A theoretical investigation of the interactions between hydroxyl-functionalized ionic liquid and water/methanol/dimethyl sulfoxide

Density functional calculations have been used to investigate the interactions of 1-(2-hydroxyethyl)-3-methylimidazolium ([C₂OHmim]⁺)-based ionic liquids (hydroxyl ILs) with water (H₂O), methanol (CH₃OH), and dimethyl sulfoxide (DMSO). It was found that the cosolvent molecules interact with the anion and cation of each ionic liquid through different atoms, i.e., H and O atoms, respectively. The interactions between the cosolvent molecules and 1-ethyl-3-methylimizolium ([C₂mim]⁺)-based ionic liquids (nonhydroxyl ILs) were also studied for comparison. In the cosolvent–[nonhydroxyl ILs] systems, a furcated H-bond was formed between the O atom of the cosolvent molecule and the C2-H and C6-H, while there were always H-bonds involving the OH group of the cation in the cosolvent–[hydroxyl ILs] systems. Introducing an OH group on the ethyl side of the imidazolium ring may change the order of solubility of the molecular liquids.     

Sugar interaction with metal ions: synthesis,spectroscopic, and structural analysis of Zn(II), Cd(II), and Hg(II) complexes,containing d-glucuronate anion

Interaction between D-glucuronic acid and Zn(II), Cd(II), and Hg(II) metal ion salts has been studied in solution and solid complexes of the type M(D-glucuronate)X · nH₂O and M(D-glucuronate)₂·nH₂O, where M = Zn(II), Cd(II), and Hg(II), X = Cl⁻ or Br⁻, and n = 0–2 were isolated and characterized. Spectroscopic and other evidence indicated that in the metal-halide-sugar complexes the Zn(II) and Cd(II) ions bind to two D-glucuronate moieties via 06, 05 of the carboxyl oxygen atoms of the first and 04, 06' of hydroxyl and carbonyl groups of the second as well as to two H₂O molecules, whereas in the corresponding M(D-glucuronate)₂ · nH₂O salts, the metal ions are bonded to two sugar anions through 06 and 06' of the ionized carboxyl groups and two water molecules, resulting in a six-coordination around each metal cation. The Hg(II) ion binds to 06 and 05 oxygen atoms of a sugar anion and to a halide anion or water molecule, in the Hg(D-glucuronate)X·nH₂O compounds, while in the corresponding metal-glucuronate salt mercury is bonded to 06 and 06' of the two glucuronate anions with four-coordination around the Hg(II) ion. The β-anomer sugar conformation is predominant in the free acid and in these series of metal-sugar complexes.     

Effect of lithium salts on lactate dehydrogenase,adenylate kinase,and 1-phosphofructokinase activities

Inhibitions of 30?nM rabbit muscle 1-phosphofructokinase (PFK-1) by lithium, potassium, and sodium salts showed inhibition or not depending upon the anion present. Generally, potassium salts were more potent inhibitors than sodium salts; the extent of inhibition by lithium salts also varied with the anion. Li₂CO₃ was a relatively potent inhibitor of PFK-1 but LiCl and lithium acetate were not. Our results suggest that extents of inhibition by monovalent salts were due to both cations and anions, and the latter needs to be considered before inhibition can be credited to the cation. An explanation for monovalent salt inhibitions is proffered involving interactions of both cations and anions at negative and positive sites of PFK-1 that affect enzyme activity. Our studies suggest that lithium cations per se are not inhibitors: the inhibitors are the lithium salts, and we suggest that in vitro studies involving the effects of monovalent salts on enzymes should involve more than one anion.     

