Copper is involved in Alzheimer’s disease (AD) where it appears to affect the aggregation of amyloid-β (Aβ) and to catalyze the production of reactive oxygen species (ROS). Oxidative stress apparently produces Aβ dimers that are covalently linked through two tyrosine residues. Such dityrosine cross-links are considered as potential markers of the disease and seem to be implicated in the pathological disorder. In the present study, pure o,o′-dityrosine (diY) was prepared enzymatically (with horseradish peroxidase; HRP), which was subsequently used to construct calibration lines aimed at quantifying nanomolar amounts of diY in reaction mixtures by fluorescence spectroscopy. Hence, diY concentrations down to 67 nM could be determined, which allowed to find that ca. 3% of dityrosine-bridged dimers of Aβ(1–40) were produced after 3 days at 37 °C in the presence of copper and dihydrogen peroxide. These cross-linked dimers in the presence of copper(II) ions completely inhibit the typical aggregation of Aβ, since β sheets could not be detected applying the usual Thioflavin T (ThT) method. Furthermore, the use of a potent Cu(II) chelator, such as the ATCUN tripeptide, l-histidyl-l-alanyl-l-histidine (HAH), efficiently prevented the copper-mediated generation of ROS and the associated dityrosine-bridged Aβ dimers, suggesting that such metal chelators may find future applications in the field of anti-AD drug design.

中文翻译：

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铜，二酪氨酸交联和β淀粉样蛋白聚集。

铜与阿尔茨海默氏病（AD）有关，在铜中似乎会影响β淀粉样蛋白（Aβ）的聚集并催化活性氧（ROS）的产生。氧化应激显然产生通过两个酪氨酸残基共价连接的Aβ二聚体。这种二酪氨酸交联被认为是该疾病的潜在标志物，似乎与病理性疾病有关。在本研究中，纯Ò，ö以酶法（用辣根过氧化物酶； HRP）制备'-二酪氨酸（diY），随后将其用于构建校准线，旨在通过荧光光谱法定量反应混合物中diY的纳摩尔量。因此，可以确定低至67 nM的diY浓度，从而可以找到该浓度。在铜和过氧化氢存在下，在37°C下放置3天后，生成3％的Aβ（1–40）的二氢酪氨酸桥联二聚体。这些交联的二聚体在存在铜（II）离子的情况下完全抑制了Aβ的典型聚集，因为使用常规的硫黄素T（ThT）方法无法检测到β片。此外，使用一种强效的Cu（II）螯合剂，如ATCUN三肽，升-histidyl-升-alanyl-升-组氨酸（HAH）有效地阻止了铜介导的ROS的产生和相关的二氢酪氨酸桥联的Aβ二聚体，这表明这种金属螯合剂可能会在抗AD药物设计领域中找到未来的应用。