Influence Of NaCl Concentration Research Articles

Experimental investigation on the influence of NaCl concentration on triaxial mechanical behaviors of a low-clay shale

During a hydraulic fracturing operation, a large quantity of salinity fracturing fluids will be retained in the shale reservoir, which may cause the problem of wellbore instability. Previous studies mainly focused on the change mechanism of clay-rich shale after brine immersion. However, the influence of NaCl concentration on mechanical behaviors of a low-clay shale is still unclear. Therefore, in this investigation, conventional triaxial compression tests were carried out on low-clay shale specimens saturated with NaCl solutions at different concentrations (0%, 5%, 15%, 25%) under different confining pressures (0 MPa, 15 MPa, 30 MPa, 45 MPa), and their mechanical properties were analyzed systematically. Optical microscopy, polarized light microscopy and scanning electron microscopy were used to understand the microscopic changes in shale samples after saturation in NaCl solutions. The brittleness indices of saturated shale specimens were evaluated based on rock strength properties and the energy evolution law. According to the experimental results, compared with the water-saturated specimens, the peak strength, elastic modulus, cohesion and internal friction angle of specimens saturated with 5%NaCl solution all showed a downward trend. However, for the specimens saturated with the NaCl solution at concentrations of 15% and 25%, higher NaCl concentration showed a greater rebound effect on the mechanical parameters compared with the 5%NaCl saturation. The microscopic observation showed that the brine could invade the interior of shale specimens from micropores, microcracks and bedding fractures, which were mainly parallel to the bedding direction. And the bedding fractures and some of micropores seemed to be filled by deposited NaCl crystals and mineral particles. The brittleness index of the brine-saturated shale specimen decreased at the low-concentration (5%) and increased at the high-concentration (15% and 25%). This investigation could provide a theoretical basis and mechanical parameters for analyzing the stability of shale wellbore affected by the salinity fracturing fluids.

Influence of NaCl concentration on the optical scattering properties of water-based aerosols.

We present the characterization of several atmospheric aerosol analogs in a tabletop chamber and an analysis of how the concentration of NaCl present in these aerosols influences their bulk optical properties. Atmospheric aerosols (e.g., fog and haze) degrade optical signal via light-aerosol interactions causing scattering and absorption, which can be described by Mie theory. This attenuation is a function of the size distribution and number concentration of droplets in the light path. These properties are influenced by ambient conditions and the droplet's composition, as described by Köhler theory. It is therefore possible to tune the wavelength-dependent bulk optical properties of an aerosol by controlling droplet composition. We present experimentation wherein we generated multiple microphysically and optically distinct atmospheric aerosol analogs using salt water solutions with varying concentrations of NaCl. The results demonstrate that changing the NaCl concentration has a clear and predictable impact on the microphysical and optical properties of the aerosol.

Study on the Corrosion Behavior of D36 Steel Plate and H62 Copper Alloy Net for Marine Aquaculture Facilities in Simulated Seawater

Marine aquaculture facilities have been working in a high salt and humidity marine environment for a long time, which makes them be inevitably affected by seawater corrosion, especially the main structures such as metal mesh and frame. Therefore, studying the corrosion behavior of net and frame steel is of great significance for the selection of materials and corrosion protection of marine aquaculture facilities. The influence of NaCl concentrations and immersion state on self-corrosion behavior and the influence of layer thickness and overlapping area on galvanic corrosion behavior of H62 copper alloy mesh/D36 steel plate was discussed in this study using weight loss and electrochemical measurements. The tensile tests were conducted to observe the influence of different corrosion conditions on maximum force and tensile strength of the net. The corrosion rate of the two materials increased rapidly with the increase of NaCl concentrations; the corrosion rate of both materials showed the decreasing trend with the extension of time, and the corrosion rate of H62 was always lower than D36 steel. When two materials were coupled, the galvanic corrosion rate would decrease with the increase of the layer thickness and overlapping area. The tensile results were consistent with the corrosion results. When these two materials work together, adding layer thickness or increasing the overlapping area is one of the ways to protect the frame steel to a certain extent.

