Browsing by Author "Basagoitia, A"

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    Determination of the rates of formation and hydrolysis of the Schiff bases formed by pyridoxal 5'-phosphate with L-tryptophan and its methyl and n-butyl esters
    (2002) Gorostidi, GRE; Santos, JG; Basagoitia, A; Blanco, FG
    The apparent rate constants of the formation (k(1)) and hydrolysis (k(2)) of the Schiff bases formed by pyridoxal 5'-phosphate with L-tryptophan and their methyl and n-butyl esters at a variable pH, 25 degreesC, and an ionic strength of 0.1 M were determined, along with the equilibrium constant (K-pH). The individual rate constants of formation and hydrolysis of the Schiff bases of systems corresponding to different chemical species present in the medium as a function of its acidity were also determined, as were the pK values for the Schiff bases. The influence of the a-carboxyl group on the formation and hydrolysis constants of the Schiff bases, and also on their pK values, is demonstrated.
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    Kinetic study of the reaction of pyridoxal 5 '-phosphate with hydrazine
    (ELSEVIER SCIENCE BV, 1998) Gorostidi, GRE; Basagoitia, A; Blanco, JGS; Blanco, FG
    The kinetics of the reaction between pyridoxal 5'-phosphate (PLP) and hydrazine in aqueous solution at a variable pH and a constant strength of 0.1 M was studied spectrophotometrically. The rate constants of formation and hydrolysis of the resulting Schiff base and its stability were also determined in a wide range of pH. A comparison of the formation rate constants with those for the models of PLP with n-hexylamine and with poly-L-lysine revealed that hydrazine formed Schiff base more quickly than lysine below pH 7 and than n-hexylamine below pH 8. The reactivity shows the sequence poly-L-lysine > n-hexylamine > hydrazine in whole studied range of pH. Schiff bases formed by hydrazine with PLP are more stable than the ones formed by n-hexylamine in the pH range studied and more stable than the formed by poly-L-lysine at pH < 7.0. (C) 1998 Elsevier Science B.V.
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    Kinetic study of the reaction of pyridoxal 5 '-phosphate with hydrazino compounds of pharmacological activity
    (WILEY-V C H VERLAG GMBH, 1998) Echevarria Gorostidi, GR; Basagoitia, A; Pizarro, E; Goldsmid, R; Blanco, JGS; Blanco, FG
    The kinetics of the reaction between pyridoxal 5'-phosphate (PLP) with carbidopa, hydralazine, and isoniazid, in aqueous solution at variable pH and constant ionic strength of 0.1M was studied spectrophotometrically. The rate constants of formation and hydrolysis of the resulting Schiff base, and its stability were determined in a wide rang of pH. A comparison is made of the formation rate constants with those of PLP with hydrazine. The reactivity shows the sequence isoniazid > hydrazine > carbidopa > hydralazine in the whole range of pH studied. The Schiff bases studied are more stable than those formed by PLP and hexylamine and as stable as those described for the reactions of PLP with poly(L-lysine) or copolypeptides containing L-lysine.
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    Schiff bases of pyridoxal and polyallylamine. The formation rate determining step
    (JOHN WILEY & SONS INC, 1998) del Vado, MAG; Gorostidi, GRE; Basagoitia, A; Blanco, JGS; Blanco, FG
    The apparent rate constants of formation (k(1)) and hydrolysis (k(2)) of the Schiff bases formed between pyridoxal and polyallylamine has been fitted to a kinetic scheme that involve the different protonated species in the reaction medium and the individual rate constants of formation (k(1)(i)) and hydrolysis (k(2)(i)). The (k(1)(i)) values precludes an acid catalyzed intramolecular process. The effects of hydrophobic medium due to the presence of the macromolecule on the reaction is also discussed. (C) 1998 John Wiley & Sons, Inc.