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Journal articles on the topic 'Carboxylic protons'

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Published: 5 June 2025

Last updated: 1 August 2025

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1

Zhang, Lei, Osasere M. Evbuomwan, Michael Tieu, Piyu Zhao, Andre F. Martins, and A. Dean Sherry. "Protonation of carboxyl groups in EuDOTA-tetraamide complexes results in catalytic prototropic exchange and quenching of the CEST signal." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2107 (2017): 20170113. http://dx.doi.org/10.1098/rsta.2017.0113.

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The CEST properties of EuDOTA-tetraamide complexes bearing pendant carboxylate and carboxyl ethyl esters were measured as a function of pH. The CEST signal from the Eu 3+ -bound water molecule decreased in intensity between pH 8.5 and 4.5 while the proton exchange rates ( k ex ) increased over this same pH range. In comparison, the CEST signal in the corresponding carboxyl ester derivatives was nearly constant. Both observations are consistent with stepwise protonation of the four carboxylic acid groups over this same pH range. This indicates that negative charges on the carboxyl groups above

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2

Smith, Graham, Catherine E. Pascoe, Colin H. L. Kennard, and Karl A. Byriel. "Molecular Adducts of 2,6-Diaminopyridine with Nitro-Substituted Aromatic Carboxylic Acids and the Crystal Structure of the 1 : 1 Adduct of 2,6-Diaminopyridine with 2-Nitrobenzoic Acid." Australian Journal of Chemistry 52, no. 1 (1999): 71. http://dx.doi.org/10.1071/c98140.

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The 1 : 1 adducts of 2,6-diaminopyridine (2,6-dap) with a series of nitro-substituted aromatic carboxylic acids have been prepared and the crystal structure of one of these, with 2-nitrobenzoic acid (2-nba), [(2,6-dap)+ (2-nba)-] has been determined by X-ray crystallography and refined to a residual R 0·034 for 655 observed reflections. Crystals are monoclinic, space group P 21/c, with four molecules in a cell of dimensions a 7·376(2), b 22·837(3), c 7·716(2) Å, β 90·01(2)°. The structure involves proton transfer with the resulting pyridinium proton and an amine proton combining with the carbo

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3

Le-Thanh, H., and D. Vocelle. "Nuclear magnetic resonance study of complexes formed between conjugated Schiff bases and carboxylic acids." Canadian Journal of Chemistry 72, no. 11 (1994): 2220–24. http://dx.doi.org/10.1139/v94-283.

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The NMR spectra of the proton located in a N+---H---−O bond formed in the reaction of a conjugated Schiff base (SB) with a carboxylic acid (HA) in a non-polar solvent indicate that this proton is rapidly exchanging with other protons present in the system. For this study, two SB were used: all-trans-retinylidene tert-butylamine (RBA) and trans, tran-2,4-heptadienylidene tert-butylamine (HBA), and five carboxylic acids having pKa's between 0.66 and 4.87.1H NMR spectra were taken at 293 and 233 K in CDCl3 of systems of SB:HA using different ratios of acid to SB. Results indicate that the rapid p

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4

Bedran, Zakhar V., Sergey S. Zhukov, Pavel A. Abramov, et al. "Water-Activated Semiquinone Formation and Carboxylic Acid Dissociation in Melanin Revealed by Infrared Spectroscopy." Polymers 13, no. 24 (2021): 4403. http://dx.doi.org/10.3390/polym13244403.

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Eumelanin is a widespread biomacromolecule pigment in the biosphere and has been widely investigated for numerous bioelectronics and energetic applications. Many of these applications depend on eumelanin’s ability to conduct proton current at various levels of hydration. The origin of this behavior is connected to a comproportionation reaction between oxidized and reduced monomer moieties and water. A hydration-dependent FTIR spectroscopic study on eumelanin is presented herein, which allows for the first time tracking the comproportionation reaction via the gradual increase of the overall aro

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5

Eisele, Roland, Keiichi Aritomo, and Wolfgang Pfleiderer. "Pteridines CI Synthesis and Properties of Lumazine-6- and -7-carboxylic Acids." Pteridines 4, no. 4 (1993): 178–86. http://dx.doi.org/10.1515/pteridines.1993.4.4.178.

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Summary Lumazine-6-(8) and 7-carboxylic acid (23) and their N-methyl derivatives (12, 13, 21, 26, 28, 29) have been synthesized and characterized by the determination of their pK values and the UV spectra of the neutral, mono and dianion species. It was noticed that the acidities of the two N-H protons of the pyrimidine moiety are almost the same indicating that the dianions of 8 and 23, respectively, are I: 1 mixtures of the corresponding N-l and N-3 deprotonated forms. The lumazine-7-carboxylic acids (23, 26, 28, 29, 31, 33) are in comparison to their 6-carboxyJic acid counterparts (8, 12, 1

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6

Tamura, Hiroki, Tatsuya Oda, and Ryusaburo Furuichi. "Ion exchange of Na+ with resin carboxylic protons." Analytica Chimica Acta 244 (1991): 275–80. http://dx.doi.org/10.1016/s0003-2670(00)82510-6.

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7

Ostapova, Elena V., Sergey Yu Lyrschikov, and Heinrich N. Altshuler. "Equilibrium constants of the sorption of pyridinecarboxylic acids by polystyrene type sulfocationite." Butlerov Communications 64, no. 10 (2020): 55–62. http://dx.doi.org/10.37952/roi-jbc-01/20-64-10-55.