Influence of Soluble Salt NaCl on Cracking Characteristics and Mechanism of Loess

Under the conditions of drought, cracks are likely to appear in loess due to shrinkage, which leads to salt precipitation and accumulation on the surface of loess. Therefore, salinized lands are created in loess areas. Deep study into the influence of soluble salt content on the cracking characteristics and mechanism of loess is of great significance to engineering constructions, geological problems, and disaster prevention for salinized lands in loess regions. In this paper, free desiccation experiments were carried out on the loess samples with different NaCl concentrations (a soluble salt). A high-resolution digital camera was used to obtain the sequence images of loess during the drying process. With the advantage of digital image correlation (DIC) technology and the non-contact full-field strain measurement method, the local displacement and strain on the surface of loess samples were calculated. The microstructure and main elements distribution of loess samples were obtained by scanning electron microscopy (SEM) and energy-dispersive spectrum (EDS) methods. Finally, the influence of NaCl concentrations on cracking characteristics and mechanism of loess was analyzed. The results show that, with the increase in NaCl concentration, the evaporation rate of loess samples decreased and the residual water content increased. The NaCl content can prevent the development of desiccation cracks in loess.

Performance Evaluation of Gum Gellan-Based Hydrogel as a Novel Adsorbent for the Removal of Cationic Dyes: Linear Regression Models.

In this work, the suitability and efficacy of the previously reported biodegradable gellan gum (GG)-based hydrogel have been thoroughly investigated with respect to the adsorption mechanisms of malachite green (MG) and methylene blue (MB) dyes. The dyes' removal from aqueous solutions using GG-cl-poly(AA) as an adsorbent material has been studied in a discontinuous system with respect to contact time, dose, pH, and temperature. The synthesized hydrogel was characterized by FT-IR, TGA, XRD, 1H NMR, and FE-SEM. The adsorption capacity of GG-cl-poly(AA) hydrogel was investigated at different pH solutions (3, 7, and 10), and it was found that neutralized charge plays a crucial role in the enhancement of dye removal. To better understand the behavior of the GG-cl-poly(AA) hydrogel in adsorbing model dyes, adsorption kinetics, isotherms, and thermodynamics were also investigated. The values of qmax for MG and MB were obtained to be 552.48 and 531.9 mg g-1. In addition, the influence of NaCl concentration on adsorption efficiency was investigated, and it was found that as the ion concentration increased, the effectiveness of the adsorption process dropped. Moreover, the synthesized hydrogel's potential application in the adsorption and separation of dyes from wastewater is enhanced by the reusability investigations conducted in convenient conditions. As a result, it is possible to conclude that reusing GG-cl-poly(AA) hydrogel as a low-cost, easy-to-handle, nontoxic material in an industrial wastewater treatment plant's adsorption process can provide a number of advantages, including high efficiency for MG and MB removal and cost savings on overall treatment plant operations.

Effect of NaCl presence caused by salting out on the heterogeneous-homogeneous coupling non-equilibrium condensation flow in a steam turbine cascade