Anion binding to nucleic acids

Nucleic acids are generally considered as efficient cation binders. Therefore, the likelihood that negatively charged ions might intrude their first hydration shell is rarely considered. Here, we show on the basis of (i) a survey of the Nucleic Acid Database, (ii) several structures extracted from the Cambridge Structural Database, and (iii) molecular dynamics simulations, that the nucleotide electropositive edges involving mainly amino, imino, and hydroxyl groups can cast specific anion binding sites. These binding sites constitute also good locations for the binding of the negatively charged groups of the Asp and Glu residues or the nucleic acid phosphate groups. Furthermore, it is observed in several instances that anions, like water molecules and cations, do mediate protein/nucleic acid interactions. Thus, anions as well as negatively charged groups are directly involved in specific recognition and folding phenomena involving polyanionic nucleic acids.     

Theoretical study on the structures and properties of mixtures of urea and choline chloride

In this work, we investigated in detail the structural characteristics of mixtures of choline chloride and urea with different urea contents by performing molecular dynamic (MD) simulations, and offer possible explanations for the low melting point of the eutectic mixture of choline chloride and urea with a ratio of 1:2. The insertion of urea molecules was found to change the density distribution of cations and anions around the given cations significantly, disrupting the long-range ordered structure of choline chloride. Moreover, with increasing urea concentration, the hydrogen bond interactions between choline cations and Cl^? anions decreased, while those among urea molecules obviously increased. From the hydrogen bond lifetimes, it was found that a ratio of 1:2 between choline chloride and urea is necessary for a reasonable strength of hydrogen bond interaction to maintain the low melting point of the mixture of choline chloride with urea. In addition, it was also deduced from the interaction energies that a urea content of 67.7 % may make the interactions of cation–anion, cation–urea and anion–urea modest, and thus results in the lower melting point of the eutectic mixture of choline chloride and urea. The present results may offer assistance to some extent for understanding the physicochemical properties of the eutectic mixture of choline chloride and urea, and give valuable information for the further development and application of deep eutectic solvents.     

Tyrammonium 4-nitrophthalate dihydrate: structural and spectroscopic elucidation

Tyrammonium 4-nitrophthalate has been synthesized and its structural and spectroscopic properties elucidated by single-crystal X-ray diffraction, solid-state polarized IR-spectroscopy of oriented colloids in a nematic host, HPLC with tandem mass spectrometry (HPLC ESI-MSMS), and TGV and DSC methods. The compound crystallizes in the monoclinic P2₁/c space group and its structure consists of a 3D network of molecules joined by intermolecular interactions with the participation of cations, anions and two solvent molecules. The tyrammonium cation adopts a T trans configuration with corresponding angles of ϕ ₁ = 76.0(4)°, ϕ ₂ = 54.8(1)° and ϕ ₃ = 63.4(1)°, respectively. In the 4-nitrophthalate anion, the COO⁻ and COOH groups are turned off the plane of the benzene ring at angles of τ ₁ = 88.1(5)° and τ ₂= 22.1(7)°, respectively.     

Interactions of hydrogen molecules with complexes of lithium cation and aromatic nitrogen-containing heterocyclic anions

Highly stable salt functional groups consisting of lithium cation and aromatic anions (C _n H _n N_5?n ?Li) are studied for hydrogen storage using ab initio calculations, force field development, and grand canonical Monte Carlo simulations. Second-order Møller–Plesset perturbation theory with the resolution of identity approximation calculations are calibrated at the CCSD(T)/complete basis set (CBS) level of theory. The calibrations on different types of binding sites are different, but can be used to correct the van der Waals interactions systematically. The anion and salt functional groups provide multiple binding sites. With increased number of nitrogen atoms in the aromatic anion, the number of binding sites increases but the average binding energy decreases. Among the functional groups considered, CHN₄-Li exhibits the largest number of binding sites (14) and a weak average binding energy of 5.7 kJ mol^–1 with CCSD(T)/CBS correction. The calculated adsorption isotherms demonstrate that the introduction of the functional group significantly enhances hydrogen uptake despite relatively weak average binding energy. Therefore, it is concluded that searching for functional groups with the larger number of binding sites is another key factor for enhancing the hydrogen storage capacity, given that other conditions such as free volume and surface area are fixed.     

