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Carboxylic acid

About: Carboxylic acid is a research topic. Over the lifetime, 48544 publications have been published within this topic receiving 605696 citations.


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Journal ArticleDOI
TL;DR: The results show that the ionizable residues surrounding C106 affect its p K a in a way that is contrary to expectations based on the typical ionization behavior of glutamic acid and arginine, which are particularly common in the DJ-1 superfamily.
Abstract: Human DJ-1, a disease-associated protein that protects cells from oxidative stress, contains an oxidation-sensitive cysteine (C106) that is essential for its cytoprotective activity. The origin of C106 reactivity is obscure, due in part to the absence of an experimentally determined p K a value for this residue. We have used atomic-resolution X-ray crystallography and UV spectroscopy to show that C106 has a depressed p K a of 5.4 +/- 0.1 and that the C106 thiolate accepts a hydrogen bond from a protonated glutamic acid side chain (E18). X-ray crystal structures and cysteine p K a analysis of several site-directed substitutions at residue 18 demonstrate that the protonated carboxylic acid side chain of E18 is required for the maximal stabilization of the C106 thiolate. A nearby arginine residue (R48) participates in a guanidinium stacking interaction with R28 from the other monomer in the DJ-1 dimer and elevates the p K a of C106 by binding an anion that electrostatically suppresses thiol ionization. Our results show that the ionizable residues (E18, R48, and R28) surrounding C106 affect its p K a in a way that is contrary to expectations based on the typical ionization behavior of glutamic acid and arginine. Lastly, a search of the Protein Data Bank (PDB) produces several candidate hydrogen-bonded aspartic/glutamic acid-cysteine interactions, which we propose are particularly common in the DJ-1 superfamily.

122 citations

Journal ArticleDOI
TL;DR: A full overview of the decarboxylative cross-coupling reaction between heteroaromatic carboxylic acids and aryl halides is described, with palladium catalysts with short reaction times providing facile synthesis of aryL-substituted heterOaromatics.
Abstract: A full overview of the decarboxylative cross-coupling reaction between heteroaromatic carboxylic acids and aryl halides is described This transformation employs palladium catalysts with short reaction times providing facile synthesis of aryl-substituted heteroaromatics The effect of each reaction parameter including solvent, base, and additive employed as well as the full substrate scope of this transformation are reported Mechanistic evidence is also disclosed that sheds light on possible reaction pathways

122 citations

Patent
17 Sep 1976
TL;DR: In this article, a substantially haze-free lubricating oil composition was proposed based on the total weight of said composition of ethylene copolymeric dispersant-viscosity index improver material, which material has been formed by grafting an ethylenecopolymer comprising about 30 to 80 wt. % ethylene and about 20 to 70 % C3 to C18 alpha olefin, with a vinyl monomer containing nitrogen.
Abstract: A substantially haze-free lubricating oil composition comprising a lubricating oil and from about 0.1 to 50 wt. %, based upon the total weight of said composition of ethylene copolymeric dispersant-viscosity index improver material, which material has been formed by (a) grafting an ethylene copolymer comprising about 30 to 80 wt. % ethylene and about 20 to 70 % C3 to C18 alpha olefin, with an ethylenically unsaturated compound selected form the group consisting of unsaturated carboxylic acid and anhydride of carboxylic acid, said ethylene copolymer when grafted with said carboxylic acid or said anhydride being further reacted with a polyfunctional reactant selected from the group consisting of polyamine, polyol and hydroxy amine, and reacting with from about 0.1 to 8 wt. % of an oil-soluble hydrocarbyl substituted strong acid containing from about 3 to about 70 total carbons to thereby inhibit haze in said composition, and wherein said strong acid is selected from the group consisting of alkyl carboxylic acids, phosphoric acid, phosphonic acid, thiophosphonic acid, phosphinic acid, thiophosphinic acid, sulfonic acid, sulfuric acid, sulfinic acid and alpha-substituted halo-or nitro- or nitrilo-carboxylic acids; or (b) grafting an ethylene copolymer comprising about 30 to 80 wt. % ethylene and about 20 to 70 wt % C3 to C18 alpha olefin, with a vinyl monomer containing nitrogen, and reacting with from about 0.1 to 8 wt. % of an oil-soluble hydrocarbyl substituted strong acid containing from about 3 to about 70 total carbons, to thereby inhibit haze in said composition.

122 citations

Journal ArticleDOI
TL;DR: A model of the substrate binding site of CYP2C9 is provided, in which substrates interact through their anionic site A- with a cationic residue of the CYP1C9 protein C+.
Abstract: Biochemical experiments, using the well-defined human liver CYP2C9 expressed in yeast, and molecular modeling techniques were used to derive a predictive model for substrates of CYP2C9. The ability of 10 2-aroylthiophenes related to tienilic acid to act as substrates for CYP2C9 was studied. Four of them were original compounds that were synthesized and completely characterized by several spectroscopic techniques. In these 10 compounds various chemical functions, such as ester, amide, alcohol, phenol, ether or tetrazole functions, replaced the OCH2COOH function of tienilic acid. Among them, only the derivatives containing an acidic function (carboxylic acids, phenol, and tetrazole whose pKaS are 4.8, 6.3, and 3.8, respectively) underwent a 5-hydroxylation of their thiophene ring like tienilic acid. Despite their close structural analogy with tienilic acid, all of the other compounds not only did not undergo any 5-hydroxylation of their thiophene ring but also failed to act as inhibitors of CYP2C9. These results strongly suggested that the presence, at pH 7.4, of a negative charge on the substrate is a very important feature in its recognition by CYP2C9. In fact, the four new substrates of CYP2C9 described in this study, a carboxylic acid, phenol, and tetrazole derivative, each of which is related to tienilic acid, and the antiinflammatory drug, suprofen (with Km between 12 and 130 microM and kcat between 0.2 and 1.3 min-1), as well as almost all CYP2C9 substrates reported in the literature, exhibit a pKa below 7 (except phenytoin whose pKa is 8.1). They mainly exist as anions at physiological pH. By using molecular modeling techniques, 12 CYP2C9 substrates were superimposed with respect to their hydroxylation site and fitted onto templates, which were rigid molecules such as (S)-warfarin and phenytoin. It was thus possible to arrange them in order that all their anionic sites were at a distance around 4 A from a common point (a putative cationic site of the protein) in space. These results provide a model of the substrate binding site of CYP2C9, in which substrates interact through their anionic site A- with a cationic residue of the CYP2C9 protein C+. In that model, the distance between the hydroxylation site (Hy) and the anionic site (A-) is 7.8 +/- 1.6 A, and the

121 citations

Journal ArticleDOI
TL;DR: Assessment of the impact of organic acids typically found in the rhizosphere on heavy metal transport in soils in the presence of simple organic acids found citric acid had the highest R(f) values for Zn, followed by malic, tartaric, fumaric, and glutaric acids, which followed the trend Zn>Cd>Pb.

121 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023198
2022457
2021459
2020738
2019842
2018813