Ion Exit Research Articles

Association of NRAMP1 Gene Polymorphism with Hemoglobin and Iron Parameters in Patients with β-Thalassemia Major

Abstract BACKGROUND: Thalassemia is an inherited disorder that is also called mediterranean anemia and is described by a lack of hemoglobin synthesis. β-thalassemia is more common in people of certain origins, particularly those from the Mediterranean region and Arabian Peninsula. The NRAMP1 protein in membranes catalyzes the exit of divalent metal ions from phagolysosomes and their entry into the cytoplasm, including iron and manganese. AIMS: To investigate the possible link between beta-thalassemia major (β-TM) illness and the single-nucleotide polymorphism (3′ untranslated region) rs3 of the NRAMP1 gene. MATERIALS AND METHODS: To investigate the relationship between the condition β-TM and the NRAMP1 gene, the study used restriction fragment length polymorphisms-polymerase chain reaction. The enzyme-linked fluorescent assay was used to quantify the ferritin level. A hematology analyzer was used to quantify hemoglobin concentration. A spectrophotometer technique was used to assess the serum iron, serum total iron-binding capacity (TIBC), and serum unsaturated iron-binding capacity. RESULTS: The results showed a difference in hemoglobin and serum iron levels, serum unbound iron-binding capacity, serum TIBC, and ferritin concentration between individuals suffering from β-thalassemia and healthy groups. In NRAMP1 gene polymorphism, a highly significant difference was observed between the distribution of two alleles (TG− 244 bp, and TG+ 211 bp). CONCLUSION: During an investigation of NRAMP1 gene polymorphism, a significant variance was observed between β-thalassemia and control groups. Those who carried the (244 bp −TG) allele were found to have a 3.6 times higher risk of developing complications of β-TM than those who carried the (211 bp −TG+) allele.

Ion transport through short nanopores modulated by charged exterior surfaces.

Short nanopores find extensive applications, capitalizing on their high throughput and detection resolution. Ionic behaviors through long nanopores are mainly determined by charged inner-pore walls. When pore lengths decrease to sub-200nm, charged exterior surfaces provide considerable modulation to ion current. We find that the charge status of inner-pore walls affects the modulation of ion current from charged exterior surfaces. For 50-nm-long nanopores with neutral inner-pore walls, the charged exterior surfaces on the voltage (surfaceV) and ground (surfaceG) sides enhance and inhibit the ion transport by forming ion enrichment and depletion zones inside nanopores, respectively. For nanopores with both charged inner-pore and exterior surfaces, continuous electric double layers enhance the ion transport through nanopores significantly. The charged surfaceV results in higher ion current by simultaneously weakening the ion depletion at pore entrances and enhancing the intra-pore ion enrichment. The charged surfaceG expedites the exit of ions from nanopores, resulting in a decrease in ion enrichment at pore exits. Through adjustment in the width of charged-ring regions near pore boundaries, the effective charged width of the charged exterior is explored at ∼20nm. Our results may provide a theoretical guide for further optimizing the performance of nanopore-based applications, such as seawater desalination, biosensing, and osmotic energy conversion.

The plasma–sheath transition and Bohm criterion in a high recycling divertor

The high recycling regime of a divertor is characterized by high plasma particle fluxes and low temperature at the target, where a strong hydrogen recirculation loop exists. Atomic processes in the high recycling regime, such as ion–neutral friction and radiation, can affect the plasma momentum and energy transport in the sheath transition region. Here, the plasma–sheath transition near a high recycling wall is investigated. The Bohm speed, which constraints the ion exit flow speed, is evaluated from a transport model that accounts for the effect of the anisotropic transport and atomic collisions in the transition layer. A first principles kinetic code vector particle-in-cell with the atomic collision package is used to investigate a 1D self-consistent slab plasma with a high recycling boundary for the tungsten and carbon divertors. The results demonstrate the accuracy of the Bohm speed model in predicting the ion exit flow speed in the transition region, as well as the reduction of the Bohm speed due to the ion–neutral friction. The effect of different wall materials, tungsten, and carbon, on the Bohm speed and near-wall plasma profile is shown.

