Crystallographic Radius Research Articles

7T MRI and molecular studies of Dotarem (gadoterate meglumine) retention in macrophages.

Gadolinium-based MRI contrast agent Dotarem is commonly used in the clinic. Free Gd3+ is very toxic. Because the crystallographic radius of Gd3+ and Ca2+ is very similar, Gd3+ can compete with Ca2+ in the regulations of cellular functions. Gadolinium is retained in organs and tissues, but the effects of gadolinium retention are mostly unknown. There is also no information how gadolinium retention impacts immune cells and signaling pathways regulated by Ca2+ such as RhoA/mTORC1 and mTORC2, which control various, including actin cytoskeleton-dependent, cellular functions. We developed the 7T MRI-based method to analyze gadolinium-based MRI contrast agent retention in isolated immune cells (macrophages) and study the effects of gadolinium retention on the expression of RhoA, mTORC1, mTORC2, and mitochondria, Golgi, and ER markers. We showed that macrophages retain gadolinium for at least seven days after exposure. Gadolinium retention downregulated the expression of RhoA, mTORC1 component Raptor and mTORC2 component Rictor proteins, and dysregulated the expression level of organelle markers. The method described here can be used for monitoring gadolinium levels and effects in isolated cells, such as the immune cells in the blood of patients exposed to contrast-enhanced MRI.

Solubility, Phase Equilibria, and Critical Phenomena in the Ternary KBr + H2O + C5H5N System from T = 283.15 to 363.15 K

The solubility of components, phase equilibria, and critical phenomena in the potassium bromide + water + pyridine system were investigated from T = 283.15 to 363.15 K by the visual polythermal method. KBr delaminates water–pyridine solutions above 323.75 K. The formation temperature of the critical tie line of the monotectic state (323.75 K) and the compositions of the solutions corresponding to the critical solubility points of liquid–liquid equilibrium at three temperatures were determined. The distribution coefficients Kd of pyridine between the organic and aqueous phases of the monotectic state at 328.15, 343.15, and 363.15 K were calculated. The salting-out effect of KBr relative to pyridine from solutions is shown to be enhanced with an increase in the temperature. A comparative analysis of the results of our polythermal study of the salting-out action of potassium salts (iodide, bromide, nitrate, and chloride) on the binary water + pyridine system was done. It has been found that a decrease in the crystallographic radius of the salt anion in the KI–KBr–KNO3–KCl series leads to a decreased formation temperature of the critical tie line of the monotectic state of the ternary salt + water + pyridine systems and an enhanced salting-out effect of pyridine from aqueous solutions.

Derivation of limiting ion mobility equation based on the application of solvation effect-incorporated Poisson-Boltzmann equation

Interaction potential energy between ion and solvent molecular dipole moments in solvation shell around ion was derived on basis of the application of the solution of linear SEI-PB (Solvation Effects-Incorporated Poisson-Boltzmann) equation. Based on application of the solution of linear SEI-PB equation, distribution of solvent molecules in solvation shell around ion in electrolyte solution at thermodynamic equilibrium was derived. In case approaching to limit of infinite dilution, analytical expression for evaluating limiting ion mobility is derived from the boundary condition that the average number of solvent molecules accompanying with translational motion of ion is equal to the mean solvation number of ion. The derived limiting ion mobility formula is different from the Stokes–Einstein relation and lies in relation to direct proportion with the cube of dynamic size of ion in solution, depending not only on the viscous coefficient, dielectric constant, the density and molecular weight of solvent but also on temperature.By virtue of the equation, it was possible to estimate dynamic sizes of ions in solution. It was found the estimated dynamic sizes of ions in aqueous solution to be compatible with the average ion–water distances, and to be always greater than crystallographic ionic radii in size.A new relation between the limiting ion mobility and the solvent molecular dipole moment in solvation shell was established based on the interaction potential energy between ion and solvent molecular dipole moments in solvation shell around ion. By virtue of the proposed relation, we could find out the average water molecular dipole moment in hydration shell to be different more or less in size from that in bulk solution according to ionic species in aqueous solution.