Steam turbine is one of the most important components in fossil-fired and nuclear power plants, its efficiency is of great importance for saving energy and decreasing consumption. The steam density rapidly decreases when the steam expanses, and NaCl dissolved in steam starts precipitating. However, the presence of NaCl will not only affect the non-equilibrium condensation decreasing the steam turbine efficiency, but also erode the steam turbine blade reducing the steam turbine safety and shortening maintenance cycle. The main objective of the current work is to investigate the effect of the NaCl presence on the non-equilibrium condensation process and the loss in steam turbine cascade. Firstly, a non-equilibrium condensation model including homogeneous and heterogeneous condensation process is presented and its accuracy is checked in a steam turbine cascade by comparing with available experimental data. And the results show the accuracy and robustness of the model is quite trustworthy. Secondly, the influence of NaCl concentration on the non-equilibrium condensation flow is investigated in a steam turbine cascade. The results show that the NaCl presence has a significant effect on condensation flow. With the NaCl concentration increasing, the droplets nucleation rate decreases, diminishing the tiny droplet emerging, which weakens homogeneous condensation. As a result, the condensation loss caused by the homogeneous condensation decreases, and even the condensation loss caused by the homogeneous condensation becomes zero when the NaCl particle number reaches 7.5×1014 per kilogram in steam flow. However, the condensation loss caused by the heterogeneous condensation shows a reverse tendence, which increases with the NaCl concentration. At last, the condensation loss and entropy generation caused by the non-equilibrium condensation are checked in steam turbine cascade under different NaCl concentration conditions. The results show that the condensation loss reduces by 9.2% and increases by 42% at the 7.5×10141/kg and 10171/kg NaCl concentrations, respectively. Meanwhile, when the NaCl particle number reaches 7.5×1014 per kilogram, the isentropic efficiency is highest, about 0.884, compared with other cases considering condensation effect. This study proves that the NaCl concentration has a nonnegligible effect on the condensation loss and entropy generation, which must be considered in future steam turbine study.

Effect of NaCl concentration on depressurization-induced methane hydrate dissociation near ice-freezing point: Associated with metastable phases

Methane hydrate (MH) has been viewed as an earth-abundant potential energy resource and attracted worldwide research attentions. Among such studies, the metastable performance of gas hydrates systems, i.e. gas hydrates decompose at slow rates or preserve for long periods of time out of the corresponding stable pressure-temperature conditions, was claimed to lead to the retarded hydrates dissociation and affect the recovery efficiency and sediment safety during exploitations. A mechanism proposed that MH decomposes and transform to supercooled water and gas below ice-freezing point before the formation of ice, which is a dominant factor of the related metastability. In this work, the influence of NaCl concentration on depressurization-induced MH dissociation behavior in porous sediments and the associated metastable property of the MH system near ice-freezing point were experimentally investigated. Effects of the metastability on methane gas recovery were studied. The results show that possible metastable states of supercooled water-MH-gas system can exist during the dissociation process of MH with NaCl concentrations of 0 wt%, 1 wt%, and 3 wt% under production pressures of 2.0 MPa and 1.9 MPa, leading to a prolonged gas production process. While a higher NaCl concentration of 5 wt% and a lower production pressure of 1.8 MPa showed no obvious system metastability. The formation of ice would drive the system out from the metastable region and accelerate the production of gas. The effect of NaCl concentration on formation of ice at 2.0 MPa and 1.9 MPa seems to be stochastic, but exhibit negative effect on the temperature-increase amplitudes of the sediment by ice formation at 1.8 MPa. This work present fundamental lab-scale experimental results of effects of NaCl concentrations on possible metastability of the MH system and ice formations for exploitation of MH under submarine brine environment.

Influence of NaCl concentration on microbiologically influenced corrosion of carbon steel by halophilic archaeon Natronorubrum tibetense

The influence of NaCl concentration on microbiologically influenced corrosion (MIC) of Q235 carbon steel by the halophilic archaeon Natronorubrum tibetense was investigated by immersion tests and electrochemical measurements. An increase in NaCl concentration from 0 g/mL to 0.1 g/mL promoted the anodic dissolution of carbon steel and accelerated its corrosion, but MIC did not occur. A further increase in NaCl concentration to 0.2 g/mL led to MIC in inoculated medium, and the occurrence of the MIC resulted in further aggravation of carbon steel corrosion. Once the NaCl concentration reached 0.3 g/mL, the high concentration of chloride ions greatly interfered with the adsorption of dissolved oxygen and the attachment of N. tibetense cells to the surface of carbon steel, thus reducing the corrosion rate of carbon steel and inhibiting the MIC.

