera Lúcia Margarido

2010-01-01

Dissertação de mestrado em Biologia Celular e Molecular apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra A especificidade espacial e temporal subjacente à diversidade de processos de plasticidade sináptica que ocorrem no sistema nervoso central está profundamente relacionada com a disponibilidade da proteína brain-derived neurotrophic factor (BDNF) em domínios sub-celulares distintos, especialmente na área pós-sinápti...

Molecular-Level Simulations of the Turbulent Taylor-Green Flow

Science.gov (United States)

Gallis, M. A.; Bitter, N. P.; Koehler, T. P.; Plimpton, S. J.; Torczynski, J. R.; Papadakis, G.

2017-11-01

The Direct Simulation Monte Carlo (DSMC) method, a statistical, molecular-level technique that provides accurate solutions to the Boltzmann equation, is applied to the turbulent Taylor-Green vortex flow. The goal of this work is to investigate whether DSMC can accurately simulate energy decay in a turbulent flow. If so, then simulating turbulent flows at the molecular level can provide new insights because the energy decay can be examined in detail from molecular to macroscopic length scales, thereby directly linking molecular relaxation processes to macroscopic transport processes. The DSMC simulations are performed on half a million cores of Sequoia, the 17 Pflop platform at Lawrence Livermore National Laboratory, and the kinetic-energy dissipation rate and the energy spectrum are computed directly from the molecular velocities. The DSMC simulations are found to reproduce the Kolmogorov -5/3 law and to agree with corresponding Navier-Stokes simulations obtained using a spectral method. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

Sodium recognition by the Na+/Ca2+ exchanger in the outward-facing conformation.

Science.gov (United States)

Marinelli, Fabrizio; Almagor, Lior; Hiller, Reuben; Giladi, Moshe; Khananshvili, Daniel; Faraldo-Gómez, José D

2014-12-16

Na(+)/Ca(2+) exchangers (NCXs) are ubiquitous membrane transporters with a key role in Ca(2+) homeostasis and signaling. NCXs mediate the bidirectional translocation of either Na(+) or Ca(2+), and thus can catalyze uphill Ca(2+) transport driven by a Na(+) gradient, or vice versa. In a major breakthrough, a prokaryotic NCX homolog (NCX_Mj) was recently isolated and its crystal structure determined at atomic resolution. The structure revealed an intriguing architecture consisting of two inverted-topology repeats, each comprising five transmembrane helices. These repeats adopt asymmetric conformations, yielding an outward-facing occluded state. The crystal structure also revealed four putative ion-binding sites, but the occupancy and specificity thereof could not be conclusively established. Here, we use molecular-dynamics simulations and free-energy calculations to identify the ion configuration that best corresponds to the crystallographic data and that is also thermodynamically optimal. In this most probable configuration, three Na(+) ions occupy the so-called Sext, SCa, and Sint sites, whereas the Smid site is occupied by one water molecule and one H(+), which protonates an adjacent aspartate side chain (D240). Experimental measurements of Na(+)/Ca(2+) and Ca(2+)/Ca(2+) exchange by wild-type and mutagenized NCX_Mj confirm that transport of both Na(+) and Ca(2+) requires protonation of D240, and that this side chain does not coordinate either ion at Smid. These results imply that the ion exchange stoichiometry of NCX_Mj is 3:1 and that translocation of Na(+) across the membrane is electrogenic, whereas transport of Ca(2+) is not. Altogether, these findings provide the basis for further experimental and computational studies of the conformational mechanism of this exchanger.

Active ingredients in Chinese medicines promoting blood circulation as Na+/K+ -ATPase inhibitors.

Science.gov (United States)

Chen, Ronald J Y; Jinn, Tzyy-rong; Chen, Yi-ching; Chung, Tse-yu; Yang, Wei-hung; Tzen, Jason T C

2011-02-01

The positive inotropic effect of cardiac glycosides lies in their reversible inhibition on the membrane-bound Na(+)/K(+)-ATPase in human myocardium. Steroid-like compounds containing a core structure similar to cardiac glycosides are found in many Chinese medicines conventionally used for promoting blood circulation. Some of them are demonstrated to be Na(+)/K(+)-ATPase inhibitors and thus putatively responsible for their therapeutic effects via the same molecular mechanism as cardiac glycosides. On the other hand, magnesium lithospermate B of danshen is also proposed to exert its cardiac therapeutic effect by effectively inhibiting Na(+)/K(+)-ATPase. Theoretical modeling suggests that the number of hydrogen bonds and the strength of hydrophobic interaction between the effective ingredients of various medicines and residues around the binding pocket of Na(+)/K(+)-ATPase are crucial for the inhibitory potency of these active ingredients. Ginsenosides, the active ingredients in ginseng and sanqi, substantially inhibit Na(+)/K(+)-ATPase when sugar moieties are attached only to the C-3 position of their steroid-like structure, equivalent to the sugar position in cardiac glycosides. Their inhibitory potency is abolished, however, when sugar moieties are linked to C-6 or C-20 position of the steroid nucleus; presumably, these sugar attachments lead to steric hindrance for the entrance of ginsenosides into the binding pocket of Na(+)/K(+)-ATPase. Neuroprotective effects of cardiac glycosides, several steroid-like compounds, and magnesium lithospermate B against ischemic stroke have been accordingly observed in a cortical brain slice-based assay model, and cumulative data support that effective inhibitors of Na(+)/K(+)-ATPase in the brain could be potential drugs for the treatment of ischemic stroke.

Na+, K+/H+ antiporters regulate the pH of endoplasmic reticulum and auxin-mediated development

Czech Academy of Sciences Publication Activity Database

Fan, B. H.; Zhao, L; Hu, X.; Li, W.; Novák, Ondřej; Strnad, Miroslav; Simon, S.; Friml, J.; Shen, J.; Jiang, L.; Qiu, Q. S.

2018-01-01

Roč. 41, č. 4 (2018), s. 850-864 ISSN 0140-7791 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Arabidopsis * AtNHX5 * AtNHX6 * endosomal Na ,K /H antiporters * pH * pin5 Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Cell biology Impact factor: 6.173, year: 2016

Human T-cell Lymphotropic Virus types I and II (HTLV-I/II in French Guiana: clinical and molecular epidemiology Os Vírus T-Linfotrópicos Humanos tipo I (HTLV-I e tipo II (HTLV-II na Guiana Francesa: epidemiologia clínica e molecular

Directory of Open Access Journals (Sweden)

Mirdad Kazanji

2003-10-01

Full Text Available We review here the epidemiological studies performed by our group on human retrovirus HTLV-I and HTLV-II infections and the associated diseases in French Guiana since 1984. French Guiana is an overseas French administrative district located between Brazil and Surinam. Its population is characterized by a large variety of ethnic groups, including several populations of African origin and various populations of Amerindian origin. Several epidemiological studies of large samples of pregnant women and in remote villages showed that HTLV-I is highly endemic in this area but is restricted to groups of African origin, especially the Noir-Marrons. In this endemic population, the results of segregation analysis in a genetic epidemiological study were consistent with the presence of a dominant major gene predisposing to HTLV-I infection, especially in children. In contrast, HTLV-II infection appears to be rare in French Guiana, having been found in only a few individuals of Brazilian origin. From a molecular point of view, the HTLV-I strains present in the Noir-Marrons, Creoles and Amerindians appear to originate from Africa, as they belong to the large cosmopolitan molecular subtype A.Os autores apresentam uma revisão dos estudos epidemiológicos realizados pelo seu grupo de pesquisa sobre a infecção pelos vírus T-linfotrópicos humanos tipo I (HTLV-I e tipo II (HTLV-II e doenças associadas na Guiana Francesa, desde 1984. A Guiana Francesa é um Departamento de Ultramar da França, situado entre o Brasil e o Suriname. A população é caracterizada por uma grande variedade de grupos étnicos, incluindo diversas comunidades de origem africana e outras de origem indígena. Diversos inquéritos epidemiológicos sobre gestantes e em aldeias remotas mostraram que o HTLV-I é altamente endêmico nessas áreas, mas que o vírus é restrito a grupos de origem africana, particularmente os Noir-Marrons. Nessa população endêmica, os resultados de uma an

Functional significance of the oligomeric structure of the Na,K-pump from radiation inactivation and ligand binding

International Nuclear Information System (INIS)

Norby, J.G.; Jensen, J.

1991-01-01

The present article is concerned with the oligomeric structure and function of the Na,K-pump (Na,K-ATPase). The questions we have addressed, using radiation inactivation and target size analysis as well as ligand binding, are whether the minimal structural unit and the functional unit have more than one molecule of the catalytic subunit, alpha. The authors first discuss the fundamentals of the radiation inactivation method and emphasize the necessity for rigorous internal standardization with enzymes of known molecular mass. They then demonstrate that the radiation inactivation of Na,K-ATPase is a stepwise process which leads to intermediary fragments of the alpha-subunit with partial catalytic activity. From the target size analysis it is most likely that the membrane-bound Na,K-ATPase is structurally organized as a diprotomer containing two alpha-subunits. Determination of ADP- and ouabain-binding site stoichiometry favors a theory with one substrate site per (alpha beta) 2. 47 references

Theoretical and experimental approach on the molecular interactions of the DL-Alanine with an electrolytic environment

Science.gov (United States)

Cantero-López, Plinio; Yañez-Osses, Osvaldo; Páez-Meza, Manuel Silvestre; López, Johana E.; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro

2017-11-01

The molecular interactions that promote the stability of proteins and amino acids in saline solutions is a central topic of molecular biophysics. However, a well-supported molecular picture of the phenomena has not been established yet. In this paper, we studied as model system the mix between DL-Alanine in aqueous solutions of STP (Na2S2O3·5H2O) at different temperatures, from volumetric and viscometric properties. The thermophysical properties obtained indicate the presence of a strong preferential solvation, structure-making action and a possible salt in effect. Quantum chemical calculations and molecular dynamic (MD) simulations provide a new insight to support these arguments.

Aspectos moleculares da anemia falciforme Molecular aspects for sickle cell anemia

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Gentil Claudino de Galiza Neto

2003-01-01

Full Text Available No presente artigo abordaram-se vários aspectos relacionados à natureza molecular da anemia falciforme, desordem hematológica de caráter hereditário que acomete expressivo número de indivíduos em várias regiões do mundo. As pesquisas realizadas em torno desta patologia da hemácia, ao longo de quase um século, a partir de 1910, cooperaram para a criação de um novo e importante segmento da ciência, denominado biologia molecular. A descoberta dos polimorfismos da mutação (GAT->GTG no gene que codifica a cadeia beta da hemoglobina, originando diferentes haplótipos da doença, permitiu um melhor e mais amplo conhecimento em torno da heterogeneidade clínica nos pacientes falcêmicos. Analisando a hemoglobina na sua estrutura normal e mutante, sua produção e evolução, pode-se ter um entendimento mais completo da fisiopatologia desta doença e da sua complexidade clínica.The present article dealt with various aspects related to molecular nature of sickle cell disease (SCD, a heritable hematology disorder that attacks a great number of people in different regions of the world. Researches done on red cell patology, in approximately half a century, starting since 1910, cooperated to gave origin a new branch of science called molecular biology. The discovery of mutation polymorphism (GAT -> GTC in the gene that codifies beta globin chain, give origin to different illness haplotypes, permitted a better and great knowledge about the clinic heterogeneity of the patients. Analysing hemoglobin in its normal and mutation structure as well as in its productions and evolution, one can have a complete understanding of the illness phisiopathology and its clinical complexity.

Single-molecule study of full-length NaChBac by planar lipid bilayer recording.

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Andrew Jo

Full Text Available Planar lipid bilayer device, alternatively known as BLM, is a powerful tool to study functional properties of conducting membrane proteins such as ion channels and porins. In this work, we used BLM to study the prokaryotic voltage-gated sodium channel (Nav NaChBac in a well-defined membrane environment. Navs are an essential component for the generation and propagation of electric signals in excitable cells. The successes in the biochemical, biophysical and crystallographic studies on prokaryotic Navs in recent years has greatly promoted the understanding of the molecular mechanism that underlies these proteins and their eukaryotic counterparts. In this work, we investigated the single-molecule conductance and ionic selectivity behavior of NaChBac. Purified NaChBac protein was first reconstituted into lipid vesicles, which is subsequently incorporated into planar lipid bilayer by fusion. At single-molecule level, we were able to observe three distinct long-lived conductance sub-states of NaChBac. Change in the membrane potential switches on the channel mainly by increasing its opening probability. In addition, we found that individual NaChBac has similar permeability for Na+, K+, and Ca2+. The single-molecule behavior of the full-length protein is essentially highly stochastic. Our results show that planar lipid bilayer device can be used to study purified ion channels at single-molecule level in an artificial environment, and such studies can reveal new protein properties that are otherwise not observable in in vivo ensemble studies.

Comparación de metodologías moleculares para identificar el gen de la kappa caseína en ganado Holstein

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Carlos Solarte P.

2012-04-01

Full Text Available Objetivo. Comparar las metodologías moleculares, PCR-RFLPs y PCR-SSCP, para identificar las variantes alélicas del gen de la kappa caseína (CSN3 en bovinos Holstein del trópico alto de Nariño-Colombia. Materiales y métodos. Se escogieron al azar 50 vacas Holstein y mediante punción en la vena coxígea media se tomaron muestras de 5cc de sangre, que se almacenaron y preservaron en tarjetas FTA® para su posterior análisis en el laboratorio. El ADN se amplificó por PCR utilizando cebadores específicos. Los cambios en la conformación de cadena sencilla (SSCP fueron visualizados en geles de poliacrilamida al 12%; mientras que los RFLPs se obtuvieron por digestión con tres enzimas de restricción y se visualizaron en geles de agarosa al 4%. Resultados. La metodología PCR-RFLPs fue útil para detectar mutaciones puntuales y por lo tanto se identificó un mayor número de alelos, lo que contribuye a una mejor estimación de las medidas de diversidad genética en poblaciones seleccionadas, ya que evita problemas de sobreestimación de los valores en las frecuencias alélicas. Por su parte, la técnica PCR-SSCP resultó más sencilla y económica, ideal para investigaciones en las que no existe información previa sobre los genotipos de las poblaciones bovinas y en estudios con bajos presupuestos. Conclusiones. Las dos metodologías evaluadas son herramientas moleculares que contribuyen a la orientación de los procesos de selección en los bovinos para leche, ya que identifican los alelos del gen CSN3. La diferencia radica en el costo de las mismas y en el número de variantes identificadas.

Vpliv toplotnih mostov na porabo energije za ogrevanje na primeru osnovne šole

OpenAIRE

Megušar, Primož

2015-01-01

Na primeru Osnovne šole Dobrova sem preveril, kakšen vpliv imajo dejanski toplotni mostovi na porabo energije za ogrevanje. Iz načrtov stavbe sem evidentiral vse toplotne mostove, kateri vplivajo na porabo energije. Tem toplotnim mostovom sem nato v standardu SIST EN ISO 14683 poiskal ustrezne približke. Nato sem s programom TOST izvedel tri simulacije. V prvem primeru toplotnih mostov nisem upošteval. V drugem primeru sem toplotne mostove upošteval na poenostavljen način, v zadnjem primeru p...

Na and K dependence of the Na/K pump in cystic fibrosis fibroblasts.

OpenAIRE

Reznik, V M; Schneider, J A; Mendoza, S A

1981-01-01

The Na and K dependence of the Na/K pump was measured in skin fibroblasts from patients with cystic fibrosis and age/sex-matched controls. Under basal conditions, there was no difference between control and cystic fibrosis cells in protein per cell, intracellular Na and K content, or Na/K pump activity (measured as ouabain-sensitive 86Rb uptake). There was no difference in the Na dependence of the Na/K pump between cystic fibrosis cells and control cells. In cells from patients with cystic fi...

The effect of aging on aortic atherosclerotic plaque inflammation and molecular calcification: A FDG and NaF PET CT imaging study

DEFF Research Database (Denmark)

Blomberg, Björn; Thomassen, Anders; Hildebrandt, Malene

2013-01-01

prospectively assessed by 18-FDG (inflammation) and Sodium 18-Fluoride (Na-18F) (calcification metabolism) PET CT imaging. Global aortic uptake of 18-FDG and Na-18F was quantified by subtracting the blood pool SUVmean from the aortic SUVmax (cSUV) [maximum SUVaorta - mean SUVblood pool]. Calculating regression...

Vliv mikroflóry na senzorické vlastnosti vína

OpenAIRE

Petrášová, Ludmila

2014-01-01

Tato bakalářská práce se zabývá vlivem mikroflóry na senzorické vlastnosti vína. Teoretická část informuje o botanickém popisu hroznů vína Veltlínské zelené, dále o jeho složení, o technologii zpracování bílého vína a o vlivu kvasinek na aromatický profil vína. V další části popisuje metodu stanovení aromaticky aktivních látek pomocí plynové chromatografie v kombinaci s mikroextrakcí tuhou fází (SPME-GC). Cílem experimentální části bylo proměřit vzorky 4 různých moštů odrůdy Veltlínské zelené...

Synthesis of cerium oxide catalysts supported on MCM-41 molecular sieve; Sintese de catalisadores de oxido de cerio suportados na peneira molecular MCM-41

Energy Technology Data Exchange (ETDEWEB)

Souza, E.L.S.; Barros, T.R.B.; Sousa, B.V. de, E-mail: emylle.souza@gmail.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia Quimica

2016-07-01

Porous materials have been widely studied as catalysts and catalyst support. The MCM-41 structure is the one that has been most studied because of its application possibilities in chemical processes. This work aimed to obtain and characterize cerium oxide catalysts supported on MCM-41 molecular sieve. The molecular sieve was synthesized by the conventional method with the following molar composition: 1 SiO2: 0.30 CTABr: NH3 11: 144 H2O. Then, 25% w/w cerium was incorporated into the MCM-41 using the wet impregnation process and the material obtained was activated by calcination. From the XRD patterns was confirmed the structure of the molecular sieve, and were identified the cerium oxide phases in its structure. The textural catalysts characteristics were investigated by isotherms of N2 adsorption/desorption (BET method). (author)

Uso da bioinformática na diferenciação molecular da Entamoeba histolytica e Entamoeba díspar - DOI: 10.4025/actascihealthsci.v30i2.2375 Molecular discrimination of Entamoeba histolytica and Entamoeba dispar by bioinformatics resources - DOI: 10.4025/actascihealthsci.v30i2.2375

Directory of Open Access Journals (Sweden)

Débora Sommer

2008-12-01

Full Text Available Amebíase invasiva, causada por Entamoeba histolytica, é microscopicamente indistinguível da espécie não-patogênica Entamoeba dispar. Com auxílio de ferramentas de bioinformática, objetivou-se diferenciar Entamoeba histolytica e Entamoeba dispar por técnicas moleculares. A análise foi realizada a partir do banco de dados da National Center for Biotechnology Information; pela pesquisa de similaridade de sequências, elegeu-se o gene da cisteína sintase. Um par de primer foi desenhado (programa Web Primer e foi selecionada a enzima de restrição TaqI (programa Web Cutter. Após a atuação da enzima, o fragmento foi dividido em dois, um com 255 pb e outro com 554 pb, padrão característico da E. histolytica. Na ausência de corte, o fragmento apresentou o tamanho de 809 pb, referente à E. dispar.Under microscopic conditions, the invasive Entamoeba histolytica is indistinguishable from the non-pathogenic species Entamoeba dispar. In this way, the present study was carried out to determine a molecular strategy for discriminating both species by the mechanisms of bioinformatics. The gene cysteine synthetase was considered for such a purpose by using the resources of the National Center for Biotechnology Information data bank in the search for similarities in the gene sequence. In this way, a primer pair was designed by the Web Primer program and the restriction enzyme TaqI was selected by the Web Cutter software program. The DNA fragment had a size of 809 bp before cutting, which is consistent with E. dispar. The gene fragment was partitioned in a first fragment with 255 bp and a second one with 554 bp, which is similar to the genetic characteristics of E. histolytica.

Highly ordered self-assembly of one-dimensional nanoparticles in amphiphilic molecular systems

International Nuclear Information System (INIS)

Kim, Tae Hwan

2009-02-01

Two kinds of one-dimensional (1D) nanoparticles, stable rod-like nanoparticles with highly controlled surface charge density (cROD) and non-covalently functionalized isolated single wall carbon nanotubes (p-SWNT) that were readily redispersible in water, have been developed. Using these 1D nanoparticles, various highly ordered superstructures of 1D nanoparticles by molecular self-assembling based on electrostatic interaction in amphiphilic molecular systems (two different cationic liposome systems) have been investigated. To our knowledge, this is the first demonstration of highly ordered self-assembly of 1D nanoparticles based on electrostatic interaction between 1D nanoparticles and amphiphilic molecules. The cRODs have been developed by free radical polymerization of a mixture of polymerizable cationic surfactant, cetyltrimethylammonium 4-vinylbenzoate (CTVB), and hydrotropic salt sodium 4-styrenesulfonate (NaSS) in aqueous solution. The surface charge of the cROD was controlled by varying the NaSS concentration during the polymerization process and the charge variation was interpreted in terms of the overcharging effect in colloidal systems. The small angle neutron scattering (SANS) measurements showed that the diameter of cROD is constant at 4 nm and the particle length ranges from 20 nm to 85 nm, depending on the NaSS concentration. The cRODs are longest when the NaSS concentration is 5 mol % which corresponds to the charge inversion or neutral point. The SANS and zeta potential measurements showed that the Coulomb interactions between the particles are strongly dependent on the NaSS concentration and the zeta potential of the cRODs changes from positive to negative (+ 12.8 mV ∼ - 44.2 mV) as the concentration of NaSS increases from 0 mol % to 40 mol %. As the NaSS concentration is further increased, the zeta potential is saturated at approximately - 50 mV. The p-SWNTs have been developed by 1) dispersing single wall carbon nanotubes (SWNTs) in water using

Genética molecular: avanços e problemas Molecular genetics: advances and problems

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Eloi S. Garcia

1996-03-01

Full Text Available Este artigo traz a discussão sobre genética molecular em saúde ao campo da saúde pública. Com a revolução produzida pela chegada da engenharia genética, é importante discutir alguns dos avanços e problemas desta tecnologia para a sociedade. Está na hora de se fazer uma avaliação clara e bem informada acerca do que já se conseguiu e do que ainda podemos conseguir através desta tecnologia. A sociedade precisa compreender as implicações éticas e práticas de uma tecnologia capaz de produzir drogas milagrosas, dagnósticos modernos e a cura de todas as doenças. Alguns pontos particularmente delicados pertinentes às questões sociais ligadas à biologia molecular e ao projeto genoma humano são discutidos.This article is an attempt to draw the discussion on molecular genetics in health into the public health domain. Now that the genetic engineering revolution has arrived, it is important to point out the advances and problems this technology poses for society. It is time for a clear, informed assessment of what we have already achieved and may soon achieve using this technology. Clearly, society needs to understand the ethical and practical implications of a technology which can produce miracle drugs and modern diagnoses and cure virtually every disease. Important points from sensitive social issues raised by molecular biology and the human genome project are discussed.

Forward flux sampling calculation of homogeneous nucleation rates from aqueous NaCl solutions.

Science.gov (United States)

Jiang, Hao; Haji-Akbari, Amir; Debenedetti, Pablo G; Panagiotopoulos, Athanassios Z

2018-01-28

We used molecular dynamics simulations and the path sampling technique known as forward flux sampling to study homogeneous nucleation of NaCl crystals from supersaturated aqueous solutions at 298 K and 1 bar. Nucleation rates were obtained for a range of salt concentrations for the Joung-Cheatham NaCl force field combined with the Extended Simple Point Charge (SPC/E) water model. The calculated nucleation rates are significantly lower than the available experimental measurements. The estimates for the nucleation rates in this work do not rely on classical nucleation theory, but the pathways observed in the simulations suggest that the nucleation process is better described by classical nucleation theory than an alternative interpretation based on Ostwald's step rule, in contrast to some prior simulations of related models. In addition to the size of NaCl nucleus, we find that the crystallinity of a nascent cluster plays an important role in the nucleation process. Nuclei with high crystallinity were found to have higher growth probability and longer lifetimes, possibly because they are less exposed to hydration water.

Secondary and tertiary structure of nucleotide-binding domain of alpha subunit of Na+/K+-ATPase

Czech Academy of Sciences Publication Activity Database

Hofbauerová, Kateřina; Kopecký ml., Vladimír; Ettrich, Rüdiger; Ettrichová, Olga; Amler, Evžen

2002-01-01

Roč. 67, 4-5 (2002), s. 242-246 ISSN 0006-3525 R&D Projects: GA ČR GA204/01/0254; GA ČR GA204/01/1001 Grant - others:Volkswagen Foundation(DE) I/74 679 Institutional research plan: CEZ:AV0Z5011922 Keywords : Na+/K+- ATPase * ATP binding * molecular modeling Subject RIV: BO - Biophysics Impact factor: 2.372, year: 2002

Two classes of ouabain binding sites in ferret heart and two forms of Na+-K+-ATPase

Energy Technology Data Exchange (ETDEWEB)

Ng, Y.C.; Akera, T.

1987-05-01

In partially purified Na+-K+-adenosinetriphosphatase (ATPase) obtained from ferret heart, ouabain produced a monophasic inhibition curve; however, the curve spanned over 5 logarithmic units, indicating the presence of more than one classes of enzyme. (/sup 3/H)ouabain binding studies revealed high-and low-affinity binding sites in approximately equal abundance, with apparent dissociation constants of 10 and 230 nM, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of phosphoenzyme formed from (gamma-/sup 32/P)ATP showed two distinct K+-sensitive bands of approximately 100,000 molecular weight. Phosphoenzyme formation from the high-molecular-weight alpha(+) form was selectively inhibited by N-ethylmaleimide. Ouabain caused a 50% inhibition of phosphorylation of the alpha(+) form at 40 nM and the lower-molecular-weight alpha form at 300 nM. In papillary muscle preparations, 1-30 nM ouabain produced a modest positive inotropic effect that reached an apparent plateau at 30 nM. Further increases in ouabain concentrations, however, produced additional and prominent inotropic effects at 0.1-10 microM. These results indicate for the first time in cardiac muscle that the high- and low-affinity ouabain binding sites are associated with the alpha(+) and alpha forms of the Na+-K+-ATPase, respectively, and that binding of ouabain to either of these sites causes enzyme inhibition and the positive inotropic effect.

Capturing Human Naïve Pluripotency in the Embryo and in the Dish.

Science.gov (United States)

Zimmerlin, Ludovic; Park, Tea Soon; Zambidis, Elias T

2017-08-15

Although human embryonic stem cells (hESCs) were first derived almost 20 years ago, it was only recently acknowledged that they share closer molecular and functional identity to postimplantation lineage-primed murine epiblast stem cells than to naïve preimplantation inner cell mass-derived mouse ESCs (mESCs). A myriad of transcriptional, epigenetic, biochemical, and metabolic attributes have now been described that distinguish naïve and primed pluripotent states in both rodents and humans. Conventional hESCs and human induced pluripotent stem cells (hiPSCs) appear to lack many of the defining hallmarks of naïve mESCs. These include important features of the naïve ground state murine epiblast, such as an open epigenetic architecture, reduced lineage-primed gene expression, and chimera and germline competence following injection into a recipient blastocyst-stage embryo. Several transgenic and chemical methods were recently reported that appear to revert conventional human PSCs to mESC-like ground states. However, it remains unclear if subtle deviations in global transcription, cell signaling dependencies, and extent of epigenetic/metabolic shifts in these various human naïve-reverted pluripotent states represent true functional differences or alternatively the existence of distinct human pluripotent states along a spectrum. In this study, we review the current understanding and developmental features of various human pluripotency-associated phenotypes and discuss potential biological mechanisms that may support stable maintenance of an authentic epiblast-like ground state of human pluripotency.

Cytotoxicity of cardiotonic steroids in sensitive and multidrug-resistant leukemia cells and the link with Na(+)/K(+)-ATPase.

Science.gov (United States)

Zeino, Maen; Brenk, Ruth; Gruber, Lisa; Zehl, Martin; Urban, Ernst; Kopp, Brigitte; Efferth, Thomas

2015-06-01

Cardiotonic steroids have long been in clinical use for treatment of heart failure and are now emerging as promising agents in various diseases, especially cancer. Their main target is Na(+)/K(+)-ATPase, a membrane protein involved in cellular ion homeostasis. Na(+)/K(+)-ATPase has been implicated in cancer biology by affecting several cellular events and signaling pathways in both sensitive and drug-resistant cancer cells. Hence, we investigated the cytotoxic activities of 66 cardiotonic steroids and cardiotonic steroid derivatives in sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. Data were then subjected to quantitative structure-activity relationship analysis (QSAR) and molecular docking into Na(+)/K(+)-ATPase, which both indicated a possible differential expression of the pump in the mentioned cell lines. This finding was confirmed by western blotting, intracellular potassium labeling and next generation sequencing which showed that Na(+)/K(+)-ATPase was less expressed in multidrug-resistant than in sensitive cells. Copyright © 2015 Elsevier Ltd. All rights reserved.