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The processes of sorption of pyridine-3-carboxylic (nicotinic) and pyridine-4-carboxylic (isonicotinic) acids by sulfonic acid cation exchangers of the polystyrene type (CU-2-4 and CU-2-8) from aqueous solutions with different pH values were studied. Analysis of the FTIR spectra of isonicotinic acid, isonicotinic acid sulfate, and CU-2-8 sulfonic cation exchanger filled with isonicotinic acid showed that pyridinecarboxylic acid is in the protonated form in the polymer phase. Experimental data of the equilibrium distribution of acids in the aqueous solution-cation exchange system have been obta

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8

Y., M. ISSA, S. RIZK M., S. TAYOR W., and H. SOLIMAN M. "IR, PMR and TG Studies on Substituted 1,3,5-Triphenylformazans Complexes with Bivalent Cobalt, Nickel, Copper and Zinc." Journal of Indian Chemical Society Vol. 70, Jan 1993 (1993): 5–7. https://doi.org/10.5281/zenodo.5902544.

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Chemistry Department. Faculty of Science, Cairo University, Cairo. Egypt Helwan University <em>Manuscript received 8 June 1992, accepted 17 September 1992</em> 1,3,5-Triphenylformazan complexes with bivalent Co, Ni, Cu and Zn have been prepared. Both 1 : 1 and 1 : 2 (M : L) complexes were isolated. The pmr spectra show the displacement of one proton from the carboxylic group of substituted phenyl ring and the second proton from the imino group to form 1 : 1 complex. For 1 : 2 (M : L) complex the number of aromatic protons (C- H) is increased to double that for (1 : 1) plus two, The structure o

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9

Jannin, Sami, Aurélien Bornet, Sonia Colombo, and Geoffrey Bodenhausen. "Low-temperature cross polarization in view of enhancing dissolution Dynamic Nuclear Polarization in NMR." Chemical Physics Letters 517, no. 4-6 (2011): 234–36. https://doi.org/10.1016/j.cplett.2011.10.042.

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Dynamic Nuclear Polarization (DNP) induced by saturation of ESR transitions of TEMPO at 1.2 K and 3.35 T is characterized by build-up rates that are typically 5 times faster for protons than for the carboxylic carbon-13 in acetate. We show that cross polarization from protons to carbon-13 allows one to achieve a polarization P(C-13) >20% in less than 10 min, twice as much as has been previously reported, in one-fifth of the time. This should open the way to an unprecedented improvement in the efficiency of dissolution DNP. (C) 2011 Elsevier B.V. All rights reserved.

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10

Kholodniak, O. V., V. V. Stavytskyi та S. I. Kovalenko. "Substituted (сycloalkylcarbonylthioureido)aryl-(benzyl-)carboxylic(sulfonic) acids: synthesis, antimicrobial and growth-regulating activity". Current issues in pharmacy and medicine: science and practice 14, № 1 (2021): 4–11. http://dx.doi.org/10.14739/2409-2932.2021.1.226726.

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Acylisothiocyanates are a promising class of organic compounds that are present in the plant world and can be used in the synthesis of disubstituted thioureas and various heterocycles. These derivatives are characterized by growth-regulating, antibacterial, fungicidal, cytotoxicity, and other activities. Modification of acylisothiocyanates by fragments of substituted aminoarylcarboxylic (sulfo) acids is promising, as some of them (anthranilic, p-aminobenzoic acids) are precursors for the auxins and other natural compounds synthesis. Their combined activity is also an important aspect. Namely t

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11

Liu, X., and H. Bisswanger. "Solvent Isotope Effect on the Reaction Catalysed by the Pyruvate Dehydrogenase Complex from Escherichia coli." Biological Chemistry 384, no. 4 (2003): 673–79. http://dx.doi.org/10.1515/bc.2003.075.

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Abstract The pyruvate dehydrogenase from Escherichia coli showed a primary kinetic isotope effect when its overall reaction or the partial reaction of the pyruvate dehydrogenase component were tested in deuterium oxide. The Michaelis constants for pyruvate were nearly unchanged, but the maximum velocities in water and deuterium oxide differed, their ratio being DV = 1.7 for the overall reaction and DV = 2.1 for the E1p reaction. The pH profile and, accordingly, the δpK1 and δpK2 values were shifted by 0.6 units to higher pL values. A linear proton inventory curve was obtained when varying the

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12

Yakovenko, G. G., and M. V. Vovk. "Convenient approaches to the synthesis of 6-amino- and 6-oxoimidazo[4,5-b]pyrazolo[3,4-e]pyridines." Journal of Organic and Pharmaceutical Chemistry 19, no. 1(73) (2021): 10–15. http://dx.doi.org/10.24959/ophcj.21.224583.

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Aim. To develop convenient approaches to the synthesis of 6-amino- and 6-oxoimidazo[4,5-b]pyrazolo[3,4-e]pyridines as promising biologically active scaﬀolds.Results and discussion. It has been found that cyclocondensation of N-Boc-4-aminopyrazole-5-carbaldehydes with creatinine can be used as an eﬀective method for obtaining 6-aminoimidazo[4,5-b]pyrazolo[3,4-e]pyridines previously unknown. For the synthesis of their 6-oxoanalogs, the reaction of 5-aminopyrazolo[4,3-b]pyridine-6-carboxylic acids used in a modifed Curtius rearrangement with diphenylphosphorylazide was successful. This method was

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13

Lin, Jiusheng, Edwin Pozharski, and Mark A. Wilson. "Short Carboxylic Acid–Carboxylate Hydrogen Bonds Can Have Fully Localized Protons." Biochemistry 56, no. 2 (2016): 391–402. http://dx.doi.org/10.1021/acs.biochem.6b00906.

