- Crystal structure and thermochemical properties of potassium pyruvate C3H3O3K(s)
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One important compound potassium pyruvate C3H3O3K(s) is synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. X-ray single-crystal structural analysis reveals that the compound is formed by one CH3COCOO? anion and one metal cation K+. An obvious feature of the crystal structure of the compound is the formation of the five-membered chelate ring, and it is good for the stability of the compound in structure. The lattice potential energy of the compound and ionic volume of the anion CH3COCOO? are obtained from crystallographic data. The lattice potential energy is determined to be: UPOT[C3H3O3K(s)]?=?567.7?kJ?mol?1. The V? (the volume of the anion CH3COCOO?) is estimated to be 0.088?nm3. Molar enthalpies of dissolution of the compound at various molalities in the double-distilled water are measured by use of an isoperibol solution-reaction calorimeter at 298.15?K. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of C3H3O3K(s) at infinite dilution is derived to be 22.9?kJ?mol?1. The values of relative apparent molar enthalpies (ΦL), relative partial molar enthalpies (Lˉ 2) of the compound, and relative partial molar enthalpies (Lˉ 1) of the solvent (water) at different concentrations m/(mol?kg?1) are derived from the experimental values of the enthalpies of dissolution of the compound. Finally, the molar enthalpy of hydration of the anion CH3COCOO?(g) is calculated to be ?227.8?kJ?mol?1 by the design of the thermochemical cycle.
- Di, You-Ying,Zhang, Yu-Han,Kong, Yu-Xia,Zhou, Chun-Sheng
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- CH-π Interactions Promote the Conversion of Hydroxypyruvate in a Class II Pyruvate Aldolase
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The class II hydroxy ketoacid aldolase A5VH82 from Sphingomonas wittichii RW1 (SwHKA) accepts hydroxypyruvate as nucleophilic donor substrate, giving access to synthetically challenging 3,4-dihydroxy-α-ketoacids. The crystal structure of holo-SwHKA in complex with hydroxypyruvate revealed CH-π interactions between the C?H bonds at C3 of hydroxypyruvate and a phenylalanine residue at position 210, which in this case occupies the position of a conserved leucine residue. Mutagenesis to tyrosine further increased the electron density of the interacting aromatic system and effected a rate enhancement by twofold. While the leucine variant efficiently catalyses the enolisation of hydroxypyruvate as the first step in the aldol reaction, the enol intermediate then becomes trapped in a disfavoured configuration that considerably hinders subsequent C?C bond formation. In SwHKA, micromolar concentrations of inorganic phosphate increase the catalytic rate constant of enolisation by two orders of magnitude. This rate enhancement was now shown to be functionally conserved across the structurally distinct (α/β)8 barrel and αββα sandwich folds of two pyruvate aldolases. Characterisation of the manganese (II) cofactor by electron paramagnetic resonance excluded ionic interactions between the metal centre and phosphate. Instead, histidine 44 was shown to be primarily responsible for the binding of phosphate in the micromolar range and the observed rate enhancement in SwHKA. (Figure presented.).
- Marsden, Stefan R.,Mestrom, Luuk,Bento, Isabel,Hagedoorn, Peter-Leon,McMillan, Duncan G. G.,Hanefeld, Ulf
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- Synthesis of 6-acyl phenanthridines by oxidative radical decarboxylation-cyclization of α-oxocarboxylates and isocyanides
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A silver catalysed synthesis of 6-acyl phenanthridines by oxidative radical decarboxylation-cyclization of α-oxocarboxylates and isocyanides was developed. This reaction provided a novel method to realize C1 insertion via a radical process and various functional groups were well-tolerated. The Royal Society of Chemistry.
- Liu, Jie,Fan, Chao,Yin, Hongyu,Qin, Chu,Zhang, Guoting,Zhang, Xu,Yi, Hong,Lei, Aiwen
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supporting information
p. 2145 - 2147
(2014/02/14)
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- Kinetic challenges facing oxalate, malonate, acetoacetate, and oxaloacetate decarboxylases
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To compare the powers of the corresponding enzymes as catalysts, the rates of uncatalyzed decarboxylation of several aliphatic acids (oxalate, malonate, acetoacetate, and oxaloacetate) were determined at elevated temperatures and extrapolated to 25 °C. In the extreme case of oxalate, the rate of the uncatalyzed reaction at pH 4.2 was 1.1 × 10-12 s-1, implying a 2.5 × 1013-fold rate enhancement by oxalate decarboxylase. Whereas the enzymatic decarboxylation of oxalate requires O 2 and MnII, the uncatalyzed reaction is unaffected by the presence of these cofactors and appears to proceed by heterolytic elimination of CO2.
- Wolfenden, Richard,Lewis, Charles A.,Yuan, Yang
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supporting information; experimental part
p. 5683 - 5685
(2011/06/18)
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- Method for producing alkali metal and alkaline earth metal pyruvates
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A method for producing alkali metal and alkaline earth metal pyruvates is disclosed, in which salts of organic acids or acidic organic keto or hydroxy compounds containing as cation one from the group comprising Li, Na, K, Rb, Cs, Mg, Sr and Ba, or mixtures of these salts, are reacted with pyruvic acid at a temperature ranging from ?20 to +120°C., if necessary in the presence of a solvent or diluent. In this way, alkali metal and alkaline earth metal pyruvates of high purity are obtained, which can be largely anhydrous and have a very long shelf life. In addition, novel Rb, Cs, Sr and Ba pyruvates are disclosed. These pyruvates are used, for example, to enhance endurance and strength in the field of sport, as protective substances for body cells and tissues, and as food supplements. They are also used for technical applications.
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- Kinetics of Oxidation of Lactic , Mandelic and Glycollic Acids by Diperiodatonickelate(IV) in Alkaline Media
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The title reactions show first order dependence in and .The rate of oxidation increases with increase in and decreases with increase in .A probable mechanism involving an adduct formation between substrate and Ni(IV) and its slow decomposition in slow step is proposed.
- Chandraiah, U,Murthy, C. P.,Kandlikar, Sushama
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p. 162 - 163
(2007/10/02)
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- Kinetics of Oxidation of Primary and Secondary Alcohols by Diperiodatoargentate(III)
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Kinetics of oxidation of ethyl, isopropyl and benzyl alcohols, and glycollic and lactic acids by diperiodatoargentate(III) has been investigated in alkaline medium.The order in and is found to be one each.The reaction rates decrease with increase in and increase with increase in .The nature of reactive species in diperiodatoargentate(III) is discussed.A probable mechanism involving a two-electron transfer from the alcohol moiety to the Ag(III) species is proposed.
- Rao, P. Jaya Prakash,Sethuram, B.,Navaneeth Rao, T.
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p. 733 - 734
(2007/10/02)
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