College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, Shandong, 273165, People's Republic of China.
Henan Key Laboratory of Biomolecular Recognition and Sensing, College of Chemistry and Chemical Engineering, Shangqiu Normal University, Shangqiu, 476000, People's Republic of China.
Mikrochim Acta. 2021 Feb 23;188(3):98. doi: 10.1007/s00604-021-04736-x.
A dual channel method is described for the determination of the amyloid-β peptide Aβ(1-40) that is associated with Alzheimer's disease. The method exploits (a) conformational changes of a G-quadruplex that are triggered by Na and K ions and (b) the strong affinity between Aβ(1-40) and Cu. A G-quadruplex DNA forms an antiparallel structure in the presence of Na and can catalyze the oxidation of tetramethylbenzidine by HO system in the presence of Cu to form a visible blue color. If, however, Cu binds to Aβ(1-40), the blue color is no longer formed. Measuring the absorption decrease at 452 nm, the determination of Aβ(1-40) is realized. If K is added to the Na-containing buffer, the antiparallel G-quadruplex DNA is transformed to parallel. This leads to the insertion of protoporphyrin IX (PPIX) into the G-quadruplex and generates enhanced fluorescent signal, with excitation/emission wavelength at 410/630 nm. The G-quadruplex then catalyzes the metalation of PPIX by Cu, and the fluorescence intensity decreases. In the presence of Aβ(1-40), the formation of Aβ(1-40)-Cu triggers the recovery of the fluorescence. The Na/K-induced tuning of the conformation of the G-quadruplex with the same sequence enables dual (colorimetric and fluorometric) determination of Aβ(1-40), with detection limits of 4.9 pM and 2.3 pM, respectively. The cost is quite low since the developed strategy is label free and enzyme free by using low-cost DNA and Cu. More importantly, the dual channel determination operation is very simple without any further modification process. Tuning the conformation of G-quadruplexes by sodium(I) and potassium(I): application to photometric and fluorometric determination of amyloid β(1-40).
一种用于测定与阿尔茨海默病相关的淀粉样β肽 Aβ(1-40)的双通道方法。该方法利用了 (a) 在 Na 和 K 离子存在下引发的 G-四链体构象变化，以及 (b) Aβ(1-40)与 Cu 之间的强亲和力。在 Na 存在下，G-四链体 DNA 形成反平行结构，并且可以在 Cu 存在下催化 HO 体系对四甲基联苯胺的氧化，形成可见的蓝色。然而，如果 Cu 与 Aβ(1-40)结合，则不再形成蓝色。通过测量 452nm 处的吸光度下降，可以实现 Aβ(1-40)的测定。如果在含 Na 的缓冲液中加入 K，反平行 G-四链体 DNA 会转化为平行。这导致原卟啉 IX (PPIX)插入 G-四链体并产生增强的荧光信号，激发/发射波长为 410/630nm。然后，G-四链体催化 Cu 对 PPIX 的金属化，荧光强度降低。在 Aβ(1-40)存在下，Aβ(1-40)-Cu 的形成触发荧光的恢复。相同序列的 G-四链体构象的 Na/K 诱导调谐使得 Aβ(1-40)的双重（比色和荧光）测定成为可能，检测限分别为 4.9pM 和 2.3pM。由于该开发策略使用低成本 DNA 和 Cu，因此是无标记和无酶的，成本相当低。更重要的是，双通道测定操作非常简单，无需任何进一步的修饰过程。通过钠(I)和钾(I)调节 G-四链体的构象：用于测定淀粉样β(1-40)的比色和荧光法。
