Undissociated Acids Research Articles

Rapid response of the plasma-membrane potential in oat coleoptiles to auxin and other weak acids

We have compared the effects of the auxin, indole-3-acetic acid (IAA) with that of other weak acids on the plasma-membrane potential of oat (Avena sativa L.) coleoptile cells. Cells treated with 1 μM IAA at pH 6 depolarize 20-25 mV in 10-12 min, but they then repolarize, until by 20-25 min their potentials are about 25 mV more negative than the initial value. Similar concentrations of benzoic and butyric acids cause the initial depolarization, but not the subsequent hyperpolarization. The hyperpolarization is therefore specific to IAA. All the weak acids, including IAA, evoke a rapid hyperpolarization when their concentrations are raised to 10 mM. This result indicates that at high concentrations, the uptake of undissociated weak acids activates electrogenic proton pumping, most likely by lowering cytoplasmic pH. In contrast, the hyperpolarization observed with concentrations of IAA four orders of magnitude lower appears to be a specific hormonal effect. This specific, auxin-induced hyperpolarization occurs at the same time as the initiation of net proton secretion and supports the hypothesis that auxin initiates extension growth by increasing proton pumping.

Influence of ionization and ion-pair formation on lipophilicity of some 4-hydroxycoumarin derivatives in the octanol-water system

The pH-dependent distribution of weak acids in the octanol-water system was investigated. For a series of six 4-hydroxycoumarins, substituted at position 3, the apparent partition coefficient or the distribution coefficient, P app, was measured in the pH range 1–11. The log P app-pH profiles obtained are in complete agreement with the theory. At high pH the value of P app is independent of pH, but dependent on the concentration of counterions (Na + in this study) in the aqueous phase; in other words ion-pair extraction occurs. The pNa (—log [Na +])-dependent distribution is analogous to the pH-dependent distribution, except in the case of 4-hydroxy-coumarin. Evidence was found that the sodium ion-pair of 4-hydroxycoumarin dissociates considerably in the octanol phase. A large discrepancy was noted between the experimentally obtained log P values and the theoretical values calculated using the hydrophobic fragmental constant system. Log P app values obtained under conditions where the compounds are ionized in the aqueous phase depend on both the partition coefficient and the dissociation constant of the acid or salt. Partition coefficients of the sodium ion-pairs obtained by extrapolation are just slightly lower than the partition coefficients of the undissociated acids.

Raman spectra of perbromate, perchlorate and fluorosulfate ions in anhydrous hydrogen fluoride

When KBrO 4, KClO 4 and KSO 3F are dissolved in anhydrous HF, partial protonation takes place, and the Raman spectra of the solutions show not only the bands of the anions BrO − 4, ClO − 4 and SO 3F − but also some that can be assigned to the corresponding undissociated acids. Some features of these spectra will be discussed. In the perbromate case, this is the first observation of the undissociated HBrO 4. By quantitative measurement of the relative intensities of the acid and anion bands as a function of concentration, it is possible to estimate the equilibrium constants for the protonation equilibria ▪ all of which lie rather far to the left. Evaluation of these constants permits us to compare the acid strengths of the three acids. Thus it appears that HBrO 4 is a significantly stronger acid than HClO 4.

Changes in Membrane Lipids of Roots Associated with Changes in Permeability

Previous work has shown that undissociated forms of organic acids, such as formic, acetic, and propionic acids, increase the permeability of barley roots to ions. The work here was undertaken to test whether these undissociated acids affect the lipids from the root membranes in such a way as to account for the permeability increase. Relative amounts of the principal fatty acids from barley root membranes were measured as a function of organic acid concentration, pH, and time of treatment of barley roots under conditions similar to those of the previous studies.Undissociated formic, acetic, and propionic acids all rapidly increase the proportions of palmitic, stearic, and oleic acids and decrease proportions of linoleic and linolenic acids. Only the undissociated species are effective. The effects on the fatty acids from membrane lipids parallel effects on ion permeability. It is concluded that the increase in permeability produced by undissociated organic acid is due to changes in the lipids of barley root membranes.