How NaCl raises blood pressure: a new paradigm for the pathogenesis of salt-dependent hypertension

Science.gov (United States)

Leenen, Frans H. H.; Chen, Ling; Golovina, Vera A.; Hamlyn, John M.; Pallone, Thomas L.; Van Huysse, James W.; Zhang, Jin; Wier, W. Gil

2012-01-01

Excess dietary salt is a major cause of hypertension. Nevertheless, the specific mechanisms by which salt increases arterial constriction and peripheral vascular resistance, and thereby raises blood pressure (BP), are poorly understood. Here we summarize recent evidence that defines specific molecular links between Na+ and the elevated vascular resistance that directly produces high BP. In this new paradigm, high dietary salt raises cerebrospinal fluid [Na+]. This leads, via the Na+-sensing circumventricular organs of the brain, to increased sympathetic nerve activity (SNA), a major trigger of vasoconstriction. Plasma levels of endogenous ouabain (EO), the Na+ pump ligand, also become elevated. Remarkably, high cerebrospinal fluid [Na+]-evoked, locally secreted (hypothalamic) EO participates in a pathway that mediates the sustained increase in SNA. This hypothalamic signaling chain includes aldosterone, epithelial Na+ channels, EO, ouabain-sensitive α2 Na+ pumps, and angiotensin II (ANG II). The EO increases (e.g.) hypothalamic ANG-II type-1 receptor and NADPH oxidase and decreases neuronal nitric oxide synthase protein expression. The aldosterone-epithelial Na+ channel-EO-α2 Na+ pump-ANG-II pathway modulates the activity of brain cardiovascular control centers that regulate the BP set point and induce sustained changes in SNA. In the periphery, the EO secreted by the adrenal cortex directly enhances vasoconstriction via an EO-α2 Na+ pump-Na+/Ca2+ exchanger-Ca2+ signaling pathway. Circulating EO also activates an EO-α2 Na+ pump-Src kinase signaling cascade. This increases the expression of the Na+/Ca2+ exchanger-transient receptor potential cation channel Ca2+ signaling pathway in arterial smooth muscle but decreases the expression of endothelial vasodilator mechanisms. Additionally, EO is a growth factor and may directly participate in the arterial structural remodeling and lumen narrowing that is frequently observed in established hypertension. These several

Molecular dynamics simulations of the electrical double layer on smectite surfaces contacting concentrated mixed electrolyte (NaCl-CaCl2) solutions.

Science.gov (United States)

Bourg, Ian C; Sposito, Garrison

2011-08-15

We report new molecular dynamics results elucidating the structure of the electrical double layer (EDL) on smectite surfaces contacting mixed NaCl-CaCl(2) electrolyte solutions in the range of concentrations relevant to pore waters in geologic repositories for CO(2) or high-level radioactive waste (0.34-1.83 mol(c) dm(-3)). Our results confirm the existence of three distinct ion adsorption planes (0-, β-, and d-planes), often assumed in EDL models, but with two important qualifications: (1) the location of the β- and d-planes are independent of ionic strength or ion type and (2) "indifferent electrolyte" ions can occupy all three planes. Charge inversion occurred in the diffuse ion swarm because of the affinity of the clay surface for CaCl(+) ion pairs. Therefore, at concentrations ≥0.34 mol(c) dm(-3), properties arising from long-range electrostatics at interfaces (electrophoresis, electro-osmosis, co-ion exclusion, colloidal aggregation) will not be correctly predicted by most EDL models. Co-ion exclusion, typically neglected by surface speciation models, balanced a large part of the clay mineral structural charge in the more concentrated solutions. Water molecules and ions diffused relatively rapidly even in the first statistical water monolayer, contradicting reports of rigid "ice-like" structures for water on clay mineral surfaces. Published by Elsevier Inc.

Analysis and manipulation of atomic and molecular collisions using laser light

International Nuclear Information System (INIS)

Grimpe, A.

2006-01-01

Optical collisions in a crossed beam experiment are examined for the atomic collision pairs LiHe, LiNe, NaNe. Differential cross sections are measured in order to probe the quality of quantum chemical calculated and spectroscopical determined molecular potentials. The linear polarization of the excitation laser is used to manipulate the contrast of the differential cross sections for NaNe. Using elliptical polarized light total control over the angular position and the contrast of the interference pattern is demonstrated. Differential cross sections for the collision pairs LiH 2 and LiD 2 show a pronounced oscillatory structure, which for the first time is observed for atom-molecule optical collisions. (orig.)

Lithium fluxes indicate presence of Na-Cl cotransport (NCC) in human lens epithelial cells.

Science.gov (United States)

Lauf, Peter K; Chimote, Ameet A; Adragna, Norma C

2008-01-01

During regulatory volume decrease (RVD) of human lens epithelial cells (hLECs) by clotrimazole (CTZ)-sensitive K fluxes, Na-K-2Cl cotransport (NKCC) remains active and K-Cl cotransport (KCC) inactive. To determine whether such an abnormal behavior was caused by RVD-induced cell shrinkage, NKCC was measured in the presence of either CTZ or in high K media to prevent RVD. NKCC transports RbCl + NaCl, and LiCl + KCl; thus ouabain-insensitive, bumetanide-sensitive (BS) or Cl-dependent (ClD) Rb and Li fluxes were determined in hyposmotic high NaCl media with CTZ, or in high KCl media alone, or with sulfamate (Sf) or nitrate as Cl replacement at varying Rb, Li or Cl mol fractions (MF). Unexpectedly, NKCC was inhibited by 80% with CTZ (IC(50) = 31 microM). In isosmotic (300 mOsM) K, Li influx was approximately 1/3 of Rb influx in Na, 50% lower in Sf, and bumetanide-insensitive (BI). In hypotonic (200 mOsM) K, only the ClD but not BS Li fluxes were detected. At Li MFs from 0.1-1, Li fluxes fitted a bell-shaped curve maxing at approximately 0.6 Li MF, with the BS fluxes equaling approximately 1/4 of the ClD-Li influx. The difference, i.e. the BI/ClD Li influx, saturated with increasing Li and Cl MFs, with K(ms) for Li of 11 with, and 7 mM without K, and of approximately 46 mM for Cl. Inhibition of this K-independent Li influx by thiazides was weak whilst furosemide (<100 microM) was ineffective. Reverse transcription polymerase chain reaction and Western blots verified presence of both NKCC1 and Na-Cl cotransport (NCC). In conclusion, in hyposmotic high K media, which prevents CTZ-sensitive K flux-mediated RVD in hLECs, NKCC1, though molecularly expressed, was functionally silent. However, a K-independent and moderately thiazide-sensitive ClD-Li flux, i.e. LiCC, likely occurring through NCC was detected operationally and molecularly. (c) 2008 S. Karger AG, Basel.

Study of the Na-C-O and Na-H-O ternary systems in the sodium rich corner

International Nuclear Information System (INIS)

Maupre, J.-P.

1978-02-01

The purpose of this study is to provide a contribution to the understanding of the sodium - carbon - oxygen and sodium - hydrogen - oxygen ternary systems in the sodium rich corner. In order to do this the Na-NaH-Na 2 O-NaOH phase diagram was completed and the Na-Na 2 O-Na 2 CO 3 -C phase diagram was outlined. This work is made up of two parts. The first is devoted to a critical literature survey essential to establish correct phase diagrams. The second is an experimental study followed by a discussion collating our finding to the literary data. The basic experimental technique used is differential thermal analysis (DTA) but it has been completed by quenching, X-ray and chemical analysis methods. The proposed phase diagrams imply that Na-NaH-Na 2 O-NaOH and Na-Na 2 O-Na 2 CO 3 -C systems are reciprocal ternary systems. Temperatures of stable pairs reversal are respectively 410 and 690 0 C. The stable pairs are Na-NaOH and Na-Na 2 CO 3 at elevated temperature, Na 2 O-NaH and Na 2 O-C at low temperature [fr

A influência dos ácidos graxos trans na disfunção da célula endotelial e o possível efeito terapêutico do exercício sobre o tecido endotelial como forma de prevenção ou regressão da aterosclerose Influence of trans fatty acids on endothelial cell dysfunction and possible therapeutic effects of physical activity on endothelial tissue for prevention or regression of atherosclerosis

Directory of Open Access Journals (Sweden)

Laureane Nunes Masi

2009-06-01

Full Text Available O endotélio atua ativamente na regulação do tônus vascular, sintetizando e liberando substâncias vasoativas. A inflamação e os fatores de risco cardiovasculares alteram a homeostase vascular, levando à disfunção endotelial e possível formação de placas de ateroma. O aumento das concentrações plasmáticas de ácidos graxos livres pode causar lipotoxicidade vascular, disfunção do endotélio e, finalmente, aterosclerose. Dieta rica em lipídeos contendo ácidos graxos trans tem correlação positiva com a progressão de doenças cardiovasculares. Mudanças no estilo de vida, na adoção de dieta balanceada e atividade física são estratégias para a prevenção de doenças cardiovasculares e a reabilitação de pacientes. Nesta revisão, discutimos a influência benéfica do exercício físico em aspectos importantes da disfunção endotelial causados pelos ácidos graxos trans, incluindo evidências recentes e/ou ainda não exploradas. Discutimos também quais seriam os mecanismos envolvidos no comprometimento funcional da célula endotelial frente ao aumento de ácidos graxos trans na circulação.The endothelium actively participates in the regulation of vascular tone through the synthesis and release of vasoactive mediators. Inflammation and cardiovascular risk factors affect vascular homeostasis, causing endothelial dysfunction and atheromatous plaque formation. Increased free fatty acid concentrations may result in vascular lipotoxicity, endothelium dysfunction and, ultimately, atherosclerosis. A lipid-rich diet including trans fatty acids has a positive correlation with the progression of cardiovascular diseases. Lifestyle changes, such as eating a well-balanced diet and participating in regular physical activity, have been proposed to prevent cardiovascular diseases and improve rehabilitation. In this review, we discuss the beneficial effects of regular exercise on important aspects of endothelial dysfunction caused by

Response of saliva Na/K ratio to changing Na supply of lactating cows under tropical conditions.

Science.gov (United States)

Thiangtum, Wandee; Schonewille, J Thomas; Verstegen, Martin Wa; Arsawakulsudhi, Supot; Rukkwamsuk, Theera; Hendriks, Wouter H

2017-06-01

Factorial determination of the sodium (Na) requirement of heat-stressed lactating cows is hindered by accurate estimates of the Na losses through sweat. Direct studies, therefore, may be needed requiring information on the time course of healthy animals to become Na depleted and the subsequent rate of repletion. The rate of Na depletion and subsequent rate of Na repletion with two levels of dietary Na to lactating dairy cows housed under tropical conditions were investigated using the salivary Na/K. The 12 lactating cows (salivary Na/K ratio 14.6) rapidly developed clinical signs of Na deficiency, including pica, polyuria and polydipsia, reduced body weight and reduced milk yield when fed a low-Na ration (0.33 g kg -1 dry matter (DM)) for 3 weeks. Deficiency symptoms were associated with a rapid decrease in salivary Na/K ratio to cows with NaCl to a ration concentration of 1.1 or 1.6 g Na kg -1 DM for 5 weeks did not restore salivary Na/K ratio to values of >6. A daily Na intake of heat-stressed lactating cows to a ration intake of 1.6 g Na kg -1 DM was insufficient to restore Na deficiency. One week was sufficient to deplete heat-stressed lactating cows of Na, allowing for rapid dose-response studies utilizing the salivary Na/K ratio as a parameter for Na status of cows under tropical conditions. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Aspectos moleculares da anemia falciforme

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Galiza Neto Gentil Claudino de

2003-01-01

Full Text Available No presente artigo abordaram-se vários aspectos relacionados à natureza molecular da anemia falciforme, desordem hematológica de caráter hereditário que acomete expressivo número de indivíduos em várias regiões do mundo. As pesquisas realizadas em torno desta patologia da hemácia, ao longo de quase um século, a partir de 1910, cooperaram para a criação de um novo e importante segmento da ciência, denominado biologia molecular. A descoberta dos polimorfismos da mutação (GAT->GTG no gene que codifica a cadeia beta da hemoglobina, originando diferentes haplótipos da doença, permitiu um melhor e mais amplo conhecimento em torno da heterogeneidade clínica nos pacientes falcêmicos. Analisando a hemoglobina na sua estrutura normal e mutante, sua produção e evolução, pode-se ter um entendimento mais completo da fisiopatologia desta doença e da sua complexidade clínica.

Strong alkalinization in the anterior midgut of larval yellow fever mosquitoes (Aedes aegypti): involvement of luminal Na+/K+-ATPase.

Science.gov (United States)

Onken, Horst; Patel, Malay; Javoroncov, Margarita; Izeirovski, Sejmir; Moffett, Stacia B; Moffett, David F

2009-03-01

Recently, Na(+)/K(+)-ATPase has been detected in the luminal membrane of the anterior midgut of larval yellow fever mosquitoes (Aedes aegypti) with immunohistochemical techniques. In this study, the possible involvement of this ATPase in strong alkalinization was investigated on the level of whole larvae, isolated and perfused midgut preparations and on the molecular level of the Na(+)/K(+)-ATPase protein. Ouabain (5 mM) did not inhibit the capability of intact larval mosquitoes to alkalinize their anterior midgut. Also in isolated and perfused midgut preparations the perfusion of the lumen with ouabain (5 mM) did not result in a significant change of the transepithelial voltage or the capacity of luminal alkalinization. Na(+)/K(+)-ATPase activity was completely abolished when KCl was substituted with choline chloride, suggesting that the enzyme cannot act as an ATP-driven Na(+)/H(+)-exchanger. Altogether the results of the present investigation indicate that apical Na(+)/K(+)-ATPase is not of direct importance for strong luminal alkalinization in the anterior midgut of larval yellow fever mosquitoes.

A fluorescent combinatorial logic gate with Na+, H+-enabled OR and H+-driven low-medium-high ternary logic functions.

Science.gov (United States)

Spiteri, Jasmine M A; Mallia, Carl J; Scerri, Glenn J; Magri, David C

2017-12-06

A novel fluorescent molecular logic gate with a 'fluorophore-spacer 1 -receptor 1 -spacer 2 -receptor 2 ' format is demonstrated in 1 : 1 (v/v) methanol/water. The molecule consists of an anthracene fluorophore, and tertiary alkyl amine and N-(2-methoxyphenyl)aza-15-crown-5 ether receptors. In the presence of threshold concentrations of H + and Na + , the molecule switches 'on' as an AND logic gate with a fluorescence quantum yield of 0.21 with proton and sodium binding constants of log β H+ = 9.0 and log β Na+ = 3.2, respectively. At higher proton levels, protonation also occurs at the anilinic nitrogen atom ether with a log β H+ = 4.2, which allows for Na + , H + -enabled OR (OR + AND circuit) and H + -driven ternary logic functions. The reported molecule is compared and contrasted to classic anthracene-based Na + and H + logic gates. We propose that such logic-based molecules could be useful tools for probing the vicinity of Na + , H + antiporters in biological systems.

Glutathionylation-Dependence of Na+-K+-Pump Currents Can Mimic Reduced Subsarcolemmal Na+ Diffusion

Science.gov (United States)

Garcia, Alvaro; Liu, Chia-Chi; Cornelius, Flemming; Clarke, Ronald J.; Rasmussen, Helge H.

2016-01-01

The existence of a subsarcolemmal space with restricted diffusion for Na+ in cardiac myocytes has been inferred from a transient peak electrogenic Na+-K+ pump current beyond steady state on reexposure of myocytes to K+ after a period of exposure to K+-free extracellular solution. The transient peak current is attributed to enhanced electrogenic pumping of Na+ that accumulated in the diffusion-restricted space during pump inhibition in K+-free extracellular solution. However, there are no known physical barriers that account for such restricted Na+ diffusion, and we examined if changes of activity of the Na+-K+ pump itself cause the transient peak current. Reexposure to K+ reproduced a transient current beyond steady state in voltage-clamped ventricular myocytes as reported by others. Persistence of it when the Na+ concentration in patch pipette solutions perfusing the intracellular compartment was high and elimination of it with K+-free pipette solution could not be reconciled with restricted subsarcolemmal Na+ diffusion. The pattern of the transient current early after pump activation was dependent on transmembrane Na+- and K+ concentration gradients suggesting the currents were related to the conformational poise imposed on the pump. We examined if the currents might be accounted for by changes in glutathionylation of the β1 Na+-K+ pump subunit, a reversible oxidative modification that inhibits the pump. Susceptibility of the β1 subunit to glutathionylation depends on the conformational poise of the Na+-K+ pump, and glutathionylation with the pump stabilized in conformations equivalent to those expected to be imposed on voltage-clamped myocytes supported this hypothesis. So did elimination of the transient K+-induced peak Na+-K+ pump current when we included glutaredoxin 1 in patch pipette solutions to reverse glutathionylation. We conclude that transient K+-induced peak Na+-K+ pump current reflects the effect of conformation-dependent β1 pump subunit

Glutathionylation-Dependence of Na(+)-K(+)-Pump Currents Can Mimic Reduced Subsarcolemmal Na(+) Diffusion.

Science.gov (United States)

Garcia, Alvaro; Liu, Chia-Chi; Cornelius, Flemming; Clarke, Ronald J; Rasmussen, Helge H

2016-03-08

The existence of a subsarcolemmal space with restricted diffusion for Na(+) in cardiac myocytes has been inferred from a transient peak electrogenic Na(+)-K(+) pump current beyond steady state on reexposure of myocytes to K(+) after a period of exposure to K(+)-free extracellular solution. The transient peak current is attributed to enhanced electrogenic pumping of Na(+) that accumulated in the diffusion-restricted space during pump inhibition in K(+)-free extracellular solution. However, there are no known physical barriers that account for such restricted Na(+) diffusion, and we examined if changes of activity of the Na(+)-K(+) pump itself cause the transient peak current. Reexposure to K(+) reproduced a transient current beyond steady state in voltage-clamped ventricular myocytes as reported by others. Persistence of it when the Na(+) concentration in patch pipette solutions perfusing the intracellular compartment was high and elimination of it with K(+)-free pipette solution could not be reconciled with restricted subsarcolemmal Na(+) diffusion. The pattern of the transient current early after pump activation was dependent on transmembrane Na(+)- and K(+) concentration gradients suggesting the currents were related to the conformational poise imposed on the pump. We examined if the currents might be accounted for by changes in glutathionylation of the β1 Na(+)-K(+) pump subunit, a reversible oxidative modification that inhibits the pump. Susceptibility of the β1 subunit to glutathionylation depends on the conformational poise of the Na(+)-K(+) pump, and glutathionylation with the pump stabilized in conformations equivalent to those expected to be imposed on voltage-clamped myocytes supported this hypothesis. So did elimination of the transient K(+)-induced peak Na(+)-K(+) pump current when we included glutaredoxin 1 in patch pipette solutions to reverse glutathionylation. We conclude that transient K(+)-induced peak Na(+)-K(+) pump current reflects the effect

Nucleotide binding induces conformational changes apparent on the Na+/K+ -ATPase large cytoplasmic loop

Czech Academy of Sciences Publication Activity Database

Šimunová, Lenka; Kubala, M.; Lánský, Zdeněk; Teisinger, Jan; Amler, Evžen

Roč.13, č.1 (2006), s. 37-37 ISSN 1211-5894. [Discussions on Structural Molecular Biology /5./. 16.03.2006-18.03.2006, Nové Hrady] R&D Projects: GA MŠk(CZ) LC554; GA AV ČR 1ET400110403; GA ČR GD305/03/H148 Grant - others:Grantová agentura UK(CZ) 200053 Keywords : Na+/K+ - ATPase * ATP binding * TNP-ATP Subject RIV: BO - Biophysics

Radiative charge-transfer lifetime of the excited state of (NaCa)+

International Nuclear Information System (INIS)

Makarov, Oleg P.; Cote, R.; Michels, H.; Smith, W.W.

2003-01-01

New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom-ion trap under high-vacuum conditions. We study the collisional cooling of laser precooled Ca + ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet A 1 Σ + state of the (NaCa) + molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and Moeller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G (3df). The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be 2.3x10 -16 cm 3 /sec, while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher (1.1x10 -8 cm 3 /sec and 2.3x10 -9 cm 3 /sec, respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer

Symbiodinium isolation by NaOH treatment.

Science.gov (United States)

Zamoum, Thamilla; Furla, Paola

2012-11-15

The presence of photosynthetic zooxanthellae (dinoflagellates) in the tissue of many cnidarians is the main reason for their ecological success (i.e. coral reefs). It could also be the main cause of their demise, as the worldwide bleaching of reef-building coral is nothing less than the breakdown of this symbiotic association. The stability of this relationship is the principal marker for the biomonitoring of cnidarian health. We have therefore developed a new, simple method to isolate zooxanthellae in a few steps using NaOH solution. The protocol was validated in three symbiotic cnidarian species: a sea anemone, a gorgonian and a coral. Our method allows the isolation of intact and viable zooxanthellae with better yields than classic methods, especially for species with a calcareous skeleton. Moreover, the isolated zooxanthellae were free of host nucleic contaminants, facilitating subsequent specific molecular analyses.

Crystal structure of a Na+-bound Na+,K+-ATPase preceding the E1P state.

Science.gov (United States)

Kanai, Ryuta; Ogawa, Haruo; Vilsen, Bente; Cornelius, Flemming; Toyoshima, Chikashi

2013-10-10

Na(+),K(+)-ATPase pumps three Na(+) ions out of cells in exchange for two K(+) taken up from the extracellular medium per ATP molecule hydrolysed, thereby establishing Na(+) and K(+) gradients across the membrane in all animal cells. These ion gradients are used in many fundamental processes, notably excitation of nerve cells. Here we describe 2.8 Å-resolution crystal structures of this ATPase from pig kidney with bound Na(+), ADP and aluminium fluoride, a stable phosphate analogue, with and without oligomycin that promotes Na(+) occlusion. These crystal structures represent a transition state preceding the phosphorylated intermediate (E1P) in which three Na(+) ions are occluded. Details of the Na(+)-binding sites show how this ATPase functions as a Na(+)-specific pump, rejecting K(+) and Ca(2+), even though its affinity for Na(+) is low (millimolar dissociation constant). A mechanism for sequential, cooperative Na(+) binding can now be formulated in atomic detail.

Na+-H+ exchange and Na+-dependent transport systems in streptozotocin diabetic rat kidneys

International Nuclear Information System (INIS)

El-Seifi, S.; Freiberg, J.M.; Kinsella, F.J.; Cheng, L.; Sacktor, B.

1987-01-01

The streptozotocin-induced diabetic rat was used to test the hypothesis that Na + -H + exchange activity in the proximal tubule luminal membrane would be increased in association with renal hypertrophy, altered glomerular hemodynamics, enhanced filtered load and tubular reabsorption of 22 Na + , and stimulated 22 Na= pump activity in the basolateral membrane, previously reported characteristics of this experimental animal model. Amiloride-sensitive H + gradient-dependent Na + uptake and Na + gradient-dependent H + flux were increased in brush-border membrane vesicles from the streptozotocin-treated animals. Na + gradient-dependent uptakes of phosphate, D-glucose, L-proline, and myoinositol were decreased in the drug-induced diabetic animals. These membrane transport alterations were not found when the streptozotocin-diabetic animals were treated with insulin

The equation of state of B2-type NaCl

International Nuclear Information System (INIS)

Ono, S

2010-01-01

The equation of state (EOS) of B2-type NaCl has been investigated to 270 GPa and 3000 K using the first-principles molecular dynamics method and high-pressure experiments in a diamond anvil cell. We used the high-pressure experimental data to determine the compressibility at room temperature, and used the generalized gradient approximation (GGA) and the projector augmented-wave method (PAW) in simulations to calculate the thermal pressure. A Vinet EOS fitted to the room temperature data yielded an isothermal bulk modulus of B T0 = 39.25 GPa and a pressure derivative of B T0 ' = 4.72. The high-temperature data from the first-principles calculations were fitted to the thermal pressure EOS. The resulting calculated parameters of the thermal pressure, αB T (V 0 ,T) and (δB T /δT) V , were 3.28 x 10 -3 (GPa/K) and 4.3 x10 -4 (GPa/K), respectively. A small volume dependence of the thermal pressure of B2-type NaCl was revealed from the analysis of our data. A significant temperature dependence of the calculated Grueneisen parameters was confirmed. This indicates that the conventional approach using the Mie-Grueneisen approximation is likely to have a significant uncertainty in determining the EOS for B2-type NaCl, and that an intrinsic anharmonicity should be considered to analyze the EOS.

The two C-terminal tyrosines stabilize occluded Na/K pump conformations containing Na or K ions.

Science.gov (United States)

Vedovato, Natascia; Gadsby, David C

2010-07-01

Interactions of the three transported Na ions with the Na/K pump remain incompletely understood. Na/K pump crystal structures show that the extended C terminus of the Na,K-adenosine triphosphatase (ATPase) alpha subunit directly contacts transmembrane helices. Deletion of the last five residues (KETYY in almost all Na/K pumps) markedly lowered the apparent affinity for Na activation of pump phosphorylation from ATP, a reflection of cytoplasmic Na affinity for forming the occluded E1P(Na3) conformation. ATPase assays further suggested that C-terminal truncations also interfere with low affinity Na interactions, which are attributable to extracellular effects. Because extracellular Na ions traverse part of the membrane's electric field to reach their binding sites in the Na/K pump, their movements generate currents that can be monitored with high resolution. We report here electrical measurements to examine how Na/K pump interactions with extracellular Na ions are influenced by C-terminal truncations. We deleted the last two (YY) or five (KESYY) residues in Xenopus laevis alpha1 Na/K pumps made ouabain resistant by either of two kinds of point mutations and measured their currents as 10-mM ouabain-sensitive currents in Xenopus oocytes after silencing endogenous Xenopus Na/K pumps with 1 microM ouabain. We found the low affinity inhibitory influence of extracellular Na on outward Na/K pump current at negative voltages to be impaired in all of the C-terminally truncated pumps. Correspondingly, voltage jump-induced transient charge movements that reflect pump interactions with extracellular Na ions were strongly shifted to more negative potentials; this signals a several-fold reduction of the apparent affinity for extracellular Na in the truncated pumps. Parallel lowering of Na affinity on both sides of the membrane argues that the C-terminal contacts provide important stabilization of the occluded E1P(Na3) conformation, regardless of the route of Na ion entry into the

Clinical study of radioisotope uptake mechanisms in 33 brain lesions by comparative use of Na131I and SAIR

International Nuclear Information System (INIS)

Gonsette, R.E.; Claeys, L.

1975-01-01

It is suggested that an isotope of small molecular size, not bound to proteins (NaI), would pass more easily into little-differentiated tumours and vascular syndromes due chiefly to a lesion of the hematoencephalic barrier (HEB). On the other hand iodinated serumalbumine (SAIR), a large organic molecule accumulating in abnormal extracellular spaces, should in principle be a better indicator in non-primitive tumours and highly differentiated tumours of the SNC. The clinical study reported confirms this hypothesis. Non-primitive tumours, meningiomas, metastases, sarcomas, are shown more clearly by SAIR (especially in meningiomas, nearly 90% of cases). In non-primitive tumours the difference in behaviour between NaI and SAIR does seem to depend on the degree of differentiation of the tumour. Thus in so-called benign gliomas the NaI uptake is greater, whereas in highly differentiated gliomas the advantage goes to SAIR. In one case of circulation deficiency a vascular type of hyperfixation was observed with NaI, while SAIR showed practically nothing [fr

21-Benzylidene Digoxin: A Proapoptotic Cardenolide of Cancer Cells That Up-Regulates Na,K-ATPase and Epithelial Tight Junctions

Science.gov (United States)

Rocha, Sayonarah C.; Pessoa, Marco T. C.; Neves, Luiza D. R.; Alves, Silmara L. G.; Silva, Luciana M.; Santos, Herica L.; Oliveira, Soraya M. F.; Taranto, Alex G.; Comar, Moacyr; Gomes, Isabella V.; Santos, Fabio V.; Paixão, Natasha; Quintas, Luis E. M.; Noël, François; Pereira, Antonio F.; Tessis, Ana C. S. C.; Gomes, Natalia L. S.; Moreira, Otacilio C.; Rincon-Heredia, Ruth; Varotti, Fernando P.; Blanco, Gustavo; Villar, Jose A. F. P.; Contreras, Rubén G.; Barbosa, Leandro A.