Enhancing the Electrochemical Doping Efficiency in Diketopyrrolopyrrole‐Based Polymer for Organic Electrochemical Transistors

AbstractThe increasing interest in organic electrochemical transistors (OECTs) for next‐generation bioelectronic applications motivates the design of novel conjugated polymers with good electronic and ionic transport. Many conjugated polymers developed for organic field‐effect transistors (OFETs) exhibit high charge carrier mobilities but they are not suitable for OECTs due to poor ion‐uptake arising from the non polar alkyl chain substituted on the conjugated backbone. They are also sensitive to moisture, resulting in poor performance in aqueous electrolytes. Herein, the widely used conjugated building block diketopyrrolopyrrole (DPP) is used and functionalized it with polar triethylene glycol side chains (PTDPP‐DT) to promote ion penetration. The electrical performance of PTDPP‐DT based OECT in two types of aqueous electrolytes is studied and the electrochemical doping response is investivated. It is found that the tetrafluoroborate (BF4−) anion with large crystallographic radius allows high‐efficiency electrochemical doping of the PTDPP‐DT polymer, and thus gives rise to the high transconductance of 21.4 ± 4.8 mS with good device stability, where it maintained over 91 % of its doped‐state drain current after over 500 cycles of pulse measurement.

NEAR SOLVATION OF TETRAALKYLAMMON IONS IN ETHYLENE GLYCOL AND IN WATER

Diffusion coefficients and microscopic characteristics of the length (), time (τ), and the rate of diffusion shift (drift) of tetraalkylammonium ions (TAA) (Me4N+, Et4N+, Pr4N+, Bu4N+, Pe4N+) in ethylene glycol (EG) and in water at temperature 298.15 K are calculated from literature data on the limiting molar electrical conductivity of these ions. From analysis of the calculated data, it was found that the value for TAA ions in ethylene glycol and in water depends on the structural radius of the ion and on the solvent. For the above ions, the parameter in the EG is less than in water, which indicates a more significant inhibitory effect of the EG on the drift of TAA ions compared to water. A correlation was established between the sign of the deviation of the length of the discrete diffusion displacement from the structural radius of the ion (ri) in the form of (– ri) and the solvability of ions according to Samoilov. When parameter exceeds the crystallographic (structural) radius of the ion, the latter is positively solvated. If value is less than the crystallographic radius of the ion, negative solvation is observed. The essence of the phenomenon of negative solvation according to Samoilov is that the ion-molecule bonds of the solvent are weaker than the bonds of the solvent molecules to each other. Our correlation between the deviation sign (– ri) from the Stokes – Einstein law and the short-range solvation of ions according to Samoilov in solvents with a spatial network of H-bonds (EG, water) indicates that ion diffusion is associated with short-range solvation, and the parameter is its quantitative characteristic, i.e. we propose a deviation from the Stokes-Einstein law (– ri) as a measure of the near solvation of ions. For the ions studied, the parameter (– ri) has positive values, and in the EG a negative value of the parameter (– ri) is observed only for the Me4N+ ion, which indicates its negative solvation. The parameter τ in the EG exceeds the same values in water by 9-14 times, which indicates the inhibitory effect of the drift of TAA ions, also caused by the influence of solvent viscosity. The rate of translational displacement of TAA ions in water is 6-12 times higher than in the EG.

Break-up behavior of droplets containing chlorine salt with the same valence cation under electric field via molecular dynamics simulation

Application of the electric field to water-in-oil system can accelerate the coalescence of droplets. However, when an excessively high electric field is applied, droplets will exhibit break-up behavior. In addition to the strength of the electric field, the salt type in droplets significantly affects their break-up behavior. However, the break-up behavior of droplets containing the same valence cation is rarely investigated, and the mechanism underlying the influence of ionic type remains unclear. In this study, the break-up behavior of droplets containing chlorine salt with the same valence cation is studied by molecular dynamics simulations. The influences of electric field strength and ionic type on the break-up behavior of droplets are analyzed. Simulation results demonstrate that the droplet deformation increases with the increase in the electric field, and the droplets break when the degree of deformation exceeds a critical value. The ionic type mainly affects the break-up time of droplets through drift velocity, which is proportional to the electric field strength and ionic mobility. Moreover, from Na+ to Cs+, the cationic mobility increases first and then decreases with the increase of crystallographic radius.

