Controlled in situ preparation of A beta(1-42) oligomers from the isopeptide "iso-A beta(1-42)", physicochemical and biological characterization.
ABSTRACT Beta-amyloid (A beta) peptides play a crucial role in the pathology of the neurodegeneration in Alzheimer's disease (AD). Biological experiments (both in vitro and animal model studies of AD) require synthetic A beta peptides of standard quality, aggregation grade, neurotoxicity and water solubility. The synthesis of A beta peptides has been difficult, owing to their hydrophobic character, poor solubility and high tendency for aggregation. Recently an isopeptide precursor (iso-A beta(1-42)) was synthesized by Fmoc-chemistry and transformed at neutral pH to A beta(1-42) by O-->N acyl migration in a short period of time. We prepared the same precursor peptide using Boc-chemistry and studied the transformation to A beta(1-42) by acyl migration. The peptide conformation and aggregation processes were studied by several methods (circular dichroism, atomic force and transmission electron microscopy, dynamic light scattering). The biological activity of the synthetic A beta(1-42) was measured by ex vivo (long-term potentiation studies in rat hippocampal slices) and in vivo experiments (spatial learning of rats). It was proven that O-->N acyl migration of the precursor isopeptide results in a water soluble oligomeric mixture of neurotoxic A beta(1-42). These oligomers are formed in situ just before the biological experiments and their aggregation grade could be standardized.
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ABSTRACT: In recent years, small protein oligomers have been implicated in the aetiology of a number of important amyloid diseases, such as type 2 diabetes, Parkinson's disease and Alzheimer's disease. As a consequence, research efforts are being directed away from traditional targets, such as amyloid plaques, and towards characterization of early oligomer states. Here we present a new analysis method, ion mobility coupled with mass spectrometry, for this challenging problem, which allows determination of in vitro oligomer distributions and the qualitative structure of each of the aggregates. We applied these methods to a number of the amyloid-β protein isoforms of Aβ40 and Aβ42 and showed that their oligomer-size distributions are very different. Our results are consistent with previous observations that Aβ40 and Aβ42 self-assemble via different pathways and provide a candidate in the Aβ42 dodecamer for the primary toxic species in Alzheimer's disease.Nature Chemistry 07/2009; 1(4):326-31. · 21.76 Impact Factor
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ABSTRACT: A novel water-soluble isopeptide of Alzheimer's disease-related peptide Aβ1-42, `26-O-acyl isoAβ1-42', which could efficiently convert to intact Aβ1-42 under physiological conditions via O–N intramolecular acyl migration, was synthesized providing a new system useful for investigation of biological function of Aβ1-42.Tetrahedron Letters - TETRAHEDRON LETT. 01/2004; 45(31):5965-5968.
- Journal of The American Chemical Society - J AM CHEM SOC. 01/2005; 127(34):11888-11889.