[A new activated metabolic intermediate of aromatic carboxylic acid--carboxylic acid glucose ester].
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Acyltransferases↗
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Determination of SQ 27,519, the active phosphinic acid-carboxylic acid of the prodrug SQ 28,555, in human serum by capillary gas chromatography with nitrogen-phosphorus detection after a two-step derivatization.
A method for the determination of SQ 27,519 (II), the active phosphinic acid-carboxylic acid of the prodrug SQ 28,555 (I), in human serum is presented. Compounds I and II are simultaneously extracted from acidified serum into ethyl acetate, and II is back-extracted into aqueous sodium bicarbonate. Compound I, in ethyl acetate, can be subsequently hydrolyzed and measured as II. The two acidic groups of II are selectively esterified, first by methylation of the carboxylic acid with methanolic hydrochloric acid and then by formation of the hexafluoroisopropyl ester of the phosphinic acid. The resulting product is measured by splitless-injection capillary gas chromatography with nitrogen-phosphorus detection. Linear standard curves were obtained for II with a detection limit of less than 10 ng/ml of serum. The method was successfully applied to the analysis of serum samples obtained from normal individuals after administration of I. In an ascending-dose study involving several human subjects the serum levels of II ranged from less than 10 to 7000 ng/ml of serum.
Chemical Phenomena↗
Influence of amino acids, carboxylic acids and sugars on the growth of Methylococcus capsulatus on methane.
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Acids↗
A comparison of the antilipolytic effects of nicotinic acid, methylisoxazole carboxylic acid, methylpyrazole carboxylic acid and insulin in isolated fat cells.
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Adipose Tissue↗
Synthesis of branched cyclomaltooligosaccharide carboxylic acids (cyclodextrin carboxylic acids) by microbial oxidation.
Novel branched cyclomaltooligosaccharide carboxylic acid (cyclodextrin carboxylic acid) derivatives were synthesized by microbial oxidation using Pseudogluconobacter saccharoketogenes to oxidize five types of branched cyclodextrins, including maltosyl beta-cyclodextrin (maltosyl-beta-CyD). For each novel cyclodextrin carboxylic acid derivative synthesized, the hydroxymethyl group of the terminal glucose residue in the branched part of the molecule was regiospecifically oxidized to a carboxyl group to give the corresponding uronic acid. In addition, the physicochemical properties of cyclomaltoheptaosyl-(6-->1)-alpha-D-glucopyranosyl-(4-->1)-alpha-D-glucopyranosiduronic acid (GUG-beta-CyD) (1) and its sodium salt were studied more extensively, as these compounds are most likely to have a practical application.
Alcohol Dehydrogenase↗
Conformational and quantum analysis of dental adhesive carboxylic acid and carboxylic acid anhydride monomers.
The conformational and quantum analyses of dental adhesive carboxylic acid and carboxylic acid anhydride monomers were preformed. Conformational analyses were carried out by a molecular mechanics calculation. 4-META and 4-AETA showed more compact conformation than 4-MET. Quantum analyses were performed by semi-empirical molecular orbital calculation. 4-MET had a higher dipole moment, polarizability, and HOMO and LUMO energy than 4-META and 4-AETA. The bond lengths and bond orders of the carbonyl groups of the trimellitic acid moiety of 4-MET were different from those of carbonyl groups of the trimellitate anhydride moieties of 4-META and 4-AETA. Oxygen of the methacryloyl or acryloyl groups showed the highest electron densities among the oxygen atoms for all monomers. The superdelocalizabilities of oxygen atoms of the trimellitic acid moiety of 4-MET were greater than that of oxygen of the methacryloyl group. A small change in the bond length of the Ca-O bond showed a large difference in the steric energies of 4-MET/Ca salt.
Adhesives↗
Sequential ethoxycarbonylation, methoximation and tert-butyldimethylsilylation for simultaneous determination of amino acids and carboxylic acids by dual-column gas chromatography.