Influence of permeant acids and bases on active Na + extrusion by Chlorella

Chlorella cells were enriched with Na + by incubation in 3.5 mM 22Na labelled NaOH for 2–3 h. The active Na + extrusion from these cells into media containing 6.5 × 10 −4 M salts of permeant acids (sodium acetate, phenylacetate, propionate, isobutyrate) or bases (ammonium and methylammonium chloride) was studied under illumination and aeration at pH 6.0 and and 7.8. The carboxylates depressed and the hydrochlorides stimulated Na + efflux efflux. The effect of the carboxylates could be attributed to acidification of the cell interior due to penetration of the undissociated acids. The strong effect of the hydrochlorides could only partially be explained by penetration of the free bases. When the external medium contained only low concentrations of K +, Na + export was increasingly inhibited with time. This effect was attibuted to acidification of the cell interior by Na +/H + exchange. The results can be explained either by secondary active Na +/H + antiport or by competition between Na + and H + at the inner site of a primary active extrusion pump, some observations favouring the latter assumption.

State of Unesterified Fatty Acids in Skim Milk

By a multiple extraction procedure the unesterified fatty acids of skim milk have been shown in at least three entities: a) free dissociated and undissociated fatty acids, b) fatty acids associated with the membrane material in skim milk, and c) fatty acids of unknown origin requiring acidification to pH 1.5 for extraction.

Dissociation and homoconjugation equilibria of some acids and bases in N, N-dimethylformamide

The following monoprotic acids have been studied in N, N-dimethylformamide (DMF): p-toluenesulphonic acid; 2,6-dichlorobenzoic acid; 2,5-dichlorophenol; the anilinium ion; the N-methyl-anilinium ion. The first dissociation step of malonic and succinic acids has also been studied. Dissociation and homoconjugation constants have been determined potentiometrically, at 25°, in buffer solutions containing either the acid and its tetraethylammonium salt or the base and its picrate. Homoconjugation equilibria between unchanged acid and univalent conjugate base have been found not only for benzoic acid and phenol derivatives, but also between undissociated diprotic carboxylic acids and the corresponding monoanions, which are strongly intramolecularly hydrogen-bonded. Results are discussed with reference to previously published values.

THE KINETICS OF THE COMPLEX FORMATION BETWEEN Fe(III) AND CHLOROACETIC, DICHLOROACETIC AND TRICHLOROACETIC ACIDS. LIGAND DEPENDENCE OF THE RATE CONSTANTS

Abstract The kinetics of the reactions between Fe(III) and mono-, di-, and trichloroacetic acids have been investigated at 25°C and an ionic strength of 1 M, using the T-jump method. The rate constants for the reaction between Fe(OH)2+ and the anions of the acids exhibited values which are “normal” for this cation. Assuming those between Fe(OH)2+ and the undissociated acids to be also normal, the rate constants for the reaction of Fe3+ with the anions were evaluated, and found to depend on the basic strength of the ligand. For the rate constants of the reaction between Fe3+ and the undissociated acids, only very approximate values could be estimated. The results are compared with the rate of water exchange. The formation constants of the complexes were measured using a spectrophotometric method.

Control of differentiation in streptomycetes: involvement of extrachromosomal deoxyribonucleic acid and glucose repression in aerial mycelia development.

When Streptomyces alboniger spores were grown in Hickey-Tresner broth containing 5 muM ethidium bromide, a high frequency of permanently cured aerial mycelia-negative (am-) colonies was recovered. The appearance an am- colonies was time dependent: a very low frequency (0.3%) at zero time, a maximum (9 to 21%) after 2 to 5 days of growth, and a decline again to low frequencies later in the growth cycle. On agar, cured am- colonies of S. alboniger still produced puromycin. The development of aerial mycelia in S. alboniger, S. scabies, and S. coelicolor was also sensitive to glucose repression. Colonies grown on Hickey-Tresner agar containing 2% glucose remained phenotypically am- throughout the observation period. Adenine (2.5 mM or greater), and to a lesser extent adenosine and guanosine, specifically reversed the repression. The accumulation of undissociated organic acids appears to be involved in glucose repression of aerial mycelia formation. However, this does not appear to be the case with puromycin production in S. alboniger; glucose repression was observed over the pH range 5.0 to 7.5.