Nanoarchitectonics of heteroatom-doped hierarchical porous carbon derived from carboxymethyl cellulose carbon aerogel and metal-organic framework for capacitive deionization

Capacitive deionization (CDI) using porous materials offers a sustainable solution for providing affordable freshwater, but the low salt adsorption rate of benchmark carbon materials significantly limit the practical implementation. Herein, we utilized carboxymethyl cellulose sodium (CMC) as the carbon skeleton to produce a composite carbon aerogel loaded with ZIF-8 (ZIF-8/CMC-CA). The presence of ZIF-8 nanoparticles improved the pore structure of the material and provides a certain pseudo capacitance by introducing N. Compared with ZIF-8 derived carbons (ZIF-8-C), the CMC provided a good three-dimensional structure for the dispersion of ZIF-8 nanoparticles, reduced the agglomeration of particles. Furthermore, numerous carboxyl and hydroxyl groups on CMC enhanced the hydrophilicity of materials. Due to the interconnected structure, ZIF-8/CMC-CA exhibited excellent conductivity, a high specific surface area, and offered suitable channels for the rapid entry and exit of ions. In a three-electrode system, the total specific capacitance of the ZIF-8/CMC-CA electrode was 357.14 F g−1. The adsorption rate of ZIF-8/CMC-CA was 2.02 mg g−1 min−1 in a 500 mg L−1 NaCl solution. This study may provide new insight for modifying and fabricating electrode materials for practical CDI applications.

Structural basis of rapid inactivation of HERG potassium channels.

The exquisite fine tuning of electrical signalling in different cells types is mediated by variations in the rates that gates open and close in different ion channels. The opening and closing of the inactivation gate in Human ether-a-go-go related gene (HERG) K+ channels is uniquely rapid, which confers upon them a critical role in protecting against cardiac arrhythmias and sudden cardiac death. The molecular mechanisms that underlie the rapidity of HERG inactivation, however, remain unclear. Here, we have determined Cryo-EM structures of the conductive state as well as HERG's elusive inactivated state to 2.4 Å resolution and propose a mechanism for the fast kinetics of inactivation. The selectivity filter is pulled upward by Asn633 upon the exit of potassium ions from the upper part of the filter. This movement allows the sidechain of Ser620, located behind the selectivity filter, to alternately hydrogen bond to the upper or lower part of the selectivity filter to stabilize the conducting and inactivated states respectively. The inactivated state is also characterized by flipping of the valine carbonyls in the centre of the selectivity filter. Using molecular dynamics simulation, we have identified a transient interaction between Ser620 and Tyr616 that reduces the free energy barrier for flipping of the valine carbonyls, thereby explaining the rapidity of HERG inactivation. Our results have demonstrated the dynamic nature of potassium channels with a new model of inactivation different from the well characterized KcsA.

Composite Cement Materials Based on β-Tricalcium Phosphate, Calcium Sulfate, and a Mixture of Polyvinyl Alcohol and Polyvinylpyrrolidone Intended for Osteanagenesis

The primary purpose of the study, presented in this article, was to obtain a composite cement material intended for osteanagenesis. The β-tricalcium phosphate powder (β-TCP, β-Ca3(PO4)2) was obtained by the liquid-phase method. Setting and hardening of the cement system were achieved by adding calcium sulfate hemihydrate (CSH, CaSO4·1/2H2O). An aqueous solution of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and a PVA/PVP mixture were used as a polymer component. The methods of capillary viscometry and Fourier-transform infrared spectroscopy (FTIR) revealed the formation of intermolecular hydrogen bonds between polymer components, which determines the good miscibility of polymers. The physicochemical properties of the synthesized materials were characterized by X-ray diffraction (XRD) and FTIR methods, and the added amount of polymers does not significantly influence the processes of phase formation and crystallization of the system. The size of crystallites CSD remained in the range of 32-36 nm, regardless of the ratio of polymer components. The influence of the composition of composites on their solubility was investigated. In view of the lower solubility of pure β-TCP, as compared to calcium sulfate dihydrate (CSD, CaSO4·2H2O), the solubility of composite materials is determined to a greater degree by the CSD solubility. Complexometric titration showed that the interaction between PVA and PVP impeded the diffusion of calcium ions, and at a ratio of PVA to PVP of 1/1, the smallest exit of calcium ions from the system is observed. The cytotoxicity analysis results allowed us to establish the fact that the viability of human macrophages in the presence of the samples varied from 80% to 125% as compared to the control.

