Ion-ion reactions in the gas phase: Proton transfer reactions of protonated pyridine with multiply charged oligonucleotide anions

Isolated triply and doubly charged anions of the single-stranded deoxynucleotide 5′-d(AAAA)-3′ were allowed to undergo ion-ion proton transfer reactions with protonated pyridine cations within a quadrupole ion trap mass spectrometer. Sufficiently high ion number densities and spatial overlap of the oppositely charged ion clouds could be achieved to yield readily measurable rates. Three general observations were made: (1) the ion-ion reaction rate constants were estimated to be 10^{? (7 ? 8)} cm³ ion^?1 s^?1; (2) the ion-ion reaction rates were found to be dependent on the reactant ion number density, which could be controlled by both the reactant ion number and the pseudopotential well depth, and (3) very little fragmentation, if any, was observed, as might normally be expected with highly exothermic proton transfer reactions.     

Negative electron transfer dissociation Fourier transform mass spectrometry of glycosaminoglycan carbohydrates

Electron transfer through gas phase ion-ion reactions has led to the widespread application of electron- based techniques once only capable in ion trapping mass spectrometers. Although any mass analyzer can in theory be coupled to an ion-ion reaction device (typically a 3-D ion trap), some systems of interest exceed the capabilities of most mass spectrometers. This case is particularly true in the structural characterization of glycosaminoglycan (GAG) oligosaccharides. To adequately characterize highly sulfated GAGs or oligosaccharides above the tetrasaccharide level, a high resolution mass analyzer is required. To extend previous efforts on an ion trap mass spectrometer, negative electron transfer dissociation coupled with a Fourier transform ion cyclotron resonance mass spectrometer has been applied to increasingly sulfated heparan sulfate and heparin tetrasaccharides as well as a dermatan sulfate octasaccharide. Results similar to those obtained by electron detachment dissociation are observed.     

Effective interaction potentials for alkali and alkaline earth metal ions in SPC/E water and polarization model of hydrated ions

In the first paper (J. Phys. Chem. B, 2006, 110, 10878), effective ion-ion potentials in SPC/E water were obtained for Me-Me, Me-Cl-, and Cl(-)-Cl- pairs, where Me is Li+, Na+, K+, Mg2+, Ca2+, Sr2+, and Ba2+ cations. In this second part of the study of effective interionic potentials, ion-ion distribution functions obtained from implicit-water Monte Carlo simulations of electrolyte solution with these potentials have been explored. This analysis verifies the range of applicability of the primitive model of electrolyte. It is shown that this approximation can be applied to monovalent electrolyte solutions in a wide range of concentrations, whereas the nature of ion-ion interactions is notably different for 2:1 electrolytes. An improved model of ions is discussed. The model includes approximations of the ion hydration shell polarization and specific short-range ion-ion interaction. It allows approximation of the potential of mean force acting on ions in strong electric fields of highly charged macromolecules and bilayers.     

Ion-ion proton transfer reactions of bio-ions involving noncovalent interactions: Holomyoglobin

Multiply protonated horse skeletal muscle holomyoglobin and apomyoglobin have been subjected to ion-ion proton transfer reactions with anions derived from perfluoro-1,3-dimethylcyclohexane in a quadrupole ion trap operated with helium as a bath gas at 1 mtorr. Neither the apomyoglobin nor holomyoglobin ions show any sign of fragmentation associated with charge state reduction to the 1 + charge state. This is particularly noteworthy for the holomyoglobin ions, which retain the noncovalently bound heme group. For example, no sign of heme loss is associated with charge state reduction from the 9 + charge state of holomyoglobin to the 1 + charge state despite the eight consecutive highly exothermic proton transfer reactions required to bring about this charge change. This result is consistent with calculations that show the combination of long ion lifetime and the high ion-helium collision rate relative to the ion-ion collision rate makes fragmentation unlikely for high mass ions in the ion trap environment even for noncovalently bound complexes of moderate binding strength. The ion-ion proton transfer rates for holo- and apomyoglobin ions of the same charge state also were observed to be indistinguishable, which supports the expectation that ion-ion proton transfer rates are insensitive to ion structure and are determined primarily by the attractive Coulomb field.     