2014-01-01

Cardiotonic steroids are used to treat heart failure and arrhythmia and have promising anticancer effects. The prototypic cardiotonic steroid ouabain may also be a hormone that modulates epithelial cell adhesion. Cardiotonic steroids consist of a steroid nucleus and a lactone ring, and their biological effects depend on the binding to their receptor, Na,K-ATPase, through which, they inhibit Na+ and K+ ion transport and activate of several intracellular signaling pathways. In this study, we added a styrene group to the lactone ring of the cardiotonic steroid digoxin, to obtain 21-benzylidene digoxin (21-BD), and investigated the effects of this synthetic cardiotonic steroid in different cell models. Molecular modeling indicates that 21-BD binds to its target Na,K-ATPase with low affinity, adopting a different pharmacophoric conformation when bound to its receptor than digoxin. Accordingly, 21-DB, at relatively high µM amounts inhibits the activity of Na,K-ATPase α1, but not α2 and α3 isoforms. In addition, 21-BD targets other proteins outside the Na,K-ATPase, inhibiting the multidrug exporter Pdr5p. When used on whole cells at low µM concentrations, 21-BD produces several effects, including: 1) up-regulation of Na,K-ATPase expression and activity in HeLa and RKO cancer cells, which is not found for digoxin, 2) cell specific changes in cell viability, reducing it in HeLa and RKO cancer cells, but increasing it in normal epithelial MDCK cells, which is different from the response to digoxin, and 3) changes in cell-cell interaction, altering the molecular composition of tight junctions and elevating transepithelial electrical resistance of MDCK monolayers, an effect previously found for ouabain. These results indicate that modification of the lactone ring of digoxin provides new properties to the compound, and shows that the structural change introduced could be used for the design of cardiotonic steroid with novel functions. PMID:25290152

Dynamical coupling of plasmons and molecular excitations by hybrid quantum/classical calculations: time-domain approach

International Nuclear Information System (INIS)

Sakko, Arto; Rossi, Tuomas P; Nieminen, Risto M

2014-01-01

The presence of plasmonic material influences the optical properties of nearby molecules in untrivial ways due to the dynamical plasmon-molecule coupling. We combine quantum and classical calculation schemes to study this phenomenon in a hybrid system that consists of a Na 2 molecule located in the gap between two Au/Ag nanoparticles. The molecule is treated quantum-mechanically with time-dependent density-functional theory, and the nanoparticles with quasistatic classical electrodynamics. The nanoparticle dimer has a plasmon resonance in the visible part of the electromagnetic spectrum, and the Na 2 molecule has an electron-hole excitation in the same energy range. Due to the dynamical interaction of the two subsystems the plasmon and the molecular excitations couple, creating a hybridized molecular-plasmon excited state. This state has unique properties that yield e.g. enhanced photoabsorption compared to the freestanding Na 2 molecule. The computational approach used enables decoupling of the mutual plasmon-molecule interaction, and our analysis verifies that it is not legitimate to neglect the backcoupling effect when describing the dynamical interaction between plasmonic material and nearby molecules. Time-resolved analysis shows nearly instantaneous formation of the coupled state, and provides an intuitive picture of the underlying physics. (paper)

Computer modelling reveals new conformers of the ATP binding loop of Na+/K+-ATPase involved in the transphosphorylation process of the sodium pump

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Gracian Tejral

2017-03-01

Full Text Available Hydrolysis of ATP by Na+/K+-ATPase, a P-Type ATPase, catalyzing active Na+ and K+ transport through cellular membranes leads transiently to a phosphorylation of its catalytical α-subunit. Surprisingly, three-dimensional molecular structure analysis of P-type ATPases reveals that binding of ATP to the N-domain connected by a hinge to the P-domain is much too far away from the Asp369 to allow the transfer of ATP’s terminal phosphate to its aspartyl-phosphorylation site. In order to get information for how the transfer of the γ-phosphate group of ATP to the Asp369 is achieved, analogous molecular modeling of the M4–M5 loop of ATPase was performed using the crystal data of Na+/K+-ATPase of different species. Analogous molecular modeling of the cytoplasmic loop between Thr338 and Ile760 of the α2-subunit of Na+/K+-ATPase and the analysis of distances between the ATP binding site and phosphorylation site revealed the existence of two ATP binding sites in the open conformation; the first one close to Phe475 in the N-domain, the other one close to Asp369 in the P-domain. However, binding of Mg2+•ATP to any of these sites in the “open conformation” may not lead to phosphorylation of Asp369. Additional conformations of the cytoplasmic loop were found wobbling between “open conformation”  “semi-open conformation  “closed conformation” in the absence of 2Mg2+•ATP. The cytoplasmic loop’s conformational change to the “semi-open conformation”—characterized by a hydrogen bond between Arg543 and Asp611—triggers by binding of 2Mg2+•ATP to a single ATP site and conversion to the “closed conformation” the phosphorylation of Asp369 in the P-domain, and hence the start of Na+/K+-activated ATP hydrolysis.

Adaptation to high salt concentrations in halotolerant/ halophilic fungi: a molecular perspective

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Ana ePlemenitas

2014-05-01

Full Text Available Molecular studies of salt tolerance of eukaryotic microorganisms have until recently been limited to the baker’s yeast Saccharomyces cerevisiae and a few other moderately halotolerant yeast. Discovery of the extremely halotolerant and adaptable fungus Hortaea werneckii and the obligate halophile Wallemia ichthyophaga introduced two new model organisms into studies on the mechanisms of salt tolerance in eukaryotes. H. werneckii is unique in its adaptability to fluctuations in salt concentrations, as it can grow without NaCl as well as in the presence of up to 5 M NaCl. On the other hand, W. ichthyophaga requires at least 1.5 M NaCl for growth, but also grows in up to 5 M NaCl. Our studies have revealed the novel and intricate molecular mechanisms used by these fungi to combat high salt concentrations, which differ in many aspects between the extremely halotolerant H. werneckii and the halophilic W. ichthyophaga. Specifically, the high osmolarity glycerol signalling pathway that is important for sensing and responding to increased salt concentrations is here compared between H. werneckii and W. ichthyophaga. In both of these fungi, the key signalling components are conserved, but there are structural and regulation differences between these pathways in H. werneckii and W. ichthyophaga. We also address differences that have been revealed from analysis of their newly sequenced genomes. The most striking characteristics associated with H. werneckii are the large genetic redundancy, the expansion of genes encoding metal cation transporters, and a relatively recent whole genome duplication. In contrast, the genome of W. ichthyophaga is very compact, as only 4,884 protein-coding genes are predicted, which cover almost three quarters of the sequence. Importantly, there has been a significant increase in their hydrophobins, cell-wall proteins that have multiple cellular functions.

Anion-coupled Na efflux mediated by the human red blood cell Na/K pump

International Nuclear Information System (INIS)

Dissing, S.; Hoffman, J.F.

1990-01-01

The red cell Na/K pump is known to continue to extrude Na when both Na and K are removed from the external medium. Because this ouabain-sensitive flux occurs in the absence of an exchangeable cation, it is referred to as uncoupled Na efflux. This flux is also known to be inhibited by 5 mM Nao but to a lesser extent than that inhibitable by ouabain. Uncoupled Na efflux via the Na/K pump therefore can be divided into a Nao-sensitive and Nao-insensitive component. We used DIDS-treated, SO4-equilibrated human red blood cells suspended in HEPES-buffered (pHo 7.4) MgSO4 or (Tris)2SO4, in which we measured 22Na efflux, 35SO4 efflux, and changes in the membrane potential with the fluorescent dye, diS-C3 (5). A principal finding is that uncoupled Na efflux occurs electroneurally, in contrast to the pump's normal electrogenic operation when exchanging Nai for Ko. This electroneutral uncoupled efflux of Na was found to be balanced by an efflux of cellular anions. (We were unable to detect any ouabain-sensitive uptake of protons, measured in an unbuffered medium at pH 7.4 with a Radiometer pH-STAT.) The Nao-sensitive efflux of Nai was found to be 1.95 +/- 0.10 times the Nao-sensitive efflux of (SO4)i, indicating that the stoichiometry of this cotransport is two Na+ per SO4=, accounting for 60-80% of the electroneutral Na efflux. The remainder portion, that is, the ouabain-sensitive Nao-insensitive component, has been identified as PO4-coupled Na transport and is the subject of a separate paper. That uncoupled Na efflux occurs as a cotransport with anions is supported by the result, obtained with resealed ghosts, that when internal and external SO4 was substituted by the impermeant anion, tartrate i,o, the efflux of Na was inhibited 60-80%. This inhibition could be relieved by the inclusion, before DIDS treatment, of 5 mM Cli,o

Molecular Mechanisms of Ultrafiltration Membrane Fouling in Polymer-Flooding Wastewater Treatment: Role of Ions in Polymeric Fouling.

Science.gov (United States)

Liu, Guicai; Yu, Shuili; Yang, Haijun; Hu, Jun; Zhang, Yi; He, Bo; Li, Lei; Liu, Zhiyuan

2016-02-02

Polymer (i.e., anionic polyacrylamide (APAM)) fouling of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes and its relationships to intermolecular interactions were investigated using atomic force microscopy (AFM). Distinct relations were obtained between the AFM force spectroscopy measurements and calculated fouling resistance over the concentration polarization layer (CPL) and gel layer (GL). The measured maximum adhesion forces (Fad,max) were closely correlated with the CPL resistance (Rp), and the proposed molecular packing property (largely based on the shape of AFM force spectroscopy curve) of the APAM chains was related to the GL resistance (Rg). Calcium ions (Ca(2+)) and sodium ions (Na(+)) caused more severe fouling. In the presence of Ca(2+), the large Rp corresponded to high foulant-foulant Fad,max, resulting in high flux loss. In addition, the Rg with Ca(2+) was minor, but the flux recovery rate after chemical cleaning was the lowest, indicating that Ca(2+) created more challenges in GL cleaning. With Na(+), the fouling behavior was complicated and concentration-dependent. The GL structures with Na(+), which might correspond to the proposed molecular packing states among APAM chains, played essential roles in membrane fouling and GL cleaning.

Selectivity of externally facing ion-binding sites in the Na/K pump to alkali metals and organic cations.

Science.gov (United States)

Ratheal, Ian M; Virgin, Gail K; Yu, Haibo; Roux, Benoît; Gatto, Craig; Artigas, Pablo

2010-10-26

The Na/K pump is a P-type ATPase that exchanges three intracellular Na(+) ions for two extracellular K(+) ions through the plasmalemma of nearly all animal cells. The mechanisms involved in cation selection by the pump's ion-binding sites (site I and site II bind either Na(+) or K(+); site III binds only Na(+)) are poorly understood. We studied cation selectivity by outward-facing sites (high K(+) affinity) of Na/K pumps expressed in Xenopus oocytes, under voltage clamp. Guanidinium(+), methylguanidinium(+), and aminoguanidinium(+) produced two phenomena possibly reflecting actions at site III: (i) voltage-dependent inhibition (VDI) of outwardly directed pump current at saturating K(+), and (ii) induction of pump-mediated, guanidinium-derivative-carried inward current at negative potentials without Na(+) and K(+). In contrast, formamidinium(+) and acetamidinium(+) induced K(+)-like outward currents. Measurement of ouabain-sensitive ATPase activity and radiolabeled cation uptake confirmed that these cations are external K(+) congeners. Molecular dynamics simulations indicate that bound organic cations induce minor distortion of the binding sites. Among tested metals, only Li(+) induced Na(+)-like VDI, whereas all metals tested except Na(+) induced K(+)-like outward currents. Pump-mediated K(+)-like organic cation transport challenges the concept of rigid structural models in which ion specificity at site I and site II arises from a precise and unique arrangement of coordinating ligands. Furthermore, actions by guanidinium(+) derivatives suggest that Na(+) binds to site III in a hydrated form and that the inward current observed without external Na(+) and K(+) represents cation transport when normal occlusion at sites I and II is impaired. These results provide insights on external ion selectivity at the three binding sites.

Experimental comparative study and fracture resistance simulation with irrigation solution of 0.2% chitosan, 2.5% NaOCl and 17% EDTA

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Ernani Ernani

2015-09-01

Full Text Available Background: Preparation in endodontic need irrigation materials as root canal debridement and disinfectant. However, irrigation materials is one of the factors that influence the tendency of fracture. Purpose: This study was aimed to see the resistance and fracture distribution if teeth irrigated with high molecular horseshoe crab chitosan at 0.2% concentration, 2.5% NaOCl solution and 17% EDTA solution in endodontic treatment with finite element method (FEM simulation study and experimental studies. Method: Endodontic treatment performed on 28 maxillary premolars with group A: irrigation solution of 17% EDTA and 2.5% NaOCl solution; group B: 2.5% NaOCl irrigation solution; group C: 2.5% NaOCl irrigation solution and 0.2% chitosan solution; group D: 0.2% chitosan solution irrigation. Final restoration was done using prefabricated glass fiber post. Cementation of post using resin cement then restored with direct composite resin restorations. Pressure test was performed with a Universal Testing Machine with a speed of 0.5 mm/min until fracture occurred. A three dimensional finite element analysis was performed for total deformation, equivalent (von-mises stress, and equivalent elastic strains. Result: Anova test showed significant differences in fracture resistance (p0.05. Statistical analysis showed no significant difference (p>0.05 between the results of experiment and FEM analysis results using the t-test. Conclusion: The results of this study demonstrated that there was effect of the use of high molecular 0.2% chitosan as a combined irrigation with NaOCl, but did not affect the fracture pattern distribution of endodontically treated teeth both experimentally and FEM analysis test.

Na5NbO5 and Na5TaO5 phases

International Nuclear Information System (INIS)

Darriet, J.; Maazaz, A.; Bouloux, J.C.; Delmas, C.

1982-01-01

New ternary oxides of formulas Na 5 NbO 5 and Na 5 TaO 5 have been prepared. They crystallize in the monoclinic system (space group C2/c). The crystal structure of Na 5 NbO 5 has been determined. It derives from a NaCl-type structure by ordering of the cations and of the oxygen vacancies in the anionic sublattice, the corresponding formula being Nasub(5/6)Nbsub(1/6)Osub(5/6)vacant sub(1/6). Sodium and niobium have a distorted square-pyramidal surrounding. (author)

Regulation of cation transporter genes by the arbuscular mycorrhizal symbiosis in rice plants subjected to salinity suggests improved salt tolerance due to reduced Na(+) root-to-shoot distribution.

Science.gov (United States)

Porcel, Rosa; Aroca, Ricardo; Azcon, Rosario; Ruiz-Lozano, Juan Manuel

2016-10-01

Rice is a salt-sensitive crop whose productivity is strongly reduced by salinity around the world. Plants growing in saline soils are subjected to the toxicity of specific ions such as sodium, which damage cell organelles and disrupt metabolism. Plants have evolved biochemical and molecular mechanisms to cope with the negative effects of salinity. These include the regulation of genes with a role in the uptake, transport or compartmentation of Na(+) and/or K(+). Studies have shown that the arbuscular mycorrhizal (AM) symbiosis alleviates salt stress in several host plant species. However, despite the abundant literature showing mitigation of ionic imbalance by the AM symbiosis, the molecular mechanisms involved are barely explored. The objective of this study was to elucidate the effects of the AM symbiosis on the expression of several well-known rice transporters involved in Na(+)/K(+) homeostasis and measure Na(+) and K(+) contents and their ratios in different plant tissues. Results showed that OsNHX3, OsSOS1, OsHKT2;1 and OsHKT1;5 genes were considerably upregulated in AM plants under saline conditions as compared to non-AM plants. Results suggest that the AM symbiosis favours Na(+) extrusion from the cytoplasm, its sequestration into the vacuole, the unloading of Na(+) from the xylem and its recirculation from photosynthetic organs to roots. As a result, there is a decrease of Na(+) root-to-shoot distribution and an increase of Na(+) accumulation in rice roots which seems to enhance the plant tolerance to salinity and allows AM rice plants to maintain their growing processes under salt conditions.

Theoretical study of the influence of intense femtosecond laser field on the evolution of the wave packet and the population of NaRb molecule

International Nuclear Information System (INIS)

Ning, Ma; Mei-Shan, Wang; Chuan-Lu, Yang; Xiao-Guang, Ma; De-Hua, Wang

2010-01-01

Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the population of ground and double-minimum electronic states of the NaRb molecule. For the different laser wavelengths, the evolution of the wave packet of 6 1 σ + state with time and internuclear distance is different, and the different laser intensity brings different influences on the population of the electronic states of the NaRb molecule. One can control the evolutions of wave packet and the population in each state by varying the laser parameters appropriately, which will be a benefit for the light manipulation of atomic and molecular processes. (atomic and molecular physics)

Synthesis of Na-A and/or Na-X zeolite/porous carbon composites from carbonized rice husk

International Nuclear Information System (INIS)

Katsuki, Hiroaki; Komarneni, Sridhar

2009-01-01

Na-A and/or Na-X zeolite/porous carbon composites were prepared under hydrothermal conditions by NaOH dissolution of silica first from carbonized rice husk followed by addition of NaAlO 2 and in situ crystallization of zeolites i.e., using a two-step process. When a one-step process was used, both Na-A and Na-X zeolites crystallized on the surface of carbon. Na-A or Na-X zeolite crystals were prepared on the porous carbonized rice husk at 90 deg. C for 2-6 h by changing the SiO 2 /Al 2 O 3 , H 2 O/Na 2 O and Na 2 O/SiO 2 molar ratios of precursors in the two-step process. The surface area and NH 4 + -cation exchange capacity (CEC) of Na-A zeolite/porous carbon were found to be 171 m 2 /g and 506 meq/100 g, respectively, while those of Na-X zeolite/porous carbon composites were 676 m 2 /g and 317 meq/100 g, respectively. Na-A and Na-X zeolites are well-known microporous and hydrophilic materials while carbonized rice husk was found to be mesoporous (pores of ∼3.9 nm) and hydrophobic. These hybrid microporous-mesoporous and hydrophilic-hydrophobic composites are expected to be useful for decontamination of metal cations as well as organic contaminants simultaneously. - Graphical Abstract: Novel Na-X zeolite/porous carbon composite.

Equilibrium chemical transformations in NaPO3 + NaCl melts

International Nuclear Information System (INIS)

Kovarskaya, E.N.; Rodionov, Yu.I.

1988-01-01

Because of the problems of the burial of solidified radioactive wastes into different geological rock formations, in particular into massives of rock-salt, the state of molten polyphosphate-chloride mixtures (taking into account the chemical character of the interaction of their components) for a prolonged period of time. The equilibrium products of the reaction in the NaPO 3 -NaCl system were studied in melts in air in the composition range of 30-70 mole % NaCl. It was shown that with increase in the NaCl content in the mixtures, the polyphosphate gradually depolymerizes to sodium tri-, di-, and monophosphates, and the composition of the equilibrium melts is dependent only on the ratio between the components in the initial molten mixtures. The time until the equilibrium is attained is shorter, the higher is the experimental temperature

Long-Range Effects of Na(+) Binding in Na,K-ATPase Reported by ATP.

Science.gov (United States)

Middleton, David A; Fedosova, Natalya U; Esmann, Mikael

2015-12-01

This paper addresses the question of long-range interactions between the intramembranous cation binding sites and the cytoplasmic nucleotide binding site of the ubiquitous ion-transporting Na,K-ATPase using (13)C cross-polarization magic-angle spinning (CP-MAS) solid-state nuclear magnetic resonance. High-affinity ATP binding is induced by the presence of Na(+) as well as of Na-like substances such as Tris(+), and these ions are equally efficient promoters of nucleotide binding. CP-MAS analysis of bound ATP with Na,K-ATPase purified from pig kidney membranes reveals subtle differences in the nucleotide interactions within the nucleotide site depending on whether Na(+) or Tris(+) is used to induce binding. Differences in chemical shifts for ATP atoms C1' and C5' observed in the presence of Na(+) or Tris(+) suggest alterations in the residues surrounding the bound nucleotide, hydrogen bonding, and/or conformation of the ribose ring. This is taken as evidence of a long-distance communication between the Na(+)-filled ion sites in the membrane interior and the nucleotide binding site in the cytoplasmic domain and reflects the first conformational change ultimately leading to phosphorylation of the enzyme. Stopped-flow fluorescence measurements with the nucleotide analogue eosin show that the dissociation rate constant for eosin is larger in Tris(+) than in Na(+), giving kinetic evidence of the difference in structural effects of Na(+) and Tris(+). According to the recent crystal structure of the E1·AlF4(-)·ADP·3Na(+) form, the coupling between the ion binding sites and the nucleotide side is mediated by, among others, the M5 helix.

Interaction between Na+/K+-pump and Na+/Ca2+-exchanger modulates intercellular communication.

Science.gov (United States)

Matchkov, Vladimir V; Gustafsson, Helena; Rahman, Awahan; Briggs Boedtkjer, Donna M; Gorintin, Sarah; Hansen, Anne Kirstine; Bouzinova, Elena V; Praetorius, Helle A; Aalkjaer, Christian; Nilsson, Holger

2007-04-13

Ouabain, a specific inhibitor of the Na(+)/K(+)-pump, has previously been shown to interfere with intercellular communication. Here we test the hypothesis that the communication between vascular smooth muscle cells is regulated through an interaction between the Na(+)/K(+)-pump and the Na(+)/Ca(2+)-exchanger leading to an increase in the intracellular calcium concentration ([Ca(2+)](i)) in discrete areas near the plasma membrane. [Ca(2+)](i) in smooth muscle cells was imaged in cultured rat aortic smooth muscle cell pairs (A7r5) and in rat mesenteric small artery segments simultaneously with force. In A7r5 coupling between cells was estimated by measuring membrane capacitance. Smooth muscle cells were uncoupled when the Na(+)/K(+)-pump was inhibited either by a low concentration of ouabain, which also caused a localized increase of [Ca(2+)](i) near the membrane, or by ATP depletion. Reduction of Na(+)/K(+)-pump activity by removal of extracellular potassium ([K(+)](o)) also uncoupled cells, but only after inhibition of K(ATP) channels. Inhibition of the Na(+)/Ca(2+)-exchange activity by SEA0400 or by a reduction of the equilibrium potential (making it more negative) also uncoupled the cells. Depletion of intracellular Na(+) and clamping of [Ca(2+)](i) at low concentrations prevented the uncoupling. The experiments suggest that the Na(+)/K(+)-pump may affect gap junction conductivity via localized changes in [Ca(2+)](i) through modulation of Na(+)/Ca(2+)-exchanger activity.

Computer simulation of aqueous Na-Cl electrolytes

Energy Technology Data Exchange (ETDEWEB)

Hummer, G. [Los Alamos National Lab., NM (United States); Soumpasis, D.M. [Max-Planck-Institut fuer Biophysikalische Chemie (Karl-Friedrich-Bonhoeffer-Institut), Goettingen (Germany); Neumann, M. [Vienna Univ. (Austria). Inst. fuer Experimentalphysik

1993-11-01

Equilibrium structure of aqueous Na-Cl electrolytes between 1 and 5 mol/l is studied by means of molecular dynamics computer simulation using interaction site descriptions of water and ionic components. Electrostatic interactions are treated both with the newly developed charged-clouds scheme and with Ewald summation. In the case of a 5 mol/l electrolyte, the results for pair correlations obtained by the two methods are in excellent agreement. However, the charged-clouds technique is much faster than Ewald summation and makes simulations at lower salt concentrations feasible. It is found that both ion-water and ion-ion correlation functions depend only weakly on the ionic concentration. Sodium and chloride ions exhibit only a negligible tendency to form contact pairs. In particular, no chloride ion pairs in contact are observed.

Computer simulation of aqueous Na-Cl electrolytes

International Nuclear Information System (INIS)

Hummer, G.; Soumpasis, D.M.; Neumann, M.

1993-01-01

Equilibrium structure of aqueous Na-Cl electrolytes between 1 and 5 mol/l is studied by means of molecular dynamics computer simulation using interaction site descriptions of water and ionic components. Electrostatic interactions are treated both with the newly developed charged-clouds scheme and with Ewald summation. In the case of a 5 mol/l electrolyte, the results for pair correlations obtained by the two methods are in excellent agreement. However, the charged-clouds technique is much faster than Ewald summation and makes simulations at lower salt concentrations feasible. It is found that both ion-water and ion-ion correlation functions depend only weakly on the ionic concentration. Sodium and chloride ions exhibit only a negligible tendency to form contact pairs. In particular, no chloride ion pairs in contact are observed

Molecular Dynamics Simulation Study of Carbon Dioxide, Methane, and Their Mixture in the Presence of Brine

KAUST Repository

Yang, Yafan; Nair, Arun Kumar Narayanan; Sun, Shuyu

2017-01-01

We perform molecular dynamics simulation study of CO2, methane, and their mixture in the presence of brine over a broad range of temperature (311–473 K), pressure (up to about 100 MPa), and NaCl concentration (up to about 14 wt %). The general

Intracellular Na(+) and metabolic modulation of Na/K pump and excitability in the rat suprachiasmatic nucleus neurons.

Science.gov (United States)

Wang, Yi-Chi; Yang, Jyh-Jeen; Huang, Rong-Chi

2012-10-01

Na/K pump activity and metabolic rate are both higher during the day in the suprachiasmatic nucleus (SCN) that houses the circadian clock. Here we investigated the role of intracellular Na(+) and energy metabolism in regulating Na/K pump activity and neuronal excitability. Removal of extracellular K(+) to block the Na/K pump excited SCN neurons to fire at higher rates and return to normal K(+) to reactivate the pump produced rebound hyperpolarization to inhibit firing. In the presence of tetrodotoxin to block the action potentials, both zero K(+)-induced depolarization and rebound hyperpolarization were blocked by the cardiac glycoside strophanthidin. Ratiometric Na(+) imaging with a Na(+)-sensitive fluorescent dye indicated saturating accumulation of intracellular Na(+) in response to pump blockade with zero K(+). The Na(+) ionophore monensin also induced Na(+) loading and hyperpolarized the membrane potential, with the hyperpolarizing effect of monensin abolished in zero Na(+) or by pump blockade. Conversely, Na(+) depletion with Na(+)-free pipette solution depolarized membrane potential but retained residual Na/K pump activity. Cyanide inhibition of oxidative phosphorylation blocked the Na/K pump to depolarize resting potential and increase spontaneous firing in most cells, and to raise intracellular Na(+) levels in all cells. Nonetheless, the Na/K pump was incompletely blocked by cyanide but completely blocked by iodoacetate to inhibit glycolysis, indicating the involvement of both oxidative phosphorylation and glycolysis in fueling the Na/K pump. Together, the results indicate the importance of intracellular Na(+) and energy metabolism in regulating Na/K pump activity as well as neuronal excitability in the SCN neurons.

Standardization of a molecular diagnostic method for Cucumber mosaic virus (cmv in Ecuadorian bananas

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Johanna Liseth Buitrón-Bustamante

2017-01-01

Full Text Available Several pests and diseases affect banana crop in Ecuador and Cucumber mosaic virus (cmv is one of the most important pathogens. The aim of this research was to standardize a new molecular approach to achieve a sensitive and highly specific detection of cmv in Ecuadorian bananas. Specific primers were designed from the sequence encodingResumoA cultura da banana no Equador vê-se afetada por uma série de doenças, das quais o cucumber mosaic vírus(cmv é um dos fitopatógenos mais impor-tantes. Com este estudo procurou-se padronizar uma técnica molecular para a detecção sensível e altamente específica deste agente viral na banana equatoriana. Para este fim, realizou-se o desenho de primers específicos, a partir da sequência que se codifica para a proteína da cápside do vírus. for the virus capsid protein. PC-F1, PC-R D1 and K-F primers, obtained from cDNA replicated from R NA of infected banana, allowed accurate virus detection by Reverse transcription and Hemi-nested PCR. Virus detection was possible even in asymptomatic plants, providing a tech-nology with potential use for the Ecuadorian banana producers.

Aspectos atuais da relação entre exercício físico, estresse oxidativo e magnésio Current aspects of the relationship between physical exercise, oxidative stress and magnesium

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Aline Guimarães Amorim

2008-10-01

Full Text Available Este trabalho visa a contribuir com informações atualizadas sobre a relação entre exercício, estresse oxidativo e magnésio. São escassos os trabalhos que discutem a produção de radicais livres nesse contexto. A deficiência de magnésio altera a fluidez das membranas celulares e mitocondriais e promove perturbações na homeostase do cálcio e na atividade das defesas antioxidantes. No exercício, a falta de magnésio nos tecidos musculares os torna mais suscetíveis à infiltração de macrófagos e neutrófilos e ao rompimento do sarcolema, dificultando o processo de regeneração e podendo ocasionar queda no desempenho físico. Conclui-se que o papel metabólico da deficiência de magnésio no estresse oxidativo induzido pelo exercício deve ser mais pesquisado, focalizando os seus efeitos na musculatura esquelética em indivíduos que praticam exercício regular e na deficiência marginal de magnésio.This article contributes to updated information about the relationship between exercise, oxidative stress and magnesium. There are few studies that discuss free radical production in this context. Magnesium deficiency alters cellular and mitochondrial membrane fluidity and promotes disturbances on calcium homeostasis and on the activity of antioxidant defenses. During exercise, lack of magnesium in muscle tissue turns them more susceptible to macrophage and neutrophil infiltration and to sarcolema damage, impairing the regeneration process and leading to decreased physical performance. In conclusion, the metabolic role of magnesium deficiency on exercise-induced oxidative stress should be further researched, focusing on its effects on skeletal muscle in individuals who practice regular physical exercise and in marginal magnesium deficiency.

Interaction of the model alkyltrimethylammonium ions with alkali halide salts: an explicit water molecular dynamics study

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M. Druchok

2013-01-01

Full Text Available We present an explicit water molecular dynamics simulation of dilute solutions of model alkyltrimethylammonium surfactant ions (number of methylene groups in the tail is 3, 5, 8, 10, and 12 in mixture with NaF, NaCl, NaBr, and NaI salts, respectively. The SPC/E model is used to describe water molecules. Results of the simulation at 298 K are presented in form of the radial distribution functions between nitrogen and carbon atoms of CH2 groups on the alkyltrimethylammonium ion, and the counterion species in the solution. The running coordination numbers between carbon atoms of surfactants and counterions are also calculated. We show that I- counterion exhibits the highest, and F- the lowest affinity to "bind" to the model surfactants. The results are discussed in view of the available experimental and simulation data for this and similar solutions.

Molecular Simulation of Adsorption in Microporous Materials

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Yiannourakou M.

2013-11-01

Full Text Available The development of industrial software, the decreasing cost of computing time, and the availability of well-tested forcefields make molecular simulation increasingly attractive for chemical engineers. We present here several applications of Monte-Carlo simulation techniques, applied to the adsorption of fluids in microporous solids such as zeolites and model carbons (pores < 2 nm. Adsorption was computed in the Grand Canonical ensemble with the MedeA®-GIBBS software, using energy grids to decrease computing time. MedeA®-GIBBS has been used for simulations in the NVT or NPT ensembles to obtain the density and fugacities of fluid phases. Simulation results are compared with experimental pure component isotherms in zeolites (hydrocarbon gases, water, alkanes, aromatics, ethanethiol, etc., and mixtures (methane-ethane, n-hexane-benzene, over a large range of temperatures. Hexane/benzene selectivity inversions between silicalite and Na-faujasites are well predicted with published forcefields, providing an insight on the underlying mechanisms. Also, the adsorption isotherms in Na-faujasites for light gases or ethane-thiol are well described. Regarding organic adsorbents, models of mature kerogen or coal were built in agreement with known chemistry of these systems. Obtaining realistic kerogen densities with the simple relaxation approach considered here is encouraging for the investigation of other organic systems. Computing excess sorption curves in qualitative agreement with those recently measured on dry samples of gas shale is also favorable. Although still preliminary, such applications illustrate the strength of molecular modeling in understanding complex systems in conditions where experiments are difficult.

