Binding Of Dicarboxylic Acids Research Articles

Inorganic salts interact with oxalic acid in submicron particles to form material with low hygroscopicity and volatility

Abstract. Volatility and hygroscopicity are two key properties of organic aerosol components, and both are strongly related to chemical identity. While the hygroscopicities of pure salts, di-carboxylic acids (DCA), and DCA salts are known, the hygroscopicity of internal mixtures of these components, as they are typically found in the atmosphere, has not been fully characterized. Here we show that inorganic–organic component interactions typically not considered in atmospheric models can lead to very strongly bound metal–organic complexes and greatly affect aerosol volatility and hygroscopicity; in particular, the bi-dentate binding of DCA to soluble inorganic ions. We have studied the volatility of pure, dry organic salt particles and the hygroscopicity of internal mixtures of oxalic acid (OxA, the dominant DCA in the atmosphere) and a number of salts, both mono- and di-valent. The formation of very low volatility organic salts was confirmed, with minimal evaporation of oxalate salt particles below 75 °C. Dramatic increases in the cloud condensation nuclei (CCN) activation diameter for particles with di-valent salts (e.g., CaCl2) and relatively small particle volume fractions of OxA indicate that standard volume additivity rules for hygroscopicity do not apply. Thus small organic compounds with high O : C ratios are capable of forming low-volatility and very low hygroscopicity particles. Given current knowledge of the formation mechanisms of OxA and M–Ox salts, surface enrichment of insoluble M–Ox salts is expected. The resulting formation of an insoluble coating of metal-oxalate salts can explain low-particle hygroscopicities. The formation of particles with a hard coating could offer an alternative explanation for observations of glass-like particles without the need for a phase transition.

2-Amino-4-methylpyrimidine: A simple supramolecular scaffold for carboxylic acid complexes both in solid and solution states

Abstract Studies concentrating on hydrogen bonding interactions between 2-amino-4-methylpyrimidine (AMPY) with selected dicarboxylic acids have been investigated in the solid state. Two pyrimidinium-dicarboxylate organic salts with stoichiometry 1:1 [AMPY: maleic acid] and 2:1 [AMPY: d (+)-malic acid] have been prepared and characterized by X-ray crystallographic analysis. Maleic and d (+)-malic acids were found to exhibit unique supramolecular polymeric structures with AMPY involving proton transfer to the specific ring nitrogen of AMPY. As an extension, AMPY has been used to build a receptor structure 1. Receptor 1 shows binding of dicarboxylic acids in CH3CN and represents a marginal selectivity with d (+)-malic acid. Binding interactions were investigated by UV–vis and fluorescence studies.

A systematic evaluation of molecular recognition phenomena. 4. Selective binding of dicarboxylic acids to hexaazamacrocyclic ligands based on molecular flexibility.

The host-guest interaction between four hexaaza macrocyclic ligands (3,6,9,17,20,23-hexaazatricyclo[23.3.1.1]triaconta-1(29),11,13,15 (30),25(27)-hexaene (Bd), 3,6,9,16,19,22-hexaazatricyclo[22.2.2.2]triaconta-1(27),11(30),12,14(29),24(28),25-hexaene (P2), 3,7,11,19,23,27-hexaazatricyclo[27.3.1.1]tetratriaconta-1(33),13, 15,17(34),29,31-hexaene (Bn), 3,7,11,18,22,26-hexaazatricyclo[26.2.2.2]tetratriaconta-1(31),13(34),14,16(33),28(32),29-hexaene (P3)) and two dicarboxylic acids (oxalic acid, H2Ox; oxydiacetic acid, H2Od) have been investigated using potentiometric equilibrium methods. Ternary complexes are formed in aqueous solution as a result of hydrogen bond formation and Coulombic interactions between the host and the guest. In the [(H6P2)(Ox)]4+ complex those bonding interactions reach a maximum yielding a log KR6 of 6.08. This species has been further characterized by means of X-ray diffraction analysis showing that the oxalate guest molecule is situated inside the macrocyclic cavity of the P2 host. X-ray diffraction analysis has also been carried out for the complex [(H6Bn)(Od)2](Br)2.6H2O, where now the oxydiacetate is bonded to the host but outside the macrocyclic cavity. Competitive distribution diagrams and total species distribution diagrams are used to graphically illustrate the most salient features of these systems, which are the following: (a) The Bd and P2 ligands bind Ox significantly much more stronger than Od. This is clearly manifested for the P2:Ox:Od competitive system, where a selectivity of 92.5% in favor of the P2-Ox complexation against P2-Od is obtained at p[H] = 2.8. (b) No isomeric effect is found when comparing binding capacities of oxalate with two isomeric ligands such as P2 and Bd since their affinity to bind the substrate is relatively similar. (c) Bn and P3 ligands have a similar behavior as described in (a) for P2 and Bd except that due to the increase of cavity size the differentiation becomes smaller. (d) Less basic ligands containing two methylenic units Bd (log betaH6 = 40.42) and P2 (40.42) bind stronger to the substrates than those containing three methylenic units Bn (50.32) and P3 (50.64) even though their relative predominance depends on p[H].