Retraction Statement: The Influence of NaCl Concentration on Salt Precipitation in Heterogeneous Porous Media

Retraction Statement: The Influence of NaCl Concentration on Salt Precipitation in Heterogeneous Porous Media

Characterizing the damage behavior of thin sheets for fuselage based on in situ corrosion fatigue test and digital image correlation technique

The effect of salt spray and salt solution on the fatigue properties of 2024-T3 aluminum alloy plate used for aircraft fuselage structure have been investigated by combining Digital Image Correlation (DIC) technology with in-situ corrosion fatigue test. For this purpose, an in-situ corrosion fatigue platform was designed for gas and liquid phases. Fatigue experimental investigation was carried out in salt spray and salt solution environments respectively, the crack propagation process was monitored by the DIC technology and the influences of NaCl concentration on fatigue life and crack growth rate were analyzed under the two kinds of corrosive environments. Moreover, the failure mechanism is discussed based on the micro-morphology of fracture and the composition of corrosion products. Experimental results demonstrated that for the corrosion fatigue in salt spray environment, there is a competition between the hydrogen embrittlement and the crack tip closure effect caused by corrosion products, which results in fatigue life decreasing with the increase of NaCl concentration first and then increasing. The fatigue life (with 3.50 wt.% NaCl salt spray) is the lowest, which is 82.9% of that in air, while the fatigue life (with 5.00 wt.% NaCl salt spray) is 112.6% of that in air. But for the corrosion fatigue in the NaCl salt solution environment, there is no obvious crack tip closure effect. In the 5.00 wt.% NaCl salt solution environment, fatigue life is 74.2% of that in air. The microfractures and strain nephogram of specimens revealed the stress concentration caused by corrosion pits, which might be the main factor for the decrease of fatigue life.

Influence of NaCl concentrations on the crack-sealing behavior of superabsorbent polymers in cementitious materials

The crack-sealing behavior of superabsorbent polymers (SAPs) in high-concentration NaCl solutions is unclear. In this study, the influences of NaCl concentrations on the filled area (S) and sealing efficiency (r) of SAPs were, respectively, analyzed with a self-designed soaking test and a water permeability test. Furthermore, the 3D morphologies of a single SAPs particle and the effects of SAPs on the healing of mortars in NaCl solutions were investigated. The results indicate that the S value and the r value of SAPs are almost constant in low-concentration NaCl solutions, whereas they decrease with an increasing concentration until the concentration reaches the critical value. Additionally, the crack-sealing capacity of SAPs in realistic cracks is weaker than that in artificial cracks. Moreover, SAPs can promote the healing of mortar in wet-dry (0.5 M NaCl) cycles. The healing products are mainly CaCO3 and C-S-H gel.

Influence of NaCl Concentration on Bicelle-Mediated SLB Formation.

The deposition of two-dimensional bicellar disks on hydrophilic surfaces is an emerging approach to fabricate supported lipid bilayers (SLBs) that requires minimal sample preparation, works at low lipid concentrations, and yields high-quality SLBs. While basic operating steps in the fabrication protocol mimic aspects of the conventional vesicle fusion method, lipid bicelles and vesicles have distinct architectural properties, and understanding how experimental parameters affect the efficiency of bicelle-mediated SLB formation remains to be investigated. Herein, using the quartz crystal microbalance-dissipation and localized surface plasmon resonance techniques, we investigated the effect of bulk NaCl concentration on bicelle-mediated SLB formation on silicon dioxide surfaces. For comparison, similar experiments were conducted with vesicles as well. In both cases, SLB formation was observed to occur rapidly provided that the NaCl concentration was sufficiently high (>50 mM). Under such conditions, the effect of NaCl concentration on SLB formation was minor in the case of bicelles and significant in the case of vesicles where it is expected to be related primarily to osmotic pressure. At lower NaCl concentrations, bicelles also formed SLBs but slowly, whereas adsorbed vesicles remained intact. These findings were complemented by time-lapsed fluorescence microscopy imaging and fluorescence recovery after photobleaching measurements that corroborated bicelle-mediated SLB formation across the range of tested NaCl concentrations. The results are discussed by comparing the architectural properties of bicelles and vesicles along with theoretical analysis of the corresponding adsorption kinetics.