Cluster models of aqueous Na{sup +} and Cl{sup -} in sea water/ice

Energy Technology Data Exchange (ETDEWEB)

Michelsen, R.; Walker, R. [Randolph-Macon College, Department of Chemistry (United States); Shillady, D., E-mail: quantummechanicsllc@msn.com [Virginia Commonwealth University, Department of Chemistry (United States)

2012-10-15

In this article, we present finite cluster models of aqueous solutes [NaCl(H{sub 2}O){sub 10}, NaCl(H{sub 2}O){sub 5}, and (H{sub 2}O){sub 6}] in terms of molecular geometry and vibrational spectra for interpretation of experimental infrared spectra of NaCl brine solutions. The quantum chemistry program GAMESS is used to optimize the model clusters to a local minimum energy gradient of less than 5.0d-6 hartrees/bohr with B3LYP in a gaussian basis of 6-31G(d,p). Harmonic frequencies are computed for comparison with the infrared spectra measured by attenuated total reflection of a temperature-controlled Ge plate under a layer of cold brine solution. The motivation for this research is to understand the mechanism by which freezing seawater excludes halide ions (mainly Cl{sup -}) and why the O-H stretching region of the spectra changes with temperature. Frost flowers, sea ice, and snow in marine environments contain concentrated halides in liquid brine at their surfaces which lead to catalytic destruction of low-altitude ozone in the polar regions of the Earth.

“Oxygen sensing” by Na,K-ATPase: these miraculous thiols

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Anna Bogdanova

2016-08-01

Full Text Available Control over the Na,K-ATPase function plays a central role in adaptation of the organisms to hypoxic and anoxic conditions. As the enzyme itself does not possess O2 binding sites its oxygen-sensitivity is mediated by a variety of redox-sensitive modifications including S-glutathionylation, S-nitrosylation and redox-sensitive phosphorylation. This is an overview of the current knowledge on the plethora of molecular mechanisms tuning the activity of the ATP-consuming Na,K-ATPase to the cellular metabolic activity. Recent findings suggest that oxygen-derived free radicals and H2O2, NO, and oxidised glutathione are the signalling messengers that make the Na,K-ATPase oxygen-sensitive. This very ancient signalling pathway targeting thiols of all three subunits of the Na,K-ATPase as well as redox-sensitive kinases sustains the enzyme activity at the optimal level avoiding terminal ATP depletion and maintaining the transmembrane ion gradients in cells of anoxia-tolerant species. We acknowledge the complexity of the underlying processes as we characterise the sources of reactive oxygen and nitrogen species production in hypoxic cells, and identify their targets, the reactive thiol groups which, upon modification, impact the enzyme activity. Structured accordingly, this review presents a summery on (i the sources of free radical production in hypoxic cells, (ii localisation of regulatory thiols within the Na,K-ATPase and the role reversible thiol modifications play in responses of the enzymes to a variety of stimuli (hypoxia, receptors’ activation control of the enzyme activity (iii redox-sensitive regulatory phosphorylation, and (iv the role of fine modulation of the Na,K-ATPase function in survival success under hypoxic conditions. The co-authors attempted to cover all the contradictions and standing hypotheses in the field and propose the possible future developments in this dynamic area of research, the importance of which is hard to overestimate

A simple, inexpensive device for nucleic acid amplification without electricity-toward instrument-free molecular diagnostics in low-resource settings.

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Paul LaBarre

2011-05-01

Full Text Available Molecular assays targeted to nucleic acid (NA markers are becoming increasingly important to medical diagnostics. However, these are typically confined to wealthy, developed countries; or, to the national reference laboratories of developing-world countries. There are many infectious diseases that are endemic in low-resource settings (LRS where the lack of simple, instrument-free, NA diagnostic tests is a critical barrier to timely treatment. One of the primary barriers to the practicality and availability of NA assays in LRS has been the complexity and power requirements of polymerase chain reaction (PCR instrumentation (another is sample preparation.In this article, we investigate the hypothesis that an electricity-free heater based on exothermic chemical reactions and engineered phase change materials can successfully incubate isothermal NA amplification assays. We assess the heater's equivalence to commercially available PCR instruments through the characterization of the temperature profiles produced, and a minimal method comparison. Versions of the prototype for several different isothermal techniques are presented.We demonstrate that an electricity-free heater based on exothermic chemical reactions and engineered phase change materials can successfully incubate isothermal NA amplification assays, and that the results of those assays are not significantly different from ones incubated in parallel in commercially available PCR instruments. These results clearly suggest the potential of the non-instrumented nucleic acid amplification (NINA heater for molecular diagnostics in LRS. When combined with other innovations in development that eliminate power requirements for sample preparation, cold reagent storage, and readout, the NINA heater will comprise part of a kit that should enable electricity-free NA testing for many important analytes.

Synthesis of zeolites Na-A and Na-X from tablet compressed and calcinated coal fly ash

Science.gov (United States)

Hu, Tao; Gao, Wenyan; Liu, Xin; Zhang, Yifu; Meng, Changgong

2017-10-01

Zeolites Na-A and Na-X are important synthetic zeolites widely used for separation and adsorption in industry. It is of great significance to develop energy-efficient routines that can synthesize zeolites Na-A and Na-X from low-cost raw materials. Coal fly ash (CFA) is the major residue from the combustion of coal and biomass containing more than 85% SiO2 and Al2O3, which can readily replace the conventionally used sodium silicate and aluminate for zeolite synthesis. We used Na2CO3 to replace the expensive NaOH used for the calcination of CFA and showed that tablet compression can enhance the contact with Na2CO3 for the activation of CFA through calcination for the synthesis of zeolites Na-A and Na-X under mild conditions. We optimized the control variables for zeolite synthesis and showed that phase-pure zeolite Na-A can be synthesized with CFA at reactant molar ratio, hydrothermal reaction temperature and reaction time of 1.3Na2O: 0.6Al2O3: 1SiO2: 38H2O at 80°C for 6 h, respectively, while phase-pure zeolite Na-X can be synthesized at 2.2Na2O: 0.2Al2O3: 1SiO2: 88H2O at 100°C for 8 h, respectively. The composition, morphology, specific surface area, vibration spectrum and thermogravimetry of synthesized Na-A and Na-X were further characterized.

The CERES / NA45 experiment

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Laurent Guiraud

2000-01-01

Ceres is one of the second generation heavy ion experiments at CERN's SPS. It is dedicated to the study of electron-positron pairs in relativistic nuclear collisions. NA45 is one of the seven experiments (NA44, NA45, NA49, NA50, NA52, WA97/NA57 and WA98) involved in CERN's Heavy Ion programme which provided evidence for the existence of a new state of matter, the quark-gluon plasma. In this state, quarks, instead of being bound up into more complex particles such as protons and neutrons, are liberated and roam freely. Theory predicts that this state must have existed at about 10 microseconds after the Big Bang, before the formation of matter as we know it today.

The rapid-onset dystonia parkinsonism mutation D923N of the Na+, K+-ATPase alpha3 isoform disrupts Na+ interaction at the third Na+ site.

Science.gov (United States)

Einholm, Anja Pernille; Toustrup-Jensen, Mads S; Holm, Rikke; Andersen, Jens Peter; Vilsen, Bente

2010-08-20

Rapid-onset dystonia parkinsonism (RDP), a rare neurological disorder, is caused by mutation of the neuron-specific alpha3-isoform of Na(+), K(+)-ATPase. Here, we present the functional consequences of RDP mutation D923N. Relative to the wild type, the mutant exhibits a remarkable approximately 200-fold reduction of Na(+) affinity for activation of phosphorylation from ATP, reflecting a defective interaction of the E(1) form with intracellular Na(+). This is the largest effect on Na(+) affinity reported so far for any Na(+), K(+)-ATPase mutant. D923N also affects the interaction with extracellular Na(+) normally driving the E(1)P to E(2)P conformational transition backward. However, no impairment of K(+) binding was observed for D923N, leading to the conclusion that Asp(923) is specifically associated with the third Na(+) site that is selective toward Na(+). The crystal structure of the Na(+), K(+)-ATPase in E(2) form shows that Asp(923) is located in the cytoplasmic half of transmembrane helix M8 inside a putative transport channel, which is lined by residues from the transmembrane helices M5, M7, M8, and M10 and capped by the C terminus, recently found involved in recognition of the third Na(+) ion. Structural modeling of the E(1) form of Na(+), K(+)-ATPase based on the Ca(2+)-ATPase crystal structure is consistent with the hypothesis that Asp(923) contributes to a site binding the third Na(+) ion. These results in conjunction with our previous findings with other RDP mutants suggest that a selective defect in the handling of Na(+) may be a general feature of the RDP disorder.

CO 2 adsorption in mono-, di- and trivalent cation-exchanged metal-organic frameworks: A molecular simulation study

KAUST Repository

Chen, Yifei; Nalaparaju, Anjaiah; Eddaoudi, Mohamed; JIANG, Jianwen

2012-01-01

A molecular simulation study is reported for CO 2 adsorption in rho zeolite-like metal-organic framework (rho-ZMOF) exchanged with a series of cations (Na +, K +, Rb +, Cs +, Mg 2+, Ca 2+, and Al 3+). The isosteric heat and Henry's constant

Proteasome Inhibition Contributed to the Cytotoxicity of Arenobufagin after Its Binding with Na, K-ATPase in Human Cervical Carcinoma HeLa Cells.

Science.gov (United States)

Yue, Qingxi; Zhen, Hong; Huang, Ming; Zheng, Xi; Feng, Lixing; Jiang, Baohong; Yang, Min; Wu, Wanying; Liu, Xuan; Guo, Dean

2016-01-01

Although the possibility of developing cardiac steroids/cardiac glycosides as novel cancer therapeutic agents has been recognized, the mechanism of their anticancer activity is still not clear enough. Toad venom extract containing bufadienolides, which belong to cardiac steroids, has actually long been used as traditional Chinese medicine in clinic for cancer therapy in China. The cytotoxicity of arenobufagin, a bufadienolide isolated from toad venom, on human cervical carcinoma HeLa cells was checked. And, the protein expression profile of control HeLa cells and HeLa cells treated with arenobufagin for 48 h was analyzed using two-dimensional electrophoresis, respectively. Differently expressed proteins in HeLa cells treated with arenobufagin were identified and the pathways related to these proteins were mapped from KEGG database. Computational molecular docking was performed to verify the binding of arenobufagin and Na, K-ATPase. The effects of arenobufagin on Na, K-ATPase activity and proteasome activity of HeLa cells were checked. The protein-protein interaction network between Na, K-ATPase and proteasome was constructed and the expression of possible intermediate proteins ataxin-1 and translationally-controlled tumor protein in HeLa cells treated with arenobufagin was then checked. Arenobufagin induced apoptosis and G2/M cell cycle arrest in HeLa cells. The cytotoxic effect of arenobufagin was associated with 25 differently expressed proteins including proteasome-related proteins, calcium ion binding-related proteins, oxidative stress-related proteins, metabolism-related enzymes and others. The results of computational molecular docking revealed that arenobufagin was bound in the cavity formed by the transmembrane alpha subunits of Na, K-ATPase, which blocked the pathway of extracellular Na+/K+ cation exchange and inhibited the function of ion exchange. Arenobufagin inhibited the activity of Na, K-ATPase and proteasome, decreased the expression of Na, K

Recikliranje plastenk na kreativen način

OpenAIRE

Pavlin, Suzana

2017-01-01

Plastenke, poleg ostalih plastičnih izdelkov, v zadnjih letih predstavljajo pravo katastrofo za okolje. Domnevamo, da se le redko kdo vpraša, kaj se zgodi z njo po tem, ko je iz nje zaužil še zadnjo kapljico vode. Plastenka je lahko kot večina ostalih komunalnih odpadkov ponovno uporabljena, reciklirana, sežgana ali odložena na deponijo. V primeru nespoštovanja Zakona o varstvu okolja pa pristane v naravi, pogosto v morju, kjer prav počasi razpada in negativno vpliva na celoten ekosistem. V d...

Plant Defensins NaD1 and NaD2 Induce Different Stress Response Pathways in Fungi

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Peter M. Dracatos

2016-09-01

Full Text Available Nicotiana alata defensins 1 and 2 (NaD1 and NaD2 are plant defensins from the ornamental tobacco that have antifungal activity against a variety of fungal pathogens. Some plant defensins interact with fungal cell wall O-glycosylated proteins. Therefore, we investigated if this was the case for NaD1 and NaD2, by assessing the sensitivity of the three Aspergillus nidulans (An O-mannosyltransferase (pmt knockout (KO mutants (An∆pmtA, An∆pmtB, and An∆pmtC. An∆pmtA was resistant to both defensins, while An∆pmtC was resistant to NaD2 only, suggesting NaD1 and NaD2 are unlikely to have a general interaction with O-linked side chains. Further evidence of this difference in the antifungal mechanism was provided by the dissimilarity of the NaD1 and NaD2 sensitivities of the Fusarium oxysporum f. sp. lycopersici (Fol signalling knockout mutants from the cell wall integrity (CWI and high osmolarity glycerol (HOG mitogen-activated protein kinase (MAPK pathways. HOG pathway mutants were sensitive to both NaD1 and NaD2, while CWI pathway mutants only displayed sensitivity to NaD2.

Mecanismos moleculares de ação anti-inflamatória e antioxidante de polifenóis de uvas e vinho tinto na aterosclerose

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M. Séfora-Sousa

2013-01-01

Full Text Available Este trabalho visa investigar os possíveis mecanismos moleculares de ação dos polifenóis de uvas e vinho tinto contra os processos oxidativos e inflamatórios envolvidos na aterosclerose. Trata-se de um estudo de revisão de literatura realizado por meio de buscas nas bases de dados PubMed e ScienceDirect utilizando os seguintes descritores: vinho tinto, uva, polifenóis, resveratrol, aterosclerose, LDL-oxidada, inflamação, estresse oxidativo, NF-kB, AP-1, Nrf2, SIRT-1, MicroRNA. Embora tais mecanismos ainda não estejam totalmente esclarecidos, os estudos indicam que compostos fenólicos presentes em uvas podem se complexar com metais (como ferro e cobre que provocam peroxidação dos lipídios, aumentam a atividade antioxidante do plasma, associam-se com a LDL-c aumentando sua resistência à oxidação, preservam a atividade da enzima paraoxonase, neutralizam radicais livres, e ativam fatores de transcrição como o Nrf2, que aumenta a expressão de genes que codificam proteínas importantes na defesa antioxidante, como a superóxido dismutase e a glutationa peroxidase. Além disso, os polifenóis inibem a fosforilação de MAP quinases, inibindo assim os fatores de transcrição NF-kB e AP-1 e, consequentemente, reduzindo a síntese do TNF-á, interleucinas, moléculas de adesão e quimiocinas. Também inibem a atividade das enzimas cicloxigenase e lipoxigenase. Outro mecanismo proposto é a ação do resveratrol sobre a atividade de deacetilases de histonas, como a SITR-1. Estas ações em conjunto reduzem a oxidação da LDL-c e o processo inflamatório, atenuando o processo aterogênico.

A patogênese genética e molecular da síndrome de Angelman

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Angelica Francesca Maris

2011-01-01

Full Text Available Objetivo: Fornecer uma revisão atualizada em língua portuguesa sobre a síndrome de Angelman, com ênfase nos mecanismos genéticos e moleculares dessa patologia, uma causa de deficiência mental severa que em alguns casos pode apresentar recorrência familiar. Método: Foi feita uma revisão bibliográfica utilizando a base de dados do PubMed, tendo como critérios de busca o termo "Angelman syndrome" isoladamente e combinado com "UBE3A", "clinical", "genetics" e "molecular" no título dos artigos. Dentre esses, foram selecionados artigos de revisão e artigos originais sobre a fisiopatologia da síndrome, com ênfase nos últimos dez anos. Resultados: Utilizando-se "Angelman syndrome" na busca, apareceram cerca de 1.100 artigos, incluindo 240 de revisão. Nos últimos dez anos são mais de 600 artigos, aproximadamente 120 de revisão, 50% dos quais publicados nos últimos cinco anos. Na base de dados SciELO, são apenas nove artigos sobre a síndrome, dos quais três em português e nenhum artigo atual de revisão. Conclusão: Após ter sido uma das principais causas que atraíram atenção ao estudo e ao entendimento dos mecanismos do imprinting genômico, a síndrome de Angelman está agora se revelando como uma patologia das sinapses. Apesar de o entendimento da fisiopatologia molecular da síndrome de Angelman ainda estar longe de ser compreendida, seu estudo está fornecendo uma visão extraordinária sobre os mecanismos que regem a plasticidade sináptica, novamente atraindo a atenção de pesquisadores que trabalham na fronteira do conhecimento.

Fluctuation-driven directional flow of energy in biochemical cycle: Electric activation of Na,K ATPase

Science.gov (United States)

Yow Tsong, Tian

1998-03-01

Na,K ATPase is an ion pump which uses chemical bond energy of ATP to pump Na ion out of, and K ion into living cell thus maintaining ionic and osmotic balances of the cell. Both are uphill transport reactions. Surprisingly we have found that electric energy can also substitute chemical energy to fuel the pump activity. However, in this case only electric fields of certain waveforms, amplitudes, and frequencies are effective. Waveform, amplitude and frequency are three elements of signal. In other words, Na,K ATPase can recognize, process, and harvest energy from an oscillating or a fluctuating electric field to drive an endergonic reaction. The enzyme is a molecular transducer of electric signal. This report will describe electric activation experiment to define electric signal. Electric signal will then mixed with electric noise of broad power spectrum for experiment. Effect of white noise (WN) on the efficiency of Na,K ATPase will be investigated. It will be shown that WN of appropriate power level can improve the pump efficiency when a sub-optimal electric field is used. WN can also carry a sub-threshold signal to cross over the threshold. Stochastic resonance will be discussed in reference to these observations.

Molecular Cloning and Functional Analysis of a Na+-Insensitive K+ Transporter of Capsicum chinense Jacq

Science.gov (United States)

Ruiz-Lau, Nancy; Bojórquez-Quintal, Emanuel; Benito, Begoña; Echevarría-Machado, Ileana; Sánchez-Cach, Lucila A.; Medina-Lara, María de Fátima; Martínez-Estévez, Manuel

2016-01-01

High-affinity K+ (HAK) transporters are encoded by a large family of genes and are ubiquitous in the plant kingdom. These HAK-type transporters participate in low- and high-affinity potassium (K+) uptake and are crucial for the maintenance of K+ homeostasis under hostile conditions. In this study, the full-length cDNA of CcHAK1 gene was isolated from roots of the habanero pepper (Capsicum chinense). CcHAK1 expression was positively regulated by K+ starvation in roots and was not inhibited in the presence of NaCl. Phylogenetic analysis placed the CcHAK1 transporter in group I of the HAK K+ transporters, showing that it is closely related to Capsicum annuum CaHAK1 and Solanum lycopersicum LeHAK5. Characterization of the protein in a yeast mutant deficient in high-affinity K+ uptake (WΔ3) suggested that CcHAK1 function is associated with high-affinity K+ uptake, with Km and Vmax for Rb of 50 μM and 0.52 nmol mg−1 min−1, respectively. K+ uptake in yeast expressing the CcHAK1 transporter was inhibited by millimolar concentrations of the cations ammonium (NH4+) and cesium (Cs+) but not by sodium (Na+). The results presented in this study suggest that the CcHAK1 transporter may contribute to the maintenance of K+ homeostasis in root cells in C. chinense plants undergoing K+-deficiency and salt stress. PMID:28083010

Complex basis functions for molecular resonances: Methodology and applications

Science.gov (United States)

White, Alec; McCurdy, C. William; Head-Gordon, Martin

The computation of positions and widths of metastable electronic states is a challenge for molecular electronic structure theory because, in addition to the difficulty of the many-body problem, such states obey scattering boundary conditions. These resonances cannot be addressed with naïve application of traditional bound state electronic structure theory. Non-Hermitian electronic structure methods employing complex basis functions is one way that we may rigorously treat resonances within the framework of traditional electronic structure theory. In this talk, I will discuss our recent work in this area including the methodological extension from single determinant SCF-based approaches to highly correlated levels of wavefunction-based theory such as equation of motion coupled cluster and many-body perturbation theory. These approaches provide a hierarchy of theoretical methods for the computation of positions and widths of molecular resonances. Within this framework, we may also examine properties of resonances including the dependence of these parameters on molecular geometry. Some applications of these methods to temporary anions and dianions will also be discussed.

Influence of incorporation method of sulfated zirconia in MCM-41 molecular sieve; Influencia do metodo de incorporacao da zirconia sulfatada na peneira molecular MCM-41

Energy Technology Data Exchange (ETDEWEB)

Pereira, C.E.; Santos, J.S.B.; Cavalcante, J.N.A.; Andrade, M.R.A.; Sousa, B.V., E-mail: eduardopereira.eq@gmail.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Centro de Ciencia e Tecnologia

2016-07-01

Sulfated metal oxides and sulfated zirconia have attracted great attention in recent years due to its high catalytic activity. The sulfated zirconia has the function of assigning the acidic material, through the formation of Bronsted acids and Lewis sites. The incorporation of sulfated zirconia in MCM-41 molecular sieve was carried out through the techniques: dry and wet. The wet process involves the use of an excess of solution on the volume of the support pores. Therefore, the concentration of the metal precursor on the support depends on the solution concentration and the pore volume of the support. In the process of incorporating by dry, the volume of the solution containing the precursor does not exceed the pore volume of the support. After either procedure, the impregnated support must be dried in order to allow the precursor compound can be converted into a catalytically active phase. This study aims to evaluate two methods of incorporation of sulfated zirconia in the mesoporous molecular sieve MCM-41. The process of merger took for wet and dry impregnation. Through the XRD patterns it was possible to identify the presence of the hexagonal structure of the molecular sieve, as well as the tetragonal and monoclinic phases of zirconia. From the spectroscopic analysis in the infrared region to the method the wet, it was possible to identify the vibrational frequencies related to the merger of sulfated zirconia in the MCM-41 structure of the molecular sieve. (author)

NA62 and NA48/2 results on search for Heavy Neutral Leptons

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Lamanna Gianluca

2018-01-01

Full Text Available In this paper we present new results on upper limits for the search of Heavy Neutral Leptons (HNL with data collected by NA48/2 (2003-2004, NA62-RK (2007 and NA62 (2015 CERN experiments. The data collected with different trigger configuration allow to search for both long and short living heavy neutrinos in the mass range below the kaon mass. In addition the status of the search for K+ → π+vv with the NA62 detector will be briefly presented.

Identification and phylogenetic analysis of Tityus pachyurus and Tityus obscurus novel putative Na+-channel scorpion toxins.

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Jimmy A Guerrero-Vargas

Full Text Available Colombia and Brazil are affected by severe cases of scorpionism. In Colombia the most dangerous accidents are caused by Tityus pachyurus that is widely distributed around this country. In the Brazilian Amazonian region scorpion stings are a common event caused by Tityus obscurus. The main objective of this work was to perform the molecular cloning of the putative Na(+-channel scorpion toxins (NaScTxs from T. pachyurus and T. obscurus venom glands and to analyze their phylogenetic relationship with other known NaScTxs from Tityus species.cDNA libraries from venom glands of these two species were constructed and five nucleotide sequences from T. pachyurus were identified as putative modulators of Na(+-channels, and were named Tpa4, Tpa5, Tpa6, Tpa7 and Tpa8; the latter being the first anti-insect excitatory β-class NaScTx in Tityus scorpion venom to be described. Fifteen sequences from T. obscurus were identified as putative NaScTxs, among which three had been previously described, and the others were named To4 to To15. The peptides Tpa4, Tpa5, Tpa6, To6, To7, To9, To10 and To14 are closely related to the α-class NaScTxs, whereas Tpa7, Tpa8, To4, To8, To12 and To15 sequences are more related to the β-class NaScTxs. To5 is possibly an arthropod specific toxin. To11 and To13 share sequence similarities with both α and β NaScTxs. By means of phylogenetic analysis using the Maximum Parsimony method and the known NaScTxs from Tityus species, these toxins were clustered into 14 distinct groups.This communication describes new putative NaScTxs from T. pachyurus and T. obscurus and their phylogenetic analysis. The results indicate clear geographic separation between scorpions of Tityus genus inhabiting the Amazonian and Mountain Andes regions and those distributed over the Southern of the Amazonian rainforest. Based on the consensus sequences for the different clusters, a new nomenclature for the NaScTxs is proposed.

Biologia molecular como ferramenta no esporte de alto rendimento: possibilidades e perspectivas

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Carlos Roberto Bueno Júnior

2010-05-01

Full Text Available Várias estratégias têm sido pensadas com o propósito de se utilizar a biologia molecular como ferramenta na pré-seleção e na seleção de talentos esportivos, na manipulação genética visando ao aumento ou à diminuição da produção de determinadas substâncias pelo organismo, na prescrição do treinamento e na recuperação de lesões. Portanto, o objetivo desta revisão é apresentar o DNA como regulador do funcionamento do organismo e de que forma alterações no perfil genético, tanto espontâneas como induzidas artificialmente, podem modular respostas fisiológicas e morfológicas por alterar a expressão de determinadas proteínas. Será dada especial atenção à descrição dos procedimentos utilizados para a manipulação genética, nos baixos riscos associados e nas estratégias que têm sido desenvolvidas com o objetivo de detectá-la. Com base em conhecimentos científicos, coerência e bom senso, diversas visões devem ser expostas e amplamente discutidas para ser definido o que é permitido e o que é proibido nas competições esportivas.

Transmural gradients in Na/K pump activity and [Na+]I in canine ventricle.

Science.gov (United States)

Gao, J; Wang, W; Cohen, I S; Mathias, R T

2005-09-01

There are well-documented differences in ion channel activity and action potential shape between epicardial (EPI), midmyocardial (MID), and endocardial (ENDO) ventricular myocytes. The purpose of this study was to determine if differences exist in Na/K pump activity. The whole cell patch-clamp was used to measure Na/K pump current (I(P)) and inward background Na(+)-current (I(inb)) in cells isolated from canine left ventricle. All currents were normalized to membrane capacitance. I(P) was measured as the current blocked by a saturating concentration of dihydro-ouabain. [Na(+)](i) was measured using SBFI-AM. I(P)(ENDO) (0.34 +/- 0.04 pA/pF, n = 17) was smaller than I(P)(EPI) (0.68 +/- 0.09 pA/pF, n = 38); the ratio was 0.50 with I(P)(MID) being intermediate (0.53 +/- 0.13 pA/pF, n = 19). The dependence of I(P) on [Na(+)](i) or voltage was essentially identical in EPI and ENDO (half-maximal activation at 9-10 mM [Na(+)](i) or approximately -90 mV). Increasing [K(+)](o) from 5.4 to 15 mM caused both I(P)(ENDO) and I(P)(EPI) to increase, but the ratio remained approximately 0.5. I(inb) in EPI and ENDO were nearly identical ( approximately 0.6 pA/pF). Physiological [Na(+)](i) was lower in EPI (7 +/- 2 mM, n = 31) than ENDO (12 +/- 3 mM, n = 29), with MID being intermediate (9 +/- 3 mM, n = 22). When cells were paced at 2 Hz, [Na(+)](i) increased but the differences persisted (ENDO 14 +/- 3 mM, n = 10; EPI 9 +/- 2 mM, n = 10; and MID intermediate, 11 +/- 2 mM, n = 9). Based on these results, the larger I(P) in EPI appears to reflect a higher maximum turnover rate, which implies either a larger number of active pumps or a higher turnover rate per pump protein. The transmural gradient in [Na(+)](i) means physiological I(P) is approximately uniform across the ventricular wall, whereas transporters that utilize the transmembrane electrochemical gradient for Na(+), such as Na/Ca exchange, have a larger driving force in EPI than ENDO.

Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

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Yang Li

Full Text Available Voltage-gated sodium (Nav channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions, a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group.

Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

Science.gov (United States)

Li, Yang; Liu, Huihui; Xia, Mengdie; Gong, Haipeng

2016-01-01

Voltage-gated sodium (Nav) channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions), a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh) to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group.

Validação de marcadores moleculares para resistência à giberela em genótipos brasileiros de trigo

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Adriana Scherloski

2015-01-01

Full Text Available O objetivo deste trabalho foi validar 19 marcadores microssatélites para resistência do trigo à giberela, em uma população não estruturada. Foram utilizados marcadores moleculares descritos na literatura como flanqueando QTLs de resistência à giberela em trigo, nos cromossomos 3B, 5A e 6B. Foram avaliadas 96 linhagens e cultivares de trigo quanto à severidade da infecção por giberela, em dois anos de avaliação. As linhagens e as cultivares foram genotipadas com 19 marcadores microssatélites. Os dados obtidos foram analisados pelo teste de Tukey e pelas análises de correlação, regressão linear simples e regressão múltipla; também foi estimada a eficiência de seleção dos marcadores moleculares. A severidade da doença variou de 1,95 a 41,3%, na média dos dois anos. Foram validados os QTLs nos três cromossomos avaliados. Os marcadores Xgwm389, Xgwm533, Xbarc180, Xbarc24, Wmc397, Xbarc101 e Wmc398 foram associados significativamente à resistência do trigo à giberela, tendo sido identificados alelos de resistência e de suscetibilidade. Os marcadores Wmc397, Xbarc101 (cromossomo 6B e Xbarc180 (cromossomo 5A têm potencial para uso na seleção assistida por marcadores moleculares, para resistência do trigo à giberela.

