Copper-modified G-Quadruplex DNA as EPR Probes for Precise Distance Measurements

DNAG-四链体表现出明显的形成高阶结构的趋势，如π堆叠的二聚体、串上珠丝和与芳香结合伙伴的聚集体，与药物靶向端粒和癌基因相关。确定这些非共价加合物结构的可靠方法很少。我们开发了基于G-四链的自旋标记，含有四方平面的铜(吡啶)4络合物，共价结合到寡核苷酸中，用于检测二聚体结构和通过脉冲偶极EPR光谱测量分子间距离。此外，可以研究平面分子插入G-四链二聚体，从而形成夹心络合物，并发现了以前未知的结合模式。这个项目应用过渡金属标记方法，结合脉冲EPR光谱，系统地研究了一组先进的非共价DNA聚集体的结构，包括金属络合物、超分子和DNA结合蛋白。此外，基于G-四链的自旋标记将被用于测量其他DNA二级和三级结构中的距离，例如双链、弯曲的双链加合物和G-四链导线。与有机自旋标记物和Endor活性的19F取代基的结合进一步增强了这一方法的适用性。

DNA G-quadruplexes show a pronounced tendency to form higher-order structures, such as π-stacked dimers, beads-on-a-string wires, and aggregates with aromatic binding partners, relevant in medicinal targeting of telomers and oncogenes. Reliable methods for determining the structure of these non-covalent adducts are scarce. We developed G-quadruplex-based spin-labels containing square-planar Cu(pyridine)4 complexes, covalently incorporated into oligonucleotides, for detecting dimeric structures and measuring intermolecular distances via pulsed dipolar EPR spectroscopy. Furthermore, intercalation of flat molecules into G-quadruplex dimers, resulting in sandwich complexes can be investigated, and previously unknown binding modes discovered. This project applies the transition metal labeling approach, combined with pulsed EPR spectroscopy, to systematically examine an advanced set of structures of non-covalent DNA aggregates, including metal-complexes, supramolecules and DNA-binding proteins. Furthermore, G-quadruplex-based spin labels will be employed to measure distances in other DNA secondary- and tertiary structures such as double strands, bent duplex adducts and G-quadruplex wires. The combination with organic spin labels and ENDOR-active 19F substituents further enhances the applicability of this approach.