The effects of salicylic acid on metabolism and potassium ion content in yeast.

Under anaerobic conditions, at low pH and 30 degrees, commercial baker's yeast loses K+ ion in the presence of salicylic acid. Glucose utilization is inhibited. In suspensions containing no glucose, carbohydrate stores of the cell are dissimilated to carbon dioxide and alcohol. The ion loss and inhibitory effects of salicylic acid on glucose utilization are reversed by washing the cells free of salicylate. The loss of K+ appears to be due at least partly to a K+-H+ exchange process. An unexplained maximum is seen in the curves of either net K+ loss or K+ efflux versus salicylic acid concentration. At 6 degrees the effects of salicylic acid on both endogenous metabolism and net K+ loss are minimal. Furthermore, no maximum is seen in the K+ loss-salicyclic concentration curve at this temperature. It is generalized that salicylic acid or salicylate may elicit K+ leakage from many types of cells, i.e., a fundamental action of this compound may be its ability to affect (reduce) K+ content of the cell; furthermore, it appears that the salicylate effects on K+ loss may be associated in an as-yet-unknown manner with the metabolic effects of this compound. The effects of salicylate on K+ loss in yeast may not be unique for this compound, since no experiments of this nature have been done with other penetrating undissociated acids.

Molecular features of organic anion permeablity in ox red blood cell.

1. The penetration of organic anions into bovine red blood cells has been studied under experimental conditions where it could be distinguished from the penetration of undissociated acids which proceeds by diffusion through lipid zones of the membrane. 2. Several lines of evidence suggest that the entry of organic anions cannot be ascribed to simple diffusion across aqueous channels limited by positive charges but needs a specific interaction of the penetrating anion with a component of the membrane. 3. The structural requirements allowing for ionic transfer is a strong polar head for the smallest molecules and in addition an amphiphilic structure for acids with chain length greater than C4. Interaction between substrate and receptor requires at least a three point attachment involving three oxygen atoms in the substrate which react with complementary loci on the receptor to form ionic and hydrogen bonds. Such a three point attachment can be made by a sulphonic group or with carboxylic acid by alpha ketosubstitution, alpha hydroxysubstitution, addition of an amidegroup or addition of a second carboxyl group spatially close to the first. 4. As suggested by the behaviour of the formate anion, in such a transport system any carboxylic acid could interact transiently with the receptor and therefore interfere with the transport of an organic anion even though such ionic interaction with the receptor were insufficient to produce transport of the acid itself.

The adsorption of benzoic acid and some of its chlorine‐substituted derivatives at an alkane/water interface

AbstractInterfacial tensions of aqueous solutions of the sodium salts of benzoic acid, and of its 2‐chloro‐, 3‐chloro‐, 4‐chloro‐, 2,6‐dichloro‐, 3,5‐dichloro‐, 2,4‐dichloro‐, 3,4‐dichloro‐, and 2,3,6‐trichloro‐ substituted derivatives and also of cyclohexane‐carboxylic acid were determined over a range of concentrations at 25 °C by the drop‐volume method. Dissociation constants were determined, for those acids where literature values were not available, by a spectrophotometric technique.The Gibbs adsorption isotherm was used to calculate surface excess data from the interfacial tension results, assuming that the adsorbed species were (a) the sodium salts of the acids and (b) the undissociated acids. For all the benzoic acids examined, but not for cyclohexane‐carboxylic acid, the surface excess attained a constant maximum value at the higher concentrations of the sodium salts used. A comparison of the areas/molecule, calculated from the surface excess values for saturated surface layers, with molecular areas estimated from Catalin molecular models, indicates that only the undissociated acid is adsorbed, the plane of the aromatic ring being approximately normal to the plane of the interface.By making the reasonable assumption that the bulk of the surface excess is contained in a monolayer at the alkane/water interface, values of the standard free energy of adsorption have been calculated. The invariance of these values with changing concentrations in the bulk phase has provided corroborative evidence for the adsorption of the undissociated acid and not the sodium salt at the interface.The relative lipophilic surface affinities depend upon the number and position of the substituted chlorine atoms. Substitution of chlorine in the 2‐position confers greatest affinity for a surface lipophilic site while substitution in the 4‐position confers the least.By calculating the relative mole fractions of the undissociated acid molecules at the alkane/water interface for solutions of the same salt concentration and bulk pH it has been shown that the rates of penetration of benzoic acid‐type herbicides into leaf discs of Phaseolus vulgaris in the dark are related to the mole fraction of the undissociated acids at the lipophilic leaf surface/water interface.There is also some correlation between the plant growth‐regulating activities of the acids and the standard free energies of adsorption at the alkane/water interface, suggesting that adsorption onto a lipophilic site of action may be important with this group of growth‐regulating compounds.