Amino acids (AAs) in alkaline solution were first ethoxycarbonylated with subsequent methoximation of keto acids (KAs). After acidification and solid-phase extraction, tert-butyldimethylsilylation was performed for direct analysis by gas chromatography (GC) on dual-columns with different polarities, which provided simultaneous separation of multiple amino acids, carboxylic acids (CAs) and keto acids, facilitating accurate peak confirmation based on matching with retention index sets characteristic of each analyte. The present method was linear (r2 > or = 0.9955) with good precision (0.1-9.4%) and accuracy (-8.6 to 9.9%), allowing simultaneous screening for diagnostic amino acids along with carboxylic acids and keto acids in urine from a phenylketonuria patient.
Amino Acids↗
[Thiazolidine-carboxylic acid, iminothiazolidine-carboxylic acid and thiazane-carboxylic acid as liver protective substances in comparison with cysteine].
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Carboxylic Acids↗
Synergism between ammonia, lactic acid and carboxylic acids as kairomones in the host-seeking behaviour of the malaria mosquito Anopheles gambiae sensu stricto (Diptera: Culicidae).
Host odours play a major role in the orientation and host location of blood-feeding mosquitoes. Anopheles gambiae Giles sensu stricto, which is the most important malaria vector in Africa, is a highly anthropophilic mosquito species, and the host-seeking behaviour of the females of this mosquito is guided by volatiles of human origin. Ammonia, lactic acid and several carboxylic acids are known to be present in the human odour blend. We investigated the effect of these compounds on naive female mosquitoes using a dual-port olfactometer. Ammonia was an attractant on its own, whereas lactic acid was not attractive. Carboxylic acids, offered as a mixture of 12 compounds, were repellent at the concentration tested. The addition of ammonia to the carboxylic acid mixture overruled the repellent effect of the latter. Combining ammonia with either lactic acid or the carboxylic acids did not enhance the attractiveness of ammonia alone. However, a synergistic effect was found when ammonia, lactic acid and the carboxylic acids were applied as a blend. Our findings indicate that An. gambiae s.s. relies on the combination of ammonia, lactic acid and carboxylic acids in its orientation to human hosts. The role of lactic acid in this tripartite synergism differs from that reported for the yellow fever mosquito Aedes aegypti.
Ammonia↗
Polar group enhanced gas-phase acidities of carboxylic acids: an investigation of intramolecular electrostatic interaction.
We studied the effects of polar groups on the gas-phase acidities of carboxylic acids experimentally and computationally. In this connection, the gas-phase acidities (DeltaH(acid), the enthalpy of deprotonation, and DeltaG(acid), the deprotonation free energy) of borane-complexed methylaminoacetic acid ((CH(3))2N(BH(3))CH(2)CO(2)H) and methylthioacetic acid (CH(3)S(BH(3))CH(2)CO(2)H) were measured using the kinetic method in a flowing afterglow-triple quadrupole mass spectrometer. The values of DeltaH(acid) and DeltaG(acid) of (CH(3))2N(BH(3))CH(2)CO(2)H were determined to be 328.8 +/- 1.9 and 322.1 +/- 1.9 kcal/mol, and those of CH(3)S(BH(3))CH(2)CO(2)H were determined to be 325.8 +/- 1.9 and 319.2 +/- 1.9 kcal/mol, respectively. The theoretical enthalpies of deprotonation of (CH(3))2N(BH(3))CH(2)CO(2)H (329.2 kcal/mol) and CH(3)S(BH(3))CH(2)CO(2)H (325.5 kcal/mol) were calculated at the B3LYP/6-31+G(d) level of theory. The calculated enthalpies of deprotonation of N-oxide-acetic acid (CH(3)NOCH(2)CO(2)H, 329.4 kcal/mol) and S-oxide-acetic acid (CH(3)SOCH(2)CO(2)H, 328.6 kcal/mol) are comparable to the experimental results for borane-complexed methylamino- and methylthioacetic acids. The enthalpy of deprotonation of sulfone-acetic acid (CH(3)SO2CH(2)CO(2)H, 326.1 kcal/mol) is about 2 kcal/mol lower than the S-oxide-acetic acid. The calculated enthalpy of deprotonation of sulfoniumacetic acid, (CH(3))2S+CH(2)CO(2)H, is 243.0 kcal/mol. Compared to the corresponding reference molecules, CH(3)NHCH(2)CO(2)H and CH(3)SCH(2)CO(2)H, the dipolar group and the monopolar group substituted carboxylic acids are stronger acids by 11-14 and 97 kcal/mol, respectively. We correlated the changes of the acidity upon a polar group substitution to the electrostatic free energy within the carboxylate anion. The acidity enhancements in polar group substituted carboxylic acids are the results of the favorable electrostatic interactions between the polar group and the developing charge at the carboxyl group.