Kinetics and solvent effects in the acid hydrolysis of potassium ethyl malonate in dioxane-water and acetone-water mixtures

The acid-catalysed hydrolysis of potassium ethyl malonate in presence of 0.05N-HCl in water and in dioxane-water as well as acetone-water mixtures containing up to about 90% by weight of the organic solvent was studied over the temperature range 30–55°C. The reaction rate decreases continuously with decreasing water content of the solvent mixtures until it reaches a minimum at about 80% dioxane and increases again. The isocomposition activation energy shows only slight changes with solvent composition. The kinetics of the reaction was investigated from the viewpoints of solvent composition, water concentration and dielectric constant. The radii and thermodynamic parameters of the activated complex were calculated and discussed. The conclusions drawn show that the reaction is better treated as an ion-dipole rather than an ion-ion interaction.With 1 Figure     

Volumetric,rheological, and optical properties of hydroxylamine hydrochloride aqueous solutions containing NaCl,KCl, and NH4Cl at 30°C

Densities, viscosities, and refractive indices of aqueous solutions of hydroxylamine hydrochloride containing 0.05, 0.10, and 0.15 mol/dm³ NaCl, KCl, and NH₄Cl were measured at different concentrations of hydroxylamine hydrochloride at 30°C. Viscosity coefficients A and B representing ion-ion and ion-solvent interactions were determined from Jones-Dole equation. Experimental properties and viscosity coefficients have been interpreted in terms of ion-ion and ion-solvent interactions. Ion-solvent interactions were found to be dominating over the ion-ion interactions in studied systems.     

Osmotic coefficients of atomistic NaCl (aq) force fields

Solvated ions are becoming increasingly important for (bio)molecular simulations. But there are not much suitable data to validate the intermediate-range solution structure that ion-water force fields produce. We compare six selected combinations of four biomolecular Na-Cl force fields and four popular water models by means of effective ion-ion potentials. First we derive an effective potential at high dilution from simulations of two ions in explicit water. At higher ionic concentration multibody effects will become important. We propose to capture those by employing a concentration dependent dielectric permittivity. With the so obtained effective potentials we then perform implicit solvent simulations. We demonstrate that our effective potentials accurately reproduce ion-ion coordination numbers and the local structure. They allow us furthermore to calculate osmotic coefficients that can be directly compared with experimental data. We show that the osmotic coefficient is a sensitive and accurate measure for the effective ion-ion interactions and the intermediate-range structure of the solution. It is therefore a suitable and useful quantity for validating and parametrizing atomistic ion-water force fields.     

Effect of mobile phase composition on the retention of selected alkaloids in reversed-phase liquid chromatography with chaotropic salts

Sodium hexafluorophosphate, perchlorate and trifluoroacetate were applied as ion-ion interaction reagents in reversed-phase liquid chromatography. The separation of chosen alkaloids was performed by changing the kind of the organic modifier (methanol, acetonitrile, tetrahydrofuran), concentration of the ion-ion-interaction reagents and the concentration of phosphate buffer at constant pH (2.7) in the mobile phase. Obtained results were analyzed in connection to a dynamic ion-exchange model of retention and ion-ion interaction effects. The perturbation method was applied to test proposed retention theories. The formation of ion-complexes controlling the retention in chaotropic systems was confirmed. On the basis of the relationships of capacity factors (k) versus salt concentrations derived experimentally, absolute increases in capacity factors, the desolvation parameters and the limiting retention factors were calculated and compared for all the investigated compounds in eluent systems studied. The selectivity of the proposed mobile phases was compared on the basis of the separation of alkaloid mixture.     

水及含水混合溶剂中动力学盐效应的理论研究

从溶质-溶剂间的造腔、静电、非静电、排斥及氢键等相互作用出发,本文根据过渡状态理论计算了乙酸乙酯皂化反应在一系列浓度的H_2O-NaCl、H_2O-KCl、H_2O-BaCl_2、H_2O-SrCl_2 水-盐二元体系中和氯代叔丁烷溶剂解反应在一定组成的H_2O-DMSO-MX、H_2O-Me_2CO-MX、H_2O-MeOH-MX、H_2O-EtOH-MX(MX=NaCl,NaNO_3,LiClO_4)水-有机溶剂-盐三元体系中的动力学速率常数,大多数溶剂体系的计算结果与文献值颇相符.还讨论了理论公式、计算结果及各相互作用项的贡献.     

Application of Kirkwood-Buff theory to electrolyte solutions. III. Activity coefficients of aqueous NaCl between 273.15 and 573.15 K

Using a theory recently developed for the interpretation of activity coefficients of 1:1 electrolytes up to high concentrations in aqueous solution at 25°C, we have analysed available data for aqueous sodium chloride solutions up to saturation in the temperature range 273.15–573.15 K. The approach, which is based on Kirkwood-Buff theory and uses the truncated Poisson-Boltzmann equation to obtain the required information about the various ion-ion radial distributions, is able to fit the results to high accuracy with minimum of parameters, viz, three, of which one is the distance of closest approach, the other two relate to ion-solvent interactions and/or higher order terms in the ion-ion interaction.     