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14

Chao, Pei-Shang, Ming-Yu Kuo, Chen-Fu Lo, et al. "Electrochemistry and spectroelectrochemistry of carboxyphenylethynyl porphyrins." Journal of Porphyrins and Phthalocyanines 17, no. 01n02 (2013): 92–98. http://dx.doi.org/10.1142/s1088424612501313.

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Zinc 5-(4-carboxy-phenylethynyl)-10,20-biphenylporphines bearing various substituents on the 10,20-phenyl rings are studied for their electrochemical and spectroelectrochemical properties. Cyclic voltammetry and optically transparent thin-layer electrochemical measurements suggest that the first reductions of these porphyrins should be the reduction reaction of the carboxylic protons. For the porphyrin ring reactions, our study shows that the redox properties can be significantly affected by the alkoxyl chains on the 10,20-phenyl rings.

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15

Cowan, John A., Judith A. K. Howard, Garry, J. McIntyre, Samuel M. F. Lo, and Ian D. Williams. "Variable-temperature neutron diffraction studies of the short, strong hydrogen bonds in the crystal structure of pyridine-3,5-dicarboxylic acid." Acta Crystallographica Section B Structural Science 61, no. 6 (2005): 724–30. http://dx.doi.org/10.1107/s0108768105030077.

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Pyridine-3,5-dicarboxylic acid has been studied by single-crystal neutron diffraction at 15 and 296 K. Pyridine-3,5-dicarboxylic acid, in which the carboxylic acid protons have been replaced by deuterons, has also been studied at 15, 150 and 296 K. The protonated structure contains a short N...H...O hydrogen bond [N...O 2.523 (2) Å at 15 K]. Temperature-dependent proton migration occurs where the N—H distance in the hydrogen bond changes from 1.213 (4) Å at 15 K to 1.308 (6) Å at 300 K. In the deuterated structure the overall hydrogen-bond length increased [N...O 2.538 (3) Å at 15 K] and the m

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16

Venianakis, Themistoklis, Michael G. Siskos, George Papamokos та Ioannis P. Gerothanassis. "Structural Studies of Monounsaturated and ω-3 Polyunsaturated Free Fatty Acids in Solution with the Combined Use οf NMR and DFT Calculations—Comparison with the Liquid State". Molecules 28, № 16 (2023): 6144. http://dx.doi.org/10.3390/molecules28166144.

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Molecular structures, in chloroform and DMSO solution, of the free fatty acids (FFAs) caproleic acid, oleic acid, α-linolenic acid, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts of the COOH protons, transient 1D NOE experiments and DFT calculations demonstrate the major contribution of low molecular weight aggregates of dimerized fatty acids through intermolecular hydrogen bond interactions of the carboxylic groups, with parallel and antiparallel interdigitated str

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17

Kobayashi, Kensei, Jun-ichi Ise, Ryohei Aoki, et al. "Formation of Amino Acids and Carboxylic Acids in Weakly Reducing Planetary Atmospheres by Solar Energetic Particles from the Young Sun." Life 13, no. 5 (2023): 1103. http://dx.doi.org/10.3390/life13051103.

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Life most likely started during the Hadean Eon; however, the environmental conditions which contributed to the complexity of its chemistry are poorly known. A better understanding of various environmental conditions, including global (heliospheric) and local (atmospheric, surface, and oceanic), along with the internal dynamic conditions of the early Earth, are required to understand the onset of abiogenesis. Herein, we examine the contributions of galactic cosmic rays (GCRs) and solar energetic particles (SEPs) associated with superflares from the young Sun to the formation of amino acids and

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18

Fantacci, Simona, Maria G. Lobello, and Angelis Filippo De. "Everything you always wanted to Know about Black Dye (but Were Afraid to Ask): A DFT/TDDFT Investigation." Chimia 67, no. 3 (2013): 121–28. https://doi.org/10.2533/chimia.2013.121.

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We report an exhaustive theoretical and computational investigation of the electronic, optical, redox and acid-base properties, along with the adsorption mode on TiO2, of Black Dye (BD), the prototypical panchromatic dye for solar cell applications. We investigated in detail the variation of the relevant dye properties as a function of the solution pH, corresponding to the stepwise deprotonation of the carboxylic groups. Our results reproduced the expected blue-shift of the optical absorption spectrum and the experimental trend of oxidation potentials by increasing pH, which turned both out to

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19

Yoo, Kwangho, Dong Gyun Jwa, Ha-Eun Lee, Hyun Jin Kim, Cheoljae Kim, and Min Kim. "Recent Organic Transformations with Silver Carbonate as a Key External Base and Oxidant." Catalysts 9, no. 12 (2019): 1032. http://dx.doi.org/10.3390/catal9121032.

