Studies on RNA Cleavage: Catalyst Design and Mechanism

这个无机、生物无机和有机金属化学项目的奖项支持纽约州立大学布法罗分校化学系的Janet R. Morrow和John P. Richard的研究。他们将设计裂解RNA和DNA的催化剂，并试图确定这些裂解反应的机制。该项目有三个主要组成部分。首先，制备新的Zn（II）和Th（IV）双核配合物。这些将具有可变的桥接配体来控制金属离子的几何形状和分离。研究人员还将在化合物中使用其他金属离子的各种组合，包括Cd、Cu、Ni、Pb和in。接下来，模型RNA底物将用于反应性研究，以确定不同金属配合物提供过渡态稳定的位点。结构-反应性对催化活性的影响将用于区分在类氧磷过渡态与亲核2′-羟基相互作用的金属配合物和在该过渡态与离氧基相互作用的配合物。我们将研究RNA切割的机制，以确定是否存在离开基团和亲核试剂的同时活化，或者是否存在通过非桥接氧的螯合而产生的“双重”路易斯酸活化，而离开基团和亲核试剂之间没有相互作用。将开发分析和计算方法来检查金属-金属距离，几何形状和RNA裂解的催化活性之间的关系。研究的第三部分将集中在类似RNA的底物上的3'-磷酸二酯键断裂的酸碱催化，以区分发生在离开基/亲核试剂上的酸碱催化和发生在磷酸基非桥接氧上的亲电催化。RNA裂解剂可能最终有实际的治疗应用，但在这一点上提出了实质性的智力挑战。该反应的机理尚不清楚，因此劈裂剂的最佳设计特征是未知的。本研究将利用各种双核金属配合物作为裂解剂，并确定其作用机制。酸碱机制的作用也将被考虑。研究生和本科生将受益于参与这个跨学科的项目，包括有机和无机合成以及动力学参数的确定。学生将参加纽约州立大学布法罗分校的化学生物学项目，并由一组具有广泛技能的调查人员指导。

This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports research by Janet R. Morrow and John P. Richard of the Chemistry Department, State University of New York at Buffalo. They will design catalysts to cleave RNA and DNA and attempt to determine the mechanism of these cleavage reactions. There are three main components to the project. First, new Zn(II) and Th(IV) dinuclear complexes will be prepared. These will have variable bridging ligands to control the geometry and separation of the metal ions. The investigators will also use various combinations of other metal ions in the compounds, including Cd, Cu, Ni, Pb, and In. Next, model RNA substrates will be used in reactivity studies to determine the site(s) at which different metal complexes provide transition state stabilization. Structure-reactivity effects on catalytic activity will be used to distinguish metal complexes that interact with the nucleophilic 2'-hydroxyl at the oxyphosphorane-like transition state from complexes that interact with the oxygen leaving group at this transition state. The mechanism of RNA cleavage will be examined to determine whether there is simultaneous activation of both the leaving group and incoming nucleophile, or if there is "double" Lewis acid activation by chelation of the nonbridging oxygens, with no interactions at the leaving group/nucleophile. Analytical and computational methods will be developed to examine relationships between metal-metal distance, geometry, and catalytic activity for cleavage of RNA. The third part of the study will focus on acid-base catalysis of the cleavage of the 3'-phosphodiester linkage at substrates that resemble RNA in order to distinguish acid-base catalysis that occurs at the leaving group/nucleophile from electrophilic catalysis at the nonbriding oxygens of the phosphate group. Cleavage agents for RNA may eventually have practical therapeutic applications, but at this point present substantial intellectual challenges. The mechanism of the reaction is not well understood and so the optimal design features of a cleavage agent are unknown. In this study, various dinuclear metal complexes will be used as cleavage agents and their mechanism of action determined. The role of acid-base mechanisms will also be considered. Graduate and undergraduate students will benefit from involvement in this interdisciplinary project that includes organic and inorganic synthesis and the determination of kinetic parameters. Students will participate in the Chemical Biology program at SUNY-Buffalo and be mentored by a team of investigators with a wide range of skills.