Anion exchange membrane adsorbers for flow‐through polishing steps: Part II. Virus,host cell protein,DNA clearance,and antibody recovery

Anion exchange membrane adsorbers are used for contaminant removal in flow‐through polishing steps in the manufacture of biopharmaceuticals. This contribution describes the clearance of minute virus of mice, DNA, and host cell proteins by three commercially available anion‐exchange membranes: Sartobind Q, Mustang Q, and ChromaSorb. The Sartobind Q and Mustang Q products contain quaternary amine ligands; whereas, ChromaSorb contains primary amine based ligands. Performance was evaluated over a range of solution conditions: 0–200 mM NaCl, pH 6.0–9.0, and flow rates of 4–20 membrane volumes/min in the presence and absence of up to 50 mM phosphate and acetate. In addition contaminant clearance was determined in the presence and absence of 5 g/L monoclonal antibody. The quaternary amine based ligands depend mainly on Coulombic interactions for removal of negatively charged contaminants. Consequently, performance of Sartobind Q and Mustang Q was compromised at high ionic strength. Primary amine based ligands in ChromaSorb enable high capacities at high ionic strength due to the presence of secondary, hydrogen bonding interactions. However, the presence of hydrogen phosphate ions leads to reduced capacity. Monoclonal antibody recovery using primary amine based anion‐exchange ligands may be lower if significant binding occurs due to secondary interactions. The removal of a specific contaminant is affected by the level of removal of the other contaminants. The results of this study may be used to help guide selection of commercially available membrane absorbers for flow‐through polishing steps. Biotechnol. Bioeng. 2013; 110: 500–510. © 2012 Wiley Periodicals, Inc.     

Noncovalent interactions and coordination reactions in the systems consisting of copper(II) ions, aspartic acid and diamines

Interactions of aspartic acid between 1,3-diaminopropane (tn) and 1,4-diaminobutane (Put) in metal-free systems as well as in the systems including copper(II) ions were studied. The composition and overall stability constants of the complexes formed were determined by the potentiometric method. The interaction centres and coordination sites were identified by spectroscopic methods. Each of the ligands has both negative and positive interaction centres. In aspartic acid such centres are carboxyl groups and amine group, while in the polyamine molecules – protonated amine groups. The centres are also the potential sites of the coordination of metal ions. Analysis of the log K_e values of the adducts in the systems with polyamines has shown that the stability of the adducts in the metal-free systems depends on a significant degree on the steric factor that is the length of the polyamine. In some species the inversion effect, hitherto not reported in literature, was found. In the ternary systems including Cu(II) ions, only protonated species are formed, including molecular complexes with intermolecular interactions and metallation through the oxygen atoms of carboxyl groups and amine groups of the amino acid. In the adducts the protonated diamine is in the outer coordination sphere and is involved in noncovalent interactions with the anchoring CuH(Asp) or Cu(Asp) complexes.     

Tetramethyl‐Bis(ethylenedithio)‐Tetrathiafulvalene (TM‐BEDT‐TTF) Revisited: Crystal Structures,Chiroptical Properties,Theoretical Calculations,and a Complete Series of Conducting Radical Cation Salts

The (S,S,S,S) and (R,R,R,R) enantiomers of tetramethyl‐bis(ethylenedithio)‐tetrathiafulvalene (TM‐BEDT‐TTF) show equatorial conformation for the four methyl groups in the solid state, according to the single‐crystal X‐ray analyses. Theoretical calculations at the Density Functional Theory (DFT) and time‐dependent (TD) DFT levels indicate higher gas phase stability for the axial conformer than the equatorial one by 1.25 kcal · mole^‐1 and allow the assignment of the UV–vis and circular dichroism transitions. A complete series of radical cation salts of 1:1 stoichiometry with the triiodide anion I₃^‐ was obtained by electrocrystallization of both enantiopure and racemic forms of the donor. In the packing the donors are organized in dimers that further interact through S · · · S intermolecular contacts and the triiodide anions lie parallel to pairs of oxidized donors. The conductivity of the racemate, which adopts the same, but disordered, structural type, is considerably lower, with much higher activation energy. Chirality 25:466–474, 2013.© 2013 Wiley Periodicals, Inc.     

