As is well-known, the nucleic acid indicator-based strategy is one of the major approaches to monitor the nucleic acid hybridization-mediated recognition events in biochemical analysis, displaying obvious advantages including simplicity, low cost, convenience, and generality. However, conventional indicators either hold strong self-fluorescence or can be lighted by both ssDNA and dsDNA, lacking absolute selectivity for a certain conformation, always with high background interference and low sensitivity in sensing; and additional processing (e.g., nanomaterial-mediated background suppression, and enzyme-catalyzed signal amplification) is generally required to improve the detection performance. In this work, a carbazole derivative, EBCB, has been synthesized and screened as a dsDNA-specific fluorescent indicator. Compared with conventional indicators under the same conditions, EBCB displayed a much higher selective coefficient for dsDNA, with little self-fluorescence and negligible effect from ssDNA. Based on its superior capability in DNA conformation-discrimination, high sensitivity with minimizing background interference was demonstrated for direct detection of nucleic acid, and monitoring nucleic acid-based circuitry with good reversibity, resulting in low detection limit and high capability for discriminating base-mismatching. Thus, we expect that this highly specific DNA conformation-discriminating indicator will hold good potential for application in biochemical sensing and molecular logic switching.

中文翻译：

---

基于构象判别指标的背景最小化和灵敏度提高的核酸直接检测

众所周知，基于核酸指示剂的策略是在生化分析中监测核酸杂交介导的识别事件的主要方法之一，具有明显的优势，包括简单，低成本，方便和通用。然而，常规指示剂要么具有很强的自发荧光性，要么可以被ssDNA和dsDNA点亮，对某种构象缺乏绝对选择性，始终具有很高的背景干扰和低的传感灵敏度。通常需要额外的处理（例如，纳米材料介导的背景抑制和酶催化的信号放大）来提高检测性能。在这项工作中，咔唑衍生物EBCB已被合成并筛选为dsDNA特异性荧光指示剂。与相同条件下的常规指标相比，EBCB对dsDNA表现出更高的选择系数，几乎没有自发荧光，而ssDNA的影响可忽略不计。基于其在DNA构象识别方面的卓越能力，证明了具有高灵敏度和最小化背景干扰的特性，可直接检测核酸，并以良好的可逆性监测基于核酸的电路，从而实现了低检测限和高分辨碱基错配的能力。因此，我们希望这种高度特异性的DNA构象鉴别指示剂将在生物化学传感和分子逻辑转换中具有良好的应用潜力。几乎没有自发荧光，而ssDNA的影响可忽略不计。基于其在DNA构象识别方面的卓越能力，证明了具有高灵敏度和最小化背景干扰的特性，可直接检测核酸，并以良好的可逆性监测基于核酸的电路，从而实现了低检测限和高分辨碱基错配的能力。因此，我们希望这种高度特异性的DNA构象鉴别指示剂将在生物化学传感和分子逻辑转换中具有良好的应用潜力。几乎没有自发荧光，而ssDNA的影响可忽略不计。基于其在DNA构象识别方面的卓越能力，证明了具有高灵敏度和最小化背景干扰的特性，可直接检测核酸，并以良好的可逆性监测基于核酸的电路，从而实现了低检测限和高分辨碱基错配的能力。因此，我们希望这种高度特异性的DNA构象鉴别指示剂将在生物化学传感和分子逻辑转换中具有良好的应用潜力。导致低检测限和高分辨碱基错配的能力。因此，我们希望这种高度特异性的DNA构象鉴别指示剂将在生物化学传感和分子逻辑转换中具有良好的应用潜力。导致低检测限和高分辨碱基错配的能力。因此，我们期望这种高度特异性的DNA构象鉴别指标将在生物化学传感和分子逻辑转换中具有良好的应用前景。