Citric acid oxidation by vanadium(V) in sulfuric acid medium: Kinetic and mechanistic study

The citric acid oxidation by vanadium(V) in sulfuric acid medium at 303 K is reported. The reaction rate was determined spectrophotometrically by monitoring the formation of vanadium(IV) at 760 nm. The oxidation showed a first‐order dependence with respect to vanadium(V) concentration and fractional order with respect to citric acid concentrations, with no control and with constant ionic strength. The reaction is also first order with respect to sulfuric acid concentration with no control and of fractional order at constant ionic strength. The reaction rate is enhanced by an increase of ionic strength and increased by a decrease of the dielectric constant. The activation parameters were calculated based on the rate constants determined in the 293 to 313 K interval. The proposed oxidation mechanisms and the derived rate laws are consistent with the experimental rate laws. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 566–572, 2000     

Acetic acid denaturing pulsed field capillary electrophoresis for RNA separation

Based on our previous work of in‐capillary denaturing polymer electrophoresis, we present a study of RNA molecular separation up to 6.0 kilo nucleotide by pulsed field CE. This is the first systematic investigation of electrophoresis of a larger molecular mass RNA in linear hydroxyethylcellulose (HEC) under pulsed field conditions. The parameters that may influence the separation performance, e.g. gel polymer concentration, modulation depth and pulse frequency, are analyzed in terms of resolution and mobility. For denaturing and separating RNA in the capillary simultaneously, 2 M acetic acid was added into the HEC polymer to serve as separation buffer. Result shows that (i) in pulsed field conditions, RNA separation can be achieved in a wide range of concentration of HEC polymer, and RNA fragments between 0.3 and 0.6 kilo nucleotide are sensitive to the polymer concentration; (ii) under certain pulsed field conditions, RNA fragments move linearly as the modulation depth increases; (iii) 12.5 Hz is the resonance frequency for RNA reorientation time and applied frequency.     

Comparison of the Catalytic Activities of Three Isozymes of Carnitine Palmitoyltransferase 1 Expressed in COS7 Cells

The enzyme carnitine palmitoyltransferase 1 (CPT1) catalyzes the transfer of an acyl group from acyl-CoA to carnitine to form acylcarnitine, and three isozymes of it, 1a, 1b, and 1c, have been identified. Interestingly, the 1c isozyme was reported to show no enzymatic activity, but it was not clearly demonstrated whether this inactivity was due to its dysfunction or due to its poor expression. In the present study, we (a) expressed individual CPT1 isozymes in COS7 cells, (b) evaluated quantitatively their expression levels by Western blotting using the three bacterially expressed CPT1 isozymes as standards, and (c) evaluated their catalytic activities. With these experiments, we successfully demonstrated that the absence of the enzymatic activity of the 1c isozyme was due to its dysfunction. In addition, experiments on the preparation of standard CPT1 isozymes revealed that the 1c isozyme did not show the standard relationship between migration in an SDS–PAGE gel and molecular size. We further tried to determine why the 1c isozyme was inert by preparing chimeric CPT1 between 1a and 1c, but no clear conclusion could be drawn because one of the chimeric CPT1s was not sufficiently expressed.     

Synthesis of [1,3,4]thiadiazolo[3,2-a]pyrimidines in the presence of formic acid

Formic acid-phosphorus pentoxide was effective for the preparation of 5,7-dimethyl[1,3,4]thiadiazolo- and -[1,3]thiazolo[3,2-a]pyrimidin-4-ium salts. Further, the pyrimidine ring transformation and the isocyanation of 5imino-6H-[1,3,4]thiadiazolo- and -[1,3]thiazolo[3,2-a]pyrimidin-7-ones were carried out in the presence of formic acid and triethyl orthoformate, respectively.     