Interactions of thiamine monophosphate (TMP) with one- and two-dimensional polymeric halogenomercurate anions. Crystal structures of (TMP)(Hg2Br5)·0.5H2O and (TMP)2(Hg3I8)

An investigation into the interactions between thiamine monophosphate (TMP) and anions has resulted in the preparation and X-ray characterization of the compounds (TMP)(Hg₂Br₅)·0.5H₂O (1) and (TMP)₂(Hg₃I₈) (2). In each compound the TMP molecule exists as a monovalent cation in the usual F conformation. The halogenomercurate anions occur in two-dimensional (2-D) network in 1 or one-dimensional (1-D) chain in 2. In both 1 and 2, the structures consist of alternating cationic sheets of the hydrogen-bonded TMP molecules and anionic sheets of the polymeric halogenomercurate anions. The TMP molecule binds to the polymeric anions through the characteristic ‘anion bridge I’, C(2)H?X?pyrimidinium (X=Br in 1 and I in 2), and electrostatic interactions between electropositive S(1) and halogen atoms. The ‘anion bridge II’ of the type N(4′1)H?X?thiazolium (X=phosphate group) plays a role in stabilizing the molecular conformation. The biological implication of the host-guest-like complexation between TMP and polymeric anions is discussed.     

Homo- and heterochiral coordination polymers of silver with diaminocyclohexane as bridging ligand: Trends in alkylbenzoates

Reaction of Ag₂CO₃ with four methyl-substituted derivatives of benzoic acid afforded silver benzoates; no additional anions are involved in these solids. One of the silver carboxylates was studied by X-ray diffraction: in the crystal, silver 3,5-dimethylbenzoate monohydrate consists of carboxylato-bridged discrete dinuclear molecules with a short Ag?Ag separation of 2.7719(5) Å and one weakly bonded hydrate water molecule per cation. The binary silver carboxylates were combined with either racemic or enantiopure trans-1,2-diaminocyclohexane and resulted in four homochiral and four heterochiral crystalline solids. All eight structures feature cationic chain polymers, carboxylate anions and hydrate water. In three of the solids derived from the racemic ligand, the individual cationic chains are homochiral. In all structures, the primary coordination of the Ag(I) centers by nitrogen is essentially linear. Despite the chemical similarity in the anions, the backbone of the polymers proved to be conformationally soft with variable Ag-N-C-C torsion angles. In the resulting structures, the diamine ligand may bridge two cations in a wide distance range between ca. 3.0 and ca. 7.2 Å. Both the chirality of the trans-1,2-diaminocyclohexane ligand and the substitution pattern of the benzoate anion have strong impact on the nature of secondary interactions perpendicular to the polymer strands: either weak coordination by carboxylato or hydrate water oxygen atoms or argentophilic interactions are encountered. The Ag?Ag contacts increase the dimensionality of the solids from chain polymers to layer structures.     

Core-dependent and ligand-dependent relativistic corrections to the nuclear magnetic shieldings in MH4−n Y n (n = 0–4; M = Si,Ge, Sn,and Y = H,F, Cl,Br, I) model compounds

The spatial geometry and local environment of hydroxyl groups of the cis-vacant (cv) crystal polymorph of dioctahedral 2:1 phyllosilicates are studied by computational methods, doing especial emphasis on the hydrogen bonds and electrostatic interactions of the hydroxyl groups with the neighbor atoms. Different types of phyllosilicates are explored: with only tetrahedral charge, with only octahedral charge, with simultaneous octahedral and tetrahedral substitution, and with different interlayer cation (IC). The effect of these interactions on the spectroscopic properties of these hydroxyl groups is also studied. All results are compared with the trans-vacant (tv) crystal forms of these minerals. Frequency differences between cv and tv polymorphs are smaller than those due to the local environments of these OH groups. This means that the changes in the interactions of the different local environments of each OH group are greater than the cv/tv differences.     