Transport physics dependence of Bohm speed in presheath–sheath transition

The ion exit flow speed at the sheath entrance is constrained by the Bohm criterion, which is used as a boundary condition for simulations that do not resolve the sheath region. Traditional Bohm criterion analysis invokes the equation of state and, thus, ignores transport physics in the sheath transition problem. An expression for the Bohm speed away from the asymptotic limit is derived from a set of anisotropic plasma transport equations. The thermal force, collisional temperature isotropization, and heat flux enter into the evaluation of the Bohm speed. By comparison with kinetic simulation results, this expression is shown to be accurate in the presheath–sheath transition region rather than a single point at the sheath entrance over a broad range of collisionality.

Crystallization‐induced suppression of intumescence in aqueous alkali silicates

AbstractThermal properties of aqueous alkali silicates have been investigated to establish a fundamental understanding of the structural state of silicate network and its impact on intumescence, up to 450°C. Foaming behavior is dependent upon the type of alkali ion (Na, K, Li) as well as composition as evidenced from a combination of tools involving thermogravimetric analysis, nuclear magnetic resonance, and X‐ray diffraction. Na silicates show extensive foaming, Li‐silicates do not foam, whereas K‐silicates exhibit an intermediate behavior depending upon the starting state and heating kinetics. Crystallization is observed for K‐ and Li‐silicates but not in the case of Na‐silicates and appears to be a limiting factor for macroscopic structural expansion. Quantitative analysis of different species reveals the network to be relatively mobile, in terms of its ability to reorganize, in pre‐dried (at 150°C) Na‐silicates. A reduction in this mobility is seen for K‐silicates as crystallization reduces K ions and silanols in the amorphous phase at and above 150°C, thus reducing the extent of foaming. In contrast, phase separation coupled with crystallization resulting in a complete exit of Li ions from the amorphous phase tends to suppress completely the intumescent phenomenon.

Molecular properties of Ca2+ transport through TRPV2 channel: a molecular dynamics simulations study

TRPV channels are a category of nonselective cation channels that are activated by heat and ligands and permeate monovalent and divalent ions. The mechanism of Ca2+ transfer through TRPV2 channel is not well known. Here, we investigated the reaction coordination and energy fluctuation of Ca2+ transition in TRPV2 channel by steered molecular dynamics (SMD) simulations and potential of mean force (PMF) calculation. Results showed that electrostatic interactions between Ca2+ and residues of the first and second gates had main roles in ions transfer through the channel. Also, we recognized important amino acids in this path. Moreover, results indicated that enter and exit of calcium ions need to overcome barrier energies in the first and second gates. Communicated by Ramaswamy H. Sarma

A Miniature Four-Channel Ion Trap Array Based on Non-silicon MEMS Technology.

With the increasing application field, a higher requirement is put forward for the mass spectrometer. The reduction in size will inevitably cause a loss of precision; therefore, it is necessary to develop a high-performance miniature mass spectrometer. Based on the researches of rectangular ion trap, the relationship between mass resolution and structural parameters of the ion trap array was analyzed by further simulation. The results indicate that, considering the balance of mass resolution and extraction efficiency, the preferable values for the field radius of exit direction y0 and ion exit slot width s0 are 1.61 mm and 200 μm, respectively. Afterwards, a miniature four-channel ion trap array (MFITA) was fabricated, by using MEMS and laser etching technology, and mass spectrometry experiments were carried out to demonstrate its performance. The mass resolution of butyl diacetate with m/z = 230 can reach 324. In addition, the consistency of four channels is verified within the error tolerance, by analyzing air samples. Our work can prove the correctness of the structural design and the feasibility of MEMS preparation for MFITA, which will bring meaningful guidance for its future development and optimization.