Reactions of metal oxides with molten NaPO3 + NaCl mixtures

International Nuclear Information System (INIS)

Kovarskaya, E.N.; Mityakhina, V.S.; Rodionov, Yu.I.; Silin, M.Yu.

1988-01-01

We consider the dissolution mechanism for iron (III), europium(III), and tin(IV) oxides in molten NaPO 3 + NaCl that are responsible for the peak solubilities. We chose Fe 2 O 3 as the basic material since this occurs in large amounts around damaged metal structures in rock salt mines in a proposed zone for storing vitrified radioactive wastes. Solubility measurement and paper chromatography show that Fe 2 O 3 dissolves in molten NaPO 3 + NaCl in air by reaction with the solvent to give double iron and sodium diphosphates and monophosphates in accordance with the initial solution-in-the-melt composition, the degree of equilibration, and the temperature. The elevated solubilities for initial NaCl contents close to 30 mole % are due to sodium triphosphates and tricyclophosphates present in these melts. Moessbauer spectroscopy confirms that double iron, europium and tin diphosphates and monophosphates containing sodium occur in these chloride-polyphosphate melts

P-type single-crystalline ZnO films obtained by (Na,N) dual implantation through dynamic annealing process

Science.gov (United States)

Zhang, Zhiyuan; Huang, Jingyun; Chen, Shanshan; Pan, Xinhua; Chen, Lingxiang; Ye, Zhizhen

2018-02-01

Single-crystalline ZnO films were grown by plasma-assisted molecular beam epitaxy technique on c-plane sapphire substrates. The films have been implanted with fixed fluence of 130 keV Na and 90 keV N ions at 460 °C. It is observed that dually-implanted single crystalline ZnO films exhibit p-type characteristics with hole concentration in the range of 1.24 × 1016-1.34 × 1017 cm-3, hole mobilities between 0.65 and 8.37 cm2 V-1 s-1, and resistivities in the range of 53.3-80.7 Ω cm by Hall-effect measurements. There are no other secondary phase appearing, with (0 0 2) (c-plane) orientation after ion implantation as identified by the X-ray diffraction pattern. It is obtained that Na and N ions were successfully implanted and activated as acceptors measured by XPS and SIMS results. Also compared to other similar studies, lower amount of Na and N ions make p-type characteristics excellent as others deposited by traditional techniques. It is concluded that Na and N ion implantation and dynamic annealing are essential in forming p-type single-crystalline ZnO films.

Na(+),K (+)-ATPase as a docking station: protein-protein complexes of the Na(+),K (+)-ATPase.

Science.gov (United States)

Reinhard, Linda; Tidow, Henning; Clausen, Michael J; Nissen, Poul

2013-01-01

The Na(+),K(+)-ATPase, or sodium pump, is well known for its role in ion transport across the plasma membrane of animal cells. It carries out the transport of Na(+) ions out of the cell and of K(+) ions into the cell and thus maintains electrolyte and fluid balance. In addition to the fundamental ion-pumping function of the Na(+),K(+)-ATPase, recent work has suggested additional roles for Na(+),K(+)-ATPase in signal transduction and biomembrane structure. Several signaling pathways have been found to involve Na(+),K(+)-ATPase, which serves as a docking station for a fast-growing number of protein interaction partners. In this review, we focus on Na(+),K(+)-ATPase as a signal transducer, but also briefly discuss other Na(+),K(+)-ATPase protein-protein interactions, providing a comprehensive overview of the diverse signaling functions ascribed to this well-known enzyme.

Characterization of Na+-linked and Na+-independent Cl-/HCO3- exchange systems in Chinese hamster lung fibroblasts

International Nuclear Information System (INIS)

Cassel, D.; Scharf, O.; Rotman, M.; Cragoe, E.J. Jr.; Katz, M.

1988-01-01

The PS120 variant of Chinese hamster lung fibroblasts which lacks Na + /H + exchange activity was used to investigate bicarbonate transport systems and their role in intracellular pH (pH/sub i/) regulation. When pH/sub i/ was decreased by acid load, bicarbonate caused pH/sub i/ increase and stimulated 36 Cl - efflux from the cells, both in a Na + -dependent manner. These results together with previous findings that bicarbonate stimulates 22 Na + uptake in PS120 cells demonstrate the presence of a Na + -linked Cl - /HCO 3 - exchange system. In cells with normal initial pH/sub i/, bicarbonate caused Na + -independent pH/sub i/ increase in Cl - -free solutions and stimulated Na + -independent 36 Cl - efflux, indicating that a Na + -independent Cl - /HCO 3 - exchanger is also present in the cell. Na + -linked and Na + -independent Cl - /HCO 3- exchange is apparently mediated by two distinct systems, since a [(tetrahydrofluorene-7-yl)oxy]acetic acid derivative selectively inhibits the Na + -independent exchanger. An additional distinctive features is a 10-fold lower affinity for chloride of the Na + -linked exchanger. The Na + -linked and Na + -independent Cl - /HCO 3 - exchange systems are likely to protect the cell from acid and alkaline load, respectively

Caracterização molecular de Staphylococcus spp. coagulase-negativos isolados do molusco bivalve Anomalocardia brasiliana (GMELIN, 1791).

OpenAIRE

Jacqueline Ellen Camelo Batista

2013-01-01

A espécie Anomalocardia brasiliana é encontrada em abundância nas praias da costa brasileira e bastante apreciada na culinária nordestina. Neste estudo, objetivou-se a caracterização molecular de enterotoxinas e do gene de resistência mecA de Staphylococcus spp. coagulase-negativos isolados de amostras da carne de A. brasiliana na região metropolitana do Recife, Brasil. Isolados de amostras in natura (n=9), coletados no balneário de Mangue Seco, Igarassu-PE, foram identificados como Staphyloc...

High-resolution internal state control of ultracold 23Na87Rb molecules

Science.gov (United States)

Guo, Mingyang; Ye, Xin; He, Junyu; Quéméner, Goulven; Wang, Dajun

2018-02-01

We report the full internal state control of ultracold 23Na87Rb molecules, including vibrational, rotational, and hyperfine degrees of freedom. Starting from a sample of weakly bound Feshbach molecules, we realize the creation of molecules in single hyperfine levels of both the rovibrational ground and excited states with a high-efficiency and high-resolution stimulated Raman adiabatic passage. This capability brings broad possibilities for investigating ultracold polar molecules with different chemical reactivities and interactions with a single molecular species. Moreover, starting from the rovibrational and hyperfine ground state, we achieve rotational and hyperfine control with one- and two-photon microwave spectroscopy to reach levels not accessible by the stimulated Raman transfer. The combination of these two techniques results in complete control over the internal state of ultracold polar molecules, which paves the way to study state-dependent molecular collisions and state-controlled chemical reactions.

Rapid Formation of Molecular Bromine from Deliquesced NaBr Aerosol in the Presence of Ozone and UV Light

Science.gov (United States)

The formation of gas-phase bromine from aqueous sodium bromide aerosols is investigated through a combination of chamber experiments and chemical kinetics modeling. Experiments show that Br2(g) is produced rapidly from deliquesced NaBr aerosols in the presence of OH radicals prod...

Thermal and single frequency counter-current ultrasound pretreatments of sodium caseinate: enzymolysis kinetics and thermodynamics, amino acids composition, molecular weight distribution and antioxidant peptides.

Science.gov (United States)

Abdualrahman, Mohammed Adam Y; Ma, Haile; Zhou, Cunshan; Yagoub, Abu ElGasim A; Hu, Jiali; Yang, Xue

2016-12-01

Due to the disadvantages of traditional enzymolysis, pretreatments are crucial to enhance protein enzymolysis. Enzymolysis kinetics and thermodynamics, amino acids composition, molecular weight distribution, fluorescence spectroscopy and antioxidant activity of thermal (HT) and single frequency counter-current ultrasound (SCFU) pretreated sodium caseinate (NaCas) were studied. Enzymolysis of untreated NaCas (control) improved significantly (P < 0.05) by SFCU and followed by HT. Values of the Michaelis-Menten constant (K M ) of SFCU and HT were 0.0212 and 0.0250, respectively. HT and SFCU increased (P < 0.05) the reaction rate constant (k) by 38.64 and 90.91%, respectively at 298 K. k values decreased with increasing temperature. The initial activation energy (46.39 kJ mol -1 ) reduced (P < 0.05) by HT (39.66 kJ mol -1 ) and further by SFCU (33.42 kJ mol -1 ). SFCU-pretreated NaCas hydrolysates had the highest contents of hydrophobic, aromatic, positively and negatively charged amino acids. Medium-sized peptides (5000-1000 Da) are higher in SFCU (78.11%) than HT and the control. SFCU induced molecular unfolding of NaCas proteins. Accordingly, SFCU-pretreated NaCas hydrolysate exhibited the highest scavenging activity on DPPH and hydroxyl radicals, reducing power, and iron chelating ability. SFCU pretreatment would be a useful tool for production of bioactive peptides from NaCas hydrolysate. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Functional characterization of the NhaA Na+/H+ antiporter from the green picoalga Ostreococcus tauri.

Science.gov (United States)

Dawut, Keatisuda; Sirisattha, Sophon; Hibino, Takashi; Kageyama, Hakuto; Waditee-Sirisattha, Rungaroon

2018-07-01

Transmembrane ion transport is a critical process in the cellular response to salt stress. Among the known functional membrane transporters that are involved in the salt stress response, Na + /H + antiporters have been extensively studied. These ubiquitous membrane proteins are crucial for salt tolerance and are associated with the regulation of internal pH, cell volume, morphogenesis, and vesicular trafficking. Molecular and functional analyses of Na + /H + antiporters have been characterized among taxa but little is known about algal Na + /H + antiporters. Here, we analyzed putative Na + /H + antiporters from the complete genome sequence of the marine picoalga Ostreococcus tauri. At least 10 putative Na + /H + antiporters belonging to the SOS1, NHX, and KEA/Kef families were found. Surprisingly, a bacterial type NhaA sequence (OtNhaA) was also found. Topological modeling of OtNhaA predicted 12 possible transmembrane segments with a long N-terminus. The full-length (FL_OtNhaA) and N-terminal truncated (ΔN112_OtNhaA) versions of OtNhaA were constructed, expressed in the salt-sensitive mutant Escherichia coli TO114, and functionally characterized. Complementation analysis revealed that FL_OtNhaA- and ΔN112_OtNhaA-expressing cells exhibited increased tolerance to high NaCl concentrations up to 700 mM. Antiporter activity assays showed that both FL_OtNhaA and ΔN112_OtNhaA proteins predominantly exhibited Na + /H + and Ca 2+ /H + antiporter activities at alkaline pH conditions. Intriguingly, the ΔN112_OtNhaA exhibited higher Na + /H + and Ca 2+ /H + antiporter activities compared to FL_OtNhaA. Kinetic analysis revealed that FL_OtNhaA has a high affinity for Na + and Ca 2+ ions with a K m of 1.1 ± 0.23 mM for Na + (at pH 8.5) and a K m of 0.3 ± 0.07 mM for Ca 2+ (at pH 8.5). Since NhaA has shown striking diversity among taxa, our results provide insight into the functional properties of the algal NhaA Na + /H + antiporter. These results will

Subnitride chemistry: A first-principles study of the NaBa3N, Na5Ba3N, and Na16Ba6N phases

International Nuclear Information System (INIS)

Oliva, Josep M.

2005-01-01

An ab initio study on the electronic structure of the subnitrides NaBa 3 N, Na 5 Ba 3 N, and Na 16 Ba 6 N is performed for the first time. The NaBa 3 N and Na 5 Ba 3 N phases consist of infinite 1 ∞ [NBa 6/2 ] strands composed of face-sharing NBa 6 octahedra surrounded by a 'sea' of sodium atoms. The Na 16 Ba 6 N phase consist of discrete [NBa 6 ] octahedra arranged in a body-cubic fashion, surrounded by a 'sea' of sodium atoms. Our calculations suggest that the title subnitrides are metals. Analysis of the electronic structure shows partial interaction of N(2s) with Ba(5p) electrons in the lower energy region for NaBa 3 N and Na 5 Ba 3 N. However, no dispersion is observed for the N(2s) and Ba(5p) bands in the cubic phase Na 16 Ba 6 N. The metallic band below the Fermi level shows a strong mixing of N(2p), Ba(6s), Ba(5d), Ba(6p), Na(3s) and Na(3p) orbitals. The metallic character in these nitrides stems from delocalized electrons corresponding to hybridized 5d l 6s m 6p n barium orbitals which interact with hybridized 3s n 3p m sodium orbitals. Analysis of the electron density and electronic structure in these nitrides shows two different regions: a metallic matrix corresponding to the sodium atoms and the regions around them and heteropolar bonding between nitrogen and barium within the infinite 1 ∞ [NBa 6/2 ] strands of the NaBa 3 N and Na 5 Ba 3 N phases, and within the isolated [NBa 6 ] octahedra of the Na 16 Ba 6 N phase. The nitrogen atoms inside the strands and octahedra are negatively charged, the anionic character of nitrogens being larger in the isolated octahedra of the cubic phase Na 16 Ba 6 N, due to the lack of electron delocalization along one direction as opposed to the other phases. The sodium and barium atoms appear to be slightly negatively and positively charged, the latter to a larger extent. From the computed Ba-N overlap populations as well as the analysis of the contour maps of differences between total density and superposition of

WPŁYW WIEKU NA WYTRZYMAŁOŚĆ NA ŚCISKANIE BETONU MODYFIKOWANEGO DODATKIEM METAKAOLINITU

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Janusz KONKOL

Full Text Available W artykule przedstawiono wyniki badań wytrzymałości na ściskanie betonów modyfikowanych dodatkiem metakaolinitu po 2, 3, 7, 14, 28 i 56 dniach dojrzewania. Dodatek metakaolinitu użyto jako częściowy substytut cementu, dokonując wymiany 10% masy cementu na metakaolinit. Udział ten uznawany jest za optymalny z uwagi na inne niż wytrzymałość na ściskanie właściwości betonu, w tym trwałość betonu modyfikowanego metakaolinitem. Badania przeprowadzono także dla betonu tła, betonu bez dodatku metakaolinitu. Betony wykonano przy założeniu stałego stosunku woda/spoiwo, względnie woda/cement wynoszącego 0,45 oraz przy użyciu cementu portlandzkiego CEM I 32,5R, piasku kwarcowego frakcji do 2 mm oraz grysu bazaltowego frakcji do 16 mm. W celu uzyskania pożądanej konsystencji mieszanki betonowej zastosowano upłynniacz na bazie estrów polikarboksylowych. Uzyskane rezultaty badań potwierdziły wysoką aktywność pucolanową metakaolinitu już we wczesnym okresie dojrzewania betonu. W okresie między 3 a 7 dniem dojrzewania stwierdzono wolniejszy przyrost wytrzymałości na ściskanie w betonie niemodyfikowanym metakaolinitem, podczas gdy w betonie, w którym 10% masy cementu zastąpiono metakaolinitem uwidocznił się znaczący przyrost wytrzymałości na ściskanie. Po 2 dniach dojrzewania wytrzymałość na ściskanie betonu tła była nieznacznie wyższa od wytrzymałości na ściskanie betonu modyfikowanego. Korzystny wpływ dodatku metakaolinitu wynikający z jego wysokiej aktywności pucolanowej, jak również z uszczelniającego charakteru tego dodatku obserwowano jest zwłaszcza w okresie między 3 a 14 dniem dojrzewania. W tym okresie obserwowano znaczny przyrost wytrzymałości na ściskanie betonu modyfikowanego w porównaniu z wytrzymałością na ściskanie betonu tła. Po 7 i 14 dniach dojrzewania stwierdzono odpowiednio prawie 25% i 21% wzrost wytrzymałości na ściskanie na skutek użycia metakaolinitu.

Teratological studies of DTPA-CaNa3, DTPA-ZnNa3 and quinamic acid in mice

International Nuclear Information System (INIS)

Luo Meichu; Ruan Tianming; Tong Shungao

1989-01-01

DTPA-CaNa 3 , DTPA-ZnNa 3 and quinamic acid are effective chelating agents for removing actinide elements from the body. In this experiment, different doses of DTPA-CaNa 3 , DTPA-ZnNa 3 and quinamic acid were given to mice on gestation days 6-10. Eight groups of mice received 0.8 and 2.0 mM/kg of DTPA-CaNa 3 , 3.8, 7.6, and 11.4 mM/kg of DTPA-ZnNa 3 and 0.42, 2.1, and 4.2 mM/kg of quinamic acid. Hypetonic saline and isotonic saline were given to two control groups. DTPA-CaNa 3 and quinamidic acid were found to be much more toxic to fetus of mice than DTPA-ZnNa 3 . When the doses of DTPA-CaMa 3 and quinamidic acid were 20 times higher than the human dose, the number of resorbed fetus was increased and the number and weight of live fetus were reduced. The result of injection with 7.6 mM/kg (200 times of human dose)DTPA-ZnNa 3 and that of injection with isotonic saline are the same. Therefore, we suggest that the DTPA-CaNa 3 and quinamidic acid should not be given to pregnant woman, if chelation therapy is needed, while the much safer DTPA-ZnNa 3 could be used

Position of the third Na+ site in the aspartate transporter GltPh and the human glutamate transporter, EAAT1.

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Turgut Bastug

Full Text Available Glutamate transport via the human excitatory amino acid transporters is coupled to the co-transport of three Na(+ ions, one H(+ and the counter-transport of one K(+ ion. Transport by an archaeal homologue of the human glutamate transporters, Glt(Ph, whose three dimensional structure is known is also coupled to three Na(+ ions but only two Na(+ ion binding sites have been observed in the crystal structure of Glt(Ph. In order to fully utilize the Glt(Ph structure in functional studies of the human glutamate transporters, it is essential to understand the transport mechanism of Glt(Ph and accurately determine the number and location of Na(+ ions coupled to transport. Several sites have been proposed for the binding of a third Na(+ ion from electrostatic calculations and molecular dynamics simulations. In this study, we have performed detailed free energy simulations for Glt(Ph and reveal a new site for the third Na(+ ion involving the side chains of Threonine 92, Serine 93, Asparagine 310, Aspartate 312, and the backbone of Tyrosine 89. We have also studied the transport properties of alanine mutants of the coordinating residues Threonine 92 and Serine 93 in Glt(Ph, and the corresponding residues in a human glutamate transporter, EAAT1. The mutant transporters have reduced affinity for Na(+ compared to their wild type counterparts. These results confirm that Threonine 92 and Serine 93 are involved in the coordination of the third Na(+ ion in Glt(Ph and EAAT1.

O papel do fator nuclear eritróide 2 relacionado ao fator 2 (Nrf2 no diabetes mellitus

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Gabriela Fernandes Hahn

2017-09-01

Full Text Available O diabetes mellitus (DM é uma doença metabólica complexa. Sua etiologia é atribuída a uma combinação entre fatores genéticos, ambientais e de estilo de vida. Contudo, sabe-se que o estresse oxidativo desempenha papel crucial na patogênese do DM, acarretando em disfunção das células β pancreáticas e resistência à insulina. Neste contexto, o fator nuclear eritroide 2 relacionado ao fator 2 (Nrf2 é considerado o regulador mestre da resposta antioxidante do organismo, sendo um mecanismo de importância crítica para a manutenção da homeostase e sobrevivência celular. Todavia, a função do Nrf2 não se limita somente à resposta antioxidante. Ao interagir com outras vias metabólicas, o Nrf2 possui importante papel na regulação do metabolismo, atuando no metabolismo dos lipídios, manutenção da glicemia, resposta inflamatória, entre outros. Entretanto, a exata relação do Nrf2 com outras vias metabólicas ainda não é totalmente conhecida. Contudo, sabe-se que o comprometimento da função do Nrf2 é evidente na fisiopatologia do DM bem como no desenvolvimento de suas complicações clínicas. A ativação do Nrf2 protege contra os danos mediados pelo DM, podendo ser adequada uma intervenção exógena para aumentar a sua atividade. Palavras-chave: Complicações do diabetes; estresse oxidativo; antioxidantes; inflamação; obesidade

Efeitos embriotóxicos do tratamento pré-natal com extrato aquoso de Ipomoea carnea em ratos

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Rosana Zoriki Hosomi

2008-02-01

Full Text Available Os efeitos embriotóxicos da exposição diária pré-natal a 0,0, 0,7, 3,0 ou 15,0mg/kg do extrato aquoso da I. carnea nos dias 5 a 21 de gestação foram estudados. Foram avaliados a performance reprodutiva materna, anormalidades esqueléticas e viscerais e malformações. Além disso, após o tratamento foram encontrados achados anatomopatológicos. Em relação às ratas mães, nossos resultados mostraram que a exposição às diferentes doses não afetou o peso corporal, ganho de peso, consumos de água e ração e performance reprodutiva. Apesar disso, apresentaram vacuolização citoplasmática de forma dose-dependente em fígado, rins, tireóide e glândula adrenal. Exames fetais não mostraram anormalidades externas ou malformações, sendo somente encontradas evidências de anormalidades esqueléticas e viscerais após altas doses do extrato. Foi observada redução dos centros de ossificação. Os presentes dados mostram que a ingestão prenatal do extrato de I. carnea induz embriotoxicidade. Estes efeitos são atribuídos à ação na homeostase maternal ou diretamente na concepção.

Na-ion dynamics in Quasi-1D compound NaV2O4

International Nuclear Information System (INIS)

Månsson, M; Umegaki, I; Nozaki, H; Higuchi, Y; Sugiyama, J; Kawasaki, I; Watanabe, I; Sakurai, H

2014-01-01

We have used the pulsed muon source at ISIS to study high-temperature Na-ion dynamics in the quasi-one-dimensional (Q1D) metallic antiferromagnet NaV 2 O 4 . By performing systematic zero-field and longitudinal-field measurements as a function of temperature we clearly distinguish that the hopping rate increases exponentially above T diff ≈ 250 K. The data is well fitted to an Arrhenius type equation typical for a diffusion process, showing that the Na-ions starts to be mobile above T diff . Such results make this compound very interesting for the tuning of Q1D magnetism using atomic-scale ion-texturing through the periodic potential from ordered Na-vacancies. Further, it also opens the door to possible use of NaV 2 O 4 and related compounds in energy related applications

Energy decomposition analysis of the interactions in adduct ions of acetophenone and Na+, NH4+ and H+ in the gas phase

Science.gov (United States)

Sugimura, Natsuhiko; Igarashi, Yoko; Aoyama, Reiko; Shibue, Toshimichi

2017-09-01

The physical origins of the interactions in the acetophenone cation adducts [M+Na]+, [M+NH4]+, and [M+H]+ were explored by localized molecular orbital-energy decomposition analysis and density functional theory. The analyses highlighted the differences in the interactions in the three adduct ions. Electrostatic energy was important in [M+Na]+ and there was little change in the acetophenone orbital shape. Both electrostatic and polarization energy were important in [M+NH4]+, and a considerable change in the orbital shape occurred to maximize the strength of the hydrogen bond. Polarization energy was the major attractive force in [M+H]+.

O Passeio Público do Rio de Janeiro na Literatura, na Pintura e na Fotografia do Século XIX

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Solange de Aragão

2012-06-01

Full Text Available Este artigo tem como objetivo geral e mais amplo chamar a atenção dos pesquisadores para a importância da literatura, da pintura e da fotografia como fontes documentais para a construção da História do Paisagismo no Brasil por meio de um estudo de caso muito particular: o Passeio Público do Rio de Janeiro no século XIX. São objetivos específicos apresentar e analisar o modo como esse espaço livre público aparece na literatura, na pintura e na fotografia desse período, considerando suas transformações paisagísticas.

Unraveling the Root Proteome Changes and Its Relationship to Molecular Mechanism Underlying Salt Stress Response in Radish (Raphanus sativus L.

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Xiaochuan Sun

2017-07-01

Full Text Available To understand the molecular mechanism underlying salt stress response in radish, iTRAQ-based proteomic analysis was conducted to investigate the differences in protein species abundance under different salt treatments. In total, 851, 706, and 685 differential abundance protein species (DAPS were identified between CK vs. Na100, CK vs. Na200, and Na100 vs. Na200, respectively. Functional annotation analysis revealed that salt stress elicited complex proteomic alterations in radish roots involved in carbohydrate and energy metabolism, protein metabolism, signal transduction, transcription regulation, stress and defense and transport. Additionally, the expression levels of nine genes encoding DAPS were further verified using RT-qPCR. The integrative analysis of transcriptomic and proteomic data in conjunction with miRNAs was further performed to strengthen the understanding of radish response to salinity. The genes responsible for signal transduction, ROS scavenging and transport activities as well as several key miRNAs including miR171, miR395, and miR398 played crucial roles in salt stress response in radish. Based on these findings, a schematic genetic regulatory network of salt stress response was proposed. This study provided valuable insights into the molecular mechanism underlying salt stress response in radish roots and would facilitate developing effective strategies toward genetically engineered salt-tolerant radish and other root vegetable crops.

Solubility of NaNd(CO3)2.6H2O(c) in concentrated Na2CO3 and NaHCO3 solutions

International Nuclear Information System (INIS)

Rao, L.; Rai, D.; Felmy, A.R.; Fulton, R.W.; Novak, C.F.

1996-01-01

NaNd(CO 3 ) 2 x 6 H 2 O(c) was identified to be the final equilibrium solid phase in suspensions containing concentrated sodium carbonate (0.1 to 2.0 M) and sodium bicarbonate (0.1 to 1.0 M), with either NaNd(CO 3 ) 2 x 6 H 2 O(c) or Nd 2 (CO 3 ) 3 x xH 2 O(s) as initial solids. A thermodynamic model, based on Pitzer's specific into-interaction approach, was developed to interpret the solubility of NaNd(CO 3 ) 2 x 6 H 2 O(c) as functions of sodium carbonate and sodium bicarbonate concentrations. In this model, the solubility data of NaNd(CO 3 ) 2 x 6 H 2 O(c) were explained by assuming the formation of NdCO 3 + , Nd(CO 3 ) 2 - and Nd(CO 3 ) 3 3- species and invoking the specific ion interactions between Na + and Nd(CO 3 ) 3 3- . Ion interaction parameters for Na + -Nd(CO 3 ) 3 3- were developed to fit the solubility data. Based on the model calculations, Nd(CO 3 ) 3 3- was the predominant aqueous neodymium species in 0.1 to 2 M sodium carbonate and 0.1 to 1 M sodium bicarbonate solutions. The logarithm of the NaNd(CO 3 ) 2 x 6 H 2 O solubility product (NaNd(CO 3 ) 2 x 6 H 2 O(c)=Na + +Nd 3+ +2 CO 3 2- +6 H 2 O) was calculated to be -21.39. This model also provided satisfactory interpretation of the solubility data of the analogous Am(III) system in less concentrated carbonate and bicarbonate solutions. (orig.)

Identification of conserved prolyl residue important for transport activity and the substrate specificity range of yeast plasma membrane Na(+)/H(+) antiporters

Czech Academy of Sciences Publication Activity Database

Zimmermannová, Olga; Zavřel, Martin; Sychrová, Hana

2005-01-01

Roč. 280, č. 34 (2005), s. 30638-30647 ISSN 0021-9258 R&D Projects: GA ČR(CZ) GP204/02/D092 Institutional research plan: CEZ:AV0Z5011922 Keywords : yeast * Na+/H+ antiporter * substrate specificity Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.854, year: 2005

Molecular Surface of JZTX-V (β-Theraphotoxin-Cj2a Interacting with Voltage-Gated Sodium Channel Subtype NaV1.4

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Ji Luo

2014-07-01

Full Text Available Voltage-gated sodium channels (VGSCs; NaV1.1–NaV1.9 have been proven to be critical in controlling the function of excitable cells, and human genetic evidence shows that aberrant function of these channels causes channelopathies, including epilepsy, arrhythmia, paralytic myotonia, and pain. The effects of peptide toxins, especially those isolated from spider venom, have shed light on the structure–function relationship of these channels. However, most of these toxins have not been analyzed in detail. In particular, the bioactive faces of these toxins have not been determined. Jingzhaotoxin (JZTX-V (also known as β-theraphotoxin-Cj2a is a 29-amino acid peptide toxin isolated from the venom of the spider Chilobrachys jingzhao. JZTX-V adopts an inhibitory cysteine knot (ICK motif and has an inhibitory effect on voltage-gated sodium and potassium channels. Previous experiments have shown that JZTX-V has an inhibitory effect on TTX-S and TTX-R sodium currents on rat DRG cells with IC50 values of 27.6 and 30.2 nM, respectively, and is able to shift the activation and inactivation curves to the depolarizing and the hyperpolarizing direction, respectively. Here, we show that JZTX-V has a much stronger inhibitory effect on NaV1.4, the isoform of voltage-gated sodium channels predominantly expressed in skeletal muscle cells, with an IC50 value of 5.12 nM, compared with IC50 values of 61.7–2700 nM for other heterologously expressed NaV1 subtypes. Furthermore, we investigated the bioactive surface of JZTX-V by alanine-scanning the effect of toxin on NaV1.4 and demonstrate that the bioactive face of JZTX-V is composed of three hydrophobic (W5, M6, and W7 and two cationic (R20 and K22 residues. Our results establish that, consistent with previous assumptions, JZTX-V is a Janus-faced toxin which may be a useful tool for the further investigation of the structure and function of sodium channels.