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Silver carbonate (Ag2CO3), a common transition metal-based inorganic carbonate, is widely utilized in palladium-catalyzed C–H activations as an oxidant in the redox cycle. Silver carbonate can also act as an external base in the reaction medium, especially in organic solvents with acidic protons. Its superior alkynophilicity and basicity make silver carbonate an ideal catalyst for organic reactions with alkynes, carboxylic acids, and related compounds. This review describes recent reports of silver carbonate-catalyzed and silver carbonate-mediated organic transformations, including cyclization

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20

Podlahová, Jana, Josef Šilha, and Jaroslav Podlaha. "Structure of the complexes of ethylenediphosphinetetraacetic acid in solution." Collection of Czechoslovak Chemical Communications 50, no. 2 (1985): 445–53. http://dx.doi.org/10.1135/cccc19850445.

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Ethylenediphosphinetetraacetic acid is bonded to metal ions in aqueous solutions in four ways, depending on the type of metal ion: 1) through an ionic bond of the carboxylic groups to form weak complexes with a metal:ligand ratio of 1 : 1 (Ca(II), Mn(II), Zn(II), Pb(II), La(III)); 2) through type 1) bond with contributions from weak interaction with the phosphorus (Cd(II)); 3) through coordination of the ligand as a monodentate P-donor with the free carboxyl groups with formation of 2 : 1 and 1 : 1 complexes (Cu(I), Ag(I)); 4) through formation of square planar or, for Hg(II), tetrahedral comp

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21

Bergkamp, Jesse J., Benjamin D. Sherman, Ernesto Mariño-Ochoa, et al. "Synthesis and characterization of silicon phthalocyanines bearing axial phenoxyl groups for attachment to semiconducting metal oxides." Journal of Porphyrins and Phthalocyanines 15, no. 09n10 (2011): 943–50. http://dx.doi.org/10.1142/s1088424611003847.

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A series of axial phenoxy substituted octabutoxy silicon phthalocyanines bearing ethyl carboxylic ester and diethyl phosphonate groups have been prepared from the corresponding phenols in pyridine. Axial bis-hydroxy silicon phthalocyanine was prepared using an adaptation of a reported protocol [1, 2] from the octabutoxy free-base phthalocyanine. The phenols bear either carboxylic ester or phosphonate groups, which upon deprotection can serve as anchoring groups for attaching the phthalocyanines to semiconducting metal oxides used in dye sensitized solar cells (DSSCs). All the phthalocyanines o

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22

Souli, Maria P., Zacharenia Nikitaki, Monika Puchalska, et al. "Clustered DNA Damage Patterns after Proton Therapy Beam Irradiation Using Plasmid DNA." International Journal of Molecular Sciences 23, no. 24 (2022): 15606. http://dx.doi.org/10.3390/ijms232415606.

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Modeling ionizing radiation interaction with biological matter is a major scientific challenge, especially for protons that are nowadays widely used in cancer treatment. That presupposes a sound understanding of the mechanisms that take place from the early events of the induction of DNA damage. Herein, we present results of irradiation-induced complex DNA damage measurements using plasmid pBR322 along a typical Proton Treatment Plan at the MedAustron proton and carbon beam therapy facility (energy 137–198 MeV and Linear Energy Transfer (LET) range 1–9 keV/μm), by means of Agarose Gel Electrop

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23

YANG, Su J., Shih S. JIANG, Soong Y. KUO, Shu H. HUNG, Ming F. TAM, and Rong L. PAN. "Localization of a carboxylic residue possibly involved in the inhibition of vacuolar H+-pyrophosphatase by N,N′-dicyclohexylcarbodi-imide." Biochemical Journal 342, no. 3 (1999): 641–46. http://dx.doi.org/10.1042/bj3420641.

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A vacuolar H+-pyrophosphatase (EC 3.6.1.1) that catalyses PPi hydrolysis and the electrogenic translocation of protons from the cytosol to the vacuole lumen, was purified from etiolated hypocotyls of mung bean seedlings (Vigna radiata L.). Group-specific modification was used to identify a carboxylic residue involved in the inhibition of vacuolar H+-pyrophosphatase. Carbodi-imides, such as N,N′-dicyclohexylcarbodi-imide (DCCD) and 1-ethyl-3-(3-dimethylamino-propyl)carbodi-imide, and Woodward's reagent K caused a progressive decline in the enzymic activity of vacuolar H+-pyrophosphatase in a ti

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24

Babbitt, P., G. Mrachko, M. Hasson, et al. "A functionally diverse enzyme superfamily that abstracts the alpha protons of carboxylic acids." Science 267, no. 5201 (1995): 1159–61. http://dx.doi.org/10.1126/science.7855594.

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25

Christl, Iso. "Ionic strength- and pH-dependence of calcium binding by terrestrial humic acids." Environmental Chemistry 9, no. 1 (2012): 89. http://dx.doi.org/10.1071/en11112.

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Environmental contextIn terrestrial environments, humic substances act as major sorbents for calcium, which is an essential nutrient for organisms. This study shows that calcium binding by terrestrial humic acids is strongly dependent on pH and ionic strength. The results indicate that calcium binding by humic acids is primarily controlled by electrostatic forces and specific binding to carboxylic groups. AbstractCalcium binding by two terrestrial humic acids was investigated at 25 °C as a function of pH, ionic strength and Ca2+ activity with calcium titration experiments. A Ca2+-selective ele

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26

Montenegro, Andrea C., Silvia Orsetti, and Fernando V. Molina. "Modelling proton and metal binding to humic substances with the NICA–EPN model." Environmental Chemistry 11, no. 3 (2014): 318. http://dx.doi.org/10.1071/en13214.