Determination of 16 organophosphate esters in human blood by high performance liquid chromatography-tandem mass spectrometry combined with liquid-liquid extraction and solid phase extraction

人体体液中有机磷酸酯(OPEs)浓度的测定对于了解人体OPEs的暴露水平以及评估人体健康风险具有重要意义。然而,目前的研究大多数集中于尿液中OPEs代谢物含量的分析测定,将其作为人体OPEs暴露的生物标志物,而对人体血液中OPEs的分析研究较少,仅有的少量研究涉及的OPEs种类有限。该研究在优化前处理过程(固相萃取,SPE)和色谱分离的基础上,建立了人体血液中16种OPEs的超高效液相色谱-串联质谱(UPLC-MS-MS)测定方法。血液样品经过乙腈摇床萃取后,经ENVI-18 SPE小柱净化,然后采用Acquity UPLC BEH C18色谱柱,以甲醇/5 mmol/L的乙酸铵水溶液为流动相进行梯度洗脱对目标物进行分离,最后进行LC-MS/MS测定。质谱分析采用电喷雾正离子模式电离,多重反应监测模式测定,内标法定量。在优化的检测条件下,16种OPEs的检出限为0.0038~0.882 ng/mL。除磷酸三甲酯(TMP)外,其余15种OPEs在3个浓度水平的血液基质加标回收率为53.1%~126%,相对标准偏差为0.15%~12.6%。样品的基质效应检测发现,4种OPEs存在明显的基质抑制,选用合适的同位素内标进行定量,可以部分消除基质影响。该方法样品前处理简单,灵敏度高,适用于人体血液样品中OPEs阻燃剂的测定。15个人体血液样本分析结果表明,OPEs的总浓度范围为1.50~7.99 ng/mL,其中8种OPEs的检出率均高于50%,磷酸三异丁酯(TiBP)、磷酸三(2-氯乙基)酯(TCEP)和磷酸三(1-氯-2-丙基)磷酸酯(TCIPP)为主要的OPEs,表明人体存在较为普遍的OPEs暴露,应该引起关注。

Theoretical investigation of the negative ionization of hydrogen particles on metal surfaces with low work function

This work addresses the negative ionization of hydrogen particles on low work function metal surfaces, which is an important process for the field of the surface plasma negative ion beams sources. We present the theoretical model for the computer calculation of the negative ionization probability which takes into account the component of atom/ion velocity, parallel to the surface. The calculated negative ionization probability of hydrogen quantitatively fits to the experimental data in the wide range of ion exit energies. The theoretical estimation shows, that for the low work function converter surfaces (φ ∼ 1.5 eV) the negative ionization probability of hydrogen can be enhanced up to 30% if the hydrogen has velocity component parallel to the surface ∼0.05 a.u. (∼60 eV). Therefore, the H- ion production rate can be increased for a negative ion source configuration that implements the oblique exit angle of hydrogen.

Performance Parameter Analysis of a Hall Effect Thruster With Modified Bohm Parameter Model

The Hall effect thruster (HET) is an electric propulsion system in which electrons confined in a certain region collide with neutral particles due to the Hall effect. The neutral particles are ionized, and the ions are accelerated by the electric field to produce thrust. Thus, a Hall thruster has a simpler structure than an ion thruster. To improve the accuracy of the HET performance analysis, the energy change of electrons is predicted by considering thermal conduction. The number of ions produced by ionization and the change in electron energy via multivalent ionization are investigated. To minimize the independent variables, the boundary condition is modified after considering the physical correlation of each variable, and a semi-experimental model equation for the Bohm parameter is proposed. The performance results have greater similarity to the experimental results than those of the previous analytical model. Based on this, the performance changes according to the thruster operating conditions are predicted and compared. It is confirmed that the thrust increases by about 10–20% according to the change of propellant mass flow rate due to the increase of ion exit velocity.