The effect of NaCl concentration and corrosion on cohesion/adhesion forces of structure-II hydrate particles

Gas hydrates are ice-like solid compounds formed from water and suitably sized gas molecules under high pressure and low temperature conditions. In typical oil and gas transportation flowlines, when water is present gas hydrates particles can form, agglomerate, and accumulate in the flowlines. These particles can also deposit on flowline walls during fluid flow or during shut-in/restart conditions. The formation of hydrate plugs can cause a blockage in the flowline, as well as other safety concerns. Although researchers have studied how temperature and annealing time would affect the cohesion/adhesion forces between hydrate particles and particle-surface systems, the effects of surface corrosion, salinity and water amount on the adhesion force have not been reported. Deep-water flowlines typically contain brine, and water condensation and corrosion can occur on flowline walls. A water layer and corrosion on flowline walls can affect hydrate film growth and deposition, and salt dissolved in the liquid phase may also influence the agglomeration of hydrate particles. Thus, the effects of free water, corrosion and salt on CH4/C2H6 hydrate particle-particle and particle-surface micromechanical forces are essential for advancing the understanding on hydrate agglomeration and deposition mechanisms in gas dominated deep-water pipelines. In order to investigate the mechanism of gas hydrate deposition and agglomeration in gas dominated flowlines, a high-pressure micromechanical force (MMF) apparatus was applied to directly measure CH4/C2H6 hydrate adhesion/cohesion forces. The influence of NaCl concentration on the cohesion force between CH4/C2H6 hydrate particles was studied, and the effect of surface corrosion on adhesion forces between hydrate particles and carbon steel (CS) were analysed. It was found that the presence of NaCl decreased the cohesion force between hydrate particles, and a possible explanation of this phenomenon was given based on the capillary liquid bridge model. For the adhesion force measurements, the results indicated that with increasing visual corrosion, the adhesion force between gas hydrate particle and CS surface increased by up to 500%.

The influence of NaCl concentration on the (LiCl-KCl) eutectic system and temperature dependence of the ternary system

To explore the complex correlation between local structure and properties in the alkali chlorides ternary system, simulations were systematically conducted for 11 different (Li, Na, K) Cl compositions from 900 K to 1200 K as the fundamental study of magnesium chloride electrolysis. For the ternary system, the density was calculated across the full composition and database was established. Furthermore, the structure simulation results revealed that the coordination of Li-Cl pair tended to be a distorted tetrahedron and the Na-Cl and K-Cl pairs tended to be an octahedron. The prediction of the properties was compared with available experiments and extrapolated analytical data, the deviations are acceptable. The temperature had no significant effects on the local structure and thermal conductivity. The results also showed that the Tosi−Fumi potential predicted positive temperature dependence of self-diffusion coefficients and ionic conductivity, and negative temperature dependence of the viscosity. In addition, the correlation between the local structure and transport properties was explored. The hydrodynamic radius of Li+ and K+ is similar in the ternary system, it can be found that whilst the K+ ion diffuses as an atomic species, the Li+ ion carries at least some of its coordinating Cl− ions in the diffusion process, giving the diffusing species a larger effective size than the bare ion.