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Environmental context The toxicity of metals in the environment is greatly influenced by natural organic matter owing to its ability to bind metals to form complexes that can be immobile and non-bioavailable. Sound mathematical models are important to reliably predict the behaviour of such contaminants, and how they are affected by organic matter and other environmental colloids. Here a new model is discussed and compared with precedent ones. Abstract The mathematical modelling of metal cation–natural organic matter interactions is a fundamental tool in predicting the state and fate of polluta

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27

Lynch, DE, G. Smith, KA Byriel, and CHL Kennard. "Molecular Cocrystals of Carboxylic Acids. VI. The Crystal Structures of the Adducts of Triphenylphosphine Oxide With Benzene-1,3,5-tricarboxylic Acid and (2,4,5-Trichlorophenoxy)acetic Acid." Australian Journal of Chemistry 45, no. 5 (1992): 835. http://dx.doi.org/10.1071/ch9920835.

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The crystal structures of the triphenylphosphine oxide adducts with benzene-1,3,5-tricarboxylic acid (2 : 1) (1) and (2,4,5-trichlorophenoxy)acetic acid (1 : 1) (2) have been determined and refined to residuals R 0.085 and 0.032 for 2531 and 3348 observed reflections, respectively. Both are triclinic with two heteromeric units in cells of dimensions a 8.66(1), b 13-58(2), c 18.17(3) �, α 99.12(8), β 101.45(8), γ 107.54(7) � for (1), and a 9.062(6), b 9.726(7), c 15.19(1) �, α 103.80(4), , β 104.94(4), γ 96.42(5)� for (2). In each structure, strong single directed hydrogen bonds are found betwe

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28

Zhong, Kai-Long, and Chao Ni. "Bis(6-nitro-1,10-phenanthrolin-1-ium) 2,5-dicarboxyterephthalate." Acta Crystallographica Section E Structure Reports Online 70, no. 3 (2014): o256—o257. http://dx.doi.org/10.1107/s1600536814002414.

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In the structure of the title 2:1 proton-transfer compound, 2C12H8N3O2+·C10H4O82−, the 6-nitro-1,10-phenanthroline molecules act as proton sponges, accepting protons from pyromellitic acid. The –NO2group of one of the 6-nitro-1,10-phenanthrolin-1-ium cations is disordered and was refined with a site-occupancy ratio of 0.624 (15):0.376 (15). Two –COOH(–COO−) groups of the 2,5-dicarboxyterephthalate dianion are disordered and were refined with site-occupancy ratios of 0.769 (4):0.231 (4) and 0.766 (5):0.234 (5). The –NO2group of the second cation is also disordered about a pseudo-twofold rotatio

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29

Lanyi, J. K. "Shuffling protons in bacteriorhodopsin: long-distance coupling between the pKas of two carboxylic groups." Biophysical Journal 71, no. 2 (1996): 541–43. http://dx.doi.org/10.1016/s0006-3495(96)79257-3.

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30

Atiko, Rejoice, Idriss Bamidele Musba�u, Andrew Kwaji, et al. "Cytotoxicity and Isolation of Betullinic Acid from Anthonotha noldeae Stem Bark." Biology, Medicine, & Natural Product Chemistry 14, no. 1 (2025): 193–97. https://doi.org/10.14421/biomedich.2025.141.193-197.

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The cytotoxicity and isolation of betullinic acid from Anthonotha noldeae stem bark were examined in this study. The stem bark was extracted using methanol (MeOH) via the cold maceration technique. The MeOH produced a crude extract of 125.18 g (6.78%), which was further divided into n-hexane, dichloromethane (DCM), and ethyl acetate (EtOAc) fractions with yields of 10.23%, 11.74%, and 12.22%, respectively. Cytotoxicity assays using brine shrimp lethality tests revealed that the DCM and EtOAc fractions exhibited substantialconcentration-dependent toxicity, achieving 100% mortality at 5001000 ?g

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Andonovski, Blagoja, and Goran Stojkovic. "Spectrophotometric study of the protonation processes of some indole derivatives in sulfuric acid." Journal of the Serbian Chemical Society 64, no. 12 (1999): 775–87. http://dx.doi.org/10.2298/jsc9912775a.

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The protonation of 3-methylindole, D-tryptophan, 3-formylindole, 3-acetylindole and indolyl-2-carboxylic acid in sulfuric acid media was studied by UV spectroscopy. The measurement of the absorbance at four selected wavelengths enabled the calculation of the corresponding molar absorptivities. The results were used to calculate the pKa value of the protonated form of the indole derivatives by the Hammett Method. The Hammett postulate (the slope of the plot log [c(BH+)/c(B)]vs. H should be equal to 1) was tested. The dissociation constants and solvent parameter m* were also obtained by applying

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32

Meychik, N. R., Yu I. Nikolaeva, and M. A. Kushunina. "Comparison of Halophyte and Glycophyte Plants from the Amaranthaceae-Chenopodiaceae Family in Their Ion-Exchange Properties of Polymeric Matrix of Cell Walls." Физиология растений 70, no. 6 (2023): 659–69. http://dx.doi.org/10.31857/s0015330323600316.

