Since abnormal metabolism of histidine (His) is defined as an indicator of several diseases, detection of His in biological fluids becomes increasingly urgent to us. However, due to similar structures and properties of different amino acids, selective quantification of His is difficulty, and typically needs the participation of special reagents. In this work, we report for the first time that nickel ions (Ni2+) can induce the allostery of G-quadruplex, and is thus able to manipulate the activity of G-quadruplex DNAzyme. Experimental results indicate the interaction between Ni2+ and guanine is critical to the allostery. In comparison with Ni2+-guanine interaction, Ni2+-His interaction exhibits higher affinity. Therefore, a colorimetric His biosensor is fabricated, and His can be facilely discriminated by naked eyes. Relying on the high activity of DNAzyme, His in a range of 50 nM-400 μM is determined with this method, and low detection limit (36 nM) is obtained. More importantly, His can be directly distinguished in the absence of other toxic reagents. In addition, the amount of His in serum is also measured, suggesting the applicability of this biosensor in real sample detection. Overall, this work provides an alternative way to design G-quadruplex DNAzyme-based analytical approaches.

中文翻译：

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镍介导的 G-四链体 DNA 酶变构操作用于高选择性检测组氨酸

由于组氨酸（His）的异常代谢被定义为几种疾病的指标，因此检测生物体液中的His对我们来说变得越来越紧迫。但是，由于不同氨基酸的结构和性质相似，His的选择性定量比较困难，通常需要特殊试剂的参与。在这项工作中，我们首次报道镍离子 (Ni2+) 可以诱导 G-四链体的变构，从而能够操纵 G-四链体 DNAzyme 的活性。实验结果表明 Ni2+ 和鸟嘌呤之间的相互作用对变构至关重要。与 Ni2+-鸟嘌呤相互作用相比，Ni2+-His 相互作用表现出更高的亲和力。因此，制作了比色His生物传感器，肉眼可以轻松辨别His。依靠DNAzyme的高活性，该方法测定了50 nM-400 μM范围内的His，获得了低检测限（36 nM）。更重要的是，His可以在没有其他有毒试剂的情况下直接区分。此外，还测量了血清中的 His 量，表明该生物传感器在实际样品检测中的适用性。总的来说，这项工作提供了一种设计基于 G-四链体 DNAzyme 的分析方法的替代方法。