Compartmentation of malate in relation to ion absorption in beet

Malate in beet discs treated in different salt solutions was labeled by a 30 min pulse of ¹⁴CO₂, and subsequent changes in specific activity were followed for several hr. In treatments which resulted in net acid synthesis in response to excess cation absorption, malate specific activity fell slowly after removal of ¹⁴CO₂. In solutions where no net acid synthesis occurred, and from which cation and anion were absorbed equally, malate specific activity fell rapidly when ¹⁴CO₂ was removed. The foregoing suggests that the net synthesis of organic acids in response to excess cation absorption leads to the removal of organic anions from cytoplasmic metabolic pools as counter-ions in salt transport to the vacuole.     

Metabolism of Propane, n-Propylamine, and Propionate by Hydrocarbon-Utilizing Bacteria

Studies were conducted on the oxidation and assimilation of various three-carbon compounds by a gram-positive rod isolated from soil and designated strain R-22. This organism can utilize propane, propionate, or n-propylamine as sole source of carbon and energy. Respiration rates, enzyme assays, and ¹⁴CO₂ incorporation experiments suggest that propane is metabolized via methyl ketone formation; propionate and n-propylamine are metabolized via the methylmalonyl-succinate pathway. Isocitrate lyase activity was found in cells grown on acetate and was not present in cells grown on propionate or n-propylamine. ¹⁴CO₂ was incorporated into pyruvate when propionate and n-propylamine were oxidized in the presence of NaAsO₂, but insignificant radioactivity was found in pyruvate produced during the oxidation of propane and acetone. The n-propylamine dissimilatory mechanism was inducible in strain R-22, and amine dehydrogenase activity was detected in cells grown on n-propylamine. Radiorespirometer and ¹⁴CO₂ incorporation studies with several propane-utilizing organisms indicate that the methylmalonyl-succinate pathway is the predominant one for the metabolism of propionate.     

Carbon Incorporation and Anion Dynamics as Synergistic Drivers for Ultrafast Diffusion in Superionic LiCB11H12 and NaCB11H12

The disordered phases of LiCB₁₁H₁₂ and NaCB₁₁H₁₂ possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB₁₁H₁₂^? anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. The symmetry‐breaking carbon atom in CB₁₁H₁₂^? also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 × 10¹⁰ s^?1, suggesting the underlying energy landscape fluctuates dynamically on diffusion‐relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon‐modified cation–anion interaction accounts for the higher ionic conductivity in CB₁₁H₁₂^? salts compared with B₁₂H₁₂^2?.     

Modeling interactions between a β‐O‐4 type lignin model compound and 1‐allyl‐3‐methylimidazolium chloride ionic liquid

Aiming at understanding the molecular mechanism of the lignin dissolution in imidazolium‐based ionic liquids (ILs), this work presents a combined quantum chemistry (QC) calculation and molecular dynamics (MD) simulation study on the interaction of the lignin model compound, veratrylglycerol‐β‐guaiacyl ether (VG) with 1‐allyl‐3‐methylimidazolium chloride ([Amim]Cl). The monomer of VG is shown to feature a strong intramolecular hydrogen bond, and its dimer is indicated to present important π‐π stacking and intermolecular hydrogen bonding interactions. The interactions of both the cation and anion of [Amim]Cl with VG are shown to be stronger than that between the two monomers, indicating that [Amim]Cl is capable of dissolving lignin. While Cl^– anion forms a hydrogen‐bonded complex with VG, the imidazolium cation interacts with VG via both the π‐π stacking and intermolecular hydrogen bonding. The calculated interaction energies between VG and the IL or its components (the cation, anion, and ion pair) indicate the anion plays a more important role than the cation for the dissolution of lignin in the IL. Theoretical results provide help for understanding the molecular mechanism of lignin dissolution in imidazolium‐based IL. The theoretical calculations on the interaction between the lignin model compound and [Amim]Cl ionic liquid indicate that the anion of [Amim]Cl plays a more important role for lignin dissolution although the cation also makes a substantial contribution.     