From 2D framework to quasi-1D nanomaterial: preparation,characterization, and formation mechanism of Cu(3)SnS(4) nanorods

An ion-ion reaction route under solvothermal condition at relatively low temperatures was first put forward to the preparation of tetragonal Cu(3)SnS(4) nanorods, on the basis of the strategy that 2D framework structure of Cu(3)SnS(4) containing layers could provide orientation for the growth of quasi-1D nanomaterials. X-ray diffraction (XRD) pattern, transmission electronic microscope (TEM) images, electronic diffraction (ED) pattern, X-ray photoelectron spectra (XPS), energy-dispersive X-ray analysis (EDXA), M?ssbauer spectrum, Raman spectrum, thermal analysis (DTA and TGA), ultraviolet and visible light (UV-vis) spectrum, and photoluminescence (PL) spectrum were used to characterize the products. On the basis of a series of supplementary experiments and the result of infrared absorption spectrum (IR), a reaction mechanism was proposed: ethanol as solvent and reductant and trace water/CH(3)CSNH(2) as sulfur source and acid-making components could form 2D network through hydrogen bonds, which provided the orientation for the formation of a 2D framework structure; appropriate concentration of CH(3)CSNH(2), warming speed, reaction constant temperatures (T(rc)), and reaction time also played important roles.     

Analysis of ion-association reaction in aqueous solution and its utilization by capillary zone electrophoresis.

Electrophoretic migration of analytes in capillary zone electrophoresis (CZE) reflects the dissolved status of analytes in solution, and the electrophoretic mobility is controlled to develop the resolution among analytes by adding a "modifier" to the migrating solution. Such addition of modifier is essentially the utilization of molecular interactions. Precise measurement of electrophoretic mobility by CZE allows analyzing molecular interactions, and CZE apparatus is very useful for physicochemical measurements. This review focuses on the advantages on using CZE to analyze equilibrium reaction; the capillary electrophoretic method and mathematical analyses that apply acid dissociation and complex formation reactions are also validated. Ion association reactions are deeply related to analytical chemistry and separation science, and CZE has been used for the investigation of ion-ion interactions. Various types of interactions have been clarified through the CZE measurements: contributions of hydrophobicity, probability, and aromatic-aromatic interaction were quantitatively evaluated. Ion association reaction in aqueous solution also elucidates the stepwise reactions of liquid-liquid distribution of ion associates. Development and applications of ion association reaction in CZE analysis are also introduced.     

Solvent-averaged potentials for alkali-, earth alkali-, and alkylammonium halide aqueous solutions

We derive effective, solvent-free ion-ion potentials for alkali-, earth alkali-, and alkylammonium halide aqueous solutions. The implicit solvent potentials are parametrized to reproduce experimental osmotic coefficients. The modeling approach minimizes the amount of input required from atomistic (force field) models, which usually predict large variations in the effective ion-ion potentials at short distances. For the smaller ion species, the reported potentials are composed of a Coulomb and a Weeks-Chandler-Andersen term. For larger ions, we find that an additional, attractive potential is required at the contact minimum, which is related to solvent degrees of freedom that are usually not accounted for in standard electrostatics models. The reported potentials provide a simple and accurate force field for use in molecular dynamics and Monte Carlo simulations of (poly-)electrolyte systems.     

Supramolecular polymeric complexes of calix[8]arenes

Formation of ionic complexes of calix[8]arenes with polymers of various basicities was studied, and previously unknown ternary polymeric complexes of calix[8]arenes of the ion-ion (polymer-calixarene-uranyl ion) and ion-hydrophilic molecule-hydrophobic molecule (polymer-calixarene-fullerene) types were prepared.     

Equations and determination of physicochemical properties of ammonium sulfate-nitrate solutions

Theoretical and correlation equations for calculation of multicomponent systems were considered in terms of a previously developed theory of ion-ion interactions in steady-and nonsteady-state processes for the example of ammonium sulfate-nitrate solutions formed from effluent gases of thermal power plants.     