Supramolecular network polymers formed from polyamidine and carboxy‐terminated telechelic poly(n‐butyl acrylate) via amidinium‐carboxylate salt bridges

We have prepared the amidinium‐carboxylate salt bridge‐based supramolecular network polymers from a carboxy‐terminated telechelic poly(n‐butyl acrylate) and a linear polyamidine having N,N′‐di‐substituted acetamidine group in the main chain. FTIR measurements indicated that the salt bridge was attributed to the three‐dimensional network formation. Virtually, no fluidity was observed for the blend containing equimolar amounts of the carboxyl group and the amidine group, which showed a high G′ value of about 1 MPa at ?5 °C. For comparison, the supramolecular network polymers crosslinked by ammonium‐carboxylate salt were prepared using a linear polyethyleneimine instead of the polyamidine. The blend with equimolar amounts of the carboxyl group and the secondary amino group showed liquid‐like fluidity with a G′ value of about 0.01 MPa at ?5 °C, which was attributed to the fact that a certain amount of the carboxyl group remained as its free form, as evidenced by FTIR analysis. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2148–2155     

Synthesis of 5-ethylpyrimidine nucleoside analogs

This paper describes the synthesis of acyclic, cyclic, and deoxy sugar nucleosides of 5-ethylpyrimidine, i.e., i) 1-(2-hydroxyethoxymethyl), 1-(2-methoxyethoxymethyl), and 1-ethoxyethyl derivatives of 5-ethyl-uracil and 5-ethylcytosine, ii) 5-ethyl-1-(tetrahydro-2H-pyran-2-yl)- and -1-(tetrahydrofuran-2-yl)uracils, and iii) 5-ethyl-2′-deoxyuridine.     

New water-soluble hydrogen donors for the enzymatic spectrophotometric determination of hydrogen peroxide

Eight N -alkyl-N-V-sulphopropylaniline derivatives have been synthesized and assessed as water-soluble hydrogen donors for the spectrophotometric determination of hydrogen peroxide in the presence of peroxidase. The sodium salts of N-ethyl-N-sulphopropylaniline (ALPS), N-ethyl-N-sulphopropyl-m-toluidine (TOPS) and N -ethyl-N-sulphopropyl-m-anisidine (ADPS) are recommended. They have excellent water solubilities, and the optimum pH range for oxidative condensation with 4-aminoantipyrine in the presence of hydrogen peroxide and peroxidase is 5.5–9.5. The absorbances of the resulting chromogens are 2–3 times higher than that achieved with phenol. The molar absorptivities of the chromogens with 4-aminoantipyrine are 41300 (ALPS, λ_max 561 nm), 37400 (TOPS, λ_max 550 nm) and 27900 (ADPS, λ_max 540 nm). Calibration graphs for the determination of hydrogen peroxide in the presence of a control serum are linear for 7–40 × 10^-6 mol H₂O₂ l^-1.     

Characterization of the molecular reorientational dynamics of the neat ionic liquid 1-butyl-3-methylimidazolium bromide in the super cooled state using 1H and 13C NMR spectroscopy

The (13)C spectra and (13)C longitudinal relaxation times (T(1)) were measured to investigate the segmental motion of the neat ionic liquid 1-butyl-3-methylimidazolium bromide ([bmim]Br) in the super cooled state. The (13)C signals of the imidazole ring significantly broadened at 283 K, whereas many other signals were unchanged. In the process of lowering temperature, the [bmim]Br changed to the solid state at ca 273 K without showing the rapid phase transition. Only the (13)C signal of the terminal methyl group in the butyl chain was still observed at 263 K, indicating that the motion of the imidazole ring was extremely restricted, whereas the methyl group in the butyl chain was active even in the solid state. The (13)C-T(1) values measured as a function of temperature also supported the discrete segmental motions of the [bmim](+) cation.     

Thiol addition to t-butyl methyl squarate. Efficient synthesis of novel sulfur-linked squaryl group-containing glutamate analogs

Novel sulfur-linked squaryl group-containing glutamate analogs were synthesized via addition and mono-substitution reactions of thiols to t-butyl methyl squarate (BMSQ: 7) in two steps. A glutamate analog prepared from Boc-l-Cys showed a potent binding affinity to KA/AMPA receptors.