Interaction between two dicarboxylate endogenous substances, bilirubin and an uremic toxin, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, on human serum albumin.

Two dicarboxylate endogenous substances, bilirubin (BR) and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), have a very high affinity to human serum albumin (HSA). This study was undertaken to clarify the existence of a dicarboxylate binding site on HSA. Chemical modification, pH dependent binding and X-ray crystallographic analysis were performed to characterize these dicarboxylate binding sites. It was found the binding behavior for dicarboxylates was different from typical site I ligands such as warfarin (WF) and phenylbutazone (PB) and that electrostatic interaction was an important factor for their binding to HSA. Moreover, His residues were considered to play an important role in pH dependent binding of dicarboxylic acids but in a different manner from the site I ligands. X-ray crystallography of CMPF and BR revealed the distances between the two carboxyl groups in their chemical structures were 5.854 A and 9.979 A, respectively. This difference may be reflected in pH dependent binding. Using fluorescent probe displacement, we attempted to identify the binding site for monocarboxylate derivatives of CMPF and investigated the role of individual carboxyl group in the recognition of the binding site. The results suggested two carboxyl groups were important for the specific binding of CMPF to site I. The binding site for dicarboxylic acids is located in subdomain IIA, which includes site I, on the HSA molecule. Electrostatic interaction is an important driving force for binding to HSA.

Mechanism of activation of the NAD-malic enzyme from Ascaris suum by fumarate

The mechanism of activation of the NAD-malic enzyme from Ascaris suum by fumarate has been probed using initial velocity studies, deuterium isotope effects, and isotope partitioning of the E:Mg:malate complex. Fumarate exerts its activating effect by decreasing the offrate for malate from the E:Mg:malate and E:NAD:Mg: malate complexes. Fumarate is a positive heterotropic effector of the NAD-malic enzyme at low concentrations ( K act ~ 0.05 mM) and an inhibitor competitive against malate ( K i ~ 25 mM). The activation by fumarate results in a decrease in the K imalate and an increase in V K malate of about 2-fold, while the maximum velocity remains constant. Isotope partitioning studies of E:Mg:[ 14C]malate indicate that the presence of fumarate results in a decrease in the malate off-rate constant by about 2.2-fold. The deuterium isotope effects on V and V K malate are both 1.6 ± 0.1 in the absence of fumarate, while in the presence of 0.5 m m fumarate DV is 1.6 ± 0.1 and D( V K malate ) is 1.1 ± 0.1. These data are also consistent with a decrease in the off-rate for malate from E:NAD:Mg:malate, resulting in an increase in the forward commitment factor for malate and manifested as a lower value for D( V K malate ). There is a discrimination between active and activator sites for the binding of dicarboxylic acids, with the activator site preferring the extended configuration of 4-carbon dicarboxylic acids, while the active site prefers a configuration in which the 4-carboxyl is twisted out of the C1-C3 plane. The physiologic importance and regulatory properties of fumarate in the parasite are also discussed.

Characterization of the binding sites for dicarboxylic acids on bovine serum albumin