A new approach for the study of gas-phase ion-ion reactions using electrospray ionization

A simple flow reactor which facilitates the study and application of ion-ion and ion-molecule reactions at near atmospheric pressures is reported. Reactant ions were generated by electrospray ionization and discharge ionization methods, although any ionization sources amenable to atmospheric pressure may be used. Ions of opposite charge are generated in spatially separate ion sources and are swept into capillary inlets where the flows are merged and where reaction(s) can occur. Among the reactions investigated were the partial neutralization of multiply protonated polypeptides and proteins such as melittin, bradykinin, cytochrome c, and myoglobin by reaction with discharge-generated anions, the partial neutralization of multiply charged anions of oligodeoxyadenylic acid (d(pA)₃) by reaction with discharge-generated cations, the partial neutralization of bovine A-chain insulin anions by reaction with myoglobin [M+nH]ⁿ⁺ ions, and the reaction of multiply protonated melittin with discharge-generated cations. The cation-anion reactions generally resulted in a shift to lower charge (higher mass-to-charge ratio) in the products’ charge state distributions and the transfer of solvent molecules to the macromolecule products. Multiply protonated melittin was detected in a less highly solvated state with the positive discharge in operation.     

Existence of optical phonons in the room temperature ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate

The technologically important properties of room temperature ionic liquids (RTILs) are fundamentally linked to the ion-ion interactions present among the constituent ions. These ion-ion interactions in one RTIL (1-ethyl-3-methylimidazolium trifluoromethanesulfonate, [C(2)mim]CF(3)SO(3)) are characterized with transmission FTIR spectroscopy and polarized attenuated total reflection (ATR) FTIR spectroscopy. A quasilattice model is determined to be the best framework for understanding the ionic interactions. A novel spectroscopic approach is proposed to characterize the degree of order that is present in the quasilattice by comparing the dipole moment derivative calculated from two independent spectroscopic measurements: (1) the TO-LO splitting of a vibrational mode using dipolar coupling theory and (2) the optical constants of the material derived from polarized ATR experiments. In principle, dipole moment derivatives calculated from dipolar coupling theory should be similar to those calculated from the optical constants if the quasilattice of the RTIL is highly structured. However, a significant disparity for the two calculations is noted for [C(2)mim]CF(3)SO(3), indicating that the quasilattice of [C(2)mim]CF(3)SO(3) is somewhat disorganized. The potential ability to spectroscopically characterize the structure of the quasilattice, which governs the long-range ion-ion interactions in a RTIL, is a major step forward in understanding the interrelationship between the molecular-level interactions among the constituent ions of an ionic liquid and the important physical properties of the RTIL.     

Synthesis and Crystal Structure of [K（2,2,2-crypt）]2HP11

[K（2,2,2-crypt]2HP11 has been prepared from the reaction of K3P11 with the mixed ethylenediamine/2,2,2-crypt solution. The crystal structure was determined by singlecrystal X-ray diffraction. The crystal is of tdgonal system, space group P^-3c1 with a = 12.068（2）, b = 12.068（2）, c = 22.319（6）A, V = 2815.0（10）A^3, Dc = 1.384 g/cm^3, C36h73K2N4O12P11, Mr = 1172.85, F（000） = 1232,μ = 0.536 mm^-1, Z= 2, R = 0.0678 and wR = 0.2211 for 1763 observed reflections （I 〉 2σ（I））. In this compound, the P11 cluster has ideal 32-D3 symmetry, and the three-fold axis, corresponds to the crystallographic c axis. The （HP11）^2- anions are stable due to the completely sequestered alkali metal cations through only ion-ion interactions.     

Targeted biomarker detection via whole protein ion trap tandem mass spectrometry: thymosin beta4 in a human lung cancer cell line

N-Terminally acetylated thymosin beta4, a species implicated for use as a cancer biomarker, was identified in a human lung cancer cell line using ion trap tandem mass spectrometry at the whole protein level. Ion-ion proton transfer reactions were used for parent ion concentration/manipulation and to simplify interpretation of product ion spectra. Dissociation data for the +6 to +3 charge states are reported. As is usually the case, structural information available from the ion trap collisional activation of the protein is sensitive to parent ion charge state. Each parent ion charge state selected, however, provided sufficient information to make a confident identification. Furthermore, each charge state provided relatively rich fragmentation. Therefore, any of the charge states can be used to detect with high specificity thymosin beta(4) in a complex protein mixture. There are advantages associated with the rapid detection of protein biomarkers at the whole protein level, as opposed to the peptide level following protein digestion, particularly for relatively small protein and polypeptide biomarkers. Having identified and characterized the protein, product ion spectra obtained directly, without recourse to ion-ion proton transfer reactions, can be used for library matching. However, ion-ion proton transfer reactions for parent ion concentration and charge state purification are advantageous in addressing relatively complex mixtures.