针对基于富G适体链形成G4结构的检测平台，存在两方面的问题：(1) 随着目标离子浓度的增加，是G4结构形成的数量逐渐增加, 还是构型渐变并趋于稳定？当目标离子浓度较低时，实际体系中的共存离子如何影响G4结构的构型和稳定性，进而改变检测响应性？目前尚存理解性误区；(2)功能化探针适体链（增加适体链3’或5’端的碱基）在特定离子诱导下形成G4结构检测目标物，增加的碱基是否改变G4结构以及G4结构与探针分子的有效键合，进而影响检测响应性？也是一个值得关注的问题。因此，本项目拟深入研究离子诱导探针适体链(含功能化)形成G4结构的过程及其与探针分子的键合，探究离子调节G4结构的可控转化，揭示传感器设计中存在的问题并提出可参考的解决方案；设计并合成能特异识别G4构型可控转化的光/电探针，研发新型光/电传感和逻辑器件。这些研究工作的逐一展开和顺利实施，为拓展G4 结构在传感领域中的应用提供新理论和新方法

Based on the conformational switches from G-rich aptamer to G-quadruplex, various detecting platforms are developed. However, there are two aspects needed to be carefully reconsidered. If the target is a metal ion, the selected functional aptamer is supposed to undergo a conformational switch to G-quadruplex. Based on the conformational change and the integrated fluorescent or electrochemical probe, the detection is achieved in buffer solution and real samples. The question is that upon increasing the concentration of metal ion, G-quadruplex is quantitatively formed, OR gradually undergone structural transfer from unstable to stable? When the concentration of metal ion is relatively lower and coexisting metal ion is relatively higher, how the coexisting metal ion alters stability and properties of the formed G-quadruplex, and further affects the sensing performance? Misconception remains common. On the other hand, when functional aptamers (through adding more nucleic bases at 3 or 5 terminal) were designed to detect targets, could the added nucleic bases alter the conformation of G-quadruplex, and further affect the binding efficiency with fluorescent or electrochemical probe? Then, how to select the proper functional aptamer to improve the sensing performance? The question is avoided. Thus, the project is supposed to find clues to answer the two mentioned questions. Firstly, it will deeply investigate the transforming process from aptamer into G-quadruplex induced by ions, and its binding efficiency with molecular probes. Meanwhile, coexisting ion mediating and controlling transformation of G-quadruplex will also be explored in detail. The remained misconceptions will be clarified, and the possible approaches will be investigated. Secondly, in order to specifically discriminate the ion-mediated and controlled transformation of formed G-quadruplex, the newly fluorescent or electrochemical probes will be designed and synthesized. Accordingly, the new fluorescent or electrochemical sensors and logic gates will be developed. All the supposed research works will provide a new theory and approach to broaden the application of G-quadruplex in sensing areas.