Molecular Dynamics Simulations on Evaporation of Droplets with Dissolved Salts

OpenAIRE

Jin-Liang Xu; Min Chen; Xiao-Dong Wang; Bing-Bing Wang

2013-01-01

Molecular dynamics simulations are used to study the evaporation of water droplets containing either dissolved LiCl, NaCl or KCl salt in a gaseous surrounding (nitrogen) with a constant high temperature of 600 K. The initial droplet has 298 K temperature and contains 1,120 water molecules, 0, 40, 80 or 120 salt molecules. The effects of the salt type and concentration on the evaporation rate are examined. Three stages with different evaporation rates are observed for all cases. In the initial...

Molecular Simulations of Graphene-Based Electric Double-Layer Capacitors

Science.gov (United States)

Kalluri, Raja K.; Konatham, Deepthi; Striolo, Alberto

2011-03-01

Towards deploying renewable energy sources it is crucial to develop efficient and cost-effective technologies to store electricity. Traditional batteries are plagued by a number of practical problems that at present limit their widespread applicability. One possible solution is represented by electric double-layer capacitors (EDLCs). To deploy EDLCs at the large scale it is necessary to better understand how electrolytes pack and diffuse within narrow charged pores. We present here simulation results for the concentrated aqueous solutions of NaCl, CsCl, and NaI confined within charged graphene-based porous materials. We discuss how the structure of confined water, the salt concentration, the ions size, and the surface charge density determine the accumulation of electrolytes within the porous network. Our results, compared to data available for bulk systems, are critical for relating macroscopic observations to molecular-level properties of the confined working fluids. Research supported by the Department of Energy.

Structures, chemotaxonomic significance, cytotoxic and Na(+),K(+)-ATPase inhibitory activities of new cardenolides from Asclepias curassavica.

Science.gov (United States)

Zhang, Rong-Rong; Tian, Hai-Yan; Tan, Ya-Fang; Chung, Tse-Yu; Sun, Xiao-Hui; Xia, Xue; Ye, Wen-Cai; Middleton, David A; Fedosova, Natalya; Esmann, Mikael; Tzen, Jason T C; Jiang, Ren-Wang

2014-11-28

Five new cardenolide lactates (1–5) and one new dioxane double linked cardenolide glycoside (17) along with 15 known compounds (6–16 and 18–21) were isolated from the ornamental milkweed Asclepias curassavica. Their structures were elucidated by extensive spectroscopic methods (IR, UV, MS, 1D- and 2D-NMR). The molecular structures and absolute configurations of 1–3 and 17 were further confirmed by single-crystal X-ray diffraction analysis. Simultaneous isolation of dioxane double linked cardenolide glycosides (17–21) and cardenolide lactates (1–5) provided unique chemotaxonomic markers for this genus. Compounds 1–21 were evaluated for the inhibitory activities against DU145 prostate cancer cells. The dioxane double linked cardenolide glycosides showed the most potent cytotoxic effect followed by normal cardenolides and cardenolide lactates, while the C21 steroids were non-cytotoxic. Enzymatic assay established a correlation between the cytotoxic effects in DU145 cancer cells and the Ki for the inhibition of Na(+),K(+)-ATPase. Molecular docking analysis revealed relatively strong H-bond interactions between the bottom of the binding cavity and compounds 18 or 20, and explained why the dioxane double linked cardenolide glycosides possessed higher inhibitory potency on Na(+),K(+)-ATPase than the cardenolide lactate.

La proteína verde fluorescente ilumina la biociencia The Green Fluorescent Protein that glows in Bioscience

Directory of Open Access Journals (Sweden)

María Inés Pérez Millán

2009-06-01

Full Text Available La proteína verde fluorescente (o GFP, por sus siglas en inglés, Green Fluorescent Protein es una proteína producida por la medusa Aequorea victoria que emite bioluminiscencia en la zona verde del espectro visible. El gen que codifica esta proteína ha sido clonado y se utiliza habitualmente en biología molecular como marcador. Los descubrimientos relacionados a la GFP merecieron el Premio Nobel de Química 2008, en conjunto a los tres investigadores, Dres Shimomura, Chalfie y Tsien que participaron escalonadamente en dilucidar la estructura y función de la proteína. El Dr. Shimomura descubrió y estudió las propiedades de GFP, el Dr. Chalfie usando técnicas de biología molecular logró introducir el gen que codificaba para la GFP en el ADN del gusano transparente C. elegans, e inició la era de GFP como marcador de procesos en células y organismos. Finalmente el Dr. Tsien modificó la estructura de la proteína para producir moléculas que emiten luz a distintas longitudes de onda, extendiendo la paleta de colores de las proteínas. Las proteínas fluorescentes, entre las cuales se encuentra la GFP, son muy versátiles y se utilizan en diversos campos como la microbiología, ingeniería genética, fisiología, e ingeniería ambiental. Permiten ver procesos previamente invisibles, como el desarrollo de neuronas, cómo se diseminan las células cancerosas, o la contaminación de agua con arsénico, por mencionar algunos usos. Con la obtención de proteínas de muchos colores complejas redes biológicas pueden ser marcadas diferencialmente, lo que permite visualizar la biología celular en acción.Green fluorescent protein (GFP is a protein produced by the jellyfish Aequorea victoria, that emits bioluminescence in the green zone of the visible spectrum. The GFP gene has been cloned and is used in molecular biology as a marker. The three researchers that participated independently in elucidating the structure and function of this and its

Structural analysis of the α subunit of Na(+)/K(+) ATPase genes in invertebrates.

Science.gov (United States)

Thabet, Rahma; Rouault, J-D; Ayadi, Habib; Leignel, Vincent

2016-01-01

The Na(+)/K(+) ATPase is a ubiquitous pump coordinating the transport of Na(+) and K(+) across the membrane of cells and its role is fundamental to cellular functions. It is heteromer in eukaryotes including two or three subunits (α, β and γ which is specific to the vertebrates). The catalytic functions of the enzyme have been attributed to the α subunit. Several complete α protein sequences are available, but only few gene structures were characterized. We identified the genomic sequences coding the α-subunit of the Na(+)/K(+) ATPase, from the whole-genome shotgun contigs (WGS), NCBI Genomes (chromosome), Genomic Survey Sequences (GSS) and High Throughput Genomic Sequences (HTGS) databases across distinct phyla. One copy of the α subunit gene was found in Annelida, Arthropoda, Cnidaria, Echinodermata, Hemichordata, Mollusca, Placozoa, Porifera, Platyhelminthes, Urochordata, but the nematodes seem to possess 2 to 4 copies. The number of introns varied from 0 (Platyhelminthes) to 26 (Porifera); and their localization and length are also highly variable. Molecular phylogenies (Maximum Likelihood and Maximum Parsimony methods) showed some clusters constituted by (Chordata/(Echinodermata/Hemichordata)) or (Plathelminthes/(Annelida/Mollusca)) and a basal position for Porifera. These structural analyses increase our knowledge about the evolutionary events of the α subunit genes in the invertebrates. Copyright © 2016 Elsevier Inc. All rights reserved.

Muscle K+, Na+, and Cl- disturbances and Na+-K+ pump inactivation: implications for fatigue

DEFF Research Database (Denmark)

McKenna, Michael J; Bangsbo, Jens; Renaud, Jean-Marc

2008-01-01

(+)-ATPase activity during exercise stabilizes Na(+) and K(+) concentration gradients and membrane excitability and thus protects against fatigue. However, during intense contraction some Na(+)-K(+) pumps are inactivated and together with further ionic disturbances, likely precipitate muscle fatigue.......Membrane excitability is a critical regulatory step in skeletal muscle contraction and is modulated by local ionic concentrations, conductances, ion transporter activities, temperature, and humoral factors. Intense fatiguing contractions induce cellular K(+) efflux and Na(+) and Cl(-) influx......, causing pronounced perturbations in extracellular (interstitial) and intracellular K(+) and Na(+) concentrations. Muscle interstitial K(+) concentration may increase 1- to 2-fold to 11-13 mM and intracellular K(+) concentration fall by 1.3- to 1.7-fold; interstitial Na(+) concentration may decline by 10 m...

Isotonic transport by the Na+-glucose cotransporter SGLT1 from humans and rabbit

DEFF Research Database (Denmark)

Zeuthen, T; Meinild, A K; Loo, D D

2001-01-01

water transport was divided about equally between cotransport, osmosis across the SGLT1 and osmosis across the native oocyte membrane. 6. Coexpression of AQP1 with the SGLT1 increased the water permeability more than 10-fold and steady state isotonic transport was achieved after less than 2 s of sugar......1. In order to study its role in steady state water transport, the Na+-glucose cotransporter (SGLT1) was expressed in Xenopus laevis oocytes; both the human and the rabbit clones were tested. The transport activity was monitored as a clamp current and the flux of water followed optically...... as the change in oocyte volume. 2. SGLT1 has two modes of water transport. First, it acts as a molecular water pump: for each 2 Na+ and 1 sugar molecule 264 water molecules were cotransported in the human SGLT1 (hSGLT1), 424 for the rabbit SGLT1 (rSGLT1). Second, it acts as a water channel. 3. The cotransport...

Route, mechanism, and implications of proton import during Na+/K+ exchange by native Na+/K+-ATPase pumps

Science.gov (United States)

Vedovato, Natascia

2014-01-01

A single Na+/K+-ATPase pumps three Na+ outwards and two K+ inwards by alternately exposing ion-binding sites to opposite sides of the membrane in a conformational sequence coupled to pump autophosphorylation from ATP and auto-dephosphorylation. The larger flow of Na+ than K+ generates outward current across the cell membrane. Less well understood is the ability of Na+/K+ pumps to generate an inward current of protons. Originally noted in pumps deprived of external K+ and Na+ ions, as inward current at negative membrane potentials that becomes amplified when external pH is lowered, this proton current is generally viewed as an artifact of those unnatural conditions. We demonstrate here that this inward current also flows at physiological K+ and Na+ concentrations. We show that protons exploit ready reversibility of conformational changes associated with extracellular Na+ release from phosphorylated Na+/K+ pumps. Reversal of a subset of these transitions allows an extracellular proton to bind an acidic side chain and to be subsequently released to the cytoplasm. This back-step of phosphorylated Na+/K+ pumps that enables proton import is not required for completion of the 3 Na+/2 K+ transport cycle. However, the back-step occurs readily during Na+/K+ transport when external K+ ion binding and occlusion are delayed, and it occurs more frequently when lowered extracellular pH raises the probability of protonation of the externally accessible carboxylate side chain. The proton route passes through the Na+-selective binding site III and is distinct from the principal pathway traversed by the majority of transported Na+ and K+ ions that passes through binding site II. The inferred occurrence of Na+/K+ exchange and H+ import during the same conformational cycle of a single molecule identifies the Na+/K+ pump as a hybrid transporter. Whether Na+/K+ pump–mediated proton inflow may have any physiological or pathophysiological significance remains to be clarified. PMID

Route, mechanism, and implications of proton import during Na+/K+ exchange by native Na+/K+-ATPase pumps.

Science.gov (United States)

Vedovato, Natascia; Gadsby, David C

2014-04-01

A single Na(+)/K(+)-ATPase pumps three Na(+) outwards and two K(+) inwards by alternately exposing ion-binding sites to opposite sides of the membrane in a conformational sequence coupled to pump autophosphorylation from ATP and auto-dephosphorylation. The larger flow of Na(+) than K(+) generates outward current across the cell membrane. Less well understood is the ability of Na(+)/K(+) pumps to generate an inward current of protons. Originally noted in pumps deprived of external K(+) and Na(+) ions, as inward current at negative membrane potentials that becomes amplified when external pH is lowered, this proton current is generally viewed as an artifact of those unnatural conditions. We demonstrate here that this inward current also flows at physiological K(+) and Na(+) concentrations. We show that protons exploit ready reversibility of conformational changes associated with extracellular Na(+) release from phosphorylated Na(+)/K(+) pumps. Reversal of a subset of these transitions allows an extracellular proton to bind an acidic side chain and to be subsequently released to the cytoplasm. This back-step of phosphorylated Na(+)/K(+) pumps that enables proton import is not required for completion of the 3 Na(+)/2 K(+) transport cycle. However, the back-step occurs readily during Na(+)/K(+) transport when external K(+) ion binding and occlusion are delayed, and it occurs more frequently when lowered extracellular pH raises the probability of protonation of the externally accessible carboxylate side chain. The proton route passes through the Na(+)-selective binding site III and is distinct from the principal pathway traversed by the majority of transported Na(+) and K(+) ions that passes through binding site II. The inferred occurrence of Na(+)/K(+) exchange and H(+) import during the same conformational cycle of a single molecule identifies the Na(+)/K(+) pump as a hybrid transporter. Whether Na(+)/K(+) pump-mediated proton inflow may have any physiological or

A New Class of Octahedral Molecular Sieve Materials for the Selective Removal and Sequestration of 90Sr2+

International Nuclear Information System (INIS)

Nyman, May D.; Nenoff, Tina M.; Tripathi, Akhilesh; Parise, John B.; Maxwell, Robert S.; Harrison, William T.A.

2000-01-01

The structure of Na 16 Nb 12.8 Ti 3.2 O 44.8 (OH) 3.2 · 8H 2 O, a member of a new family of Sandia Octahedral Molecular Sieves (SOMS) having a Nb/Na/M IV (M= Ti, Zr) oxide framework and exchangeable Na and water in open channels, was determined from Synchrotron X-ray data. The SOMS phases are isostructural with variable M IV :Nb(1:50--1:4) ratios. The SOMS are extremely selective for sorption of divalent cations, particularly Sr 2+ . The ion-exchanged SOMS undergo direct thermal conversion to a perovskite-type phase, indicating this is a promising new method for removal and sequestration of radioactive Sr-90 from mixed nuclear wastes

Studies on a microbially derived, high molecular weight inhibitor of plasma cholesteryl ester transfer protein

International Nuclear Information System (INIS)

Marschke, C.K.; McGee, J.E.; Melchior, G.W.; Castle, C.K.

1989-01-01

The authors have isolated an organism which accumulates an inhibitor of Cholesteryl Ester Transfer Protein (CETP). Purification of 100,000-fold was achieved by ammonium sulfate precipitation followed by Hydroxyl Apatite, Agarose AO.5, and Mono Q (Pharmacia) chromatographies. The use of 14 C-labelled protein molecular weight standards followed by SDS-PAGE revealed some proteolytic activity. However, inhibition of the proteases did not affect the inhibitor potency. The inhibitor has an estimated molecular weight of 40 Kd and appears to exist as two forms. One form was eluted from a Mono Q column by 100 mM NaCl while the other was not bound. Our evidence indicated that the bound form was progressively denatured, or proteolyzed, during storage of the fermentation beer, to the unbound form. Importantly though this molecular change did not affect either inhibitory activity or the apparent molecular weight

Electrospinning and characterization of polyamide 66 nanofibers with different molecular weights

Directory of Open Access Journals (Sweden)

Lilia Muller Guerrini

2009-06-01

Full Text Available Polyamide 66 (PA66 nanofibers of different molecular weights were obtained by electrospinning of formic acid solutions. An ionic salt, NaCl, was also added to the solutions to increase the conductivity. PA66 concentrations between 15-17 wt.(%/v and electrical fields between 2.0 and 2.5 kV/cm were the best conditions to produce the smallest nanofibers; however, the addition of NaCl increased the fibers average diameters.The characterization of the fibers was done by scanning electron microscopy (SEM, differential scanning calorimetry (DSC, wide angle X rays diffraction (WAXD and Fourier Transformed Infrared (FTIR. As the molecular weight decreased, the nanofibers average diameters also decreased; however, critical number average and weight average molecular weights were necessary for electrospinning. As the amounts of carboxyl terminal groups (CTG increased, the nanofibers average diameters decreased; however, above CTG's critical values of 8.7 x 10-5 mol.g-1 no electrospinning was possible. The addition of ionic salt increased the electrical conductivity of the solutions and increased the nanofibers' average diameters. By DSC, residual solvent in all the electrospun mats was found; two melting endotherms, one between 248 and 258 °C and the other one between 258 and 267 °C, depending on the sample were also observed. These endotherms were attributed to the melting, re-crystallization and re-melting of the PA66 α-phase. The nanofibers had low % of crystallinity compared to a textile fiber. By WAXS and FTIR, confirmation of the presence of α-phase crystals, of small dimensions and highly imperfect and of a very small amount of β and γ-phases crystals in the nanofibers structure was obtained.

Growth mechanism of NaClO 3 and NaBrO 3 crystals from aqueous ...

Indian Academy of Sciences (India)

A study of growth rates of NaClO3 and NaBrO3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO3 and {111} faces of NaBrO3 along ⟨ 110 ⟩ direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, {100}, ...

Proteasome Inhibition Contributed to the Cytotoxicity of Arenobufagin after Its Binding with Na, K-ATPase in Human Cervical Carcinoma HeLa Cells.

Directory of Open Access Journals (Sweden)

Qingxi Yue

Full Text Available Although the possibility of developing cardiac steroids/cardiac glycosides as novel cancer therapeutic agents has been recognized, the mechanism of their anticancer activity is still not clear enough. Toad venom extract containing bufadienolides, which belong to cardiac steroids, has actually long been used as traditional Chinese medicine in clinic for cancer therapy in China. The cytotoxicity of arenobufagin, a bufadienolide isolated from toad venom, on human cervical carcinoma HeLa cells was checked. And, the protein expression profile of control HeLa cells and HeLa cells treated with arenobufagin for 48 h was analyzed using two-dimensional electrophoresis, respectively. Differently expressed proteins in HeLa cells treated with arenobufagin were identified and the pathways related to these proteins were mapped from KEGG database. Computational molecular docking was performed to verify the binding of arenobufagin and Na, K-ATPase. The effects of arenobufagin on Na, K-ATPase activity and proteasome activity of HeLa cells were checked. The protein-protein interaction network between Na, K-ATPase and proteasome was constructed and the expression of possible intermediate proteins ataxin-1 and translationally-controlled tumor protein in HeLa cells treated with arenobufagin was then checked. Arenobufagin induced apoptosis and G2/M cell cycle arrest in HeLa cells. The cytotoxic effect of arenobufagin was associated with 25 differently expressed proteins including proteasome-related proteins, calcium ion binding-related proteins, oxidative stress-related proteins, metabolism-related enzymes and others. The results of computational molecular docking revealed that arenobufagin was bound in the cavity formed by the transmembrane alpha subunits of Na, K-ATPase, which blocked the pathway of extracellular Na+/K+ cation exchange and inhibited the function of ion exchange. Arenobufagin inhibited the activity of Na, K-ATPase and proteasome, decreased the

The system NaVO3-Na2WO4-Na2W2O7

International Nuclear Information System (INIS)

Kazanbekov, V.R.; Gasanaliev, A.M.; Kazanbekov, R.G.

1994-01-01

Phase diagrams of sodium metavanadate-sodium ditungstate, sodium metavanadate-sodium tungstate systems and surface of primary crystallization of sodium metavabadate-sodium tungstate-sodium ditungstate system were studied. The system sodium metavanadate-sodium ditungstate is eutectic one. Compound NaVO 3 x2Na 2 WO 4 is formed in solid state in sodium metavanadate-sodium tungstate system. Liquidus surface of sodium metavanadate-sodium tungstate-sodium ditungstate is presented by three crystallization fields of initial components. Composition and melting point of ternary eutectics are determined

Potential New H1N1 Neuraminidase Inhibitors from Ferulic Acid and Vanillin: Molecular Modelling, Synthesis and in Vitro Assay

Science.gov (United States)

Hariono, Maywan; Abdullah, Nurshariza; Damodaran, K. V.; Kamarulzaman, Ezatul E.; Mohamed, Nornisah; Hassan, Sharifah Syed; Shamsuddin, Shaharum; Wahab, Habibah A.

2016-12-01

We report the computational and experimental efforts in the design and synthesis of novel neuraminidase (NA) inhibitors from ferulic acid and vanillin. Two proposed ferulic acid analogues, MY7 and MY8 were predicted to inhibit H1N1 NA using molecular docking. From these two analogues, we designed, synthesised and evaluated the biological activities of a series of ferulic acid and vanillin derivatives. The enzymatic H1N1 NA inhibition assay showed MY21 (a vanillin derivative) has the lowest IC50 of 50 μM. In contrast, the virus inhibition assay showed MY15, a ferulic acid derivative has the best activity with the EC50 of ~0.95 μM. Modelling studies further suggest that these predicted activities might be due to the interactions with conserved and essential residues of NA with ΔGbind values comparable to those of oseltamivir and zanamivir, the two commercial NA inhibitors.

Summer sudden Na number density enhancements measured with the ALOMAR Weber Na Lidar

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D. Heinrich

2008-05-01

Full Text Available We present summer Na-densities and atmospheric temperatures measured 80 to 110 km above the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR. The Weber Na Lidar is part of ALOMAR, located at 69° N in Norway, 150 km north of the Arctic Circle. The sun does not set here during the summer months, and measurements require a narrowband Faraday Anomalous Dispersion Optical Filter (FADOF.

We discuss an observed sudden enhancement in the Na number density around 22:00 UT on 1 to 2 June 2006. We compare this observation with previous summer measurements and find a frequent appearance of Na number density enhancements near local midnight. We describe the time of appearance, the altitude distribution, the duration and the strength of these enhancements and compare them to winter observations. We investigate possible formation mechanisms and, as others before, we find a strong link between these Na number density enhancements and sporadic E layers.

Summer sudden Na number density enhancements measured with the ALOMAR Weber Na Lidar

Directory of Open Access Journals (Sweden)

D. Heinrich

2008-05-01

Full Text Available We present summer Na-densities and atmospheric temperatures measured 80 to 110 km above the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR. The Weber Na Lidar is part of ALOMAR, located at 69° N in Norway, 150 km north of the Arctic Circle. The sun does not set here during the summer months, and measurements require a narrowband Faraday Anomalous Dispersion Optical Filter (FADOF. We discuss an observed sudden enhancement in the Na number density around 22:00 UT on 1 to 2 June 2006. We compare this observation with previous summer measurements and find a frequent appearance of Na number density enhancements near local midnight. We describe the time of appearance, the altitude distribution, the duration and the strength of these enhancements and compare them to winter observations. We investigate possible formation mechanisms and, as others before, we find a strong link between these Na number density enhancements and sporadic E layers.

Molecular dynamics study of salt–solution interface: Solubility and surface charge of salt in water

International Nuclear Information System (INIS)

Kobayashi, Kazuya; Liang, Yunfeng; Matsuoka, Toshifumi; Sakka, Tetsuo

2014-01-01

The NaCl salt–solution interface often serves as an example of an uncharged surface. However, recent laser-Doppler electrophoresis has shown some evidence that the NaCl crystal is positively charged in its saturated solution. Using molecular dynamics (MD) simulations, we have investigated the NaCl salt–solution interface system, and calculated the solubility of the salt using the direct method and free energy calculations, which are kinetic and thermodynamic approaches, respectively. The direct method calculation uses a salt–solution combined system. When the system is equilibrated, the concentration in the solution area is the solubility. In the free energy calculation, we separately calculate the chemical potential of NaCl in two systems, the solid and the solution, using thermodynamic integration with MD simulations. When the chemical potential of NaCl in the solution phase is equal to the chemical potential of the solid phase, the concentration of the solution system is the solubility. The advantage of using two different methods is that the computational methods can be mutually verified. We found that a relatively good estimate of the solubility of the system can be obtained through comparison of the two methods. Furthermore, we found using microsecond time-scale MD simulations that the positively charged NaCl surface was induced by a combination of a sodium-rich surface and the orientation of the interfacial water molecules

Ansiedade na performance musical: estudo molecular de associação e validação da escala de \\"K-MPAI

OpenAIRE

Sergio de Figueiredo Rocha

2012-01-01

A performance musical requer um alto nível de habilidade em diversos parâmetros como coordenação motora, atenção e memória, o que a torna uma atividade particularmente susceptível aos estados de ansiedade. Pesquisas nessa área têm avançado com a introdução de instrumentos específicos para abordar a ansiedade na performance musical (MPA), como é o caso da the Kenny Music Performance Anxiety Inventory (K-MPAI). Estudos recentes apontam polimorfismos genéticos envolvidos na base do quadro de ans...

Molecular detection and immunological localization of gill Na+/H+ exchanger in the dogfish (Squalus acanthias).

Science.gov (United States)

Claiborne, James B; Choe, Keith P; Morrison-Shetlar, Alison I; Weakley, Jill C; Havird, Justin; Freiji, Abe; Evans, David H; Edwards, Susan L

2008-03-01

The dogfish (Squalus acanthias) can make rapid adjustments to gill acid-base transfers to compensate for internal acidosis/alkalosis. Branchial Na+/H+ exchange (NHE) has been postulated as one mechanism driving the excretion of H+ following acidosis. We have cloned gill cDNA that includes an open reading frame coding for a 770-residue protein most homologous (approximately 71%) to mammalian NHE2. RT-PCR revealed NHE2 transcripts predominantly in gill, stomach, rectal gland, intestine, and kidney. In situ hybridization with an antisense probe against NHE2 in gill sections revealed a strong mRNA signal from a subset of interlamellar and lamellae cells. We developed dogfish-specific polyclonal antibodies against NHE2 that detected a approximately 70-kDa protein in Western blots and immunologically recognized branchial cells having two patterns of protein expression. Cytoplasmic and apical NHE2 immunoreactivity were observed in cells coexpressing basolateral Na+-K+-ATPase. Other large ovoid cells more generally staining for NHE2 also were strongly positive for basolateral H+-ATPase. Gill mRNA levels for NHE2 and H+-ATPase did not change following systemic acidosis (as measured by quantitative PCR 2 h after a 1- or 2-meq/kg acid infusion). These data indicate that posttranslational adjustments of NHE2 and other transport systems (e.g., NHE3) following acidosis may be of importance in the short-term pH adjustment and net branchial H+ efflux observed in vivo. NHE2 may play multiple roles in the gills, involved with H+ efflux from acid-secreting cells, basolateral H+ reabsorption for pHi regulation, and in parallel with H+-ATPase for the generation of HCO3(-) in base-secreting cells.

Genética molecular: avanços e problemas

Directory of Open Access Journals (Sweden)

Garcia Eloi S.

1996-01-01

Full Text Available Este artigo traz a discussão sobre genética molecular em saúde ao campo da saúde pública. Com a revolução produzida pela chegada da engenharia genética, é importante discutir alguns dos avanços e problemas desta tecnologia para a sociedade. Está na hora de se fazer uma avaliação clara e bem informada acerca do que já se conseguiu e do que ainda podemos conseguir através desta tecnologia. A sociedade precisa compreender as implicações éticas e práticas de uma tecnologia capaz de produzir drogas milagrosas, dagnósticos modernos e a cura de todas as doenças. Alguns pontos particularmente delicados pertinentes às questões sociais ligadas à biologia molecular e ao projeto genoma humano são discutidos.

Complex Formation by the mrpABCDEFG Gene Products, Which Constitute a Principal Na+/H+ Antiporter in Bacillus subtilis▿

OpenAIRE

Kajiyama, Yusuke; Otagiri, Masato; Sekiguchi, Junichi; Kosono, Saori; Kudo, Toshiaki

2007-01-01

The Bacillus subtilis Mrp (also referred to as Sha) is a particularly unusual Na+/H+ antiporter encoded by mrpABCDEFG. Using His tagging of Mrp proteins, we showed complex formation by the mrpABCDEFG gene products by pull-down and blue native polyacrylamide gel electrophoresis analyses. This is the first molecular evidence that the Mrp is a multicomponent antiporter in the cation-proton antiporter 3 family.

Muziki wa Hip Hop na Haki Za Kijamii: Dhima, Changamoto na ...

African Journals Online (AJOL)

Ni dhahiri kuwa haki za kijamii zinaweza kuwasilishwa kwa jamii pana kupitia sanaa ya hip hop. Makala haya basi, yanabainisha dhima na mchango wa muziki wa hip hop katika masuala ya haki za kijamii, yanafafanua changamoto za muziki huu katika kuwasilisha haki za kijamii na kutoa mapendekezo kwa makundi ...

Agrobacterium-assisted selenium nanoparticles: molecular aspect of antifungal activity

Science.gov (United States)

Kumar, Anil; Bera, Smritilekha; Singh, Man; Mondal, Dhananjoy

2018-03-01

Selenium nanoparticles (SeNPs) were synthesized through the bioreduction of sodium selenite (Na2SeO3) using gram-negative agrobacterium (AGBT) species. Subsequently, their physicochemical properties (pH, viscosity and surface tension) and medicinal activities as anti-dermatophyte against soil keratinophilic fungi at the molecular level were assessed. UV-visible and FTIR spectroscopic data of the biologically synthesized SeNPs were then recorded for confirming the presence of native biological materials adhered to nanoparticles, which are inherently required to enhance the stability and solubility through inhibition of the nanoparticle’s natural aggregation and agglomeration. The λ max value between 290-300 nm in the absorption spectra of the biogenic materials in different concentrations of the Na2SeO3 corroborated the presence of SeNPs in the solution. The interaction of SeNPs in solution state was further studied through the determination of pH, viscosity and surface tension values of agrobacterium-derived SeNPs in different solvents. The pH value of SeNPs dispersed in water is reported as above 7.0 and the average viscosity, and surface tensions of the SeNPs are appeared as near to the water. The particle size distribution was further determined by DLS and the highest % of particle size of the synthesized SeNPs is found in between 200-300 nm. The anti-dermatophyte activity and molecular interaction with fungi DNA molecules were assessed providing the highest anti-dermatophyte activity at 0.1 M concentration and it is observed that the quantities and qualities of fungi DNA were affected by SeNPs. Considering all the outcomes of the studies together, our findings suggest that agrobacterium-mediated synthesis of SeNPs is dependent on bacterial metabolisms but not on the concentration of Na2SeO3 and are promising selenium-derived species with potential application in the prevention of fungal infection through denaturation of fungi DNA.

