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The interaction between Cu(ii) and the rat amyloid β (1–28) fragment in micellar solutions at pH 7.5 was investigated by CD and NMR spectroscopy; the proton–copper distances were used in restrained molecular dynamics simulations to obtain a structural model of the Cu(ii) complex. [ABSTRACT FROM AUTHOR]

The interaction between metal ions and nucleotides is well characterized, as is their importance for metabolic processes, e.g. in the synthesis of nucleic acids. Hence, it is surprising to find that no detailed comparison is available of the metal ion-binding properties between nucleoside 5′-phosphates and 2′-deoxynucleoside 5′-phosphates. Therefore, we have measured here by potentiometric pH titrations the stabilities of several metal ion complexes formed with 2′-deoxyadenosine 5′-monophosphate (dAMP2−), 2′-deoxyadenosine 5′-diphosphate (dADP3−) and 2′-deoxyadenosine 5′-triphosphate (dATP4−). These results are compared with previous data measured under the same conditions and available in the literature for the adenosine 5′-phosphates, AMP2−, ADP3− and ATP4−, as well as guanosine 5′-monophosphate (GMP2−) and 2′-deoxyguanosine 5′-monophosphate (dGMP2−). Hence, in total four nucleotide pairs, GMP2−/dGMP2−, AMP2−/dAMP2−, ADP3−/dADP3− and ATP4−/dATP4− (= NP/dNP), could be compared for the four metal ions Mg2+, Ni2+, Cu2+ and Zn2+ (= M2+). The comparisons show that complex stability and extent of macrochelate formation between the phosphate-coordinated metal ion and N7 of the purine residue is very similar (or even identical) for the AMP2−/dAMP2− and ADP3−/dADP3− pairs. In the case of the complexes formed with ATP4−/dATP4− the 2′-deoxy complexes are somewhat more stable and show also a slightly enhanced tendency for macrochelate formation. This is different for guanine nucleotides: the stabilities of the M(dGMP) complexes are clearly higher, as are the formation degrees of their macrochelates, than is the case with the M(GMP) complexes. This enhanced complex stability and greater tendency to form macrochelates can be attributed to the enhanced basicity (ΔpKaca. 0.2) of N7 in the 2′-deoxy compound. These results allow general conclusions regarding nucleic acids to be made. [ABSTRACT FROM AUTHOR]

Waglerin I is a 22 amino acid snake venom toxin. Its three fragments (GGKPDLRPCHP-NH2, PCHYIPRPKPR-NH2, PCHPPCHYIPR-NH2), due to the presence of two Cys and His residues, are potentially very attractive ligands for transition metal ions. The main aim of this work was to establish the impact of these two adjacent residues on Ni2+ ion binding, especially because this kind of motif is very common in nature, and the study of low molecular weight models could be helpful in understanding larger systems. In this work waglerin fragments and their N-protected analogues were studied with Ni2+ (and Cu2+ for peptides with disulfide bridges) ions using combined potentiometric and spectroscopic measurements (UV-Vis, CD, EPR and NMR). In all peptides, except PCHPPCHYIPR-NH2 with a disulfide bridge, the Cys–His motif was found to be crucial for the coordination of Ni2+ ions. In the case of the N-unprotected analogues, the N-terminal amino group participates in the coordination as well. [ABSTRACT FROM AUTHOR]

The synthesis and description of eight polymeric complexes formed by transition metals with the bifurcated ligand bis(3,5-dimethyl-1H-pyrazolyl)selenide are discussed together with X-ray crystal analysis as well as variable temperature magnetic susceptibility and characterization by Mössbauer spectroscopy. Preferable types of binding patterns of the ligand were determined, which include a variation of the bridging modes (cis- and trans-) and of the separation length, where the latter parameter together with bending of the ligand molecule were found to be dependent on the type of co-ordination geometry of the central atom and the nature of the anion. A strategy for increasing the structure dimensionality was explored using bridging properties of anions yielding 2D hybrid organic-inorganic polymers. [ABSTRACT FROM AUTHOR]