Differentiating Abeta40/42 in plaques with small molecule fluorescent probes

淀粉样β蛋白(Aβ)斑块是阿尔茨海默病最显著的形态特征之一 (Ad)。在过去的几十年里，β斑块对AD患者整体认知能力下降的作用一直存在争议 广泛地。尸检研究表明，斑块的丰度与高血压的严重程度没有很强的相关性。 零星的AD。相反，临床前研究提供了强有力的证据，证明斑块是明确的病理部位。 并与营养不良的神经突起、树突棘的丧失和神经细胞的快速死亡有关 周围的环境。在斑块中，A40和A42是主要成分。尽管如此，与这个角色不同的是 在斑块方面，几乎没有人认为A42的神经毒性比A40高得多。可想而知， 区分A40和A42可以很好地阐明斑块在AD病理中的作用。 长期以来，区分A40和A42一直被认为是小分子探测器不可能完成的任务， 由于这些多肽的氨基酸序列差异很小。很明显，A的C末端 多肽是设计小分子探针区分它们的关键，因为两者唯一的区别是 氨基酸(异亮氨酸-丙氨酸)位于A40/42肽的C末端。没有事先知道的 教我们如何设计这样的探头。尽管如此，常规使用抗A42抗体进行治疗 测定细胞培养液和脑提取液中A42的含量。这些抗A42抗体是设计的 根据该多肽的C-末端的表位。这一事实使我们相信， 我们可以依靠C端来设计我们的小分子探针。在过去，全长的X射线结构 一个S是罕见的。然而，最近先进的低温电磁技术令人印象深刻地促进了结构 学习。在我们的初步结果中，基于C终端的独特环境，我们设计了小型- 能在体外和脑内光谱分辨A40/42的分子荧光探针ICTAD-1 幻灯片。在这项提案中，我们计划设计新的探针并验证它们区分A40/42的能力。

Amyloid beta (Aβ) plaques constitute one of the most distinctive morphological hallmarks of Alzheimer’s disease (AD). In the past decades, the contribution of Aβ plaques to the overall cognitive decline in AD has been debated extensively. Postmortem studies suggest that plaque abundance does not correlate strongly with the severity of sporadic AD. Conversely, preclinical studies provide strong evidence that plaques are clear sites of pathology and are associated with dystrophic neurites, the loss of dendritic spines and rapid neuron cell death in their surroundings. In the plaques, A40 and A42 peptides are the major constituents. Nonetheless, unlike the role of plaque, there is nearly no argument that A42 has a much higher neurotoxicity than A40 does. Conceivably, differentiating A40 and A42 can considerably clarify the role of plaque in AD pathology. Differentiating A40 and A42 has long been considered as an impossible mission with small-molecule probes, due to the small difference in the amino acid sequence of the peptides. It is obvious that the C-terminal of A peptide is the key for designing small-molecule probes to distinguish them, because the only difference of two amino acids (isoleucine-alanine) is within the C-terminals of A40/42 peptides. There is no prior knowledge to teach us how to design such probes. Nonetheless, it has been routinely performed with anti-A42 antibodies to determine the contents of A42 in cell media and brain extracts. These anti-A42 antibodies were designed based on the epitope of the C-terminal of the peptide. This fact has bolstered us to believe that the properties of the C-terminal can be relied on to design our small molecule probes. In the past, X-ray structures of full-length As were rare. However, recently the advanced Cryo-EM technology has impressively facilitated A structure studies. In our preliminary results, based on the unique environment of the C-terminal, we designed small- molecule fluorescence probe ICTAD-1 that has the capacity to spectrally differentiate A40/42 in vitro and brain slides. In this proposal, we plan to design new probes and validate their capacity for differentiating A40/42.