Studies on the Formation of Bacitracin by Bacillus licheniformis: Role of Catabolite Repression and Organic Acids

Summary: Bacitracin production by Bacillus licheniformis atcc10716 is markedly inhibited by glucose. This inhibitory effect is due to the lowered pH and undissociated organic acids produced by the metabolism of glucose. The possibility that catabolite repression is an incidental result of low pH and the production of organic acids from glucose during growth is discussed.

Electronic structure of amino acids and ureas

Abstract The outer electronic levels of glycine, alanine, glycine ethyl ester, urea, and thiourea have been investigated by means of photoelectron spectroscopy using He I (584 A) and He II (304 A) radiation and CNDO/2 molecular orbital calculations. In the amino acids the molecular orbital (MO) ordering ha been found to be [σ core and carbonyl π > a″(O) a′(O) > a″(N)] with a first ionization potential of ∼8.8 eV. Glycine and alanine are foun to exist as the undissociated amino carboxylic acids rather than zwitterions in the high temperature vapor. In urea the three lowest energy molecular o are near-degenerate [σ(4b 1 ) ∼ π(1a 2 ) ∼ π(2b 2 )] while in thiourea only the two lowest energy MO's are near-degenerate [π(1a 2 σ(4b 1 ) ∼ π(2b 2 )]. The first ionization potentials of urea and thiourea are 9.7 and 7.9 eV respectively.

Transfer of anions across phospholipid membranes.

The permeability of phospholipid spherules to 11 anions was examined by measuring volume alterations under conditions in which these alterations reflect changes in anion movement. Chloride and bromide cross the membrane by some type of electrically neutral process not involving the species HCl or HBr. By comparison, iodide, thiocyanate, and salicylate are permeable in the charged form. Furthermore, the transport of these three anions is reduced by incorporation of cholesterol into the bilayer structure; iodide being affected more than thiocyanate or salicylate. Formate, acetate, propionate, benzoate, p-hydroxybenzoate, and p-aminobenzoate all permeate as undissociated acids. The relative permeabilities of these anions correlate well with organic solvent – water partition coefficients. Salicylate (o-hydroxybenzoate) can penetrate both in the undissociated and dissociated states. As opposed to the other aromatic anions, salicylate is capable of adsorbing to the lipid membrane in the ionic form. This property may partially explain the ability of this benzoate derivative to traverse the membrane as an ion. Salicylate can also facilitate the movement of anions such as acetate by virtue of its ability to make the lipid bilayer more permeable to hydrogen ions.

Effect of colon flora and short-chain fatty acids on growth in vitro of Pseudomonas aeruginsoa and Enterobacteriaceae.

Heat-stable antibacterial activity in the following suspensions was demonstrated against Pseudomonas aeruginosa at pH 6.5, 6.0, and 5.5: (i) pooled colon contents of normal mice; (ii) an anaerobic, 48-h culture of normal mouse feces; and (iii) anaerobic, 48-h cultures of different bacteria from human colon flora (Escherichia coli, Bacteroides fragilis, Klebsiella pneumoniae, and Proteus mirabilis). The lower the pH of the medium, the greater was the antibacterial activity of these suspensions. The antibacterial activity of five fatty acids (propionic, butyric, isobutyric, acetic, and formic acids) was greater against P. aeruginosa than against three Enterobacteriaceae (E. coli, K. pneumoniae, and P. mirabilis) at all fatty acid concentrations (0.16 M to 0.005 M) and at the 3 pH values studied (5.5, 6.0, and 6.5). As the pH value increased, the antibacterial activity decreased. Antibacterial activity was greater at higher fatty acid concentrations, and at each pH value it was greatest for the fatty acids having high pK(a) values. Lactic acid, with the lowest pK(a), exhibited little or no antibacterial activity. Acetic and butyric acids, two of the three predominant volatile fatty acids determined by gas chromatography in the mouse colon contents and in the anaerobic culture of mouse feces, occurred in vivo in concentrations which inhibited growth of P. aeruginosa in vitro at the pH of the mouse cecum. These results suggest that undissociated short-chain fatty acids produced by the colon flora may be a mechanism of intestinal resistance to colonization by P. aeruginosa.

