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The region 1–16 of the amyloid-β peptides associated with Alzheimer’s disease can be considered as the metal-binding domain, and the residues His6, His13, and His14 have been identified as ligands that coordinate heavy metal ions. To establish the role played by the three histidine residues of the Aβ(1–16) sequence in binding metal ions, two variants of Aβ(1–16) peptide fragment (H-1DAEFRHDSGYEVHHQK16-NH2) were synthesized by Fmoc/tBu Solid Phase Peptide Synthesis strategy and purified by RP-HPLC. The three histidine residues were replaced by either three serine residues to form Ser-Aβ(1–16): H-1DAEFRSDSGYEVSSQK16-NH2 or three alanine ones to form Ala–Aβ(1–16): H-1DAEFRADSGYEVAAQK16-NH2. The three peptides were comparatively characterized by mass spectrometry (MS), circular dichroism spectroscopy (CD) and atomic force microscopy (AFM), being subsequently used to study their interaction with metal ions at various pH values. During our experiments, significant pH-dependent changes in the conformation of these peptides have been observed and reported. AFM images showed dramatic changes in the film morphology of peptides upon binding metal ions. In the MS spectra we have unambiguously identified several metal–peptide molecular ions, thus confirming the affinity of Aβ(1–16) peptides to copper and nickel ions. The newly synthesized peptides may bring new evidence on the relationship of histidine residues in amyloid-β peptides with metal ions. In addition, new directions for research and experimental works are suggested.

Aluminium (Al) is clearly neurotoxic and considerable evidence exists that Al may play a role in the aetiology or pathogenesis of Alzheimer&rsquo, s disease (AD). Nevertheless, the link between AD pathology and Al is still open to debate. Therefore, we investigated here the interaction of aluminium ions with two A&beta, peptide fragments and their analogues. First, we synthesised by the Fmoc/tBu solid-phase peptide synthesis (SPPS) strategy using an automated peptide synthesiser two new peptides starting from the A&beta, (1&ndash, 16) native peptide fragment. For this purpose, the three histidine residues (H6, H13, and H14) of the A&beta, 16) peptide were replaced by three alanine and three serine residues to form the modified peptides A&beta, 16)A36,13,14 and A&beta, 16)S36,13,14 (primary structures: H-1DAEFRADSGYEVAAQK16-NH2 and H-1DAEFRSDSGYEVSSQK16-NH2). In addition, the A&beta, (9&ndash, 16) peptide fragment (H-9GYEVHHQK16-NH2) and its glycine analogues, namely A&beta, 16)G110, (H-9GGEVHHQK16-NH2), A&beta, 16)G213,14 (H-9GYEVGGQK16-NH2), and A&beta, 16)G310,13,14 (H-9GGEVGGQK16-NH2), were manually synthesised in order to study Al binding to more specific amino acid residues. Both the peptides and the corresponding complexes with aluminium were comparatively investigated by mass spectrometry (MS), circular dichroism spectroscopy (CD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). Al&ndash, peptide molecular ions and Al-fragment ions were unambiguously identified in the MS and MS/MS spectra. AFM images showed dramatic changes in the film morphology of peptides upon Al binding. Our findings from the investigation of N-terminal 1-16 and even 9-16 normal and modified sequences of A&beta, peptides suggest that they have the capability to be involved in aluminium ion binding associated with AD.

The octapeptide NAP (NAPVSIPQ) is a small sequence from the activity-dependent neuroprotective protein (ADNP), which is able to provide neuroprotection against Aβ toxicity even at low concentration. NAP provides protection against oxidative stress to brain cells and stimulates neurite outgrowth providing a neurotrophic and neuroprotective function. Therefore, we have investigated copper and silver binding to two NAP-like peptides, since our previous research revealed unexpected iron binding to such peptides. Here, we report on Cu(I) and Ag(I) binding to NAP and its Cys5 mutant. Our results revealed that NAP bind up to two silver ions but only one of copper as shown by Fourier transform infrared (FTIR) spectroscopy and MALDI-ToF mass spectrometry (MS). Surprisingly, its Cys5 mutant can bind four silver ions or three of copper, despite the fact that it is a small peptide molecule. The results were discussed in the view of NAP protection against Aβ induced neurotoxicity associated with Alzheimer disease (AD) and the relationship between Aβ peptides and heavy metal ions.

We explore the chemical space of Pseudomonas quinolone signal analogs as privileged structures and report the discovery of a thioquinolone as a potent inhibitor of the important virulence factor elastase of the human pathogen Pseudomonas aeruginosa. We provide evidence that the derivative binds to the active site zinc of elastase and additionally acts as a fluorescent zinc sensor. published