链霉亲和素适配体广泛应用于RNA及其结合蛋白、重金属离子、小分子药物等分析。应用传统的SELEX方法优化适配体具有盲目性，耗费大、效率低，且往往达不到预期目的。本课题在链霉亲和素-适配体（SA-Apt）二元复合物结晶取得突破性进展的基础上，拟通过解析复合物晶体三维结构，阐明影响两者结合模式的关键因素，提出基于三维结构理性高效设计优化适配体的方法；以铂类药物为研究模型分子，利用SA-Apt复合物结构初步优化铂检测适配体探针序列，结晶并解析链霉亲和素-探针-铂（SA-Probe-Pt）三元复合物结构，精细优化探针序列，提高探针亲和力和对铂的利用效率，最终建立高灵敏的分析方法，用于生物样品中奥沙利铂的测定。本研究将为不同分析方法和应用中链霉亲和素适配体的设计优化提供通用结构模型，且从分子水平阐明了SA-Probe-Pt三元复合物的作用机制，为基于适配体的药物检测方法提供通用技术。

Streptavidin aptamer has continuously generated lots of interest in bio-analytical field, such as detection of RNA, RNA binding proteins, heavy metal ions and small molecules. SELEX method is time-consuming and high-cost for aptamer optimization, and it often fails to achieve the expected aims. In the previous research, a breaking through of crystallization of streptavidin-aptamer (SA-Apt) binary complexes had been gained. Three-dimensional structure based aptamer design and optimization is proposed based on the above research progress. A comprehensive study of SA-Apt binding mode will be executed through X-ray structure elucidation of SA-Apt complexes in this project. Furthermore, platinum (Pt) based anti-tumor drug is selected as a model molecule for 3D-structure based aptamer optimization. SA-Apt binary complex structural model can be used for the preliminary optimization the sequence of platinum detection aptamer probe. Crystallization and X-ray 3D-structure elucidation of SA-probe-Pt ternary complex will be carried out, and further optimize the sequence of the probe based on the ternary complex structure. The sensitivity of the aptameric platform for platinum detection can be improved by increasing the probe affinity to SA and Pt utilization efficiency. A high sensitive platinum detection method will be constructed and used to determine the concentration of oxaliplatin in biological samples. We aim to provide both a general structural model for various streptavidin aptamer optimization and a general technology for aptamer based pharmaceutical analysis.