Helicase Dependent Isothermal Amplification of DNA and RNA using Self-Avoiding Molecular Recognition Systems

Science.gov (United States)

Yang, Zunyi; McLendon, Chris; Hutter, Daniel; Bradley, Kevin M.; Hoshika, Shuichi; Frye, Carole; Benner, Steven A.

2015-01-01

Assays that target DNA or RNA (xNA) are highly sensitive, as small amounts of xNA can be amplified by PCR. Unfortunately, PCR is inconvenient in low resource environments, requiring equipment and power that may not be available in these environments. However, isothermal procedures that avoid thermal cycling are often confounded by primer dimers, off-target priming, and other artifacts. Here, we show how a “self avoiding molecular recognition system” (SAMRS) eliminates these artifacts to give clean amplicons in a helicase-dependent isothermal amplification (SAMRS-HDA). We also show that incorporating SAMRS into the 3′-ends of primers facilitates the design and screening of primers for HDA assays. Finally, we show that SAMRS-HDA can be twofold multiplexed, something difficult to achieve with HDA using standard primers. This shows that SAMRS-HDA is a more versatile approach than standard HDA with a broader applicability for xNA-targeted diagnostics and research. PMID:25953623

Formation of ultracold NaRb Feshbach molecules

International Nuclear Information System (INIS)

Wang, Fudong; He, Xiaodong; Li, Xiaoke; Zhu, Bing; Chen, Jun; Wang, Dajun

2015-01-01

We report the creation of ultracold bosonic 23 Na 87 Rb Feshbach molecules via magneto-association. By ramping the magnetic field across an interspecies Feshbach resonance (FR), at least 4000 molecules can be produced out of the near degenerate ultracold mixture. Fast loss due to inelastic atom–molecule collisions is observed, which limits the pure molecule number, after residual atoms removal, to 1700. The pure molecule sample can live for 21.8(8) ms in the optical trap, long enough for future molecular spectroscopy studies toward coherently transferring to the singlet ro-vibrational ground state, where these molecules are stable against chemical reaction and have a permanent electric dipole moment of 3.3 Debye. We have also measured the Feshbach molecule’s binding energy near the FR by the oscillating magnetic field method and found these molecules have a large closed-channel fraction. (paper)

Sequential growth of sandwiched NaYF{sub 4}:Yb/Er@NaYF{sub 4}:Yb@NaNdF{sub 4}:Yb core–shell–shell nanoparticles for photodynamic therapy

Energy Technology Data Exchange (ETDEWEB)

Peng, Huang-Yong; Ding, Bin-Bin; Ma, Yin-Chu [Department of Medical Materials and Rehabilitation Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009 (China); Sun, Shi-Qi [State Key Laboratory of Veterinary Etiological Biology and Key Laboratory of Animal Virology of Ministry of Agriculture, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Xujiaping 1, Lanzhou, Gansu 730046 (China); Tao, Wei [Department of Medical Materials and Rehabilitation Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009 (China); Guo, Yan-Chuan [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Guo, Hui-Chen, E-mail: ghch-2004@hotmail.com [State Key Laboratory of Veterinary Etiological Biology and Key Laboratory of Animal Virology of Ministry of Agriculture, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Xujiaping 1, Lanzhou, Gansu 730046 (China); Yang, Xian-Zhu, E-mail: yangxz@hftu.edu.cn [Department of Medical Materials and Rehabilitation Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009 (China); Qian, Hai-Sheng, E-mail: shqian@hfut.edu.cn [Department of Medical Materials and Rehabilitation Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009 (China)

2015-12-01

Graphical abstract: The monodisperse elliptical NaYF{sub 4}:Yb/Er@NaYF{sub 4}:Yb@NaNdF{sub 4}:Yb core–shell–shell nanoparticles have been synthesized successfully by a facile sequential growth process, which can be used as transducer for photodynamic therapy of cancer cells. - Highlights: • The NaYF{sub 4}:Yb/Er@NaYF{sub 4}:Yb@NaNdF{sub 4}:Yb nanoparticles have been fabricated successfully. • The as-prepared nanoparticles show strong fluorescence excited at 980 or 808 nm. • The nanoparticles were transferred into the aqueous phase via a facile process. • Photosensitizers were loaded into the composites for photodynamic therapy. - Abstract: Upconversion (UC) nanostructures have attracted much interest for their extensive biological applications. In this work, we describe a sequential synthetic route to prepare sandwiched NaYF{sub 4}:Yb/Er@NaYF{sub 4}:Yb@NaNdF{sub 4}:Yb core–shell upconversion nanoparticles. The as-prepared products were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM, JEM 2100F), respectively. The as-prepared core–shell nanoparticles of NaYF{sub 4}:Yb/Er@NaYF{sub 4}:Yb@NaNdF{sub 4}:Yb are composed of elliptical nanoparticles with a length of 80 nm and width of 42 nm, which show efficient upconversion fluorescence excited at 808 nm indicating the formation of core–shell–shell sandwiched nanostructures. In addition, the as-prepared sandwiched NaYF{sub 4}:Yb/Er@NaYF{sub 4}:Yb@NaNdF{sub 4}:Yb core–shell upconversion nanoparticles also show strong upconversion fluorescence excited at 980 nm. Amphiphilic mPEG{sub 2k}-b-PEBEP{sub 6K} copolymers (denoted as PPE) were chosen to transfer these hydrophobic UCNPs into the aqueous phase for biological application. In vitro photodynamic therapy of cancer cells show that the viability of cells incubated with the nanoparticles loaded with MC 540 was significantly lower as compared to the nanoparticles without photosensitizers exposed to NIR laser.

Intracellular Na+ regulation of Na+ pump sites in cultured vascular smooth muscle cells

International Nuclear Information System (INIS)

Allen, J.C.; Navran, S.S.; Seidel, C.L.; Dennison, D.K.; Amann, J.M.; Jemelka, S.K.

1989-01-01

Enzymatically dispersed cells from canine saphenous vein and femoral artery were grown in fetal calf serum and studied at day 0 (freshly dispersed) through confluence in primary culture. Intracellular Na levels (Nai), but not intracellular K (Ki), were increased after 24 h in culture and then decreased to a steady state by 4 days. Na+ pump site number [( 3 H] ouabain binding) increased through day 3 and remained elevated. Nai was still elevated at 2 days when the Na+ pump site number began to increase. Total pump turnover (maximum ouabain-inhibited 86 Rb uptake) reflected the increase in Na+ pump site number. These key events precede the observed increases in both protein production and cellular proliferation. If the same cells are maintained in defined medium, without fetal calf serum, Nai, Ki, and the number of [ 3 H]ouabain binding sites do not change with time. These data are consistent with the suggestion that the initial mitogenic response of vascular smooth muscle cells to fetal calf serum involves an increased Na+ influx, and a Nai accumulation, caused by low Na+ pump density. The synthesis of new pump sites effects a decrease in the accumulated Nai, which may be related to cell proliferation

On the Stability of NaO2 in Na-O2 Batteries.

Science.gov (United States)

Liu, Chenjuan; Carboni, Marco; Brant, William R; Pan, Ruijun; Hedman, Jonas; Zhu, Jiefang; Gustafsson, Torbjörn; Younesi, Reza

2018-04-25

Na-O 2 batteries are regarded as promising candidates for energy storage. They have higher energy efficiency, rate capability, and chemical reversibility than Li-O 2 batteries; in addition, sodium is cheaper and more abundant compared to lithium. However, inconsistent observations and instability of discharge products have inhibited the understanding of the working mechanism of this technology. In this work, we have investigated a number of factors that influence the stability of the discharge products. By means of in operando powder X-ray diffraction study, the influence of oxygen, sodium anode, salt, solvent, and carbon cathode were investigated. The Na metal anode and an ether-based solvent are the main factors that lead to the instability and decomposition of NaO 2 in the cell environment. This fundamental insight brings new information on the working mechanism of Na-O 2 batteries.

NaK handling and removal

International Nuclear Information System (INIS)

Desreumaux, J.; Rodriguez, G.; Guigon, A.; Verdelli, J.; Thomine, G.

1997-01-01

Sodium-potassium alloy is used in specific application in French Fast Breeder Reactors as: cold traps, NaK bubbler for argon purification, valves and also in experimental irradiation devices. lt has been preferred to sodium because it is liquid from + 7 deg. C for the most common peritectic alloy. After its use, NaK is considered as a hazardous waste (nuclear or not) due to its high reactivity with air and water. The most important risk remains in handling NaK systems which have not been operated for some time. The NaK will be covered with a crust of the superoxide K02 which is a strong oxidising agent. Thermodynamically, K02 will react with most organic material or metallic dust or swarfs and can also react with additional NaK to give sufficient heat to boil part of the NaK, resulting in a sudden increase in pressure and small explosions. We describe the formation given to experimenters in our Sodium School and the CEA's experience in treating specific devices for transportation, decanting of tanks, tank opening and NaK removal. (author)

Angiotensin II-induced hypertension increases plasma membrane Na pump activity by enhancing Na entry in rat thick ascending limbs.

Science.gov (United States)

Gonzalez-Vicente, Agustin; Garvin, Jeffrey L

2013-11-01

Thick ascending limbs (TAL) reabsorb 30% of the filtered NaCl load. Na enters the cells via apical Na-K-2Cl cotransporters and Na/H exchangers and exits via basolateral Na pumps. Chronic angiotensin II (ANG II) infusion increases net TAL Na transport and Na apical entry; however, little is known about its effects on the basolateral Na pump. We hypothesized that in rat TALs Na pump activity is enhanced by ANG II-infusion, a model of ANG II-induced hypertension. Rats were infused with 200 ng·kg(-1)·min(-1) ANG II or vehicle for 7 days, and TAL suspensions were obtained. We studied plasma membrane Na pump activity by measuring changes in 1) intracellular Na (Nai) induced by ouabain; and 2) ouabain-sensitive oxygen consumption (QO2). We found that the ouabain-sensitive rise in Nai in TALs from ANG II-infused rats was 12.8 ± 0.4 arbitrary fluorescent units (AFU)·mg(-1)·min(-1) compared with only 9.9 ± 1.1 AFU·mg(-1)·min(-1) in controls (P Na pump expression, the number of Na pumps in the plasma membrane, or the affinity for Na. When furosemide (1.1 mg·kg(-1)·day(-1)) was coinfused with ANG II, no increase in plasma membrane Na pump activity was observed. We concluded that in ANG II-induced hypertension Na pump activity is increased in the plasma membrane of TALs and that this increase is caused by the chronically enhanced Na entry occurring in this model.

A importância da craniometria na criminalística: revisão de literatura

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Fernanda Bordignon Nunes

2014-08-01

Full Text Available A utilização dos estudos cranianos na criminalística tem grande importância, principalmente no que concerne aos propósitos de identificação, podendo ser utilizada também na determinação das causas da morte. A identificação de vítimas e autores é parte fundamental, e na maioria das vezes principal objetivo, da investigação de um crime. O propósito desta revisão é destacar a importância e as principais aplicações da utilização da craniometria nas ciências criminais. Para tal, foi realizado levantamento bibliográfico acerca da história da craniometria forense, desde os primórdios de sua utilização na chamada Antropologia Criminal de Lombroso, até seu papel nas investigações atuais. Apesar das ferramentas de estudos genéticos e de biologia molecular serem muito utilizadas na atualidade, o uso desta linha de abordagem se mostra ineficaz, dispendiosa ou financeiramente desvantajosa em casos onde há muita degradação do material biológico, como incêndios e exumações. Nestes casos, o uso das análises de crânio se mostra importante, podendo ser a principal fonte de dados para elucidação de um crime. Concluindo, procura-se estabelecer a importância dos estudos cranianos, como alternativa ou complemento a outras técnicas mais comumente utilizadas para os fins de identificação e investigação criminal, ressaltando-se a necessidade de investimentos na área no Brasil.

Active compounds in Chinese herbs and medicinal animal products which promote blood circulation via inhibition of Na+, K+-ATPase.

Science.gov (United States)

Tzen, Jason Tc; Chen, Ronald Jy; Chung, Tse-Yu; Chen, Yi-Ching; Lin, Nan-Hei

2010-01-01

The therapeutic effect of cardiac glycosides for congestive heart failure lies in their reversible inhibition on Na+, K+-ATPase located in human myocardium. Several steroid-like compounds containing a core structure similar to cardiac glycosides have been found in many Chinese herbs and medicinal animal products conventionally used to promote blood circulation. They are putatively responsible for the therapeutic effect of those medicinal products via the same mechanism of inhibiting Na+, K+-ATPase. Inhibitory potency on Na+, K+-ATPase by ginsenosides, one of the identified steroid-like compounds, is significantly affected by sugar attachment that might cause steric hindrance of their binding to Na+, K+-ATPase. Ginsenosides with sugar moieties attached only to the C-3 position of the steroid-like structure, equivalent to the sugar position in cardiac glycosides, substantially inhibit Na+, K+-ATPase. However, their inhibitory potency is abolished when sugar moieties are linked to the C-6 or C-20 position of the steroid-like structure. In contrast, no appreciable contents of steroid-like compounds are found in danshen, a well-known Chinese herb traditionally regarded as an effective medicine promoting blood circulation. Instead, magnesium lithospermate B (MLB), the major soluble ingredient in danshen, is assumed to be responsible for the therapeutic effect by inhibiting Na+, K+-ATPase in a manner comparable to cardiac glycosides. Neuroprotective effects of cardiac glycosides, ginsenosides and MLB against ischemic stroke were accordingly observed in a cortical brain slice-based assay model. Whether the neuroprotection is also triggered by inhibition of Na+, K+-ATPase remains to be investigated. Molecular modeling suggests that cardiac glycosides, ginsenosides and MLB presumably bind to the same extracellular pocket of the Na+, K+-ATPase alpha subunit.

Comparative molecular analyses of select pH- and osmoregulatory genes in three freshwater crayfish Cherax quadricarinatus, C. destructor and C. cainii.

Science.gov (United States)

Ali, Muhammad Y; Pavasovic, Ana; Dammannagoda, Lalith K; Mather, Peter B; Prentis, Peter J

2017-01-01

Systemic acid-base balance and osmotic/ionic regulation in decapod crustaceans are in part maintained by a set of transport-related enzymes such as carbonic anhydrase (CA), Na + /K + -ATPase (NKA), H + -ATPase (HAT), Na + /K + /2Cl - cotransporter (NKCC), Na + /Cl - /HCO[Formula: see text] cotransporter (NBC), Na + /H + exchanger (NHE), Arginine kinase (AK), Sarcoplasmic Ca +2 -ATPase (SERCA) and Calreticulin (CRT). We carried out a comparative molecular analysis of these genes in three commercially important yet eco-physiologically distinct freshwater crayfish , Cherax quadricarinatus, C. destructor and C. cainii , with the aim to identify mutations in these genes and determine if observed patterns of mutations were consistent with the action of natural selection. We also conducted a tissue-specific expression analysis of these genes across seven different organs, including gills, hepatopancreas, heart, kidney, liver, nerve and testes using NGS transcriptome data. The molecular analysis of the candidate genes revealed a high level of sequence conservation across the three Cherax sp. Hyphy analysis revealed that all candidate genes showed patterns of molecular variation consistent with neutral evolution. The tissue-specific expression analysis showed that 46% of candidate genes were expressed in all tissue types examined, while approximately 10% of candidate genes were only expressed in a single tissue type. The largest number of genes was observed in nerve (84%) and gills (78%) and the lowest in testes (66%). The tissue-specific expression analysis also revealed that most of the master genes regulating pH and osmoregulation (CA, NKA, HAT, NKCC, NBC, NHE) were expressed in all tissue types indicating an important physiological role for these genes outside of osmoregulation in other tissue types. The high level of sequence conservation observed in the candidate genes may be explained by the important role of these genes as well as potentially having a number of

Silicene for Na-ion battery applications

KAUST Repository

Zhu, Jiajie

2016-08-19

Na-ion batteries are promising candidates to replace Li-ion batteries in large scale applications because of the advantages in natural abundance and cost of Na. Silicene has potential as the anode in Li-ion batteries but so far has not received attention with respect to Na-ion batteries. In this context, freestanding silicene, a graphene-silicene-graphene heterostructure, and a graphene-silicene superlattice are investigated for possible application in Na-ion batteries, using first-principles calculations. The calculated Na capacities of 954mAh/g for freestanding silicene and 730mAh/g for the graphenesilicene superlattice (10% biaxial tensile strain) are highly competitive and potentials of >0.3 V against the Na/Na potential exceed the corresponding value of graphite. In addition, the diffusion barriers are predicted to be <0.3 eV.

Hydrolysis of Rice Straw Pretreated by Na2SO3 Over Fe-resin/NaCl

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YANG Hui

2017-05-01

Full Text Available To increase the conversion of rice straw(RS and the yield of products, we employed three methods, which were ultrasonic wave, steam explosion and Na2SO3 pretreatment to pretreat RS(the treated RS noted as CS-RS, ZQ-RS and Na2SO3-RS, respectively and found that Na2SO3 treatment was the best pretreatment method based on XRD, SEM, elemental analysis and content of cellulose, hemicellulose and lignin. The conversion of Na2SO3-RS and the yield of total reducing sugar(TRS and levulinic acid(LA were 97.3%, 29.6% and 13.5%, respectively by 10% Fe-resin in 3.3% NaCl solution under 200 ℃.

Na+/H+ and Na+/NH4+ exchange activities of zebrafish NHE3b expressed in Xenopus oocytes

Science.gov (United States)

Ito, Yusuke; Kato, Akira; Hirata, Taku; Hirose, Shigehisa

2014-01-01

Zebrafish Na+/H+ exchanger 3b (zNHE3b) is highly expressed in the apical membrane of ionocytes where Na+ is absorbed from ion-poor fresh water against a concentration gradient. Much in vivo data indicated that zNHE3b is involved in Na+ absorption but not leakage. However, zNHE3b-mediated Na+ absorption has not been thermodynamically explained, and zNHE3b activity has not been measured. To address this issue, we overexpressed zNHE3b in Xenopus oocytes and characterized its activity by electrophysiology. Exposure of zNHE3b oocytes to Na+-free media resulted in significant decrease in intracellular pH (pHi) and intracellular Na+ activity (aNai). aNai increased significantly when the cytoplasm was acidified by media containing CO2-HCO3− or butyrate. Activity of zNHE3b was inhibited by amiloride or 5-ethylisopropyl amiloride (EIPA). Although the activity was accompanied by a large hyperpolarization of ∼50 mV, voltage-clamp experiments showed that Na+/H+ exchange activity of zNHE3b is electroneutral. Exposure of zNHE3b oocytes to medium containing NH3/NH4+ resulted in significant decreases in pHi and aNai and significant increase in intracellular NH4+ activity, indicating that zNHE3b mediates the Na+/NH4+ exchange. In low-Na+ (0.5 mM) media, zNHE3b oocytes maintained aNai of 1.3 mM, and Na+-influx was observed when pHi was decreased by media containing CO2-HCO3− or butyrate. These results provide thermodynamic evidence that zNHE3b mediates Na+ absorption from ion-poor fresh water by its Na+/H+ and Na+/NH4+ exchange activities. PMID:24401990

The relation between aging, aortic NaF avidity and coronary artery NaF avidity: A NaF PET CT study

DEFF Research Database (Denmark)

Blomberg, Björn; Thomassen, Anders; Hildebrandt, Malene

2013-01-01

volunteers without traditional cardiovascular risk factors were prospectively assessed by Sodium 18-Fluoride (Na-18F) PET CT imaging. Global aortic uptake of Na-18F was determined by calculating the average aortic blood pool subtracted maximum standardized uptake value (cSUV) [maximum SUVaorta - mean...

Rescue of Na+ and H+ binding in Na+,K+-ATPase M8 aspartate mutants by secondary mutation

DEFF Research Database (Denmark)

Holm, Rikke; Einholm, Anja P.; Andersen, Jens Peter

A mutation replacing the aspartate in transmembrane segment M8 in the a3-isoform of Na,K-ATPase with asparagine has been found in patients with rapid-onset dystonia parkinsonism or alternating hemiplegia of childhood. This aspartate may be a critical Na+ coordinating residue, but the crystal......-isoforms of Na,K-ATPase, and much smaller effects were seen for other mutations to the M8 aspartate, which were less disruptive of Na+ binding than mutations to other residues related to Na+ site III. The D928 (rat a1 numbering) mutations strongly diminished the cooperativity of Na+ binding. Moreover the p......H optimum of Na,K-ATPase activity was left-shifted, again with D928N being most disruptive. The reduced affinity for activating Na+ and for inhibitory protons, caused by D928N and D928A mutations, could be rescued by introduction of an additional mutation of a glutamate located far away from D928....

Salinity tolerance in barley (hordeum vulgare l.): effects of varying NaCl, K/sup +/ Na/sup +/ and NaHCO/sub 3/ levels on cultivars differing in tolerance

International Nuclear Information System (INIS)

Mahmood, K.

2011-01-01

Although barley (Hordeum vulgare L.) is regarded as salt tolerant among crop plants, its growth and plant development is severely affected by ionic and osmotic stresses in salt-affected soils. To elucidate the tolerance mechanism, growth and ion uptake of three barley cultivars, differing in salt tolerance, were examined under different levels of NaCl, K/sup +/ Na/sup +/ and NaHCO/sub 3/ in the root medium. The cultivars differed greatly in their responses to varying root medium conditions. Plant growth was more adversely affected by NaHCO/sub 3/ than NaCl. In general, biomass yields were comparable under control and 100 mM NaCl. However, growth of all three cultivars was significantly inhibited by NaHCO/sub 3/ even at low concentration (10 mM). Improved K/sup +/ supply in saline medium increased K/sup +/ uptake and growth of less tolerant cultivars. K/sup +/ uptake was more adversely affected by NaHCO/sub 3/ than NaCl salinity. Selective K/sup +/ uptake and lower Cl/sup -/ in shoots seemed to be associated with the growth responses. K application would help better growth of these cultivars on K-deficient saline-sodic soils and under irrigation with poor quality water having high Residual Sodium Carbonate (RSC) and/or Sodium Adsorption Ratio (SAR). (author)

Molecular imaging of enhanced Na + expression in the liver of total sleep deprived rats by TOF-SIMS

Science.gov (United States)

Chang, Hung-Ming; Chen, Bo-Jung; Wu, Un-In; Huang, Yi-Lun; Mai, Fu-Der

2008-12-01

Sleep disorder is associated with metabolic disturbances, which was related to oxidative stress and subsequently sodium overload. Since liver plays important roles in metabolic regulation, present study is aimed to determine whether hepatic sodium, together with oxidative stress, would significantly alter after total sleep deprivation (TSD). Sodium ion was investigated by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Parameter for oxidative stress was examined by heat shock protein-25 (HSP-25) immunohistochemistry. TOF-SIMS spectrum indicated that hepatic Na +/K + ratio counting as 82.41 ± 9.5 was obtained in normal rats. Sodium ions were distributed in hepatocytes with several aggregations. However, following TSD, the intensity for Na +/K + ratio was relatively increased (101.94 ± 6.9) and signals for sodium image were strongly expressed throughout hepatocytes without spatial localization. Quantitative analysis revealed that HSP-25 staining intensity is 1.78 ± 0.27 in TSD rats, which was significantly higher than that of normal ones (0.68 ± 0.15). HSP-25 augmentation suggests that hepatocytes suffer from oxidative stress following TSD. Concerning oxidative stress induced sodium overload would impair metabolic function; enhanced hepatic sodium expression after TSD may be a major cause of TSD relevant metabolic diseases.

Glutathionylation-Dependence of Na+-K+-Pump Currents Can Mimic Reduced Subsarcolemmal Na+ Diffusion

OpenAIRE

Garcia, Alvaro; Liu, Chia-Chi; Cornelius, Flemming; Clarke, Ronald?J.; Rasmussen, Helge?H.

2016-01-01

The existence of a subsarcolemmal space with restricted diffusion for Na+ in cardiac myocytes has been inferred from a transient peak electrogenic Na+-K+ pump current beyond steady state on reexposure of myocytes to K+ after a period of exposure to K+-free extracellular solution. The transient peak current is attributed to enhanced electrogenic pumping of Na+ that accumulated in the diffusion-restricted space during pump inhibition in K+-free extracellular solution. However, there are no know...

Myocardial Na,K-ATPase: Clinical aspects

OpenAIRE

Kjeldsen, Keld

2003-01-01

The specific binding of digitalis glycosides to Na,K-ATPase is used as a tool for Na,K-ATPase quantification with high accuracy and precision. In myocardial biopsies from patients with heart failure, total Na,K-ATPase concentration is decreased by around 40%; a correlation exists between a decrease in heart function and a decrease in Na,K-ATPase concentration. During digitalization, around 30% of remaining pumps are occupied by digoxin. Myocardial Na,K-ATPase is also influenced by other drugs...

Down-Regulation of the Na+-Coupled Phosphate Transporter NaPi-IIa by AMP-Activated Protein Kinase

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Miribane Dërmaku-Sopjani

2013-11-01

Full Text Available Background/Aims: The Na+-coupled phosphate transporter NaPi-IIa is the main carrier accomplishing renal tubular phosphate reabsorption. It is driven by the electrochemical Na+ gradient across the apical cell membrane, which is maintained by Na+ extrusion across the basolateral cell membrane through the Na+/K+ ATPase. The operation of NaPi-IIa thus requires energy in order to avoid cellular Na+ accumulation and K+ loss with eventual decrease of cell membrane potential, Cl- entry and cell swelling. Upon energy depletion, early inhibition of Na+-coupled transport processes may delay cell swelling and thus foster cell survival. Energy depletion is sensed by the AMP-activated protein kinase (AMPK, a serine/threonine kinase stimulating several cellular mechanisms increasing energy production and limiting energy utilization. The present study explored whether AMPK influences the activity of NAPi-IIa. Methods: cRNA encoding NAPi-IIa was injected into Xenopus oocytes with or without additional expression of wild-type AMPK (AMPKα1-HA+AMPKβ1-Flag+AMPKγ1-HA, of inactive AMPKαK45R (AMPKα1K45R+AMPKβ1-Flag+AMPKγ1-HA or of constitutively active AMPKγR70Q (AMPKα1-HA+AMPKβ1-Flag+AMPKγ1R70Q. NaPi-IIa activity was estimated from phosphate-induced current in dual electrode voltage clamp experiments. Results: In NaPi-IIa-expressing, but not in water-injected Xenopus oocytes, the addition of phosphate (1 mM to the extracellular bath solution generated a current (Ip, which was significantly decreased by coexpression of wild-type AMPK and of AMPKγR70Q but not of AMPKαK45R. The phosphate-induced current in NaPi-IIa- and AMPK-expressing Xenopus ooocytes was significantly increased by AMPK inhibitor Compound C (20 µM. Kinetic analysis revealed that AMPK significantly decreased the maximal transport rate. Conclusion: The AMP-activated protein kinase AMPK is a powerful regulator of NaPi-IIa and thus of renal tubular phosphate transport.

Digitalis-induced cell signaling by the sodium pump: on the relation of Src to Na(+)/K(+)-ATPase.

Science.gov (United States)

Gable, Marjorie E; Abdallah, Simon L; Najjar, Sonia M; Liu, Lijun; Askari, Amir

2014-04-18

In addition to performing its essential transport function, the sodium pump also activates multiple cell signaling pathways in response to digitalis drugs such as ouabain. Based mainly on cell-free studies with mixtures of purified Src kinase and Na(+)/K(+)-ATPase, a well-advocated hypothesis on how ouabain initiates the activation of signaling pathways is that there is a preexisting physiological complex of inactive Src bound to the α-subunit of Na(+)/K(+)-ATPase, and that ouabain binding to this subunit disrupts the bound Src and activates it. Because of the published disagreements of the results of such cell-free experiments of two other laboratories, our aim was to attempt the resolution of these discrepancies. We reexamined the effects of ouabain, vanadate, and oligomycin on mixtures of Src, Na(+)/K(+)-ATPase, Mg(2+), and ATP as specified in prior studies; and assayed for Src-418 autophosphorylation as the measure of Src activation. In contrast to the findings of the proponents of the above hypothesis, our results showed similar effects of the three inhibitors of Na(+)/K(+)-ATPase; indicating that Src activation in such experiments is primarily due to the ATP-sparing effect of the ATPase inhibitor on the mixture of two enzymes competing for ATP. We conclude that there is no solid evidence for direct molecular interaction of Src with Na(+)/K(+)-ATPase under physiological conditions. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Thermodynamic study of NaFe complex oxides. High temperature properties of Na sub 5 FeO sub 4 and Na sub 3 FeO sub 3

CERN Document Server

Furukawa, T

2002-01-01

In order to contribute the investigation into corrosion mechanism of the structural materials by leakage sodium, thermodynamic study of Na-Fe complex oxides formed by the reactions was carried out. Na sub 5 FeO sub 4 and Na sub 3 FeO sub 3 were used as the sample. Its high temperature properties (i.e. melting, solidification and transformation) were observed by Differential Scanning Calorimetry, DSC. Moreover, the original test named 'melting point confirmation test' was performed for the observation of traces of melting and solidification after the tests. Following contents have been obtained by this study. (1) Na sub 5 FeO sub 4 was stably as the solid without phase transformation and melting until 800degC. However, the compound was showing a tendency to change into Na sub 4 FeO sub 3 with temperature increasing under the low oxygen potential. (2) The stability of Na sub 3 FeO sub 3 is the same as that of Na sub 5 FeO sub 4 until 700degC. Over the temperature, the compound was changed differential compound ...