Boranes↗
Gustatory responses of eel palatine receptors to amino acids and carboxylic acids.
The gustatory receptors of the eel palate were found to be extremely sensitive to amino acids and carboxylic acids. The results obtained are as follows: (a) 11 amino acids which are among naturally occurring amino acids elicited responses in the palatine nerve, but 9 amino acids did not elicit a response even at a high concentration. The effect of D-amino acids was always much less than that of their corresponding L-isomers. There was no appreciable difference in the effectiveness of an alpha-amino acid (alpha-alanine) and beta-amino acid (beta-alanine). (b) The threshold concentrations of the most potent amino acids (arginine, glycine) were between 10(-8) and 10(-9) M. A linear relation between the magnitude of the response and log stimulus concentration held for a wide concentration range for all the amino acids examined. (c) The palatine receptors responded sensitively to various carboxylic acid solutions whose pH was adjusted to neutral. The threshold concentrations varied between 10(-4) and 10(-7) M. The magnitude of the response at 10(-2) M increased with an increase of carbon chain length. (d) The extent of cross-adaptation was examined with various combinations of amino acids. A variety of the response patterns showing complete cross-adaptation, no cross-adaptation, or synergetic interaction was observed. The synergetic interaction was also observed when one amino acid below its threshold concentration was added to the other amino acid below its threshold concentration was added to the other amino acid. No cross-adaptation was observed between amino acids and fatty acids. (e) The treatment of the palate with papain led to loss of the responses to arginine, glycine, and histidine without affecting those to proline and acetic acid. The treatment with pronase E eliminated selectively the response to proline. The possibility that the eel gustatory receptors are responsible for sensing food at a distance was discussed.
Adaptation, Physiological↗
Hydrogen bonds in carboxylic acid-carboxylate systems in solution. 1. In anhydrous, aprotic media
Preliminary NMR studies on hydrogen bonding of carboxylic acid-carboxylate systems in an anhydrous, aprotic solvent are presented. In all cases, a low-field resonance (16-20 ppm) indicative of strong hydrogen bonding was observed. From these results, it seems probable that this characteristic downfield shift should be exhibited by all carboxylic acid-carboxylate systems in anhydrous, aprotic media.
Journal Article↗
Quantitative structure-anticonvulsant activity relationships of valproic acid, related carboxylic acids and tetrazoles.
Valproic acid and several structurally related carboxylic acids and tetrazole analogues have been shown to antagonize seizures induced by pentylenetetrazole in mice. To investigate the influence of the alkyl substituents on the anticonvulsant activity, the octanol-water partition coefficients and relative pKa values were determined. Within the series of active carboxylic acids, there was a good correlation between the anticonvulsant activity and the partition coefficient (r = 0.86). The influence of pKa on the anticonvulsant activity was small but of statistical significance. When the most active compound, 5-heptyltetrazole was added to the carboxylic acid series, a low correlation between the anticonvulsant activity and a linear combination of lipophilicity and pKa resulted. The effect of the polar moieties in alkyl-substituted anticonvulsant compounds was assessed by comparison of the regression equations with either an added pKa or dipole moment term to the term for lipophilicity. It appears that other factors, such as the nature of the alkyl substituent, influence the anticonvulsant activity. The inactivity of the cyclohexylmethyl-substituted compounds, cyclohexylacetic acid and 5-cyclohexylmethyltetrazole may be due to subtle steric effects at a critical step, either involving oxidative metabolism or an interaction at an active site.
