Burckhardt G, Votavova H, Sponar J, Luck G, Zimmer C
Akademie der Wissenschaften der DDR, G.D.R.
J Biomol Struct Dyn. 1985 Feb;2(4):721-36. doi: 10.1080/07391102.1985.10506319.
Using CD measurements we show that the interaction of netropsin to poly(dA-dT).poly(dA-dT) involves two binding modes at low ionic strength. The first and second binding modes are distinguished by a defined shift of the CD maximum and the presence of characteristic isodichroic points in the long wavelength range from 313 nm to 325 nm. The first binding mode is independent of ionic strength and is primarily determined by specific interaction to dA.dT base pairs. Employing a netropsin derivative and different salt conditions it is demonstrated that ionic contacts are essential for the second binding mode. Other alternating duplexes and natural DNA also exhibit more or less a second step in the interaction with netropsin observable at high ratio of ligand per nucleotide. The second binding mode is absent for poly(dA).poly(dT). The presence of a two-step binding mechanism is also demonstrated in the complex formation of poly(dA-dT).poly(dA-dT) with the distamycin analog consisting of pentamethylpyrrolecarboxamide. While the binding mode I of netropsin is identical with its localization in the minor groove, for binding mode II we consider two alternative interpretations.
利用圆二色光谱测量，我们发现，在低离子强度下，纺锤菌素与聚（dA-dT）·聚（dA-dT）的相互作用涉及两种结合模式。第一种和第二种结合模式通过圆二色光谱最大值的特定位移以及在313纳米至325纳米长波长范围内特征性等吸收点的存在来区分。第一种结合模式与离子强度无关，主要由与dA·dT碱基对的特异性相互作用决定。利用一种纺锤菌素衍生物和不同的盐条件，证明了离子接触对于第二种结合模式至关重要。其他交替双链体和天然DNA在配体与核苷酸的高比例下，与纺锤菌素的相互作用或多或少也表现出第二步。聚（dA）·聚（dT）不存在第二种结合模式。在聚（dA-dT）·聚（dA-dT）与由五甲基吡咯甲酰胺组成的偏端霉素类似物的复合物形成中，也证明了两步结合机制的存在。虽然纺锤菌素的结合模式I与其在小沟中的定位相同，但对于结合模式II，我们考虑两种不同的解释。
