Aluminium Binding to Modified Amyloid-ß Peptides: Implications for Alzheimer's Disease.

Aluminium (Al) is clearly neurotoxic and considerable evidence exists that Al may play a role in the aetiology or pathogenesis of Alzheimer'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 Aß 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 Aß(1-16) native peptide fragment. For this purpose, the three histidine residues (H6, H13, and H14) of the Aß(1-16) peptide were replaced by three alanine and three serine residues to form the modified peptides Aß(1-16)A36,13,14 and Aß(1-16)S36,13,14 (primary structures: H-1DAEFRADSGYEVAAQK16-NH2 and H-1DAEFRSDSGYEVSSQK16-NH2). In addition, the Aß(9-16) peptide fragment (H-9GYEVHHQK16-NH2) and its glycine analogues, namely Aß(9-16)G110, (H-9GGEVHHQK16-NH2), Aß(9-16)G213,14 (H-9GYEVGGQK16-NH2), and Aß(9-16)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-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 Aß peptides suggest that they have the capability to be involved in aluminium ion binding associated with AD.

Stoichiometry of Heavy Metal Binding to Peptides Involved in Alzheimer's Disease: Mass Spectrometric Evidence.

Mass spectrometry is a powerful analytical technique becoming increasingly important in different biomedical research area. Mass spectrometric based methods were developed and applied to detect and identify multiple metal ion complexes of peptides and proteins with high sensitivity and high mass accuracy. Aggregation of amyloid-ß (Aß) peptides is one of the main pathological features of Alzheimer's disease (AD), and some metal ions seem to play a key role in AD pathogenesis. Consequently, mass spectrometry was used to investigate heavy metal binding to AD-related peptides. Therefore, the purpose of this chapter is to review the methodology and application of identifying coordination chemistry and binding properties of several metal ion-binding sites to synthetic ß-amyloid (Aß) and anti-amyloid model peptides. The selective metal-amyloid-ß peptide interaction studies using (a) Matrix-assisted laser desorption/ionization mass spectrometry (MALDI); (b) Electrospray ionization mass spectrometry (ESI-MS), and (c) Tandem mass spectrometry (MS/MSn) will be reported.

Synthetic quinolone signal analogues inhibiting the virulence factor elastase of Pseudomonas aeruginosa.

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.