Dicarboxylic acids are prominent features of several diseases, including Reye's syndrome and inborn errors of mitochondrial and peroxisomal fatty acid oxidation. Moreover, dicarboxylic acids are potentially toxic to cellular processes. Previous studies [Tonsgard, Mendelson & Meredith (1988) J. Clin. Invest. 82, 1567-1573] demonstrated that long-chain dicarboxylic acids have a single high-affinity binding site and between one and three lower-affinity sites on albumin. Medium-chain-length dicarboxylic acids have a single low-affinity site. We further characterized dicarboxylic acid binding to albumin in order to understand the potential effects of drugs and other ligands on dicarboxylic acid binding and toxicity. Progesterone and oleate competitively inhibit octadecanedioic acid binding to the single high-affinity site. Octanoate inhibits binding to the low-affinity sites. Dansylated probes for subdomain 2AB inhibit dodecanedioic acid binding whereas probes for subdomain 3AB do not. In contrast, low concentrations of octadecanedioic acid inhibit the binding of dansylated probes to subdomain 3AB and 2AB. L-Tryptophan, which binds in subdomain 3AB, inhibits hexadecanedioic acid binding but has no effect on dodecanedioic acid. Bilirubin and acetylsalicylic acid, which bind in subdomain 2AB, inhibit the binding of medium-chain and long-chain dicarboxylic acids. Our results suggest that long-chain dicarboxylic acids bind in subdomains 2C, 3AB and 2AB. The single low-affinity binding site for medium-chain dicarboxylic acids is in subdomain 2AB. These studies suggest that dicarboxylic acids are likely to be unbound in disease states and may be potentially toxic.

Molecular recognition. 8. Two-point hydrogen-bonding interaction: a remarkable chain-length selectivity in the binding of dicarboxylic acids with resorcinol-aldehyde cyclotetramer as a multidentate host

Molecular recognition. 8. Two-point hydrogen-bonding interaction: a remarkable chain-length selectivity in the binding of dicarboxylic acids with resorcinol-aldehyde cyclotetramer as a multidentate host

Binding of straight-chain saturated dicarboxylic acids to albumin.

Dicarboxylic acids are prominent features of several diseases, including Reye's syndrome. Long-chain dicarboxylic acids have profound effects on the function and structure of isolated mitochondria, suggesting that they could contribute to the mitochondrial dysfunction in Reye's syndrome. Binding of fatty acids to albumin and the intracellular fatty acid-binding proteins is important in regulating the transport and metabolism of fatty acids and protects against the toxic effects of unbound fatty acids. We studied the binding of dicarboxylic acids to defatted albumin using equilibrium dialysis to assess to what extent dicarboxylic acids are likely to be bound in the plasma of patients. Dicarboxylic acids bind weakly to albumin in a molar ratio of 3.8, 4.2, 1.6, 0.8, and 0.7 to 1 for octadecanedioic, hexadecanedioic, tetradecanedioic, dodecanedioic, and decanedioic acid, respectively. The dissociation constants for long-chain dicarboxylic acids are 100-1,000-fold larger than those of comparable monocarboxylic acids. Oleate competes with dicarboxylic acid and reduces the moles of dicarboxylic acid bound per mol of albumin to less than 1. Octanoate inhibits dicarboxylic acid binding. Our observations indicate that in Reye's syndrome, substantial concentrations of dicarboxylic acids of patients may be free and potentially toxic to mitochondria and other cellular processes.

ChemInform Abstract: Molecular Recognition: Size and Shape Specificity in the Binding of Dicarboxylic Acids.

AbstractThe mode of interaction of carboxylic diacids with the enzyme model receptors (I) is studied.

Molecular recognition: size and shape specificity in the binding of dicarboxylic acids

Molecular recognition: size and shape specificity in the binding of dicarboxylic acids

Heparin-like activity of insoluble sulphonated polystyrene resins Part III: Binding of dicarboxylic amino acids

It has been demonstrated previously that polystyrene sulphonate possesses anticoagulant properties and that the binding of some amino acids could enhance the heparin-like properties of such resins. These properties depend on the surface density of the active groups, the nature and binding of the group and on the net charge borne by the polymer. In this paper, we describe the preparation of copolystyrene (sulphonate-dicarboxylic amino acid sulphamide) resins. By measuring their antithrombic-surface-activity, we demonstrate that the activity developed by each carboxyl group is at least roughly the same as the activity of one sulphonate group, except in the case of aspartic acid sulphamide resin for which a cooperative effect is shown. The anticoagulant properties of resins bearing phosphonate or mono-carboxylic amino acid sulphamides are also examined.

