作者:Xuemei Wang、Hans-Jörg Schneider
DOI:10.1039/a801609g
日期:——
Dansylamideâ has been modified by the introduction of several side chains into the sulfonamide substituent. Compounds with no, or with only one positive charge at the side chains were found not to be useful for association studies with nucleotides or nucleic acids. Relatively high binding constants with moderate base selectivities have been observed with a ligand obtained from dansyl chloride and N,Nâ²-bis(3-aminopropyl)piperazine, which contains two dansyl units and two permanently charged peralkylammonium centers. Interactions of this ligand with double-stranded nucleic acids show a biphasic binding, the first at base pair concentrations below 10â7 M being only detectable by a decrease of fluorescence intensity. The second phase is characterized by increased fluorescence and by wavelength changes similar to effects observed in lipophilic solvents and by affinities of up to 5Â ÃÂ 105 M. At higher concentrations bathochromic shifts and extinction changes in UV spectra of the dye suggest an intercalation mechanism, in line with preliminary circular dichroism studies.
Dansylamide已经通过在磺酰胺取代基上引入多个侧链进行了修改。发现没有或仅在侧链上带有一个正电荷的化合物,不适用于与核苷酸或核酸的结合研究。由dansyl氯和N,N'-双(3-氨基丙基)哌嗪获得的配体显示出相对较高的结合常数和适中的碱基选择性,该配体包含两个dansyl单元和两个永久带电的烷基铵中心。该配体与双链核酸的相互作用表现出双相结合,第一个相在碱基对浓度低于10^-7 M时仅通过荧光强度的下降可检测到。第二个相的特征是荧光增强,波长变化类似于在脂溶性溶剂中观察到的效应,亲和力可高达5 × 10^5 M。在更高浓度下,染料的紫外光谱出现红移和消光变化,暗示了一种插层机制,这与初步的圆二色性研究结果一致。