Electrochemical studies of Pd-doped Cu and Pd-doped Cu-Al intermetallics for understanding corrosion behavior in wire-bonding packages

This study investigated the electrochemical characterizations in the field of wire metallurgy (Pd concentration) and molding compound chemistry (chloride concentration) to find ways to reduce metallic entities' susceptibility to corrosion at ball-pad interfaces. The open circuit potentials and potentiodynamic polarization curves of various metallic entities found in a Cu(Pd)-Al bonding interface were obtained in near-neutral electrolytes of 100ppm, 20ppm, and 1ppm of NaCl in high-purity water. From X-ray diffraction spectra, it was found that Pd could be homogeneously incorporated into Cu9Al4, the Cu-rich intermetallic compound (IMC) also referred to as γ but not into CuAl2, the Al-rich IMC also referred to as θ for arc-melted specimens. For Cu-Pd alloys, at a given chloride concentration, increasing Pd concentration causes the value of open-circuit potential (Eoc) to increase and corrosion current density (icorr) to decrease. Likewise, for a given amount of Pd in Cu-Pd alloy, decrease in the NaCl concentration causes the value of Eoc to increase and icorr to decrease. Interestingly, for high concentration of Pd as in the case of Cu-9Pd, Eoc and icorr became less sensitive to the NaCl concentrations investigated. This can be attributed to the Pd enrichment on the corroding surface that reduces the anodic dissolution rate of Cu. For Pd-doped γ intermetallics, increasing Pd concentration causes a systemic increase in the value of Eoc, but at a lower concentration of Pd, the value of icorr was increased. The addition of Pd to γ causes an increase in the cathodic current density due to the high cathodic activity of Pd, while the passivation of Al in γ reduces the extent of the anodic current density reduction due to the addition of Pd, which leads to a higher value of icorr at a low Pd concentration. This is true even when the NaCl concentration is as low as 1ppm. On the other hand, the influence of NaCl concentration on the Eoc and icorr of γ IMC was always observed, even with Pd addition.

Removal of Glyphosate from Aqueous Solution Using Nanosized Copper Hydroxide Modified Resin: Equilibrium Isotherms and Kinetics

To remove glyphosate from water, nanosized copper hydroxide modified resin (D201Cu) was synthesized and characterized. The influence of NaCl concentration, temperature, pH, time, humid acid, and fulvic acid on glyphosate adsorption onto D201Cu resins were fully investigated. Glyphosate uptake on D201Cu was 113.7 mg/g in the presence 18% NaCl. The adsorption isotherms and kinetic data fitted well to the Langmuir model and pseudo-second-order model, respectively. In NaOH and NaCl mixed solution, the D201Cu regeneration efficiency can be 90% after five cycles. On the basis of the adsorption results, the schematic diagrams of adsorption mechanism of glyphosate onto D201Cu resins were proposed.

Retracted: The influence of NaCl concentration on salt precipitation in heterogeneous porous media

AbstractEvaporation of saline solutions from porous media is governed by the complex interactions between the transport properties of the porous media, the evaporating solution, and the external boundary conditions. In the present study, we have investigated the effects of salt concentration on the evaporation process from porous media in the presence of a sharp textural discontinuity, a common heterogeneity in natural porous media formed due to the weathering or formation of soil horizons, wind deposition, and erosion. We have conducted a comprehensive series of macroscale and microscale experiments to delineate how the precipitation pattern is modified as salt concentration varies from relatively low values to a concentration close to the solubility limit. For concentrations much less than the solubility limit, the precipitation begins at the coarse‐textured part of the heterogeneous porous media (which is a counter‐intuitive result considering the preferential evaporation of water from the fine‐textured part of the heterogeneous surface). However, when the concentration is close to the solubility limit, precipitation initiates preferentially at the fine‐textured part of the heterogeneous porous surface. This behavior results from the interaction between the transport properties of the porous media and the properties of the evaporating solution which must be considered. Additionally, using pore‐scale images obtained by X‐ray microcomputed tomography (CT), we have visualized the dynamics of precipitation in the presence of heterogeneity at high spatial and temporal resolution. The pore‐scale results corroborate the mechanisms controlling the precipitation patterns in the presence of textural discontinuities inferred from the macroscale experiments.

