Dicarboxylic Acid Anions Research Articles

Towards thermodynamically stable anionic dimers with “anti-electrostatic” hydrogen bonds overcoming like-charge repulsion

We provide quantum chemical evidence for thermodynamically stable anionic dimers, wherein short-range, attractive hydrogen bonds overcome long-range, repulsive Coulomb interaction. We employed ab initio and density functional theory for studying the kinetic and thermodynamic stability for homodimers of singly deprotonated dicarboxylic acid anions. For the dimeric structures (HOOC(CH2)nCOO−)2 with n = 0–4 we calculated robust local minima with clear dissociation barriers preventing “Coulomb explosion” into separated anions. Already for n = 5 hydrogen bonding and dispersion forces fully compensate for the repulsive Coulomb forces between the anions allowing for the quantification of the two equivalent hydrogen bonds and dispersion interaction in the order of 62 kJmol−1 and 11 kJmol−1 respectively. The increasing kinetic stability even turns into thermodynamic stability with increasing number of methylene groups tethering the negative charges at the carboxylate groups. For n > 5 quantum-type short-range attraction wins over classical long-range electrostatic repulsion resulting in negative binding energies and providing the first energetically stable anionic dimers. For n = 6 and n = 7 we calculated negative free energies below 50 and 100 K, respectively. Even considering pressure effects, the dimers of the singly deprotonated octanedioic acid and nonanedioic acid anions should be detectable by means of cryogenic ion vibrational spectroscopy at temperatures from 10 to 30 K. We rationalize the H-bond characteristics of the dimers by the Natural Bond Orbital (NBO) approach, emphasizing the strong correlation between NBO-based and experimental descriptors.

Molecular mechanistic insights into coupling of ion transport to ATP synthesis

A wealth of molecular mechanistic insights has been provided into the coupling of ion transport to ATP synthesis based on a two-ion theory of biological energy coupling. A kinetic scheme that considers the mode of functioning of a single F1FO-ATP synthase molecule with H+-A− cotransport and unidirectional rotation of the c-rotor in the membrane-bound FO-portion of the enzyme has been developed. Mathematical analysis leads to a detailed enzyme kinetic model applicable to a population of molecules which is compared with experimental data on the pH dependence of ATP synthesis. The model agrees well with the experimental data, and a single equation with a single set of standard enzymological kinetic parameters has been shown to explain the experimental data over the entire range of conditions for the chloroplast ATP synthase. The analysis gives novel insights into kinetic and mechanistic characteristics of ATP synthesis in FO. These include an order imposed on ion binding and unbinding events in FO, the essential role of the anion in direct activation of the ATP synthase (in addition to its role as a permeant ion), and the integration in a novel way of the functions of cooperativity and cotransport of dicarboxylic acid anions and protons during physiological ATP synthesis. Further, Wyman's pioneering classical work on the thermodynamics of linked functions has been shown to offer a new approach to distinguish between various models of energy coupling in ATP synthesis. All these results have been found to be inconsistent with Mitchell's chemiosmotic theory and are shown to be in agreement with Nath's torsional mechanism of energy transduction and ATP synthesis.

Synthesis and plant growth modulation of tris (2-hydroxyethyl)ammonium boron-containing compounds

To develop boron deficiency treatment composite preparations for significant agricultural crops tris(2-hydroxyethyl)ammonium complexes containing boron and lower dicarboxylic acid (C2-C4) anions were synthesized and characterized. It was shown, that formation and stabilization of complexes containing a greater number of carbon atoms or intermolecular ?- conjugation (e.g. maleic acid) is related to space and electrostatical hurdles, respectively. According to NMR spectroscopy, in case of tartaric acid complex vicinal hydroxyl bounding with boron was found. The preexisted boratrane azeotropic water distillation synthetic method was modernized (videlicet optimal solvent mixture and raw materials ratio were chosen). Various triethanolamine and boric acid reaction mediums, i.e. nonpolar (toluene), polar aprotic (dimethylsulphoxide), protic (isopropanol, 2-butanol) solvents and their mixtures, were tested. In the issue optimal synthetic method, utilizing isopropanol/2-butanol mixture in ratio 3 to 1, was elaborated. In comparison to standard azeotropic water-isopropanol distillation the yield of the process was exceeded to 12.08% (from 82.70% to 94.78%) and low impurity concentrations in product was committed. Besides alternative laboratory solvent-free boratrane synthetic method was developed and optimal rinsing fluid composition was found. During agricultural experiments substance effectiveness in germination power and germinability of beet seeds and productivity of sugar beet was studied. Boratrane was found to be slightly effective for seed germinability stimulation. Boratrane-containing composition (i.e. boratrane + tris(2-hydroxyethyl)ammonium o-cresoxyacetate + 1-chloromethylsilatrane) was shown to have the best results in apical root length, average root-crop and average plant weigth increasing in comparison with the control.