Animals↗
Enantiomeric separation of hydroxy acids and carboxylic acids by diamino-beta-cyclodextrins (AB,AC,AD) in capillary electrophoresis.
Selectively modified 6,6'-dideoxy-6,6'-L-diamino-beta-cyclodextrins (AB, AC, AD) were successfully used as chiral selectors for the enantiomeric separation of hydroxy acids and carboxylic acids (in particular, phenoxyalkanoic acid herbicides) in capillary electrophoresis (CE). Chiral separations were obtained at a low selector concentration (1 mM) with good enantioselectivity and resolution factors. Separations were optimized as a function of pH. The different position of the charged groups on the upper rim greatly influenced the separation, accounting for electrostatic interactions between the protonated amino groups of the cyclodextrins (CDs) and the carboxylate of the selectands. The best enantiomeric separation of hydroxy acids was obtained with the AC regioisomer, whereas carboxylic acids were well resolved only by the AB regioisomer. A recognition model is proposed, based on two-dimensional nuclear magnetic resonance (2-D NMR) experiments, in which the orientation of the guest in the inclusion complex is determined by the electrostatic interactions between the selectand and the CD upper rim.
Carboxylic Acids↗
Acidity of carboxylic acids: a rebuttal and redefinition.
A recent theory of ionization of carboxylic acids divided the process of ionization into two steps and attributed the main importance to the electrostatic potential of the acid molecule. The origin of the acidity was thus seen in the high energy of the acid molecule and not in the stabilization of the anion by resonance. In this paper, the theory was revised on the basis of further calculations at an MP2/6-31++G(2d,p) level which followed in two steps the reverse process, protonation of the formate anion. The results were compared to those of the methanolate anion as reference. A contradictory conclusion was obtained: the reason for the acidity is in the electrostatic potential of the anion. As a model compound without resonance, 2,2,2-trifluoroethanol was investigated in the same way. The results were qualitatively similar, although any resonance in the anion is not possible. One can conclude that the acidity of carboxylic acids is due to the low energy of their anions; this follows unambiguously from the isodesmic reactions on the basis of either the experimental enthalpies of formation or the calculated energies. It is more difficult to decide whether this low energy is caused by resonance, because any model of the carboxylate anion without resonance is necessarily imperfect and the whole concept is not exactly defined. Several such models were reexamined and improved by separating the effect operative in the anion from those in the neutral acid molecule. While the electrostatic model did not allow any significant conclusion, two models based on VB calculation and on correlation analysis, respectively, furnished qualitatively concordant results: resonance in the anion is diminished by the resonance in the acid molecule, and both together are responsible for less than one-half of the acidity enhancement as compared to the acidity of alcohols. The ratio is reversed in water solution: resonance is then the more important factor responsible for some two-thirds of the enhanced acidity.
Carboxylic Acids↗
Simultaneous retention index analysis of urinary amino acids and carboxylic acids for graphic recognition of abnormal state.
