Study of cavity size and nature of bridging units on recognition of nucleotides by cyclophanes
作者:Prakash P. Neelakandan、Paramjyothi C. Nandajan、Baby Subymol、Danaboyina Ramaiah
DOI:10.1039/c0ob00673d
日期:——
We synthesized a few novel cyclophanes CP-1 to CP-4 containing anthracene units linked together through different bridging and spacer groups and have investigated their interactions with various nucleosides and nucleotides. Of these systems, CP-1 and CP-3 showed selectivity for 5′-GTP and 5′-ATP as compared to other nucleotides and nucleosides, whereas negligible selectivity was observed with CP-2 and CP-4. Interestingly, CP-1, CP-2 and CP-3 exhibited significant binding interactions with the fluorescent indicator, 8-hydroxy-1,3,6-pyrene trisulfonate (HPTS), resulting in the formation of non-fluorescent complexes. Titration of these complexes with nucleosides and nucleotides resulted in the displacement of HPTS, leading to the revival of its fluorescence intensity. It was observed that 5′-GTP induced the maximum displacement of HPTS from the complex [CP-1·HPTS] with an overall fluorescence enhancement of ca. 150-fold, while 5′-ATP induced ca. 45-fold. Although the displacement of HPTS from the complexes [CP-2·HPTS] and [CP-3·HPTS] was found to be similar to that of [CP-1·HPTS], these complexes showed lesser selectivity and sensitivity. In contrast, negligible displacement of HPTS was observed from the complex [CP-4·HPTS] under similar conditions. These results indicate that CP-1, having a well-defined cavity and good electron acceptor (viologen), is capable of forming selective and stable complexes. Though CP-2 and CP-3 retain the good electron acceptor (viologen), their reduced aromatic surface and larger cavity, respectively, resulted in lesser sensitivity. In contrast, CP-4 having a large cavity and a poor acceptor (1,2-bis(pyridin-4-yl)ethene) showed negligible selectivity, thereby indicating the importance of cavity size, bridging unit and aromatic surface on biomolecular recognition properties of cyclophanes.
我们合成了一系列新型冠醚CP-1至CP-4,这些冠醚包含蒽单元,通过不同的桥连和间隔基团连接在一起,并研究了它们与各种核苷和核苷酸的相互作用。在这些系统中,CP-1和CP-3对5′-GTP和5′-ATP表现出选择性,而CP-2和CP-4的选择性则微乎其微。有趣的是,CP-1、CP-2和CP-3与荧光指示剂8-羟基-1,3,6-芘三磺酸盐(HPTS)表现出显著的结合相互作用,形成非荧光复合物。这些复合物与核苷和核苷酸的滴定导致HPTS的置换,从而恢复其荧光强度。观察到5′-GTP从复合物[CP-1·HPTS]中诱导出最大程度的HPTS置换,总体荧光增强约150倍,而5′-ATP则诱导约45倍。尽管从复合物[CP-2·HPTS]和[CP-3·HPTS]中HPTS的置换与[CP-1·HPTS]相似,但这些复合物表现出较低的选择性和敏感性。相比之下,在类似条件下,复合物[CP-4·HPTS]中HPTS的置换可以忽略不计。这些结果表明,CP-1具有良好的空腔和良好的电子受体(紫精),能够形成选择性和稳定的复合物。尽管CP-2和CP-3保留了好的电子受体(紫精),但它们的减少的芳香表面和较大的空腔分别导致了较低的敏感性。相比之下,CP-4具有较大的空腔和较差的受体(1,2-双(4-吡啶基)乙烯),表现出微乎其微的选择性,从而表明空腔大小、桥连单元和芳香表面在环芳烃的生物分子识别特性中的重要性。