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Ion-exchanging properties of the polymeric matrix of the cell walls isolated from leaves were examined. The glycophyte 55-day-old plants of spinach (Spinacia oleracea L., cv. Matador) grown on a nutrient solution containing 0.5, 150, or 250 mM NaCl and the halophyte seepweed (Suaeda altissima (L.) Pall.) of the same age grown at 0.5, 250, or 750 mM NaCl were compared. The ion-exchange capacity of the cell walls was estimated at different pH and ionic strength of a solution. In the structure of the leaf cell walls, three types of cation-exchange groups were found, namely, two types of carboxyli

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33

Samage, Anita, Pooja Gupta, Mahaveer A. Halakarni, Sanna Kotrappanavar Nataraj, and Apurba Sinhamahapatra. "Progress in the Photoreforming of Carboxylic Acids for Hydrogen Production." Photochem 2, no. 3 (2022): 580–605. http://dx.doi.org/10.3390/photochem2030040.

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Photoreforming is a process that connects the redox capability of photocatalysts upon light illumination to simultaneously drive the reduction of protons into hydrogen and the oxidation of organic substrates. Over the past few decades, researchers have devoted substantial efforts to enhancing the photocatalytic activity of the catalyst in hydrogen production. Currently, the realization of the potential of photocatalysts for simultaneous hydrogen production with value-added organics has motivated the research field to use the photo-oxidation path. As a distinct benefit, the less energetically d

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Babbitt, Patricia C., Miriam S. Hasson, Joseph E. Wedekind та ін. "The Enolase Superfamily: A General Strategy for Enzyme-Catalyzed Abstraction of the α-Protons of Carboxylic Acids†". Biochemistry 35, № 51 (1996): 16489–501. http://dx.doi.org/10.1021/bi9616413.

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Lay, Peter A., Robert K. Norris, and Paul K. Witting. "Electrochemical Studies on the Competition Between Intramolecular Electron Transfer and Intermolecular Protonation of Nitroaryl Radical Anions in the Reductions of Apical Carboxylic Acid Substituents of 2- and 3-Nitro- 9,10-dihydro-9,10-ethanoanthracene-9-carboxylic Acids." Australian Journal of Chemistry 50, no. 10 (1997): 999. http://dx.doi.org/10.1071/c97076.

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The results obtained from variable scan rate cyclic voltammetry (c.v.) on 2-nitro- and 3-nitro-9,10- dihydro-9,10-ethanoanthracene-9-carboxylic acids [(4) and (5), respectively], combined with simulations of various c.v. responses, are consistent with reduction of a benzylic acid group being facilitated by an intramolecular electron transfer process. This intramolecular process involves a one-electron reduction of the nitroaromatic group, followed by a rapid and irreversible π*(ArNO2)•- → π*(RCO2H)•- intramolecular electron transfer to the carboxylic acid group at a benzylic bridgehead positio

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He, Chen, Hanxiong Che, Zier Bao, et al. "Evolution of nucleophilic high molecular-weight organic compounds in ambient aerosols: a case study." Atmospheric Chemistry and Physics 24, no. 3 (2024): 1627–39. http://dx.doi.org/10.5194/acp-24-1627-2024.

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Abstract. Nucleophilic high molecular-weight organic compounds (HMWOCs) are sensitive to protons (H+) in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. A comprehensive evaluation of the diurnal evolution of nucleophilic HMWOCs was performed. HMWOCs aged significantly in daily cycles, accompanied by functionality shifts, particularly oxygenated and reduced nitrogen (CHON and CHN) as well as oxygenated organics. The intensities of high molecular-weight (HMW) oxygenated compounds increased during both daytime and nighttime. The daytime evolution produced more ni

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Pérez-Ponce, Amparo, and Bernhard Lendl. "Mid-IR Spectroscopy for the Quantification of Metal Ions in Aqueous Solution in the Nanogram Range." Applied Spectroscopy 54, no. 5 (2000): 676–80. http://dx.doi.org/10.1366/0003702001950157.

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A novel mid-infrared (IR) flow-through sensor system for the determination of metal ions in aqueous solution was developed. The flow-through sensor comprised weak cation exchanger beads (Sephadex with carboxylic acid moieties) placed in the optical path of a 37 μm IR transmission cell. The combination of the flow-through sensor with a sequential injection analysis (SIA) system allowed us to carry out the whole analysis procedure including analyte–sensor interaction and sensor regeneration, as well as data acquisition, under computer control. The first step of an analysis sequence was regenerat

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Wei, Wenguang, Yao Jin, Tao Han, et al. "A Fluorescent Chemosensor for Zn2+ Based on a C3-Symmetrical and Pre-Organized 2,2′,2″-Nitrilotribenzoic Acid Material." Australian Journal of Chemistry 71, no. 11 (2018): 890. http://dx.doi.org/10.1071/ch18308.

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A C3-symmetrical 4,4″,4⁗-nitrilotris(2′-methyl-[1,1′-biphenyl]-3-carboxylic acid) (4) derived from nitrilotriacetic acid (NTA) was found to selectively bind Zinc(ii) ions both in DMSO or MeOH. A synergistic effect of the anionic counter ion SO42− on the sensing behaviour of 4 to metal ions was clearly observed in DMSO. Interestingly, 4 showed a rapid hypochromatic shift in emission ascribed to the deprotonation and the concomitant formation of a 4–metal complex upon the addition of Zn2+ ions, instead of the bathochromic shift and emission enhancement attributed to the SO42−-involved hydrogen-b

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Vesna, O., S. Sjogren, E. Weingartner, et al. "Changes of fatty acid aerosol hygroscopicity induced by ozonolysis under humid conditions." Atmospheric Chemistry and Physics 8, no. 16 (2008): 4683–90. http://dx.doi.org/10.5194/acp-8-4683-2008.

