1,721,094 research outputs found
Iron(III) complexing ability of carbohydrate derivatives
No full textA solution study on the coordinative ability of galactaric acid (GalAH(2)), D-glucosamine (GlcN) and D-glucosaminic acid (GlcNAH) toward Fe3+ ion is reported. UV spectroscopic study provides useful information to identify complex species formation and their stability constants are determined by means of potentiometric measurements. GalAH(2) behaves as chelating ligand through carboxylic oxygen and alpha-hydroxylic oxygen in the protonated or dissociated form depending on pH value. Two complex species [Fe(2)GalA(OH)(4)] and Na[FeGalAH(-2)](.)2H(2)O are also isolated in the solid state and characterised through IR spectroscopy. Glc-NAH also binds the Fe3+ ion through carboxylic and hydroxylic groups, while NH2 group is probably involved in metal coordiantion up to pH 4. GlcN demonstrates low ligating ability at acidic pH and does not prevent metal hydroxyde precipitation
Characterization and metal affinity of Tirofiban, a pharmaceutical compound used in acute coronary syndromes
No full textThe crystal and molecular structure of Tirofiban [ N-(n-butanesulfonyl)-O-(4-(4-piperidinyl)-butyl)-(S)-tyrosine] is here reported. In the solid state the carboxylic group is in the anionic form while the piperidine molecule appear in the protonated form. By H NMR spectroscopy and potentiometric study three pK(a) are found: pKa(COOH) = 3.1(1), pKa(NHPIP) = 11.6(1) and pKa(NHSO2) = 13.8(1). The complexing ability of Tirofiban towards various metal ions (Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Zn(II) and Ca(II)) is also determined by means of potentiometric studies. The prevailing species are [M(TirH)(2)](2+) where the ligand coordinates the metal ion through carboxylic group, while the piperidine nitrogen is still protonated. The great stability of these complexes may be due to the presence of hydrogen bond interactions, as well as the formation of stacking interactions involving the phenyl ring of the tyrosine residue
Characterization and Metal affinity of tyrofiban®, a pharmaceutical compound used in acute coronary syndromes
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Co-ordination of transition metal ions by galactaric acid: a potentiometric and spectroscopic study
No full textA solution study on the ability of galactaric acid [GalaH(2), HOOC(CH)(4) COOH] in the complexation of biological metal ions such as Co(II) and Ni(II) and toxic metal ions such as Cd(II), Pb(II) and Hg(II), is reported. The stability constants of the complex species are determined by means of potentiometric measurements. Galactaric acid behaves as chelate ligand through carboxylic oxygen and alpha-hydroxy group towards Co(II) and Ni(II), while in the Pb(II) and Cd(II) containing system it co-ordinates the metal ion with carboxylic oxygen and two alcoholic hydroxy groups. The prevailing species at acidic or neutral pH is [MGala] which is also isolated in the solid state and characterized by means of IR spectroscopy. On increasing pH, the [MGalaH_(1)](-) species is also formed where the co-ordinated OH group undergoes deprotonation in all metal ion complexes except those with Hg(II), where the co-ordination of hydroxide ion is suggested as the precipitation of the metal hydroxide occurs at pH 7. (C) 2002 Elsevier Science Inc. All rights reserved
Synthesis and characterization of new glycosyl-curcuminoids ligands with iron(III) chelating ability
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Il gioco degli scacchi. Il tempo dell'autorevolezza del Sé.
No full textQuesto scritto offre una lettura psicodinamica riguardo al gioco degli scacchi all’interno del contesto terapeutico. Lo scopo è di aggiungere alcuni elementi di riflessione teorica e clinica e di promuovere la comprensione del giovane paziente. Infatti, attraverso il gioco degli scacchi nella seduta di psicoterapia, il preadolescente e l’adolescente possono rappresentare il loro personale modo di gestire la realtà, muovendo sulla scacchiera i diversi pezzi con schemi che riflettono le proprie dinamiche interne. Da un punto di vista psicodinamico, la scacchiera può divenire il luogo in cui i giocatori e il loro spazio emozionale si incontrano ed entrano in relazione. I diversi psicoanalisti che si sono interessati al gioco degli scacchi hanno illustrato alcuni concetti utili per la conoscenza psicologica della persona. A partire dai diversi riferimenti storici sulla origine degli scacchi, sono stati presi in considerazione i ruoli e i significati dei singoli pezzi della scacchiera, alcuni stili di gioco e le strategie prevalenti utilizzate dai giocatori. Il gioco degli scacchi può rivelare il modo in cui il giovane mette in gioco la propria mente, la propria autonomia ed energia aggressiva, e questo può essere uno spunto di riflessione nell'ambito della clinica psicoterapeutica
NMR study on Pt(II) interaction with Amadori compounds
No full textAbstractHere we report the first evidence of Pt(II) interaction with Amadori compound [N-(1-deoxy-d-Fructos-1-yl)glycine (Fru-Hgly)]. The 1H and 195Pt NMR results show that complexation of Pt(II) by Fru-Hgly is strongly dependent on pH and reaction molar ratio. In 1/1 Pt/Fru-Hgly molar ratio, at acidic pH, the first coordination site is the carboxylic oxygen, while at physiological pH the anchoring group is the aminic one, in both cases the system slowly evolves towards an N,O chelating mode. In 1/2 Pt/Fru-Hgly molar ratio the only coordination site is nitrogen atom while the carboxylic oxygen is not involved in metal coordination
Amide group coordination to the Hg2+ ion. Potentiometric, 1H NMR and structural study on Hg2+-N-protected amino acid systems
No full textThe binary complexes of Hg2+ formed by N-carbonyl and N-sulfonyl amino acids, which are ligands containing peptide and sulfonamide groups respectively, are investigated in aqueous solution by H-1 NMR, UV spectroscopy and potentiometry. The corresponding ternary systems with 2,2'-bipyridine are studied in aqueous solution by potentiometry and in DMSO solutions by H-1-NMR. All the amino acids behave as simple carboxylate ligands at acid pH, while, around neutrality, N-p-tolylsulfonylglycine (tsglyH(2)), N-p-tolylsulfonyl-beta -alanine (ts-beta -alaH(2)) and N-2-nitrophenylsulfonylglycine (NO(2)psglyH(2)) switch to dianionic N,O-bidentate chelating ligands due to the involvement of the deprotonated amide nitrogen as an additional donor site. The Hg2+ ion is ineffective in promoting peptide nitrogen deprotonation in N-benzoylglycine (bzglyH). The binary and ternary species formed in aqueous solution and their stability constants are determined and compared with those of the homologous complexes of Pd2+, Cu2+, Cd2+ and Pb2+. The molecular structure of [Hg(bpy)(2)(NO2-psgly-N,O)].0.5H(2)O is determined by X-ray crystallography. It represents a rare example of Hg2+ N,O coordination by an amino acid molecule. In the complex Hg2+ shows a distorted octahedral environment with a N5O donor set. Four nitrogen atoms are derived from the two bpy ligands, while the oxygen and the fifth nitrogen are from the NO2-psgly dianion. New information on the solution and solid state chemistry of Hg2+ with ligands of biological interest is provided which may be of great relevance in understanding the mechanism of metal toxicity
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