Bauer C, Wang A H
Department of Chemistry, University of Illinois at Urbana-Champaign 61801, USA.
J Inorg Biochem. 1997 Nov 1;68(2):129-35. doi: 10.1016/s0162-0134(97)00083-4.
Cobalt(III) hexaamine ion [Co(NH3)6]3+ is known to facilitate the transition of B- to Z-DNA or B- to A-DNA depending on the DNA sequences. Specific interactions are found between the amines of [Co(NH3)6]3+ and DNA atoms of A-DNA or Z-DNA. Bridged Co(III)pentaamine complexes, with multiple amine groups arranged in a rigid framework, may enhance the effectiveness of the conformational transition by occupying simultaneously two of the Co(III) hexaamine binding sites. Therefore, the imidazole-bridged Co(III)pentaamine complexes have been synthesized and their interactions with DNA oligonucleotides investigated by circular dichroism (CD) and NMR spectroscopy. CD studies of the titrations of d(A2C15G15T2) with [(NH3)5Co(Im)Co(NH3)5]Br5 and [(NH3)5Co(Im)2Co(NH3)4]Br7 showed that the former metal compound indeed is more effective than [Co(NH3)6]3+ in inducing the transition from B- to A-DNA. The conversion of B- to A-DNA was also supported by one- and two-dimensional NMR studies. Similarly for the titrations of poly(dC-dG). poly(dC-dG) and d(m5C-G)15 with these two bridged Co(III) complexes, efficient induction of Z-DNA was observed. Our studies suggest that bridged Co(III)pentaamine complexes may be useful agents for studying nucleic acid structures.
已知六氨合钴（III）离子[Co(NH₃)₆]³⁺可促进B-DNA向Z-DNA或B-DNA向A-DNA的转变，具体取决于DNA序列。在[Co(NH₃)₆]³⁺的胺与A-DNA或Z-DNA的DNA原子之间发现了特异性相互作用。具有多个胺基团排列在刚性框架中的桥联Co（III）五胺配合物，可能通过同时占据两个六氨合钴（III）结合位点来增强构象转变的有效性。因此，已合成了咪唑桥联的Co（III）五胺配合物，并通过圆二色性（CD）和核磁共振（NMR）光谱研究了它们与DNA寡核苷酸的相互作用。用[(NH₃)₅Co(Im)Co(NH₃)₅]Br₅和[(NH₃)₅Co(Im)₂Co(NH₃)₄]Br₇滴定d(A₂C₁₅G₁₅T₂)的CD研究表明，前一种金属化合物在诱导从B-DNA向A-DNA转变方面确实比[Co(NH₃)₆]³⁺更有效。一维和二维NMR研究也支持了B-DNA向A-DNA的转变。同样，用这两种桥联的Co（III）配合物滴定聚（dC-dG）、聚（dC-dG）和d(m⁵C-G)₁₅时，观察到了Z-DNA的有效诱导。我们的研究表明，桥联的Co（III）五胺配合物可能是研究核酸结构的有用试剂。