Structure and SO2 Absorption Properties of Guanidinium-Based Dicarboxylic Acid Ionic Liquids

A new series of functionalized ionic liquids (ILs) with 1,1,3,3-tetramethylguanidine ([TMG]+) cations as well as dicarboxylic acid anions {[−OOC–(CH2–CH2)n–COO–], where n = 1, 3, and 5} was synthesized, and their SO2 absorption properties were investigated. A high SO2 absorption capacity of the prepared ILs was achieved. The molar ratios of SO2 to [TMG][succinic acid] {([TMG][SUC]) (n = 1)}, [TMG][suberic acid] {([TMG][SUB]) (n = 3)}, and [TMG][dodecanedioic acid] {([TMG][DOD]) (n = 5)} were 4.76, 5.96, and 5.96, respectively. The evidence of spectroscopic measurements and quantum chemical calculations confirmed that SO2 could interact with the carboxyl and adjacent methylene groups on the anion as well as the amino group on the cation. The SO2 absorption capacity of these ILs was strongly influenced by their asymmetry and space resistance. The high symmetry and large steric hindrance could reduce the SO2 absorption capacity of ILs.

Noncovalent interactions underlying binary mixtures of amino acid based ionic liquids: insights from theory

Mixtures of ionic liquids formed by blending a common 1-methyl-3-butylimidazolium [Bmim] cation with the dicarboxylic amino acid anions viz., aspartic acid [Asp], asparagine [Asn], glutamic acid [Glu], and glutamine [Gln], have been investigated by employing dispersion corrected density functional theory. Binary mixtures of [Bmim]2[Asp][Asn] and [Bmim]2[Glu][Gln] ionic liquids emerge with distinct structural patterns. Competition between the constituting anions towards cationic binding sites in acidic and basic (polar) amino acid binary mixtures engenders diverse noncovalent interactions, viz., C-HO hydrogen bonding, π-π stacking, and lpπ and CHπ interactions, which impart local liquid structure to these systems governing the structural and physicochemical properties of such double salt ionic liquids (DSILs). The DSIL conformers reveal distinct structural features arising from the middle, normal and front arrangements of anions combined with parallel, antiparallel, rotated or displaced orientations of the cations. The inclusion of dispersion corrections through the D3 method affects their binding energies significantly bringing forth alteration in their energy rank order. Molecular insights accompanying the ion aggregates provide directives for the use of DSILs with improved performance in tribological applications.

Role of Fumarate in the Operation of the Bacterial Flagellar Motor

Fumarate has previously been identified as a ‘switch factor’ that can alter the switching frequency and bias of the sense of rotation of the bacterial flagellar motor; however, despite numerous studies during the past fifty years, the molecular mechanism by which fumarate causes these effects could not be understood. We studied the motility of Salmonella by bright field and by monitoring rotation in a tethered cell assay. We carried out a detailed computerized analysis of the swimming and rotational behavior in real time under various conditions of external pHs (5.0 ± 8.0) and added fumarate concentrations (0 ± 12 mM). Based on our experimental results, we make the novel proposal that the bacterial flagellar motor contains access channels permeable to the fumarate monoanion, and that it catalyzes the overall electroneutral transport of fumarate and protons. We further postulate that each ionic species provides ∼50% of the total energy for rotation of the bacterial flagellar motor. These predictions are applicable to both the normal (say CW) mode of motor rotation as well as to the so-called “switched” (CCW) sense of rotation, depending on the direction of translocation of the ions. Hence previous proposals of fumarate as a ‘switch factor’, are false, or at best incomplete, because fumarate participates in the rotation of the flagellar motor in both normal and switched modes of operation. The new hypothesis extends to bacterial motility the essential and vital role played by dicarboxylic acid anions in oxidative phosphorylation and photosynthesis according to Nath's torsional mechanism of energy transduction and ATP synthesis (Nath, S., Beyond the Chemiosmotic Theory, Journal of Bioenergetics and Biomembranes 2010,42, 301-309).

Evidence of aerosols as a media for rapid daytime HONO production over China.