New Vanadium Germanium Garnets

New vanadatogermanates Ca3–xMe2 + xV2GeO12, Ca3Mе2VGe2O12, and Ca3Me2Ge3O12, where Me = Mg, Mn, Co, Ni, Fe, Zn, and x = 0–1, have been synthesized through coupled substitutions of cations in the initial garnets Ca2.5Mn2V3O12 or Ca3Fe2Ge3O12. The unit cell parameters of the synthesized samples have been determined. Probability analysis of the cation distribution in the octahedral positions of the crystal lattice as a function of crystallographic radii has been performed taking into account the spin state of the cations.

The Stokes-Einstein equation and the diffusion of ferrocene in imidazolium-based ionic liquids studied by cyclic voltammetry: Effects of cation ion symmetry and alkyl chain length

The diffusion of ferrocene (Fc) molecules in ionic liquids (ILs) was studied using cyclic voltammetry. The symmetric ILs 1,3-dialkylimidazolium bis[(trifluoromethane)sulfonyl]amide ([(CN/2)2im][NTf2] with N = 4, 6, 8, and 10) and non-symmetric ILs 1-alkyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]amide ([CN−1C1im][NTf2] with N = 3, 4, 6, 8, and 10) were used to examine the effect of the symmetry of alkyl substitution on the cation and the role of alkyl chain length on the diffusion of Fc. The diffusion coefficient D of Fc was determined by applying the Randles-Sevcik equation to the peak current in the cyclic voltammograms. The diffusion coefficient was found to be higher in a symmetric IL than in a non-symmetric IL with the same number of alkyl carbon atoms N, with the difference decreasing with increasing N. The diffusion of Fc in these ILs is well described by the Stokes-Einstein equation with slip boundary conditions, but with an effective hydrodynamic radius of 0.23 ± 0.01 nm, which is less than the 0.27 nm crystallographic radius of Fc, in agreement with previous studies of the diffusion of solutes in ILs that show the hydrodynamic radius to be less than the van der Waals radius of the solute.

Dyfuziya i mikroskopichni xarakterystyky dovzhyny, chasu ta shvydkosti perenosu odnozaryadnyx ioniv u hranychno rozbavlenyx vodnyx rozchynax

Diffusion coefficients and microscopic characteristics of the length ( ¯d), time, and rate of ion diffusion displacement have been calculated for 19 singly charged ions (Li+, Na+, K+, Rb+, Cs+, F−, Cl−, Br−, I−, NO−3 , CNS−, ClO−4 , NH+4 , Me4N+, Et4N+, Pr4N+, Bu4N+, Pent4N+, and BPh−4 ) in water at temperatures from 273.15 to 473.15 K. The calculations are based on the literature data concerning the limiting molar electric conductivity of those ions. The analysis of the data obtained shows that the length of the ion diffusion displacement ¯d correlates with the type of ion solvation. If the average value ¯d exceeds the crystallographic (structural) radius ri of an ion, the latter is solvated positively. However, if ¯d is less than ri, the ion solvation is negative.

Intra-cage dynamics of molecular hydrogen confined in cages of two different dimensions of clathrate hydrates.

In porous materials the molecular confinement is often realized by means of weak Van der Waals interactions between the molecule and the pore surface. The understanding of the mechanism of such interactions is important for a number of applications. In order to establish the role of the confinement size we have studied the microscopic dynamics of molecular hydrogen stored in the nanocages of clathrate hydrates of two different dimensions. We have found that by varying the size of the pore the diffusive mobility of confined hydrogen can be modified in both directions, i.e. reduced or enhanced compared to that in the bulk solid at the same temperatures. In the small cages with a mean crystallographic radius of 3.95 Å the confinement reduces diffusive mobility by orders of magnitude. In contrast, in large cages with a mean radius of 4.75 Å hydrogen molecules displays diffusive jump motion between different equilibrium sites inside the cages, visible at temperatures where bulk H2 is solid. The localization of H2 molecules observed in small cages can promote improved functional properties valuable for hydrogen storage applications.

Sorption Selectivity of Rare-Earth Elements Ions by KB-2E Macroreticular Carboxylic Cation Exchanger

Sorption selectivity of a number of REE ions (Pr3+, Nd3+, Sm3+, Yb3+) was studied with the help of the KB-2E macroreticular carboxylic cation exchanger with a different content of a crosslinking agent. Selectivity was weakly dependent on the degree of crosslinking of the cation exchanger and concentration of the sorbed metal ion, which could be explained by the macroreticular structure of the cation exchanger. An increase in sorption selectivity of heavier REEs (Yb3+) correlated with a decrease in their crystallographic radius. It was concluded that a coordinate link of REE ions and oxygen donor atoms - a part of the cation exchanger - had been formed.