Aromatic protonation. XI. Catalysis by undissociated acids in concentrated aqueous mineral acid solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAromatic protonation. XI. Catalysis by undissociated acids in concentrated aqueous mineral acid solutionsA. J. Kresge, S. G. Mylonakis, and L. E. HakkaCite this: J. Am. Chem. Soc. 1972, 94, 12, 4197–4199Publication Date (Print):June 1, 1972Publication History Published online1 May 2002Published inissue 1 June 1972https://doi.org/10.1021/ja00767a026RIGHTS & PERMISSIONSArticle Views37Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (331 KB) Get e-Alerts Get e-Alerts

Rates of hydrated electron reactions with undissociated carboxylic acids

The rate constants for the reaction series RCOOH+ e aq −, with different substituents R (H, CH 3, C 2H 5, CHO, CH 2OH, CH 3CHOH, C 6H 5, CH 2COOH, (CH 2) 2, COOH, CH 2COO −) have been determined by steady-state competition kinetics. The competing reaction was the reaction of the hydrated electron with the hydronium ion. The effect of the substituents on the rate constants was shown to be mainly of the inductive type. The reaction rates can be correlated by means of Taft's equation with positive slope ϱ ∗ = 1·94±0·15 . As expected, significant deviations are observed in the cases in which other interactions besides inductive ones are possible. H atoms are not formed in these reactions. In the case of formic, acetic and propionic acids reactions proceed in two paths at comparable rates. H atoms are formed as a product in one of them.

Growth of Escherichia coli on short-chain fatty acids: nature of the uptake system.

Mutants of Escherichia coli K-12 which grow on butyrate and valerate were studied with respect to uptake of these substrates. To utilize short-chain and medium-chain fatty acids, E. coli must synthesize the beta-oxidation enzymes constitutively. In addition, growth on the C(4) and C(5) acids requires a second mutation which permits entry of these substrates. At pH 5, both in the parent and mutant strains, butyrate and valerate penetrate as the undissociated acids but appear not to be activated and thus inhibit growth. At pH 7, the parent strain is not permeable to the anions, whereas the mutant concentrates these substrates. There appear to be two components of the uptake system, a nonspecific diffusion component and an energy-linked activating enzyme. Two mutant types which take up short-chain fatty acids are described. One synthesizes the uptake system constitutively and is inhibited by 4-pentenoate when cultured on acetate. In the other, the uptake system is inducible, and the strain is pentenoate-resistant when grown on acetate but pentenoate-sensitive when cultured on butyrate or valerate.

Rates of Hydrated Electron Reactions with Undissociated Carboxylic Acids

AbstractThe rate constants for the reaction series RCOOH + eaq−, with different substituents R(H, CH3, C2H5, CHO, CH2OH, CH3CHOH, C6H5, CH2COOH, (CH2)2 · COOH, CH2COO−) have been determined by the steady state competition kinetics. The competing reaction was the reaction of hydrated electrons with hydronium ions. The effect of the substituents on the rate constants was shown to be mainly of inductive type. The reaction rates can be correlated by means of Taft's equation with the positive slope ρ* = 1.94 ± 0.15. As expected, significant deviations are observed in the cases in which other interactions besides inductive are possible. H atoms are not formed in these reactions. In the case of formic acid, acetic acid and propionic acid reactions proceed in two paths at comparable rates. H atoms are formed as a product in one of them.