Current knowledge of daytime HONO sources remains incomplete. A large missing daytime HONO source has been found in many places around the world, including polluted regions in China. Conventional understanding and recent studies attributed this missing source mainly to ground surface processes or gas-phase chemistry, while assuming aerosols to be an insignificant media for HONO production. We analyze in situ observations of HONO and its precursors at an urban site in Beijing, China, and report an apparent dependence of the missing HONO source strength on aerosol surface area and solar ultraviolet radiation. Based on extensive correlation analysis and process-modeling, we propose that the rapid daytime HONO production in Beijing can be explained by enhanced hydrolytic disproportionation of NO2 on aqueous aerosol surfaces due to catalysis by dicarboxylic acid anions. The combination of high abundance of NO2, aromatic hydrocarbons, and aerosols over broad regions in China likely leads to elevated HONO levels, rapid OH production, and enhanced oxidizing capacity on a regional basis. Our findings call for attention to aerosols as a media for daytime heterogeneous HONO production in polluted regions like Beijing. This study also highlights the complex and uncertain heterogeneous chemistry in China, which merits future efforts of reconciling regional modeling and laboratory experiments, in order to understand and mitigate the regional particulate and O3 pollutions over China.

Study on a Structure of 2,6-Pyridine Dicarboxylic Acid Gallium, (NH<sub>4</sub>)Ga(C<sub>7</sub>H<sub>3</sub>NO<sub>4</sub>)<sub>2</sub>

A novel Ga complex (NH4)Ga(C7H3NO4)2 has been synthesized from a solution reaction and the crystal structure has been determined by means of single-crystal X-ray diffraction. The Ga atom is six-coordinated by two N atoms and four O atoms from two 2,6-pyridine dicarboxylic acid anions. The crystal packing is stabilized by O-H...N hydrogen bonding interactions.

English

A simple and highly selective method for determination of enalaprilat (ENT), lisinopril (LSP) and benazepril hydrochloride (BZP) in pharmaceutical dosage forms as well as spiked human plasma by ion chromatography with UV detection has been developed. ENT and LSP are compounds with little inherent hydrophobicity that make their analysis using HPLC essentially sophisticated necessitating either complex extraction procedures or especial detection methods. The method proposed is based upon ionization of those two drugs in basic medium to be well retained and readily resolved as dicarboxylic acid anions using IonPac AS11 (13 μm particle size, 4 × 250 mm, Dionex) anion exchange column adopting a very simple clean-up procedure via a single-step protein precipitation with UV detection at 215 nm. The three drugs were successfully determined in pharmaceutical dosage forms as well as in spiked human plasma with tyrosine as internal standard with a recovery approaching 100%. Adopting this proposed procedure, the analytes produce well shaped peaks with good linear relationship over the investigated concentration ranges and values of (r) higher than 0.998 for all drugs. ion level of200 ng ml-1 of the three drugs, therefore being satisfactory for their purposed analysis. The method was validated with respect to specificity, recovery, accuracy, precision and linearity. Moreover, the method could be applied to the determination of the drugs in pharmaceutical preparations. The method was validated with respect to specificity, recovery, accuracy, precision and linearity and the method proved applicable for routine fast analysis of the studied drugs. Key words: Benazepril, enalaprilat, lisinopril, ion chromatography, pharmaceutical, plasma.

Noncovalent complexation of glucosylthioureidocalix[4]arenes with carboxylates and their gas‐phase characteristics: an ESI‐FTICR mass spectrometric study

The noncovalent complexation of three glucosylcalix[4]arenes (1-3) towards 23 mono- and dicarboxylic acid anions were studied by ESI-FTICR mass spectrometry. Competitive complexation, collision-induced dissociation and gas-phase H/D-exchange experiments were performed to obtain information on selectivity of calixarenes towards carboxylates and characteristics of their complexes. The flexibility and number of glucose units of the host and the spatial disposition of the hydrogen bonding groups on the carboxylate guests were found to affect the selectivity of complexation strongly. The glucosylcalixarenes exhibited particular selectivity for dicarboxylic acid anions incorporating π-systems, and clear isomeric selectivity was observed for isophthalic among phthalic acid anions and for fumaric acid over maleic acid anion.

High‐pressure Raman spectroscopic and other structural studies of hydrotalcites containing intercalated dicarboxylic acid anions

AbstractThe results of pressure‐tuning Raman spectroscopic, X‐ray powder diffraction and solid‐state 13C‐NMR studies of selected dicarboxylate anions intercalated in a Mg–Al layered double hydroxide lattice are reported. The pressure dependences of the vibrational modes are linear for pressures up to 4.6 GPa, indicating that no phase transitions occur. The interlayer spacings show that the oxalate, malonate and succinate dianions are oriented perpendicular to the layers, but the glutarate and adipate are tilted. The solid‐state 13C‐NMR spectra of these materials show full chemical shift anisotropy and, therefore, the anions are not mobile at room temperature. Copyright © 2011 John Wiley & Sons, Ltd.