Simultaneous profiling analysis of urinary amino acids (AAs) and carboxylic acids (CAs) was combined with retention index (I) analysis for graphic recognition of abnormal metabolic state. The temperature-programmed I values of the AA and CA standards measured as ethoxycarbonyl (EOC)/methoxime (MO)/tert-butyldimethylsilyl (TBDMS) derivatives were used as the reference I values. Urine samples were subjected to the sequential EOC, MO and TBDMS reactions for the analysis by gas chromatography (GC) and GC-mass spectrometry. The complex GC profiles were then transformed into their respective I patterns in bar graphic forms by plotting the normalized peak area ratios (%) of the identified AAs and CAs against their reference I values as the identification numbers. When the present method was applied to infant urine specimens from normal controls and patients with inherited metabolic diseases such as phenylketonuria, maple syrup urine disease, methylmalonic aciduria or isovaleric aciduria, each I pattern of bar graph more distinctly displayed quantitative abundances of urinary AAs and CAs in qualitative I scale, thus allowing graphic discrimination between normal and abnormal states.
Acetamides↗
Histamine-modified cationic beta-cyclodextrins as chiral selectors for the enantiomeric separation of hydroxy acids and carboxylic acids by capillary electrophoresis.
The enantiomeric separation of alpha-hydroxy acids and carboxylic acids was successfully performed by using 6-deoxy-6-N-histamino-beta-cyclodextrin (CD-hm), a monosubstituted positively charged beta-cyclodextrin (beta-CD) bearing a histamine moiety linked to the C6 of a glucose unit in the upper CD rim via the amino group. Good results were obtained at a low selector concentration (1 mM). The number of positive charges on the upper rim may be modulated as a function of pH, because of the different pKa of the amino and the imidazolyl groups, and was found to affect both the enantioselectivity and resolution factors. With the analogous 6-deoxy-[4-(2-aminoethyl)imidazolyl]-beta-cyclodextrin (CD-mh) bearing the histamine moiety linked to the C6 via the imidazolyl group, very poor results were obtained, showing that the proximity of the positive charge to the cavity plays an important role in the enantiomeric recognition. The complexation mode was studied by electrospray ionization-mass spectrometry (ESI-MS) and two-dimensional nuclear magnetic resonance (2-D NMR) ROESY experiments: the recognition model is consistent with an inclusion complexation of the aromatic ring of the analyte within the CD cavity coupled to electrostatic interactions between the carboxylate and the protonated amino group of the cyclodextrin.
Carboxylic Acids↗
Analysis of the binding of hydroxamic acid and carboxylic acid inhibitors to the stromelysin-1 (matrix metalloproteinase-3) catalytic domain by isothermal titration calorimetry.
Matrix metalloproteinases (MMPs) are implicated in diseases such as arthritis and cancer. Among these enzymes, stromelysin-1 can also activate the proenzymes of other MMPs, making it an attractive target for pharmaceutical design. Isothermal titration calorimetry (ITC) was used to analyze the binding of three inhibitors to the stromelysin catalytic domain (SCD). One inhibitor (Galardin) uses a hydroxamic acid group (pK(a) congruent with 8.7) to bind the active site zinc; the others (PD180557 and PD166793) use a carboxylic acid group (pK(a) congruent with 4.7). Binding affinity increased dramatically as the pH was decreased over the range 5.5-7.5. Experiments carried out at pH 6.7 in several different buffers revealed that approximately one and two protons are transferred to the enzyme-inhibitor complexes for the hydroxamic and carboxylic acid inhibitors, respectively. This suggests that both classes of inhibitors bind in the protonated state, and that one amino acid residue of the enzyme also becomes protonated upon binding. Similar experiments carried out with the H224N mutant gave strong evidence that this residue is histidine 224. DeltaG, DeltaH, DeltaS, and DeltaC(p) were determined for the three inhibitors at pH 6.7, and DeltaC(p) was used to obtain estimates of the solvational, translational, and conformational components of the entropy term. The results suggest that: (1) a polar group at the P1 position can contribute a large favorable enthalpy, (2) a hydrophobic group at P2' can contribute a favorable entropy of desolvation, and (3) P1' substituents of certain sizes may trigger an entropically unfavorable conformational change in the enzyme upon binding. These findings illustrate the value of complete thermodynamic profiles generated by ITC in discovering binding interactions that might go undetected when relying on binding affinities alone.
Binding Sites↗