Pathogenic properties of enterobacteria isolated from calves in the Far Eastern Federal District

Methods of modern control of infectious animal diseases have led to a change in the etiological structure of infectious agents. Irrational use of antibiotic therapy may be the cause of bacterial variability and involvement in the infectious process of opportunistic bacteria that are present in the normal microflora of the animal body. Opportunistic bacteria are the cause of many animal diseases. Infections caused by them have a prolonged character, the pathogenetic basis of which is the persistence of the pathogen in the host body. Bacterial exotoxins damage the plasma membrane of cells. Pore-forming toxins and enzymes disrupt the selective entry and exit of ions through the plasma membrane. This group of toxins includes cytolysins, hemolysins of gram-negative opportunistic enterobacteria, leukotoxins, metalloproteases, and lipases. When pores are formed under the action of hemolysin, secondary processes are triggered that cause the development of pathological consequences. The vaccines and serums produced by biofactories lag behind the practical needs in terms of antigenicity and do not provide protection for newborn calves in the system of anti-epizootic measures. Of particular importance in the etiopathogenesis of acute intestinal disorders is a decrease in colonization resistance of the gastrointestinal mucosa, resulting in an expansion of the spectrum of pathogenic and opportunistic microorganisms that lead to the development of diarrhea.

Measurement of Copper ion Extrusion from the Apex of Human Teeth with Single Canals Following of Electrophoresis.

Objective:Preventing bacterial overgrowth is an essential component of successful root canal treatment. Increasing the penetration of antimicrobial substances into the canal through electrophoresis is one of the possible methods. This study aimed to measure the copper ions extruding from the root apex after using an electrophoresis device (Depotphorese®) in human teeth with single canals.Methods:In this ex-vivo study, thirty extracted human teeth with single canals were randomly divided into 2 groups. Group 1 as root canal preparation (WP) and group 2 as control (without root canal preparation). Each sample was individually fixed by alginate in a 5 ml sterile Eppendorf tube (microcentrifuge tube), and the root end was in contact with the distilled water solution. Ions derived from calcium hydroxide plus cupper paste (Cupral®) which mobilized via a low current electric field (1.5 mA/min for10 min) by Depotphorese® device. The copper ions in water solution were measured by spectrophotometric and supernatant methods.Results:Copper ions were extruded from the end of the apex in two groups. However, based on the results of the t-test; copper ion penetration was significantly lower in the control group compared to the WP group (P<0.05).Conclusion:Electrophoresis increased copper extrusion from the apical foramen. Although the root canal preparation increases the copper ion output in an ex-vivo environment, the amount of copper extruded from the root apex end was lower than the toxic dose. It seems that electrophoresis of copper plus calcium hydroxide mixture in endodontic treatments can be a safe procedure.

Quantum Calculation of Proton and Other Charge Transfer Steps in Voltage Sensing in the Kv1.2 Channel.

Ion channels in cell membranes control entry and exit of ions; their gating (opening and closing) is key to their functioning. It is known that protons can pass through the voltage-sensing domain (VSD) of channels such as Kv1.2. Quantum calculations for a section of the VSD show the steps protons take in responding to voltage and show no major displacement of the protein backbone with voltage change; 70 amino acids are included, 42 with side chains (9 directly in the proton path), 28 as backbone only, and 24 water molecules. Protons provide much of the gating current, the capacitative current immediately preceding channel opening with significant additional contributions from charge transfer to other groups. Most gating models, in contrast, require major protein displacement during gating. Energy terms without classical analogues (exchange plus correlation energy, which are greater than thermal energy) show that quantum calculations are required. Energy as a function of voltage for a key proton transfer leads to, approximately, the correct voltage for channel opening. Calculated total charge transfer (not only protons) for gating is reasonable compared to experimental values. We are also able to account, at least qualitatively, for two mutations, one with the gating current curve left-shifted and one right-shifted, and show the alternate proton paths that are required to account for these.