Non-innocent electrolyte effects on bimolecular pseudo-self-exchange reactions of ruthenium ammine complexes: Evidence for electron-transfer catalysis in H-bonded ternary assemblies

The kinetics of bimolecular pseudo-self-exchange reactions such as that between pentaammine(pyridine)ruthenium(II) and pentaammine(3-fluoropyridine)ruthenium(III) shown below, ( NH 3 ) 5 Ru II ( py ) 2 + + ( NH 3 ) 5 Ru III ( 3 - Fpy ) 3 + ⇄ k ex ( NH 3 ) 5 Ru III ( py ) 3 + + ( NH 3 ) 5 Ru II ( 3 - Fpy ) 2 + reveal a novel form of non-covalently mediated electron transfer over distance when salts of non-innocent electrolytes such as the conjugated dicarboxylic acid anions trans, trans-muconate 2− or terephthalate 2− are added to the solution. The kinetic accelerations are distinct from those seen with simple electrolytes such as KCl or CaCl 2, and are thus outside the realm of classical electrolyte effects described by the Debye–Huckel theory of ion atmospheres. Kinetic simulations are presented, and the rate acceleration is interpreted in the context of possible superexchange-type interactions taking place in hydrogen-bonded ternary (or higher) association complexes which create new kinetic pathways for electron transfer over distance in aqueous solution.

Organic ligand distribution and speciation in sedimentary basin brines, diagenetic fluids and related ore solutions

Abstract The nature, distribution, and interactions of dissolved organic ligands in the shallower zones of sedimentary basins are highly variable and poorly understood. Better understood is the chemistry of dissolved aqueous carboxylic acid species in the deeper regions of sedimentary basins. In most oil-field brines, acetate is generally the dominant organic ligand and is followed in level of concentration by longer chained aliphatic monocarboxylic acid anions. The total concentration of dicarboxylic acid anions is probably lower than previously reported and likely less than 500 mg l −1 with succinate and glutarate being the dominant species. The highest concentrations of organic acid anions are present in formation waters at 80–120° C. Based on the available field and laboratory evidence, the concentrations of organic anions are controlled mainly by the rates of their generation from kerogen and their destruction thermally or by bacteria. An extensive compilation of experimentally determined stability constants and other thermodynamic data for a large number of non-humic organic ligands is available for temperatures near 25° C. However, corresponding high-temperature data are available for only a few species of interest; most notably, acetate complexes of some rock- and ore-forming metals and protonated species of several carboxylate ligands. Simulations of speciation in oil-field brines show that significant amounts of Ca, Mg, Fe, and Al can be complexed by carboxylate ligands, in the pH range 4–6, if ligand concentrations are on the order of 10–100 mg l −1 . Calculated speciation in model ore fluids for Mississippi Valley-type deposits and red-bed related base metal deposits show that optimum conditions for Pb and Zn transport by organic ligand complexation are oxidized ore fluids with total reduced inorganic sulphide concentration less than 10 −9 molal.

Distribution and significance of dicarboxylic acid anions in oil field waters

The origin, distribution, and interactions of low-molecular-weight organic acid anions have become an intensively studied field in geochemistry since their widespread occurrence in formation waters of sedimentary basins was first documented by Carothers and Kharaka ( 1978 ). High concentrations (up to 10,000 mg 1~ ) of monocarboxylic (mainly acetate, propionate, and butyrate) and dicarboxylic (mainly oxalate, malonate, and succinate ) acid anions have been reported from many sedimentary basins, with the highest values present in relatively young (Cenozoic age) petroleum reservoir rocks at subsurface temperatures of 80-120 ° C [ see Lundegard and Kharaka (1990) for a recent review with references ]. Geochemical interest in these organic anions stems mainly from their important role in mineral diagenesis in sedimentary basins (Kharaka et al., 1986; MacGowan and Surdam, 1990). In particular, these species act as sources or sinks of protons, as a source of CO2 and as pH and Eh buffering agents (Lundegard and Kharaka, 1990). They also form complexes with cations and metals such as Ca, A1, Fe, Pb, and Zn (Kharaka et al., 1985; Harrison and Thyne, 1992). Data on the concentrations of monocarboxylic acid anions in subsurface waters from many sedimentary basins worldwide are available and are generally accepted as representing the aqueous concentrations at depth. Data on the concentrations of dicarboxylic acid anions are much more limited, some reported values are controversial, and the total values reported range widely from 0 to 2640 mg 1-~ (Surdam et al., 1984; Kharaka et al., 1986; Barth, 1987; MacGowan and Surdam, 1988, 1990). Because of the wide range in the reported concentrations and because dicarboxylic acid anions generally form stronger complexes with A1, Fe, and other cations than do monocarboxylic acid anions, we resampled four oil wells in the San Joaquin basin, California, in order to better assess the role of these acid anions in water-rock interactions in sedimentary basins.