Metallic Na formation in NaCl crystals with irradiation of electron or vacuum ultraviolet photon

Energy Technology Data Exchange (ETDEWEB)

Owaki, Shigehiro [Osaka Prefecture Univ., Sakai, Osaka (Japan). Coll. of Integrated Arts and Sciences; Koyama, Shigeko; Takahashi, Masao; Kamada, Masao; Suzuki, Ryouichi

1997-03-01

Metallic Na was formed in NaCl single crystals with irradiation of a variety of radiation sources and analyzed the physical states with several methods. In the case of irradiation of 21 MeV electron pulses to the crystal blocks, the optical absorption and lifetime measurement of positron annihilation indicated appearance of Na clusters inside. Radiation effects of electron beam of 30 keV to the crystals in vacuum showed the appearance of not only metallic Na but atomic one during irradiation with Auger electron spectroscopy. Intense photon fluxes in vacuum ultraviolet region of synchrotron radiation were used as another source and an analyzing method of ultraviolet photoelectron spectroscopy. The results showed the metallic Na layered so thick that bulk plasmon can exist. (author)

Coherent Control of Ground State NaK Molecules

Science.gov (United States)

Yan, Zoe; Park, Jee Woo; Loh, Huanqian; Will, Sebastian; Zwierlein, Martin

2016-05-01

Ultracold dipolar molecules exhibit anisotropic, tunable, long-range interactions, making them attractive for the study of novel states of matter and quantum information processing. We demonstrate the creation and control of 23 Na40 K molecules in their rovibronic and hyperfine ground state. By applying microwaves, we drive coherent Rabi oscillations of spin-polarized molecules between the rotational ground state (J=0) and J=1. The control afforded by microwave manipulation allows us to pursue engineered dipolar interactions via microwave dressing. By driving a two-photon transition, we are also able to observe Ramsey fringes between different J=0 hyperfine states, with coherence times as long as 0.5s. The realization of long coherence times between different molecular states is crucial for applications in quantum information processing. NSF, AFOSR- MURI, Alfred P. Sloan Foundation, DARPA-OLE

Insulin regulation of (Na+, K+)-ATPase

International Nuclear Information System (INIS)

Lytton, J.

1985-01-01

This thesis describes an investigation into the mechanism of insulin stimulation of (Na + ,K + )=ATPase in rat adipocytes. Two molecular forms of the catalytic subunit of the enzyme were identified and denoted α and α(+), due to their similarity to those isozymes previously described from rat brain. Insulin specifically stimulated the α(+) form of the enzyme. The two forms of the enzyme had quite different affinities for intracellular sodium ion; insulin affected only the lower affinity of α(+), shifting it toward a higher value. However, the sodium affinity of (Na + ,K + )-ATPase activity in isolated membranes was equally high for both forms of the enzyme. This suggests that the difference in sodium affinity between the two forms observed in the cell is not inherent within the structure of the sodium pump, but must depend upon a selective interaction with another molecule which has been lost upon membrane isolation. Immunoprecipitation of both the catalytic subunits either from extracts of whole cells which had been labelled with [ 32 P] orthophosphate, or from membranes which had been labelled with γ-[ 32 P]ATP demonstrated that less than 1 in 100 molecules had a covalently bound phosphate insulin had no influence on this value. The amino terminal sequences of the first 4 amino acids of the catalytic subunits of both α (isolated from rat kidney) and α(+) (from rat brainstem axolemma) were determined. The result shows two highly homologous but clearly different molecules. It can thus be concluded that the insulin sensitive version of the enzyme is not derived from the common α form by a post-translational modification

Na, K-ATPase α3 is a death target of Alzheimer patient amyloid-β assembly.

Science.gov (United States)

Ohnishi, Takayuki; Yanazawa, Masako; Sasahara, Tomoya; Kitamura, Yasuki; Hiroaki, Hidekazu; Fukazawa, Yugo; Kii, Isao; Nishiyama, Takashi; Kakita, Akiyoshi; Takeda, Hiroyuki; Takeuchi, Akihide; Arai, Yoshie; Ito, Akane; Komura, Hitomi; Hirao, Hajime; Satomura, Kaori; Inoue, Masafumi; Muramatsu, Shin-ichi; Matsui, Ko; Tada, Mari; Sato, Michio; Saijo, Eri; Shigemitsu, Yoshiki; Sakai, Satoko; Umetsu, Yoshitaka; Goda, Natsuko; Takino, Naomi; Takahashi, Hitoshi; Hagiwara, Masatoshi; Sawasaki, Tatsuya; Iwasaki, Genji; Nakamura, Yu; Nabeshima, Yo-ichi; Teplow, David B; Hoshi, Minako

2015-08-11

Neurodegeneration correlates with Alzheimer's disease (AD) symptoms, but the molecular identities of pathogenic amyloid β-protein (Aβ) oligomers and their targets, leading to neurodegeneration, remain unclear. Amylospheroids (ASPD) are AD patient-derived 10- to 15-nm spherical Aβ oligomers that cause selective degeneration of mature neurons. Here, we show that the ASPD target is neuron-specific Na(+)/K(+)-ATPase α3 subunit (NAKα3). ASPD-binding to NAKα3 impaired NAKα3-specific activity, activated N-type voltage-gated calcium channels, and caused mitochondrial calcium dyshomeostasis, tau abnormalities, and neurodegeneration. NMR and molecular modeling studies suggested that spherical ASPD contain N-terminal-Aβ-derived "thorns" responsible for target binding, which are distinct from low molecular-weight oligomers and dodecamers. The fourth extracellular loop (Ex4) region of NAKα3 encompassing Asn(879) and Trp(880) is essential for ASPD-NAKα3 interaction, because tetrapeptides mimicking this Ex4 region bound to the ASPD surface and blocked ASPD neurotoxicity. Our findings open up new possibilities for knowledge-based design of peptidomimetics that inhibit neurodegeneration in AD by blocking aberrant ASPD-NAKα3 interaction.

Osmotic Pressure of Aqueous Electrolyte Solutions via Molecular Simulations of Chemical Potentials: Application to NaCl.

Czech Academy of Sciences Publication Activity Database

Smith, W.R.; Moučka, F.; Nezbeda, Ivo

2016-01-01

Roč. 407, Sl (2016), s. 76-83 ISSN 0378-3812 Grant - others:NSERC(CA) OGP1041 Institutional support: RVO:67985858 Keywords : osmotic pressure * chemical potential * molecular simulation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.473, year: 2016

Unbiased simulations reveal the inward-facing conformation of the human serotonin transporter and Na+ ion release

DEFF Research Database (Denmark)

Koldsø, Heidi; Noer, Pernille Rimmer; Grouleff, Julie

2011-01-01

transporter has resulted in homology models of the monoamine transporters. Here we present extended molecular dynamics simulations of an experimentally supported homology model of hSERT with and without the natural substrate yielding a total of more than 1.5 µs of simulation of the protein dimer....... The simulations reveal a transition of hSERT from an outward-facing occluded conformation to an inward-facing conformation in a one-substrate-bound state. Simulations with a second substrate in the proposed symport effector site did not lead to conformational changes associated with translocation. The central...... substrate binding site becomes fully exposed to the cytoplasm leaving both the Na+-ion in the Na2-site and the substrate in direct contact with the cytoplasm through water interactions. The simulations reveal how sodium is released and show indications of early events of substrate transport. The notion...

NaOHを含むアルコール溶液へのフロン溶解度における塩析効果

OpenAIRE

荒井, 茉衣

2013-01-01

当研究室では常温常圧でフロンを分解する方法を発見した。NaOHを溶かした低級のアルコールにフロンをバブリングし紫外線を当てることで脱塩素を可能にした。しかしNaOHがフロンの溶解度に影響を及ぼしており、塩析効果がみられた。塩析効果はNa+とアルコールの2種間で起こっている現象であると考えていたが塩析効果定数を決定する際に用いるグループ寄与法において、フロン分子の寄与分を用いていることから3種間で起こるものと考えた。この推測を検証するべく研究をおこなった。フロンの種類はHFC-134a、HFC-152a、を使用し、アルコールはメタノール、エタノールを用いて実験をおこなった。Solubility of fluorocarbons is affected by NaOH concentration. This phenomenon is salting effect. We think that Na+ion attract only alcohol molecular. But fluorocarbon molecular gravitate toward Na+ion too, b...

Efeitos do exercicio físico em parâmetros moleculares da via de sinalização da insulina e obesidade

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Joni Marcio de Farias

2014-08-01

Full Text Available http://dx.doi.org/10.5007/1980-0037.2014v16n5p588 A prevalência da obesidade e diabetes mellitus tem aumentado significativamente nos últimos anos e o conhecimento de que o tecido adiposo tem atividade endócrina e desempenha funções importantes na regulação da inflamação e no metabolismo energético por meio de mecanismos moleculares entre outros é fonte de novas pesquisas. Este trabalho versa sobre os mecanismos moleculares envolvidos na obesidade e diabetes principalmente em tecidos periféricos bem como a relação do exercício físico neste contexto, em forma de revisão bibliográfica. A metodologia foi levantamento bibliográfico nas principais bases de dados: Scielo e PubMed, publicados no período de 1998 a 2012. Os estudos tem demonstrado uma inter-relação entre os mecanismos moleculares envolvidos no desenvolvimento da obesidade e diabetes em tecidos periféricos e centrais. Do ponto de vista do exercício físico, vários estudos demonstram uma contribuição muito grande na diminuição da prevalência, no controle e até mesmo no tratamento da obesidade e diabetes. No entanto há necessidade de estudos mais aprofundados relacionando diversos tipos de exercício físico, em volumes e intensidades diferentes e preferencialmente com humanos, bem como o modelo de estudo, que quando utilizado animais, os programas de exercício devem ser desenvolvidos concomitantemente com alimentação rica em gordura, verificando mais intensamente o exercício físico e o seu real papel na prevenção destas doenças.

Reconstruction of the complete ouabain-binding pocket of Na,K-ATPase in gastric H,K-ATPase by substitution of only seven amino acids

NARCIS (Netherlands)

Qiu, L.Y.; Krieger, E.; Schaftenaar, G.; Swarts, H.G.P.; Willems, P.H.G.M.; Pont, J.J.H.H.M. de; Koenderink, J.B.

2005-01-01

Although cardiac glycosides have been used as drugs for more than 2 centuries and their primary target, the sodium pump (Na, K-ATPase), has already been known for 4 decades, their exact binding site is still elusive. In our efforts to define the molecular basis of digitalis glycosides binding we

Reconstruction of the complete ouabain-binding pocket of Na,K-ATPase in gastric H,K-ATPase by substitution of only seven amino acids.

NARCIS (Netherlands)

Qiu, L.; Krieger, E.; Schaftenaar, G.; Swarts, H.G.P.; Willems, P.H.G.M.; Pont, J.J.H.H.M. de; Koenderink, J.B.

2005-01-01

Although cardiac glycosides have been used as drugs for more than 2 centuries and their primary target, the sodium pump (Na,K-ATPase), has already been known for 4 decades, their exact binding site is still elusive. In our efforts to define the molecular basis of digitalis glycosides binding we

Scintillation efficiency measurement of Na recoils in NaI(Tl) below the DAMA/LIBRA energy threshold

Energy Technology Data Exchange (ETDEWEB)

Xu, Jingke; Shields, Emily; Calaprice, Frank; Westerdale, Shawn; Froborg, Francis; Suerfu, Burkhant; Alexander, Thomas; Aprahamian, Ani; Back, Henning O.; Casarella, Clark; Fang, Xiao; Gupta, Yogesh K.; Ianni, Aldo; Lamere, Edward; Lippincott, W. Hugh; Liu, Qian; Lyons, Stephanie; Siegl, Kevin; Smith, Mallory; Tan, Wanpeng; Kolk, Bryant Vande

2015-07-01

The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3 to 52 keVnr, covering the whole DAMA/LIBRA energy region for dark matter-Na scattering interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.

Yeast plasma membrane Na/H antiporter - importance of OH groups in the 5th tms for activity and substrate specificity

Czech Academy of Sciences Publication Activity Database

Zimmermannová, Olga; Sychrová, Hana

2007-01-01

Roč. 274, Suppl.1 (2007), s. 127-127 ISSN 1742-464X. [FEBS Congress Molecular Machines /32./. 07.07.2007-12.07.2007, Vienna] R&D Projects: GA MŠk(CZ) LC531; GA AV ČR(CZ) IAA5011407 Institutional research plan: CEZ:AV0Z50110509 Keywords : cpo1 * Na/H antiporter * yeast * substrate specificity Subject RIV: EE - Microbiology, Virology

Synthesis of Ag or Pt Nanoparticles by Hydrolysis of Either Ag2Na or PtNa

Directory of Open Access Journals (Sweden)

Huabin Wang

2008-01-01

Full Text Available Ag and Pt nanoparticles have successfully been synthesized by hydrolysis of either Ag2Na or PtNa at room temperature. The oxidation of sodium in the Pt-Na pellets was much faster than that in the Ag-Na pellets since Pt is a catalyst for H2O formation reaction from hydrogen and oxygen at room temperature. The hydrolysis byproduct, NaOH, has a high solubility and easily is removed. This method offers a simple method of preparing transition metal nanoparticles. The Ag and Pt nanoparticles prepared by this method were crystalline in nature, and spherical in shape with a mean size of around 10 nm.

Dynamic polarizabilities and Van der Waals coefficients for alkali atoms Li, Na and alkali dimer molecules Li2, Na2 and NaLi

Science.gov (United States)

Mérawa, M.; Dargelos, A.

1998-07-01

The present paper gives an account of investigations of the polarizability of the alkali atoms Li, Na, diatomics homonuclear and heteronuclear Li2, Na2 and NaLi at SCF (Self Consistent Field) level of approximation and at correlated level, using a time Time-Dependent Gauge Invariant method (TDGI). Our static polarizability values agree with the best experimental and theoretical determinations. The Van der Waals C6 coefficients for the atom-atom, atom-dimer and dimer-dimer interactions have been evaluated. Les polarisabilités des atomes alcalins Li, Na, et des molécules diatomiques homonucléaires et hétéronucléaire Li2, Na2 et NaLi, ont été calculées au niveau SCF (Self Consistent Field) et au niveau corrélé à partir d'une méthode invariante de jauge dépendante du temps(TDGI). Nos valeurs des polarisabilités statiques sont en accord avec les meilleurs déterminations expérimentales et théoriques. Les coefficients C6 de Van de Waals pour les interactions atome-atome, atome-dimère et dimère-dimère ont également été évalués.

Indentification of amino - acid residues important for the substrate specificity range of yeast plasma membrane Na+/H+-antiporters

Czech Academy of Sciences Publication Activity Database

Zimmermannová, Olga; Zavřel, Martin; Sychrová, Hana

2005-01-01

Roč. 22, č. S1 (2005), S178-S178 ISSN 0749-503X. [International Conference on Yeast Genetics and Molecular Biology /22./. 07.08.2005-12.08.2005, Bratislava] R&D Projects: GA ČR(CZ) GP204/02/D092; GA AV ČR(CZ) IAA5011407 Institutional research plan: CEZ:AV0Z50110509 Keywords : yeast * Na+/H+ antiporter * K+ transport * substrate specificity Subject RIV: CE - Biochemistry

Interactions of oxytetracycline with a smectite clay: a spectroscopic study with molecular simulations.

Science.gov (United States)

Aristilde, Ludmilla; Marichal, Claire; Miéhé-Brendlé, Jocelyne; Lanson, Bruno; Charlet, Laurent

2010-10-15

Binding of antibiotics to clay minerals can decrease both their physical and biological availability in soils. To elucidate the binding mechanisms of tetracycline antibiotics on smectite clays as a function of pH, we probed the interactions of oxytetracycline (OTC) with Na-montmorillonite (MONT) using X-ray diffraction (XRD), infrared (IR), and solid-state nuclear magnetic resonance (NMR) spectroscopies, and Monte Carlo molecular simulations. The XRD patterns demonstrate the presence of OTC in the MONT interlayer space at acidic pH whereas complexation of OTC by external basal and edge sites seems to prevail at pH 8. At both pH, the (1)H-(13)C NMR profile indicates restricted mobility of the adsorbed OTC species; and, -CH(3) deformation and C-N stretching IR vibration bands confirm a binding mechanism involving the protonated dimethylamino group of OTC. Changes in the (23)Na NMR environments are consistent with cation-exchange and cation complexation reactions at the different sites of adsorption. Molecular simulations indicate that MONT interlayer spacing and structural charge localization dictate favorable binding conformations of the intercalated OTC, facilitating multiple interactions in agreement with the spectroscopic data. Our results present complementary insights into the mechanisms of adsorption of TETs on smectites important for their retention in natural and engineered soil environments.

Structure-function relationships of Na+, K+, ATP, or Mg2+ binding and energy transduction in Na,K-ATPase

DEFF Research Database (Denmark)

Jorgensen, Peter L.; Pedersen, Per Amstrup

2000-01-01

Na,K-ATPase; Mutagenesis; Na+ binding; K+ binding; Tl+ binding; Mg2+ binding; ATP binding; Cation binding site; Energy transduction......Na,K-ATPase; Mutagenesis; Na+ binding; K+ binding; Tl+ binding; Mg2+ binding; ATP binding; Cation binding site; Energy transduction...

Helicase-Dependent Isothermal Amplification of DNA and RNA by Using Self-Avoiding Molecular Recognition Systems.

Science.gov (United States)

Yang, Zunyi; McLendon, Chris; Hutter, Daniel; Bradley, Kevin M; Hoshika, Shuichi; Frye, Carole B; Benner, Steven A

2015-06-15

Assays that detect DNA or RNA (xNA) are highly sensitive, as small amounts of xNA can be amplified by PCR. Unfortunately, PCR is inconvenient in low-resource environments, and requires equipment and power that might not be available in these environments. Isothermal procedures, which avoid thermal cycling, are often confounded by primer dimers, off-target priming, and other artifacts. Here, we show how a "self avoiding molecular recognition system" (SAMRS) eliminates these artifacts and gives clean amplicons in a helicase-dependent isothermal amplification (SAMRS-HDA). We also show that incorporating SAMRS into the 3'-ends of primers facilitates the design and screening of primers for HDA assays. Finally, we show that SAMRS-HDA can be twofold multiplexed, difficult to achieve with HDA using standard primers. Thus, SAMRS-HDA is a more versatile approach than standard HDA, with a broader applicability for xNA-targeted diagnostics and research. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

At NA2

CERN Multimedia

1977-01-01

One of the NA2 calorimeter sections is moved in. The NA2 calorimeter was divided in two halves, to the left and the right of the beam, each half consisting of sheets of passive high Z material interleaved with blades of plastic scintillators. The photo shows on the right, the upstream 'electron' module with eleven lead plates for a total radiation length of 20.

Resíduos de plantas de cobertura e mobilidade dos produtos da dissolução do calcário aplicado na superfície do solo Cover plant residues and mobility of dissolution products of surface applied lime

Directory of Open Access Journals (Sweden)

A. S. Amaral

2004-02-01

Full Text Available As plantas de cobertura têm recebido atenção adicional em função da liberação de ácidos orgânicos de baixo peso molecular capazes de formar complexos orgânicos com alumínio, cálcio e magnésio. Dessa forma, além de neutralizarem o alumínio tóxico, esses ácidos podem aumentar a mobilidade, no perfil do solo, dos produtos originados da dissolução do calcário aplicado na superfície. Os objetivos deste trabalho foram (a identificar os ácidos orgânicos de baixo peso molecular presentes nos resíduos de plantas de cobertura e na solução do solo; (b avaliar o efeito desses resíduos, juntamente com a aplicação superficial de calcário, na correção da acidez das camadas subsuperficiais do solo no sistema plantio direto, e (c verificar a relação dos ácidos orgânicos de baixo peso molecular, liberados na decomposição de resíduos vegetais, com os efeitos, na profundidade do solo, da aplicação superficial de calcário. O experimento foi realizado em casa de vegetação em colunas de PVC com amostras indeformadas de um Cambissolo Húmico Alumínico Léptico argiloso há cinco anos no sistema plantio direto. Os tratamentos constaram da aplicação de resíduos (10 Mg ha-1 de aveia preta (1, ervilhaca (2 e nabo forrageiro (3, calcário (13 Mg ha-1 (4, calcário mais resíduo de aveia preta (5, de ervilhaca (6 e de nabo forrageiro (7 calcário mais ácido cítrico (0,91 Mg ha-1 (8 e uma testemunha (9, dispostos em blocos ao acaso. O uso da cromatografia líquida permitiu identificar os ácidos orgânicos de baixo peso molecular nos resíduos vegetais utilizados. Na aveia preta, houve predomínio do ácido transaconítico, na ervilhaca predominou o ácido málico e no nabo forrageiro os ácidos cítrico e málico. Não foi possível detectar nenhum tipo de ácido orgânico de baixo peso molecular tanto na solução percolada como na solução do solo. Os resíduos vegetais não tiveram efeito na correção da acidez do solo

Síntesis in vitro de la proteína de la envoltura del virus peruano de la fiebre amarilla

Directory of Open Access Journals (Sweden)

Carlos Yábar V

2001-01-01

Full Text Available Objetivo: Sintetizar la proteína recombinante de la envoltura (Er del virus peruano de la Fiebre Amarilla (FA utilizando técnicas moleculares. Materiales y métodos: El gen de la proteína de interés fue amplificado por transcripción reversa - reacción en cadena de la polimerasa (RT-PCR y clonado en un vector plasmídico para ser analizado mediante secuenciamiento de ADN. El inserto de ADN fue subdonado en un vector de expresión para ser traducido a proteína. Se purificó la proteína mediante cromatografía de afinidad bajo condiciones denaturantes, siendo visualizada por electroforesis en SDS-PAGE. Resultados: Se sintetizó y purificó la pr E del virus de la FA. Presentó un peso de 66 kDa, y luego de tres horas de inducción a partir de 1x108 células (OD=0.5 se obtuvo 10 mg/mL de la proteína a miniescala. Conclusión: El análisis de la secuencia de aminoácidos demostró que Er podría ser un buen candidato a ser evaluado serológicamente y luego ser usado como herramienta de diagnóstico específico para la FA.

Caracterização de genótipos de mirtilo utilizando marcadores moleculares Characterization of blueberry genotypes using molecular markers

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Sergio Delmar dos Anjos e Silva

2008-03-01

Full Text Available O cultivo do mirtilo está em expansão no Brasil, em especial em regiões de clima temperado, onde há grande demanda em relação a cultivares adaptadas às condições edafoclimáticas regionais. O objetivo deste trabalho foi caracterizar genótipos de mirtilo do programa de melhoramento da Embrapa Clima Temperado, utilizando marcadores moleculares do tipo RAPD e SSR. Foram caracterizados 40 genótipos de mirtilo por RAPD e oito cultivares por microssatélites. Os nove primers utilizados na técnica de RAPD geraram 89 marcadores. A similaridade genética entre os genótipos variou de 64 a 89%. Utilizando a similaridade média (66%, foram obtidos quatro grupos. Foram gerados 11 marcadores a partir de três pares de primers de microssatélites. A similaridade genética entre as cultivares variou de 25 a 75%. Com similaridade média (42,4%, foram obtidos três grupos. Com apenas três pares de primers de SSR, foi possível definir o padrão das oito cultivares de mirtilo, revelando a eficiência da técnica de microssatélite na caracterização de genótipos dessa espécie. Esses resultados revelam a eficiência dos marcadores tipo RAPD e SSR na caracterização de genótipos de mirtilo. Entretanto, os marcadores tipo microssatélites geram resultados mais precisos, sendo os mais recomendados para uso em programas de melhoramento e identificação de cultivares.The blueberry crop planting area is increasing in Brazil, especially in Temperate Climate Zones, generating demands relating to suitable cultivars adapted to regional climate and soil conditions. This work aimed to characterize blueberry genotypes from Embrapa Clima Temperado breeding program, using RAPD and SSR molecular markers. There were characterized 40 blueberry genotypes using RAPD and 8 cultivars using SSR molecular markers. The 9 RAPD primers generated 89 markers. The genetic similarity ranged from 64 to 89%. Through the average similarity (66%, it was possible to identify four

Na+-K+ pump in chronic renal failure

International Nuclear Information System (INIS)

Deepak, K.; Kahn, T.

1987-01-01

This review summarizes the evidence for the defect in Na + -K + pump in chronic renal failure, considers the role of various factors in causing this defect, and discusses the clinical implications thereof. Intracellular Na is elevated in erythrocytes, leukocytes, and muscle cells from some patients with chronic renal failure (CRF). Recent evidence suggest that this elevation of cell Na may be, in large part, a consequence of decreased number of Na + -K + pump units per cell. Maintenance dialysis over a period of weeks ameliorates the defect in intracellular Na + , and this improvement is contemporaneous with an increase in the number of Na + -K + pump sites per cell. In erythrocytes with normal cell Na + , acute hemodialysis increases the rate of 22 Na + and 42 K + transport. Many factors such as the presence of retained toxic metabolite or circulating inhibitor in the uremic plasma, or biochemical changes produced by acute hemodialysis, may explain this finding. In cells with high cell Na + , the pump-mediated 42 K + transport is normalized at the expense of a raised cell Na + . The decreased muscle membrane potential in uremic subjects has been attributed to a decreased activity of Na + -K + pump. The authors discuss the role of hormonal abnormalities and circulating inhibitors, which may cause an acute inhibition of the pump and of other factors such as K + depletion, which may cause more chronic alterations. The implications of alteration of Na + and K + pump transport and raised cell Na + on other non-pump-mediated transport pathways are discussed. Raised cell Na + may be a marker for the adequacy of maintenance dialysis in patients with end-stage renal failure

Uso de marcadores moleculares na análise da variabilidade genética em acerola (Malpighia emarginata D.C.

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SALLA MARIA FERNANDA SPEGIORIN

2002-01-01

Full Text Available A acerola (Malpighia emarginata é uma frutífera tropical encontrada nativa na América Central e no Norte da América do Sul, sendo de grande importância econômica e social devido ao seu alto conteúdo de vitamina C (ácido ascórbico. Pomares de acerola têm sido preferencialmente estabelecidos por métodos de propagação vegetiva. No entanto, a propagação sexuada por sementes é igualmente utilizada e permite revelar um alto grau de polimorfismo na cultura, possibilitando a identificação de genótipos portadores de características de interesse agronômico. Vinte e quatro acessos de acerola, pertencentes ao Banco Ativo de Germoplasma da Universidade Estadual de Londrina, foram analisados, usando marcadores RAPD (Random amplified Polymorphic DNA e obtidos com iniciadores (primers de seqüência simples repetidas (SSRs. Um total de 164 e 73 marcadores foram obtidos com primers de RAPD e SSR, respectivamente. Os marcadores obtidos foram analisados, usando o método de agrupamentos UPGMA. A análise comparativa dos dendrogramas gerados com os primers de RAPD e com os primers SSR mostrou que, enquanto alguns acessos se associaram em grupos diferentes, outros apresentaram a mesma associação. Entretanto, maior polimorfismo entre acessos foi detectado com os primers de RAPD. A análise dos resultados revelou a alta variabilidade contida na coleção, permitindo associar o grau de similaridade genética, obtido por marcadores de DNA, com caracteres morfológicos compartilhados entre os acessos.

Effects of NaCl on Fermentative Metabolism of Mature Green Tomatoes cv. Ailsa Craig in Brine

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Sotirios Fragkostefanakis

2010-01-01

Full Text Available The effect of osmotic strength on gene expression and activity of the major enzymes of fermentative metabolism of mature green tomato fruit (Solanum lycopersicum cv. Ailsa Craig has been studied by exposing fruit to brine containing 0 (water, 5 and 10 % NaCl. The fruits were surface sterilized prior to treatment to prevent the growth of microbes naturally present on the skin of the fruit. Changes in fruit expression of fermentation genes and the activity of the respective enzymes as well as physicochemical quality characteristics (soluble solid content, titratable acidity, pH and firmness were studied in both fruit and brine for 0.5, 1, 1.5, 2, 3, 7 and 14 days. Discrepancies in responses that resulted from the different salt concentrations were obtained at molecular and quality levels. The complex kinetics of solutes between the fruit and the surrounding solution due to osmotic potential has led to different responses of the tissue to fermentation. Tomato fruit showed cracking soon after storage in water; water-stored fruit had higher titratable acidity, lower soluble solid content, and higher induction of anaerobic metabolism as indicated by the expression or the activity of the fermentation enzymes compared to fruit stored in brine with 5 or 10 % NaCl. No cracking was observed in fruit stored in 5 (isotonic or 10 % NaCl (hypertonic brine, though in the latter, signs of dehydration were observed. The presence of salt in brine reduced the intensity of fermentative metabolism as indicated by the lower gene expression and enzyme activity. However, fruit stored in brine with 5 % NaCl survived longer than with 0 or 10 % NaCl. The presence of 5 % NaCl in brine caused mild changes of both the fermentative metabolism and the physicochemical characteristics and prevented fruit deterioration during storage.

Pozitivni in negativni vplivi risank na otroke

OpenAIRE

Povše, Nika