Using reactive artificial muscles to determine water exchange during reactions

Artificial muscles based on films of conducting polymers translate film volume variations, driven by electrochemical reactions (Faradaic motors), into macroscopic movements with generation of mechanical energy. The reaction promotes exchange of counterions (anions here) and solvent molecules with the electrolyte. Attributing here both the film volume variation and the movement originated by these exchanges of ions and solvent, the described angles can be used to quantify the exchanged solvent. Different angles described by bending muscles consuming equal driving charges in electrolytes having the same cation and different anions were measured. The number of exchanged counterions is given by the consumed charge and the ion valence: this is a Faradaic reaction. The described angle fraction due to the exchanged anions is given by the number of anions and the crystallographic radius. Taking as reference the anion giving the shorter angle, whatever the consumed charge, the relative number of solvent molecules exchanged by the polymeric membrane during a reversible reaction was determined. Actuators and artificial muscles can be used as useful tools for, at least, an initial study of the solvent exchange during reactions in reactive gels.

Laws and mechanism of adsorption of cations by different ion-exchange forms of silica gel

Using radioactive tracer method, the regularities of adsorption of over 30 mono-, di- and trivalent cations including transition metal and lanthanide ions on the H, Ca- and Al-forms of silica gel are established. It has been shown that the affinity of cations of the same charge to the silica gel surface depends both on the nature of the adsorbing ion and the nature of exchangeable cation on the surface. Adsorption of alkali earth metal ions on the Ca-form of silica gel increases with a decrease of their radius i.e. an inversion of the sequence of adsorption compared to H- or Al-form of this adsorbent or polymeric cation-exchange resins takes place. For lanthanide ions the sequence of adsorption is the same for all ion-exchange forms of the silica gel studied, namely, an increase of adsorption with a decrease of their crystallographic radius, i.e. from La 3+ to Lu 3+ takes place. The laws observed are explained by taking into account the fact that adsorption of cations by silica gel is determined by both electrostatic interactions and additional covalent/donor–acceptor interactions between the surface and cations. The latter is due to formation of π-bonds between the electron pair in surface oxygen and vacant p-, d- or f-orbital of adsorbing cations.

Crystallographic orientation and indenter radius effects on the onset of plasticity during nanoindentation

Abstract

Artificial Muscles: A Tool To Quantify Exchanged Solvent during Biomimetic Reactions

Artificial muscles (bending or linear) from films of conducting polymers are faradic and biomimetic gel motors consuming the same charge to move through the same space in a specific electrolyte. The driven volume variation of the film requires the exchange with the electrolyte of a number of counterions, defined by the charge, and solvent molecules during reactions. Working in aqueous solution with different anions using bilayer (polypyrrole/tape) bending artificial muscles, the charge consumed to describe a constant angle changes with the anion. Volume variations in the polypyrrole film due to the anionic exchange are calculated from the involved charge and the crystallographic radius of every anion. A parallel exchange of water molecules is required to explain the described angles. The number of solvent molecules exchanged between the polymeric membrane and the electrolyte at the same time that an anion (apparent solvation number) or when an electron was extracted from the chains (apparent hydration num...

General Anesthetics Predicted to Block the GLIC Pore with Micromolar Affinity

Although general anesthetics are known to modulate the activity of ligand-gated ion channels in the Cys-loop superfamily, there is at present neither consensus on the underlying mechanisms, nor predictive models of this modulation. Viable models need to offer quantitative assessment of the relative importance of several identified anesthetic binding sites. However, to date, precise affinity data for individual sites has been challenging to obtain by biophysical means. Here, the likely role of pore block inhibition by the general anesthetics isoflurane and propofol of the prokaryotic pentameric channel GLIC is investigated by molecular simulations. Microscopic affinities are calculated for both single and double occupancy binding of isoflurane and propofol to the GLIC pore. Computations are carried out for an open-pore conformation in which the pore is restrained to crystallographic radius, and a closed-pore conformation that results from unrestrained molecular dynamics equilibration of the structure. The GLIC pore is predicted to be blocked at the micromolar concentrations for which inhibition by isofluorane and propofol is observed experimentally. Calculated affinities suggest that pore block by propofol occurs at signifcantly lower concentrations than those for which inhibition is observed: we argue that this discrepancy may result from binding of propofol to an allosteric site recently identified by X-ray crystallography, which may cause a competing gain-of-function effect. Affinities of isoflurane and propofol to the allosteric site are also calculated, and shown to be 3 mM for isoflurane and for propofol; both anesthetics have a lower affinity for the allosteric site than for the unoccupied pore.