Nuclear Magnetic Resonance of Aspartate Transaminase: A 19F AND 1H INVESTIGATION OF THE BINDING OF DICARBOXYLIC ACIDS TO VARIOUS FORMS OF EACH ISOENZYME

Abstract The binding of succinate and perfluorosuccinate to the supernatant and mitochondrial isoenzymes of aspartate transaminase has been studied using 1H and 19F nuclear magnetic resonance (NMR) as probes. The binding was measured for the pyridoxal (El) and pyridoxamine (Em) forms of the holoenzyme, the apoenzyme, and the pyridoxal form after reduction of the internal Schiff's base with NaBH4 (reduced holoenzyme). The NMR parameters studied were band broadening or chemical shift changes upon dicarboxylic acid binding to the enzyme. The dissociation constant values of succinate and perfluorosuccinate for the active forms of each isozyme, El and Em, are in the 1 to 4 mm range. Kd values of the inactive forms of the supernatant transaminase for perfluorosuccinate are 18.3 mm, reduced form, and 12.0 mm, apoenzyme form. Anions are competitive with dicarboxylic acid binding and, because of mutual exclusion, do not alter the correlation time, τc of bound succinate. This competition allows for the calculation of the chloride affinity of the pyridoxal, Kd = 9 mm (supernatant), 3 mm (mitochondrial), and pyridoxamine forms, Kd = 5 mm (supernatant), 1.6 mm (mitochondrial), of each isoenzyme. Because amino acids and glutarate also compete with perfluorosuccinate binding in the El, Em, and apoenzyme forms, it is concluded that dicarboxylic acids bind to these forms of the enzyme and that amino acids can form complexes with the pyridoxamine form. The correlation time of bound dicarboxylic acid shows an increase, i.e. more restricted segmental motion of succinate, with decreasing pH and is particularly critical in the pH 5 and pH 8 regions. The fastest correlation time of perfluorosuccinate (greatest segmental motion) corresponds to that bound to the reduced holoenzyme. The above effects agree with the competition-pH dependence between dicarboxylic acids and anions. Since there is evidence of the active center histidyl residue as the anion binding site (Cheng, S., and Martinez-Carrion, M. (1972) J. Biol. Chem. 247, 6597–6602) and of the Schiff's base nitrogen as the low pH ligand of a carboxyl group in glutaric acid (Jenkins, W. T., and D'Ari, L. (1966) J. Biol. Chem. 241, 5667), a proposal for the binding of dicarboxylic acids is made. Dicarboxylic acids inhibit because they form a bridge between the active center histidyl residue and the pyridoxal phosphate internal aldimine with the e-amino group of a lysyl residue. Thus, the binding subsites for a competitive inhibitor such as succinate, although structurally similar to the substrates, differ from the productive mode of binding of the amino or keto acids which form covalent enzyme-substrate complexes.

The Isozymes of Glutamate-Aspartate Transaminase: MECHANISM OF INHIBITION BY DICARBOXYLIC ACIDS

Abstract The binding of α-keto acids and other dicarboxylic acids to the pyridoxal form of the isozymes of pig heart glutamate-aspartate transaminase (EC 2.6.1.1) can be studied spectrophotometrically because the absorption of the resultant complexes differs from that of the free enzymes. Spectroscopic and catalytic rate data indicate a correlation of the inhibition of transamination with the affinity of the dicarboxylic acids for the pyridoxal form of the enzymes. Maleate and succinate are the most effective inhibitors of mitochondrial transaminase, whereas succinate, maleate, glutarate, and adipate inhibit the supernatant isozyme. The amino acid erythro-β-hydroxy-l-aspartate forms distinctive binary complexes of unique absorption maxima with either isozyme; the equilibria between these complexes are pH insensitive. Competition of dicarboxylic acids with erythro-β-hydroxy-l-aspartate shows that inhibition by 4- or 5-carbon dicarboxylic acids is accomplished through competition with the amino acid for the pyridoxal (aldimine) and pyridoxamine forms of the supernatant isozyme. In contrast, the mitochondrial isozyme is more highly affected by 4-carbon inhibitors. They compete with the amino acid for the pyridoxal form of the enzyme and also form ternary complexes of the nature enzyme-substrate-dicarboxylic acid. Combination of the keto acid with the enzyme shifts the proton ionization (pK) of the active site chromophore (bound pyridoxal phosphate) to higher pH values in both transaminases. Oxalacetate is much more effective than α-ketoglutarate in the mitochondrial isozyme. Differences for each isozyme in the effect of the pH on the aspartate-α-ketoglutarate and glutamate-oxalacetate transaminations are explained by preferential binding of oxalacetate to the mitochondrial enzyme and of either α-ketoglutarate or oxalacetate to the supernatant isozyme.