蛋白-配基的相互作用模式是理性药物发现的核心。复合物晶体常受限于靶点蛋白动态特性和先导化合物的水溶性，这类化合物又恰处于核磁中等交换尺度，导致结合界面的核磁共振信号谱线严重增宽甚至无法检测。在极低的蛋白/配基比例下，我们开发的配基氟赝接触位移和化学交换饱和传递联用新技术可解决这一难题。以抗肿瘤迁移靶点RhoGDI2为例，在我们已鉴定的多个中等亲和力的抑制剂基础上，拟进一步开发核磁中等交换极限下，配基氢的赝接触位移和弛豫弥散联用的新技术，以及配基氢的顺磁弛豫增强技术,获取低丰度结合态的分子间结构约束, 搭建复合物结构模型。进而在结构指导下，设计合成更高活性和选择性的小分子抑制剂，尝试解析高水溶性类似物的复合物晶体结构，分析其抗肿瘤细胞迁移活性。这将拓展核磁共振波谱在基于结构的药物发现中的应用，并为后续RhoGDI2的功能研究提供重要的化学探针和潜在的抗肿瘤迁移药物前体。

The protein-ligand interaction modes are at the heart of rational drug discovery. The availability of complex crystal structures is often limited by the dynamic nature of the targets and/or the low aqueous solubility of the lead compounds. These leads normally fall into the NMR intermediate exchange scale, which can cause severe line broadening beyond detection of interface resonances. Using a highly skewed protein/ligand ratio, we have combined the ligand fluorine Pseudocontact shifts (PCSs) with chemical exchange saturation transfer to solve this bottleneck problem. As exemplified in the anti-cancer-metastasis target RhoGDI2, we have identified several lead-like inhibitors at intermediate affinities. We plan to develop new approaches to determine the ligand-observed proton PCSs using relaxation dispersion, and proton paramagnetic relaxation enhancement, even in the limit of NMR intermediate exchange. These intermolecular structural restraints of the low-populated bound states of the ligands will be used to generate the complex structural models, which will guide further design and synthesis of more potent and more selective inhibitors. We will try to solve the complex crystal structures of the highly soluble analogs to cross validate our NMR model. The anti-invasion and metastasis activities of these inhibitors will be assayed as well. Our study shall enlarge the application of NMR spectroscopy in the field of structure-based drug discovery. Meanwhile, it will provide essential chemical probes for the functional studies of RhoGDI2, and prototypical candidates to suppress tumor cell metastasis.