Search

Abstract: In chiral separation, capillary electrophoresis (CE) is a leading technique and, due to the absence of any stationary phase, it is an all-in-solution process, thus allowing accurate study of separation mechanisms. This review focuses on the leading role played by knowledge of solution equilibria for a deep understanding of the phenomena involved in the chiral-discrimination mechanisms at a molecular level in chiral ligand-exchange CE. Speciation diagrams have been accurately calculated on the basis of the stability-constant values reported in the literature for the evaluation of the species present in solution and their concentrations. This analytical approach turned out to be very useful in understanding electrophoretic behavior and should be used systematically to predict and to optimize chiral separations. [Copyright &y& Elsevier]

The 3A-deoxy-3A-(2-methylaminopyridine)-2A(S),3A(R)-β-cyclodextrin (CDampy3) was synthesized and characterized by NMR spectroscopy. The proton and copper(II) complex formation and stability of this new β-cyclodextrin derivative were determined by potentiometric and calorimetric investigations, carried out in aqueous solution at 25 °C and I=0.1 mol dm−3 (KNO3). The ΔH° and ΔS° values allowed to bring to light the role of the hydrogen bond between the amine and the hydroxyl groups in the basicity decrease of NH group of this 3-functionalized β-cyclodextrin. The comparison between the log K values of copper(II) complexes with CDampy3 and those of 6-deoxy-6-(2-methylaminopyridine)-β-cyclodextrin (CDampy6) allowed to determine the donor atoms involved in the coordination to metal ion. The high stability constant of [Cu(CDampy3)]2+ in comparison with [Cu(CDampy6)]2+ was attributed to the involvement of the OH groups in the binding to copper(II) ion. [Copyright &y& Elsevier]

Abstract: Sulfonato groups were introduced into the backbone of a dipyridyl-based calixarene to obtain a novel water-soluble compound able to complex Co(II) and Cu(II). Spectrophotometric titrations pointed out that the new ligand complexes Co(II) and Cu(II) in water, but with stoichiometries and stabilities that are different from the analogous water insoluble calixarene. [Copyright &y& Elsevier]

Abstract: Potentiometric and spectroscopic (UV–Vis, CD and EPR) studies were carried out on copper(II) complexes with chicken prion protein N-terminal fragments, Ac-(PHNPGY)4-NH2, and the mutated residue, Ac-(PHNPGF)4-NH2, to assess the role of tyrosine in the copper coordination. Both thermodynamic and spectroscopic results indicate that chicken prion fragments are not able to bind more than two copper ions and only with the involvement of side chain tyrosine groups. The prevailing complex shows one copper ion bound to four imidazole nitrogen atoms in the 1:1 metal to ligand ratio systems. The superoxide dismutase (SOD)-like activity of copper(II) complexes with the avian peptides and mammal analogue, Ac-(PHGGGWGQ)4-NH2, was also investigated by means of Pulse radiolysis. The copper(II) complexes with avian peptides do not display SOD-like activity, while very low activity has been detected for the copper(II) complexes with mammalian tetraoctarepeat. [Copyright &y& Elsevier]

Abstract: The 3-hydroxy group of one glucopyranosinic ring of γ-cyclodextrin was selectively substituted with an amino moiety to obtain a new compound able to complex copper(II). Indeed, the new ligand, an altro-γ-CD, forms stable complexes with Cu(II), as the analogous 3-amino derivative β-CD previously exploited for the chiral separation of some amino acids by ligand exchange mechanism in capillary electrophoresis. Furthermore, the ligand forms a stable inclusion complex with anthraquinone-2-sulfonate. [Copyright &y& Elsevier]