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Abstract. Unsaturated fatty acids are important constituents of the organic fraction of atmospheric aerosols originating from biogenic or combustion sources. Oxidative processing of these may change their interaction with water and thus affect their effect on climate. The ozonolysis of oleic and arachidonic acid aerosol particles was studied under humid conditions in a flow reactor at ozone exposures close to atmospheric levels, at concentrations between 0.5 and 2 ppm. While oleic acid is a widely used proxy for such studies, arachidonic acid represents polyunsaturated fatty acids, which may d

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Safronov, Nikita E., Irena P. Kostova, Mauricio Alcolea Palafox, and Nataliya P. Belskaya. "Combined NMR Spectroscopy and Quantum-Chemical Calculations in Fluorescent 1,2,3-Triazole-4-carboxylic Acids Fine Structures Analysis." International Journal of Molecular Sciences 24, no. 10 (2023): 8947. http://dx.doi.org/10.3390/ijms24108947.

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The peculiarities of the optical properties of 2-aryl-1,2,3-triazole acids and their sodium salts were investigated in different solvents (1,4-dioxane, dimethyl sulfoxide DMSO, methanol MeOH) and in mixtures with water. The results were discussed in terms of the molecular structure formed by inter- and intramolecular noncovalent interactions (NCIs) and their ability to ionize in anions. Theoretical calculations using the Time-Dependent Density Functional Theory (TDDFT) were carried out in different solvents to support the results. In polar and nonpolar solvents (DMSO, 1,4-dioxane), fluorescenc

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Aminov, Daniel, Dina Pines, Philip M. Kiefer, Snehasis Daschakraborty, James T. Hynes, and Ehud Pines. "Intact carbonic acid is a viable protonating agent for biological bases." Proceedings of the National Academy of Sciences 116, no. 42 (2019): 20837–43. http://dx.doi.org/10.1073/pnas.1909498116.

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Carbonic acid H2CO3 (CA) is a key constituent of the universal CA/bicarbonate/CO2 buffer maintaining the pH of both blood and the oceans. Here we demonstrate the ability of intact CA to quantitatively protonate bases with biologically-relevant pKas and argue that CA has a previously unappreciated function as a major source of protons in blood plasma. We determine with high precision the temperature dependence of pKa(CA), pKa(T) = −373.604 + 16,500/T + 56.478 ln T. At physiological-like conditions pKa(CA) = 3.45 (I = 0.15 M, 37 °C), making CA stronger than lactic acid. We further demonstrate ex

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Lounasvuori, Mailis M., Martin Rosillo-Lopez, Christoph G. Salzmann, Daren J. Caruana, and Katherine B. Holt. "Electrochemical characterisation of graphene nanoflakes with functionalised edges." Faraday Discuss. 172 (2014): 293–310. http://dx.doi.org/10.1039/c4fd00034j.

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Graphene nanoflakes (GNF) of diameter ca. 30 nm and edge-terminated with carboxylic acid (COOH) or amide functionalities were characterised electrochemically after drop-coating onto a boron-doped diamond (BDD) electrode. In the presence of the outer-sphere redox probe ferrocenemethanol there was no discernible difference in electrochemical response between the clean BDD and GNF-modified electrodes. When ferricyanide or hydroquinone were used as redox probes there was a marked difference in response at the electrode modified with COOH-terminated GNF in comparison to the unmodified BDD and amide

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Sabah, Rusul Saad, Zahraa S. Al-Garawi, and Mahmoud N. Al-jibouri. "The utilities of pyrazolines encouraged synthesis of a new pyrazoline derivative via ring closure of chalcone, for optimistic neurodegenerative applications." Al-Mustansiriyah Journal of Science 33, no. 1 (2022): 21–31. http://dx.doi.org/10.23851/mjs.v33i1.1067.

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Pyrazolines and their derivatives have been extensively studied as coordinated ligands of high potential applications in diverse chemical and biological systems. This work explores some methods of synthesis of pyrazolines, such as the preparation of pyrazole derivatives via chalcones. It also demonstrates that 2-pyrazoline complexes were biologically active and have had a range of clinical applications. Palladium (II) complex of pyrazole was active as antitumor when tested against murine mammary adenocarcinoma (LM3). Copper (II) and Cobalt (II) complex are biologically active in the living sys

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Flakus, Henryk T., and Anna Jarczyk-Jędryka. "Temperature and H/D Isotopic Effects in the IR Spectra of the Hydrogen Bond in Solid-State 2-Furanacetic Acid and 2-Furanacrylic Acid." Journal of Atomic, Molecular, and Optical Physics 2012 (September 11, 2012): 1–17. http://dx.doi.org/10.1155/2012/125471.

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Polarized IR spectra of 2-furanacetic acid and of 2-furanacrylic acid crystals were measured at 293 K and 77 K in the vO−H and vO−H band frequency ranges. The corresponding spectra of the two individual systems strongly differ, one from the other, by the corresponding band shapes as well as by the temperature effect characterizing the bands. The crystal spectral properties remain in a close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen bond protons and the electrons on the π-electronic systems in

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Lay, PA, RK Norris, and PK Witting. "Cyclic Voltammetric and E.P.R. Spectroscopic Studies on Apical Substituent Effects in Radical Anions of 9-Substituted and 9,10-Disubstituted Nitroethanoanthracenes." Australian Journal of Chemistry 49, no. 12 (1996): 1279. http://dx.doi.org/10.1071/ch9961279.

