Department of Medical Chemistry, University of Szeged, Szeged, Hungary.
Peptides. 2010 Feb;31(2):248-56. doi: 10.1016/j.peptides.2009.12.001. Epub 2009 Dec 6.
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.
β-淀粉样蛋白（Aβ）肽在阿尔茨海默病（AD）的神经退行性变病理中起着至关重要的作用。生物实验（包括 AD 的体外实验和动物模型研究）需要具有标准质量、聚集度、神经毒性和水溶性的合成 Aβ肽。由于 Aβ肽具有疏水性、较差的溶解性和高聚集倾向，因此其合成一直具有难度。最近，通过 Fmoc 化学合成了一种异肽前体（iso-Aβ（1-42）），并在中性 pH 下通过 O→N 酰基迁移在短时间内转化为 Aβ（1-42）。我们使用 Boc 化学合成了相同的前体肽，并研究了通过酰基迁移转化为 Aβ（1-42）的过程。通过几种方法（圆二色性、原子力和透射电子显微镜、动态光散射）研究了肽的构象和聚集过程。通过离体（大鼠海马切片的长时程增强研究）和体内实验（大鼠空间学习）测量了合成的 Aβ（1-42）的生物学活性。结果证明，前体异肽的 O→N 酰基迁移导致具有神经毒性的水溶性 Aβ（1-42）低聚物混合物的形成。这些低聚物在进行生物学实验之前原位形成，并且可以标准化其聚集度。
