Delepierre M, Milhe C, Namane A, Dinh T H, Roques B P
Department de Chimie Organique U 266 INSERM, UA 498 CNRS, UER des sciences pharmaceutiques et biologiques 4, Paris, France.
Biopolymers. 1991 Feb 15;31(3):331-53. doi: 10.1002/bip.360310307.
The structures of the complexes formed in aqueous solution between ditercalinium, a bis-intercalating drug, and both the self-complementary tetranucleotide d(GCGC)2 and octanucleotide d(CCTATAGG)2, have been investigated by 400-MHz 1H-nmr and 162-MHz 31P-nmr. All the nonexchangeable protons, as well as the exchangeable imino protons and the phosphorus signals, have been assigned. Both oligonucleotides have been shown to adopt a right-handed B-DNA type structure. The addition of ditercalinium to the oligonucleotides lead to the formation of complexes in slow exchange at the nmr time scale with the free helices. At all drug-to-helix ratios studied, the ditercalinium was found in the bound form, whereas free and complexed oligonucleotides were in slow exchange, allowing resonance assignments through two-dimensional chemical exchange experiments. for d(GCGC)2 the strong upfield shifts induced on all aromatic protons of both the bases and the drug by complexation with ditercalinium suggest an interaction by intercalation of the two rings. However, the loss of twofold symmetry upon binding, as well as the chemical shift variation of the drug proton signals of one of the chromophores with temperature and concentration, favor a model in which the drug-nucleotide complexes have one ring of the drug intercalated and the other stacked on top of the external base pair. The intermolecular contacts between drug protons and nucleotide protons give a defined geometry for complexation that is consistent with the proposed model. In contrast, with d(CCTATAGG)2 several drug-nucleotide complexes were formed and a large increase in line broadening was observed at high drug-to-DNA ratios, precluding a detailed analysis of these complexes. However, the large upfield shift in the imino proton resonances together with the shielding of the ditercalinium ring protons favor a model with bis-intercalation of ditercalinium. This model is supported by the downfield shift of at least 4 out of 14 phosphorus signals. The results are compared with those obtained on ditercalinium binding to the homologous sequences d(CGCG)2 and d(TTCGCGAA)2, and discussed in terms of sequence specificity.
通过400兆赫的1H核磁共振和162兆赫的31P核磁共振研究了双插入药物二萜卡林ium与自互补四核苷酸d(GCGC)2和八核苷酸d(CCTATAGG)2在水溶液中形成的复合物的结构。所有不可交换质子以及可交换亚氨基质子和磷信号都已被归属。已证明两种寡核苷酸均采用右手B-DNA型结构。向寡核苷酸中加入二萜卡林ium会导致在核磁共振时间尺度上与游离螺旋形成缓慢交换的复合物。在所研究的所有药物与螺旋的比例下，发现二萜卡林ium处于结合形式，而游离和复合的寡核苷酸处于缓慢交换状态，这使得通过二维化学交换实验进行共振归属成为可能。对于d(GCGC)2，与二萜卡林ium络合时在碱基和药物的所有芳香族质子上引起的强烈高场位移表明两个环通过插入相互作用。然而，结合时二重对称性的丧失以及其中一个发色团的药物质子信号随温度和浓度的化学位移变化，支持了一种模型，即药物-核苷酸复合物中药物的一个环插入而另一个堆叠在外部碱基对之上。药物质子与核苷酸碱基质子之间的分子间接触给出了与所提出模型一致的明确络合几何形状。相比之下，对于d(CCTATAGG)2，形成了几种药物-核苷酸复合物，并且在高药物与DNA比例下观察到线宽大幅增加，这使得无法对这些复合物进行详细分析。然而，亚氨基质子共振的大幅高场位移以及二萜卡林ium环质子的屏蔽有利于二萜卡林ium双插入的模型。该模型得到了14个磷信号中至少4个的低场位移的支持。将结果与二萜卡林ium与同源序列d(CGCG)2和d(TTCGCGAA)2结合所获得的结果进行了比较，并从序列特异性方面进行了讨论。