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Cyclic voltammetry and electron paramagnetic resonance spectroscopy were used to examine apical substituent effects on the properties of Me2SO solutions of the radical anions from 9-substituted and 9,10-disubstituted 2- and 3-nitro-9,10-dihydro-9,10-ethanoanthracenes (1)-(24). The reductions of the nitro group are, in general, reversible at 100 mV s-1 and at 20°, except where there are coupled intra-or inter-molecular electron or proton transfer reactions with aliphatic bridgehead substituents, such as a carboxylic acid or iodine. The substituent effects for the meta- and para-nitroethanoanthr

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Gilbertson, T. A., P. Avenet, S. C. Kinnamon, and S. D. Roper. "Proton currents through amiloride-sensitive Na channels in hamster taste cells. Role in acid transduction." Journal of General Physiology 100, no. 5 (1992): 803–24. http://dx.doi.org/10.1085/jgp.100.5.803.

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The activity of taste cells maintained in the intact hamster tongue was monitored in response to acid stimulation by recording action currents from taste receptor cells with an extracellular "macro" patch pipette: a glass pipette was pressed over the taste pore of fungiform papillae and perfused with citric acid, hydrochloric acid, or NaCl. Because this technique restricted stimulus application to the small surface area of the apical membranes of the taste cells, many nonspecific, and potentially detrimental, effects of acid stimulation could be avoided. Acid stimulation reliably elicited fast

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Schabelnyk, K. P., S. V. Kholodnyak, N. M. Polishchuk та S. І. Kоvalenko. "2-Сycloalkyl-(hetaryl-)-[1,2,4]triazol[1,5-с]quinazolines: synthesis, physical and chemical properties and antibacterial activity". Farmatsevtychnyi zhurnal, № 6 (9 грудня 2020): 65–77. http://dx.doi.org/10.32352/0367-3057.6.20.07.

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In spite of the achievements in the chemistry of triazoloquinazolines, the synthetic possibilities of this class of compounds are not exhausted, some problems remain unresolved and require further study. 2-R-[1,2,4]triazolo[1,5-с]quinazolines are among them due to insufficiently explored but at the same time interesting in both chemical and biological aspects. Undoubtedly «pharmacophore» has the crucial role in the response of a biological action. It is contained in this heterocycle namely the substitute position 2. In view of the above, we attempted to modify triazolo[1,5-с]quinaz

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Fong, Andy, Wei Lun Toh, Hai-Xu Wang, and Yogesh Surendranath. "Potential-Dependent Competitive Adsorption of Electrolytes Kinetically Inhibits High-Current Hydrogen Oxidation in Non-Aqueous Media." ECS Meeting Abstracts MA2023-01, no. 50 (2023): 2571. http://dx.doi.org/10.1149/ma2023-01502571mtgabs.

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Performing electrochemical transformations in non-aqueous media can unlock new reactivities and selectivities unattainable in aqueous media. For instance, non-aqueous media (e.g. acetonitrile (MeCN), dimethylformamide (DMF), dimethylsulfoxide (DMSO)) allow the dissolution of organic compounds and enable water-incompatible organic electrosynthesis reactions. On the other hand, the lithium-mediated nitrogen reduction reaction (NRR) carried out electrochemically in tetrahydrofuran (THF) is one of the most promising routes towards electrifying the Haber-Bosch reaction and thus eliminating the need

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Copello, Federico dos Reis, Leonardo Lizarraga, Silvia Orsetti, and Fernando V. Molina. "Swelling and aggregation of Leonardite upon pH change and PbII binding: an AFM study." Environmental Chemistry 15, no. 3 (2018): 162. http://dx.doi.org/10.1071/en17224.

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Environmental contextNatural organic materials, such as humic substances, play key roles in the binding and environmental fate of metals. We study the interaction of protons and metal ions with humic acids, and show changes to the mechanical properties of the particles and their capability to fix metal pollutants. The results will help refine current models of metal behaviour in the environment. AbstractThe swelling and aggregation of Leonardite humic acid, due to acid–base and PbII binding interactions, was studied through atomic force microscopy (AFM) tapping mode measurements and correlated

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Mohamed Zabidi, Zubainun, Nurul Batrisyia Muhamad Suhaimy, Ahmad Nazib Alias, Nur Diyana Nazihah Fuadi, and Nur Hanisah Hamzi. "Prediction Of Carboxylic Acid Toxicity Using Machine Learning Model." Malaysian Journal of Applied Sciences 8, no. 2 (2023): 28–36. http://dx.doi.org/10.37231/myjas.2023.8.2.357.

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Carboxylic acids are organic compounds characterized by the presence of a carboxyl functional group capable of donating a proton and forming carboxylate ions in aqueous solutions. The carboxylic acid has widely been used in in manufacturing and medical applications. The rapid growth in carboxylic acid has established a need to predict its toxicity. The purpose of this paper to build predictive toxicity of carboxylic acid models by using five molecular descriptors (refractive index, The octanol/water partition coefficient (log P), acid dissociation constant (pKa), density, and dipole moment) th

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