Multi-Functional Metal Complexes with DNA Base-Sequence Selectivity

我们已经研究了DNA-配体相互作用的分子基础，特别是，由各种DNA结合蛋白和抗生素显示的多功能的序列示意图和相互作用。我们选择卟啉作为探针分子，合成了各种新型卟啉化合物。游离碱卟啉或其Cu、Ni配合物插入DNA碱基对之间，而Mn配合物以非插入方式与DNA轴向配体结合。在DNA拓扑异构酶I存在下，通过螺旋稳定化和DNA解旋研究测量，携带四个带电侧链的卟啉类似地结合并插入DNA中。尽管它们的庞大侧链不同，但这些复合物给出了基本上相同的DNA酶I足迹模式。与具有较小体积侧链的单电荷卟啉的比较表明，卟啉上的带电侧链的存在而不是它们的身份似乎对有效的DNA嵌入至关重要。所有以嵌入方式与DNA结合的卟啉均对Rsa Ⅰ酶切DNA有位点特异性抑制作用。在两个识别位点中，具有富含GC的侧翼序列的位点被选择性抑制。涉及这两个位点的DNA的DNA酶I足迹显示，紧邻受抑制的切割位点的5'端被保护免于DNA酶I消化。我们将工作扩展到合成一系列新的化合物，其与DNA的相互作用可以通过引入化合物中的第二结合部分来控制。在卟啉的侧链末端，连接已知表现出与博来霉素或光裂解剂相同的序列特异性的嵌入剂。用螺旋稳定法、可见吸收光谱法研究了它们与DNA的结合。已经获得了DNA六聚体-卟啉复合物的晶体，尽管不幸的是它们对于X射线结构分析来说太小了。

We have studied the molecular basis of DNA-ligand interactions, particularly, sequence recognitions and interplay of multi-functions displayed by various DNA-binding proteins and antibiotics. We have chosen porphyrins as a probe for this study and synthesized various novel porphyrins. Free base porphyrins or their Cu, Ni complexes intercalated between the base pairs of DNA, while Mn complexes with axial ligands bound to DNA by nonintercalative mode. Porphyrins carrying four charged sidechains bound and intercalated similarly into DNA as measured by helix stabilization and DNA unwinding studies in the presence of DNA topoisomerase I. Despite their different bulky sidechains, these complexes gave essentially identical DNase I footprinting patterns. Comparison with single charged porphyrins with less bulky sidechains has shown that the presence of charged sidechains on the porphyrin rather than their identity appears to be critical for efficient DNA intercalation. All the porphyrins which bind to DNA by intercalative mode showed site-specific inhibition of Rsa I digestion of DNA. Out of two recognition sites, a site with GC-rich flanking sequence was selectively inhibited. DNase I footprinting of DNA involving the two sites has shown that 5' immediate to the inhibited cutting-site was protected from DNase I digestion. The protected regions were unexpectedly AT-rich.We have extended the work to a synthesis of a new series of compounds whose interaction with DNA can be controlled by the second binding part introduced into the compound. At the end of hexamethylene sidechain of a porphyrin, an intercalator which is known to exhibit the same sequence specificity as bleomycin or a photocleaving agent was attached. Their binding with DNA has also been studied with helix stabilization, visible absorption spectroscopy. A crystals of a DNA hexamer-porphyrin complex have been obtained, although they are unfortunately too small for X-ray structural analysis.