活细胞内核酸非经典结构i-motif的高度专一性荧光探针的设计

I-motif（iM）是一种新兴的核酸结构靶标，其活细胞研究不仅有助于全面认识生物遗传调控机制，也为肿瘤等重大疾病的精准诊疗提供了新的靶标。但示踪工具的缺乏，特别是可用于活细胞成像的分子荧光探针的空缺，已经严重制约了相关领域的研究。本项目针对目前绝大多数iM配体对iM和G-四链体的选择性低这一瓶颈科学问题，提出了基于“配体作用模式差异”的独创探针设计思路，拟通过多位点的分子结构设计，调控探针与核酸结合模式的倾向，实现专一性靶向活细胞内iM的荧光探针“从无到有”的突破。在此基础上，细致研究探针对iM的识别与调控机制，深入阐释iM的结构特性及其配体特征；继而利用该探针定位与追踪活细胞内的iM，探讨iM的生理功能，为全面认识核酸非经典结构、精确调控遗传信息、开发新型诊疗药物提供新的方法与靶标。

I-motif (iM) is a novel nucleic acid structural target. The study on its location, motion and function in living cells would contribute to the comprehensive understanding of biological genetic regulation mechanism and may provide a new target for the precise diagnosis and treatment of several serious diseases including tumors. However, the lack of monitoring tools, especially the absence of molecular fluorescent probes for living cell imaging, has seriously restricted the development of this field. The reported few iM probes are not suitable for living cell imaging and researching because they could hardly avoid from the interfere of G-quadruplex, another noncanonical structure with similar topologies to iM. To break through this bottleneck issue, we pose an original "ligand model differentiation" strategy to design probes with exclusiveness for iM in this project. We are going to modify multiple sites on cyanine frame to regulate the tendency of ligand binding modes and synthesize a series of probes. On this basis, the identification and regulation mechanisms of iM by the probes would be studied in detail, and the structural features and ligand characteristics of iM be further investigated. Further, we will apply the probes in living cell imaging, including to locate and track iM in situ and to study its physiological functions. This project would provide new sights on understanding the nucleic acid noncanonical structures, new methods for precisely genetic information regulating and new targets for novel diagnostic and therapeutic drugs.