The Zn(II) ion has been linked to Alzheimer’s disease (AD) due to its ability to modulate the aggregating properties of the amyloid-β (Aβ) peptide, where Aβ aggregation is a central event in the etiology of the disease. Delineating Zn(II) binding properties to Aβ is thus a prerequisite to better grasp its potential role in AD. Because of (i) the flexibility of the Aβ peptide, (ii) the multiplicity of anchoring sites, and (iii) the silent nature of the Zn(II) ion in most classical spectroscopies, this is a difficult task. To overcome these difficulties, we have investigated the impact of peptide alterations (mutations, N-terminal acetylation) on the Zn(Aβ) X-ray absorption spectroscopy fingerprint and on the Zn(II)-induced modifications of the Aβ peptides’ NMR signatures. We propose a tetrahedrally bound Zn(II) ion, in which the coordination sphere is made by two His residues and two carboxylate side chains. Equilibria between equivalent ligands for one Zn(II) binding position have also been observed, the predominant site being made by the side chains of His6, His13 or His14, Glu11, and Asp1 or Glu3 or Asp7, with a slight preference for Asp1.

The adsorption of iron(III) and manganese(II) onto lignin extracted from wheat straw was investigated at 20 °C using batch adsorption experiments. Two solid substrates were studied : the Ligno-cellulosic Substrate (LS), which resulted from successive acido-basic treatments, and the Cell Wall Residue substrate (CWR), which was obtained by solvent extraction. Comparisons between these two lignin-containing substrates were made. Experiments were conducted as a function of the pH for a wide range of metal concentrations. The percentage of metal adsorbed increased with the pH and the results indicate that Fe(III) was strongly adsorbed at low pH (<3) while Mn(II) formed far less stable surface complexes from pH = 8.0. Moreover, in contrast to Fe(III), Mn(II) adsorption was significantly affected by the presence of calcium and carbonate, which are abundant ions in the soils of the Champagne-Ardenne region. The presence of calcium ions decreased the manganese adsorption by 25% to 40%. EPR spectroscopy was used to investigate the geometrical environment of the metal in the surface complexes. As the metal was adsorbed, redox processes took place, which could be observed by the change in the amount of quinonic species present in the lignin surface. Then, the evolution of quinonic species amount as a function of the metal concentration was examined by EPR measurements considering the signal centred at g = 2.0025. Mechanisms involved in the electronic transfer between the metal ion and the surface organic radicals are discussed.

Reaction of hydrated copper(II) ibuprofenate with various nitrogen donor ligands, β-picoline, γ-picoline, pyrrolidine and unsymetrical dimethyl ethylenediamine (unsym-dmen), at room temperature in a methanol : water mixture (4 : 1 v/v) yielded four new complexes, [Cu(Ibu)₂(β-picoline)₂(H₂O)], 1; [Cu(Ibu)₂(γ-picoline)₂(H₂O)]·H₂O, 2; [Cu(Ibu)₂(pyrrolidine)₂]·H₂O, 3; and [Cu(unsym-dmen)₂(H₂O)](Ibu)₂, 4, respectively, where Ibu = deprotonated Ibuprofen (HIbu). The newly synthesized complexes have been characterized by elemental analyses, spectroscopic methods (FT-IR, UV-Vis and EPR), TGA and single crystal X-ray structure determination. Crystallographic investigations revealed that all the complexes are monomeric in nature, in contrast to the dimeric nature of copper(II) ibuprofenate solvates. EPR studies clearly revealed that the chromophore present in all complexes (1–4) is consistent with the structures determined by X-ray crystallography. The cytotoxic effects of all complexes were tested by a colorimetric assay on three human cell lines; though the activity was affected by the nature of the cell line, the newly synthesized complexes 1–4 showed higher cytotoxicity than the parent molecule against all the tumoral cell lines.