Revisiting the hydrolysis of ampicillin catalyzed by Temoneira-1 β-lactamase, and the effect of Ni(II), Cd(II) and Hg(II).

β-Lactamases grant resistance to bacteria against β-lactam antibiotics. The active center of TEM-1 β-lactamase accommodates a Ser-Xaa-Xaa-Lys motif. TEM-1 β-lactamase is not a metalloenzyme but it possesses several putative metal ion binding sites.

Equilibria and Dynamics of Sodium Citrate Aqueous Solutions: The Hydration of Citrate and Formation of the NaCit Ion Aggregate.

Sodium citrate (NaCit) has a crucial role in many biological and industrial processes. Yet, quantitative information on its hydration and the ion association between Na and Cit ions in a broad range of salt concentrations is still lacking. In this work, we study both ion association equilibria and relaxation dynamics of sodium citrate solutions by combining potentiometry, spectrophotometry, and dielectric spectroscopy.

Magnesium(II) d-Gluconate Complexes Relevant to Radioactive Waste Disposals: Metal-Ion-Induced Ligand Deprotonation or Ligand-Promoted Metal-Ion Hydrolysis?

The complexation equilibria between Mg and d-gluconate (Gluc) ions are of particular importance in modeling the chemical speciation in low- and intermediate-level radioactive waste repositories. NMR measurements and potentiometric titrations conducted at 25 °C and 4 M ionic strength revealed the formation of the MgGluc, MgGlucOH, MgGluc(OH), and MgGluc(OH) complexes. The trinuclear species provides indirect evidence for the existence of multinuclear magnesium(II) hydroxido complexes, whose formation was proposed earlier but has not been confirmed yet.

The acidity and self-catalyzed lactonization of l-gulonic acid: Thermodynamic, kinetic and computational study.

Lactonization and proton dissociation of sugar acids take place simultaneously in acidic aqueous solutions. The protonation-deprotonation processes are always fast, whilst the formation and hydrolysis of γ- and δ-lactones are usually slower. Thus, both thermodynamic and kinetic information are required for the complete understanding of these reactions.

Configuration-dependent complex formation between Ca(II) and sugar carboxylate ligands in alkaline medium: Comparison of L-gulonate with D-gluconate and D-heptaguconate.

The calcium sugar carboxylate interactions in hyperalkaline solutions are of relevance in radioactive waste repositories and in certain industrial processes. The complex formation between L-gulonate and Ca ions was studied in strongly alkaline medium at 25 °C and 1 M ionic strength and was compared with previous results reported for D-gluconate and D-heptagluconate. The deprotonation of the ligand was confirmed by potentiometric and C NMR spectroscopic measurements.