Comparing the salting-out effects of alkali-metal nitrates on the water-isopropanol system

The salting-out effects of sodium, potassium, and cesium nitrates on the water-isopropanol system, which is homogeneous throughout its liquid-state temperature range, are compared at different temperatures. The alkali-metal nitrates, which undergo homoselective solvation in aqueous-organic solvents, exert a salting-out effect on aqueous isopropanol. As the crystallographic radius of the cation decreases in the order CsNO3-KNO3-NaNO3, the monotectic critical tie line temperature for the salt-water-isopropanol system decreases (79.0, 47.2, and 6.1°C, respectively). In each ternary system, the salting-out effect on isopropanol strengthens with an increasing temperature, particularly in the system containing sodium nitrate. Among the salts examined, the strongest salting-out effect between 6.1 and 90.0°C is produced by sodium nitrate.

Resolvation thermodynamics of individual ions in water-ethanol mixtures at 298.15 K

The standard real and chemical thermodynamic characteristics of resolvation for magnesium ions in the water-ethanol mixtures of different composition were determined by their Volta potential differences at 298.15 K. Based on our analysis of these characteristics, the regularities and peculiarities of solvation of investigated ions in the mixed solvent were established. It was shown that the energies of ion resolvation in dependence on their crystallographic radii correspond to the series Ba2+< Ca2+ < Cd2+ < Cu2+ < Mg2+ < Al3+.

Physical and Transport Properties of Bis(trifluoromethylsulfonyl)imide-Based Room-Temperature Ionic Liquids: Application to the Diffusion of Tris(2, 2 ′ -bipyridyl)ruthenium(II)

The densities, viscosities, molar conductivities, and surface tensions of room temperature ionic liquids based on the bis(trifluoromethylsulfonyl)imide anion and the 1-(1-butyl)-3-methylimidazolium, 1-butyltrimethylammonium, 1-(1-butyl)-1-methyl- pyrrolidinium, 1-(1-butyl) pyridinium, and 1-ethyl-3-methylimidazolium cations were measured as a function of temperature over the range from . The surface tension of tri-(1-butyl)methylammonium bis(trifluoromethylsulfonyl)imide is also reported. Linear equations were fitted to the experimental density and surface tension data, and the Vogel–Tammann–Fulcher equation for glass-forming liquids was fitted to the experimental viscosity and conductivity data. The surface energies, surface entropies, and critical temperatures were estimated from the temperature dependence of the surface tension data. All of the liquids studied obey the fractional Walden rule and fall only slightly below the ideal line, indicating that they possess high ionicity. In each case, the viscosity shows only modest decoupling from the conductivity as the temperature is increased. Diffusion coefficients for the oxidation of tris(2,-bipyridyl)ruthenium(II) were measured in the six ionic liquids as a function of temperature. The hydrodynamic radius of tris(2,-bipyridyl)ruthenium(II) was estimated from the Stokes–Einstein equation and was found to be remarkably close to the crystallographic radius of this species.

Thermodynamics of resolvation of Mg2+, Ca2+, Cd2+, and Cu2+ ions in aqueous-ethanol mixtures on the basis of volta potential difference method

The volta potential difference method at 298.15 K was used to determine the real primary medium effect for magnesium, calcium, cadmium, and copper ions, and also the real Gibbs transfer energy of these ions from water into a mixed water ethanol (EtOH) solution. The surface potential value at the nonaqueous solution/gas phase interface \( \Delta \chi _{H_2 O}^{EtOH} \) was obtained. With account for this value, chemical thermodynamic characteristics of the studied ions in the water-ethanol solvent were calculated and the effect of composition and nature of the mixed solvent on the values obtained was analyzed. The dependence of variation in the thermodynamic characteristics of cation resolvation was established on their crystallographic radius that corresponds to the following sequence: Ca2+ < Cd2+ < Cu2+ < Mg2+.