Interaction of beta-amyloid(1-40) peptide with pairs of metal ions : an electrospray ion trap mass spectrometric model study
2009, Drochioiu, Gabi, Manea, Marilena, Drăguşanu, Mihaela, Murariu, Manuela, Dragan, Ecaterina Stela, Petre, Brînduşa-Alina, Mezö, Gábor, Przybylski, Michael
The stoichiometries and the affinity toward simple and paired metal ions of synthetic amyloid-β(1-40) peptide (Aβ1-40) were investigated by electrospray ion trap mass spectrometry (ESI-MS), circular dichroism (CD), and atomic force microscopy (AFM). The results lead to the working hypothesis that pH-dependent metal binding to Aβ1-40 may induce conformational changes, which affect the affinity toward other metals. A significant copper and zinc binding to Aβ1-40 peptide at pH 5.5 was found, whereas nickel ions commonly bind to each molecule of β-amyloid peptide. Some complexes of Aβ1-40 with more than one nickel ion were identified by ESI-MS. In addition, nickel ions proved to enhance Aβ oligomerization. On increasing pH, up to 12 ions of zinc may bind to a single Aβ molecule. Under the same pH and concentration conditions, the binding pattern of the independent copper and silver ions to Aβ1-40 was different from that of the equimolecular mixture of the two metal ions. One might assume that some conformational changes due to water loss altered the capacity of Aβ peptide to bind certain heavy metal ions. As a consequence, copper silver interaction with the binding process to Aβ1-40 became highly complex. A competition between silver and nickel ions for Aβ1-40 binding sites at high pH was also observed. New strategies were proposed to identify the characteristic signals for some important metal ion peptide complexes in the spectra recorded at high pH or high concentrations of metal ions. To explain the formation of such a large number of high metal ion Aβ complexes, we took into consideration the participation of both histidine residues and free amino groups as well as carboxylate ones in the binding process. Finally, CD and AFM studies supported the mass spectrometric data.
Synthesis and characterization of a nonapeptides with specific properties for Cu binding
2007, Drochioiu, Gabi, Murariu, Manuela, Petre, Brînduşa-Alina, Manea, Marilena, Przybylski, Michael
A nonapeptide with the following sequence of amino acid residues CHQYHHNRE has been synthesized and characterized. The peptide is useful to investigate the binding of copper ions to histidine-containing peptides and proteins. It was synthesised manually by Solid Phase Peptide Synthesis (SPPS) using Fmoc protection strategy. The peptide was subjected to final purification by Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) and characterised by matrix assisted laser desorption ionization with time of flight mass spectrometry (MALDI-TOF MS). The GPMAW 6.11 (General Protein/Mass Analysis for Window) program was used for theoretical characterization of the peptide.