Reversible Inhibition of Carboxypeptidase A. II. Inhibition of Esterase Activity by Dicarboxylic Acid Anions

Reversible inhibition of the hydrolysis of O-hippuryl-L-3-phenyllactic acid by carboxypeptidase A has been studied for a series of decarboxylic acids at 25°, pH 7.5, and ionic strength 0.2. All inhibitors studied displayed either strictly competitive or partially competitive inhibition kinetics. For the series CO2H(CH2)nCO2H, strictly competitive inhibition was observed for n = 1, 3, 4, 8, 10, whereas partially competitive inhibition occurs for n = 2, 5, 6, 7. A series of 11 alkyl- and aryl-substituted malonic acids were all strictly competitive inhibitors; for a series of six alkylmalonic acids the inhibition constants are correlated with the Hansch π-parameter by the equation –log K1 = 2.257π + 1.75; arylmalonic acids are poorer inhibitors than expected on the basis of their π-parameters, in accord with a similar observation for monocarboxylic acids. Phthalic acid is a strictly competitive inhibitor (K1 = 1.7 mM), whereas the isomeric isophthalic and terephthalic acids cause relatively little inhibition even at 0.1 M; maleic acid is a partially competitive inhibitor, whereas the isomeric fumaric acid gives only 15% inhibition at 0.1 M. Homophthalic acid and 2,2-dimethyl- and 3,3-dimethylglutaric acids were also investigated.The characteristics of partially competitive inhibition displayed by all dicarboxylic acids and also monomethyl succinate and succinamic acid are consistent with a scheme which assumes the formation of an E.I2 complex. The observed specificity of dicarboxylic acid binding is used to postulate a schematic diagram for binding of these species to the enzyme, and an interpretation of this diagram is suggested on the basis of the crystallographically determined structure of the enzyme.

The induction of translocators for di- and tricarboxylic-acid anions in Azotobacter vinelandii.

The conditions under which translocators for Krebs‐cycle intermediates can be induced in Azotobacter vinelandii were determined. With the exception of mesotartrate and d‐malate, only Krebs‐cycle intermediates themselves are good inducers. Glucose is needed for the induction of a translocator for C4‐dicarboxylic acid anions. Glucose at higher concentrations represses the translocator for C4‐tricarboxylic acid anions. This repression can be released by 3′: 5′‐AMP.Induction of the translocator for C4‐dicarboxylic acid anions probably occurs on the outside of the cell, because intracellularly generated dicarboxylic acid anions do not lead to synthesis of their translocator. Furthermore, contact between the cell and the inducer is necessary only during the first 20–30 min of induction, synthesis of the translaocator going on for another 60 min at least.Induction of a malonate translocator leads to the simultaneous induction of two malonate‐metabolizing enzymes: malonyl‐CoA synthetase and malonyl‐CoA decarboxylase.

Autoxydation von CuI‐Komplexen III. Das System CuI/CH3CN in Wasser mit und ohne Zusatz. von Dicarbonsäuren

AbstractThe autoxidation of cuprous copper in aqueous CH3CN is studied spectrophotometrically and by following O2‐as well as H+‐consumption. The rate of the reaction is greatly enhanced by the addition of chelating dicarboxylic acid anions such as oxalate and malonate, at low pH it increases proportional to H+‐concentration. This is explained by proton attack on the coordinated O2‐group in an oxygen adduct. The reaction is of first order with respect to [CuI] and [O2] and proceeds via one‐electron steps.

LIVER ACETYL COA CARBOXYLASE: THE DISSOCIATION-REASSOCIATION PROCESS AND ITS RELATION TO CATALYTIC ACTIVITY

In a previous paper' we reported that acetyl CoA carboxylase (E.C. 6.4.1.2) isolated in homogeneous form from chicken liver is an unusually large and asymmetric protein structure. The enzyme (in phosphate buffer, pH 7) has a molecular weight of about 8 million and a sedimentation coefficient of 53-58S. Its characteristic filamentous structure, revealed by electron microscopy, was easily dissociated into subunits with concomitant loss of enzymatic activity. Active filaments (70-100 A X up to 4000 A) were rapidly reconstituted by addition of isocitrate or other triand dicarboxylic acid anions. The present paper provides a more complete physicalchemical characterization of the protomeric and polymeric forms of acetyl CoA carboxylase, as well as an insight into the reversible dissociation-reassociation process and its relation to catalytic activity.