Incorporating post translational modification information for enhancing the predictive performance of membrane transport proteins

Transporters involved in the cellular entry and exit of ions or molecules throughout the membrane proteins and thereby play an essential role in recognizing the immune system and energy transducers. According to their relevance in proteomics, numerous studies have been conducted to analyze the transporters; especially the discrimination of their classes and subfamilies. We realized that post translational modification information had a critical role in the process of transport proteins. Therefore, in this study, we aim to incorporate post translational information with radial basis function networks to improve the predictive performance of transport proteins in major classes (channels/pores, electrochemical transporters, and active transporters) and six different families (α-type channels, β-barrel porins, pore-forming toxins, porters, PP bond hydrolysis-driven transporters, and oxidoreduction-driven transporters). The experiment results by using PSSM profiles combined with PTM information could classify the transporters into three classes and six families with five-fold cross-validation accuracy of 87.6% and 92.5%, respectively. For the independent dataset of 444 proteins, the performance with post translational modification attained the accuracy of 82.13% and 89.34% for classifying three classes and six families, respectively. Compared with the other methods and previous works, our result shows that the predictive performance is better with the accuracy improvement by 12%. We suggest that our study could become a robust model for biologists to discriminate transport proteins with high performance and understand better the function of transport proteins. Further, the contributions of this study could be fundamental for further research that can use PTM information to enhance numerous computational biology problems.

A versatile ion beam spectrometer for studies of ion interaction with 2D materials.

We present an ultrahigh vacuum setup for ion spectroscopy of freestanding two-dimensional solid targets. An ion beam of different ion species (e.g., Xe with charge states from 1 to 44 and Ar with charge states from 1 to 18) and kinetic energies ranging from a few 10 eV to 400 keV is produced in an electron beam ion source. Ions are detected after their transmission through the 2D target with a position sensitive microchannel plate detector allowing the determination of the ion's exit charge state as well as the scattering angle with a resolution of approximately 0.04°. Furthermore, the spectrometer is mounted on a swiveling frame covering a scattering angle of ±8° with respect to the incoming beam direction. By utilizing a beam chopper, we measure the time-of-flight of the projectiles and determine the energy loss when passing a 2D target with an energy uncertainty of about 2%. Additional detectors are mounted close to the target to observe emitted secondary particles and are read-out in coincidence with the position and time information of the ion detector. A signal in these detectors can also be used as a start trigger for time-of-flight measurements, which then yield an energy resolution of 1% and an approximately 1000-fold larger duty cycle. First results on the interaction of slow Xe30+ ions with a freestanding single layer of graphene obtained with the new setup are compared to recently published data where charge exchange and energy were measured by means of an electrostatic analyzer.

Improvement of extracted ion beam from cold cathode Penning ion source

A direct current cold cathode Penning ion source is operated at the optimum parameters and pressure equal to 7×10−4 mmHg using argon gas. It consists of a copper cylindrical hollow anode and two movable molybdenum discs cathodes are placed symmetrically at two ends of the anode. Argon ion beam is extracted from the ion source by using extractor of different aperture diameter equal to 2.5, 3, 3.5, 4 and 4.5mm respectively. The extractor is placed at different distances from the ion exit aperture equal to 5, 10, 15 and 20mm respectively. It is found that at extractor aperture diameter equal to 3.5mm, ion exit aperture - extractor distance equal to 10mm and extraction potential applied on the extractor is equal to −500V, the optimum extracted ion beam current equal to 543 μA can be obtained. A comparison for Penning ion source without and with the extractor is made at the same optimum operating parameters, it is found that the extracted ion beam current from Penning ion source with the extractor increases about twice its initial value of Penning ion source without the extractor.

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview on how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.