Influence of NaCl concentration on pitting corrosion of extruded Al-Mg-Si alloy AA6060

Extruded Al-Mg-Si alloys (AA6xxx series alloys) are the most common aluminum alloys for structural application due to reliable mechanical characteristics and corrosion properties. Spontaneously formed adherent aluminum oxide film on the surface protects Al and Al -alloys from corrosive attack in neutral media, but in chloride containing solutions, such thin and compact passive film is prone to breakdown. In this study the corrosion behavior of commercial extruded Al-Mg-Si alloy AA6060 was investigated in NaCl solutions of different concentrations using anodic potentiodynamic polarization measurements under deaerated conditions at room temperature. It was shown that sensitivity to chloride attack increase with increasing Cl- concentration and depends on cathodic micro constituents in extruded Al-Mg-Si alloy.

Hybrid triboelectric nanogenerator for harvesting water wave energy and as a self-powered distress signal emitter

In this paper, a hybrid triboelectric nanogenerator (TENG) has been developed for simultaneously harvesting the electrostatic energy and mechanical impact energy from water wave. It is comprised of two parts: an interfacial electrification enabled TENG (IE-TENG) and an impact-TENG. The IE-TENG, composed of a fluorinated ethylene propylene thin film and an array of electrodes underneath, is used to harvest electrostatic energy arising from the water-solid interface. The impact-TENG, constructed with nanostructured polytetrafluoroethylene (PTFE) thin films and elastic wavy electrodes, is used to scavenge the mechanical impact energy from water wave. Under water waves propagating at a speed of 0.5m/s, the short-circuit current of the IE-TENG and impact-TENG can reach 5.1µA and 4.3µA, respectively, which is able to drive nearly 50 LEDs simultaneously. Considering that natural water bodies may contain minerals and salt, the influence of NaCl concentration on the electric output of device has been investigated. Moreover, the hybrid TENG was developed as a self-powered distress signals emitter that may be used for life saving in water landing or swimming in evening. Considering the scalability of this technology, this work demonstrates the great potential of TENG in areas of hydropower harvesting, environmental monitoring and maritime search and rescue.

Mathematical analysis of the sodium sensitivity of the human histamine H3 receptor.

PurposeIt was shown by several experimental studies that some G protein coupled receptors (GPCR) are sensitive to sodium ions. Furthermore, mutagenesis studies or the determination of crystal structures of the adenosine A2A or δ-opioid receptor revealed an allosteric Na+ binding pocket near to the highly conserved Asp2.50. Within a previous study, the influence of NaCl concentration onto the steady-state GTPase activity at the human histamine H3 receptor (hH3R) in presence of the endogenous histamine or the inverse agonist thioperamide was analyzed. The purpose of the present study was to examine and quantify the Na+-sensitivity of hH3R on a molecular level.MethodsTo achieve this, we developed a set of equations, describing constitutive activity and the different ligand-receptor equilibria in absence or presence of sodium ions. Furthermore, in order to gain a better understanding of the ligand- and Na+-binding to hH3R on molecular level, we performed molecular dynamic (MD) simulations.ResultsThe analysis of the previously determined experimental steady-state GTPase data with the set of equations presented within this study, reveals that thioperamide binds into the orthosteric binding pocket of the hH3R in absence or presence of a Na+ in its allosteric binding site. However, the data suggest that thioperamide binds preferentially into the hH3R in absence of a sodium ion in its allosteric site. These experimental results were supported by MD simulations of thioperamide in the binding pocket of the inactive hH3R. Furthermore, the MD simulations revealed two different binding modes for thioperamide in presence or absence of a Na+ in its allosteric site.ConclusionThe mathematical model presented within this study describes the experimental data regarding the Na+-sensitivity of hH3R in an excellent manner. Although the present study is focused onto the Na+-sensitivity of the hH3R, the resulting equations, describing Na+- and ligand-binding to a GPCR, can be used for all other ion-sensitive GPCRs.