Protein-mediated hydroxyl radical generation--the primary event in NADH oxidation and oxygen reduction by the granule rich fraction of human resting leukocytes.

The granule rich-fraction isolated from human resting polymorphonuclear leukocytes is capable of CN-insensitive NADH oxidation and O₂-uptake, accompanied by production of superoxide anion, hydroxyl radicals and H₂O₂. We showed that H₂O₂ initiates and maintains NADH oxidation and O₂-uptake but is also necessary for the formation of superoxide anion and hydroxyl radicals. It acts as a primary substrate for CN-insensitive protein-mediated formation of hydroxyl radicals, which in turn produce superoxide anions, probably through univalent oxidation of NADH as an intermediary.     

A density functional theory study on the interactions between dibenzothiophene and tetrafluoroborate-based ionic liquids

The interactions between dibenzothiophene (DBT) and N-butyl-N-methylimidazolium tetrafluoroborate ([BMIM][BF₄]), N-butyl-N-methylmorpholinium tetrafluoroborate ([Bmmorpholinium][BF₄]), N-butyl-N-methylpiperdinium tetrafluoroborate ([BMPiper][BF₄]), N-butyl-N-methylpyrrolidinium tetrafluoroborate ([BMPyrro][BF₄]), and N-butylpyridinium tetrafluoroborate ([BPY][BF₄]) were investigated using density functional theory approach. Geometric, electron, and topological properties were analyzed using natural bond orbital, atoms in molecules theory, and noncovalent interaction methods in order to understand intermolecular interactions between DBT and ionic liquids. The result shows that hydrogen bond and van der Waals interactions are widespread in all the ionic liquids-DBT systems. Ion-π interactions between DBT and cation or anion are also observed, while π⁺-π interactions are only found in the [BMIM][BF₄]-DBT and [BPY][BF₄]-DBT systems. The order of interaction energy is [BPY][BF4]-DBT > [BMIM][BF₄]-DBT >> [BMPiper][BF₄]-DBT > [BMPyrro][BF₄]-DBT > [BMmorpholinum][BF₄]-DBT. The energies between DBT and the two ionic liquids containing aromatic cations are significantly higher.     

Aqueous biphasic systems composed of ionic liquids and sodium carbonate as enhanced routes for the extraction of tetracycline

Aqueous biphasic systems (ABS) using ionic liquids (ILs) offer an alternative approach for the extraction, recovery, and purification of biomolecules through their partitioning between two aqueous liquid phases. In this work, the ability of a wide range of ILs to form ABS with aqueous solutions of Na₂CO₃ was evaluated. The ABS formed by IL + water + Na₂CO₃ were determined at 25°C, and the respective solubility curves, tie‐lines, and tie‐line lengths are reported. The studied ILs share the common chloride anion, allowing the IL cation core, the cation isomerism, the presence of functionalized groups, and alkyl side chain length effects to be evaluated. An increase in the cation side alkyl chain length leads to a higher ability for liquid–liquid demixing whereas different positional isomers and the presence of an allyl group have no major influence in the phase diagrams behavior. Quaternary phosphonium‐ and ammonium‐based fluids are more able to form an ABS when compared with imidazolium‐, pyridinium‐, pyrrolidinium‐, and piperidium‐based ILs. Moreover, the presence of an aromatic cation core has no major contribution to the formation of ABS when compared to the respective nonaromatic counterparts. Finally, to appraise on the systems applicability in downstream processing, selected systems were used for the partitioning of tetracyclines (neutral and salt forms) — a class of antibiotics produced by bacteria fermentation. Single‐step extraction efficiencies for the IL‐rich phase were always higher than 99% and confirm the great potential of ILs to be applied in the biotechnological field. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:645–654, 2013