Water-soluble amino derivatives of free-base dppz – syntheses and DNA binding studies
作者:Tim Phillips、Itshamul Haq、Jim A. Thomas
DOI:10.1039/c0ob00869a
日期:——
The syntheses of two water soluble dipyrido-[3,2-a:2â²,3â²-c]-phenazine analogues containing one or two appended amino/amide chains are reported. Steady state optical studies on the two new compounds reveal high-energy dppz-based luminescence in water and non-aqueous solvents. Optical titrations with duplex DNA show that the luminescence is quenched on the addition of DNA. Binding curves constructed from absorption and emission changes indicate that, while one of the compounds display negligible binding properties, the other binds DNA with relatively high affinity (>105 Mâ 1). Isothermal calorimetry experiments, designed to investigate the higher binding compound in more detail, reveals that its interaction with CT-DNA is actually biphasic with one tight (>105 Mâ 1) and one weaker binding site (â¼105 Mâ 1). In both cases binding is entropically driven. Further calorimetry studies involving the interaction of the new compound with a variety of polynucleotides were carried out. To aid comparisons, similar experiments involving a previously reported bipyridyldiylium derivative of dppz were also carried out. These studies reveal that the bipyridyldiylium derivative binds all these sequences monophasically with relatively low affinities (â¼104 Mâ 1). However, while the amino/amide chain appended derivative binds to Poly(dA).poly(dT) monophasically with relatively low affinities, it binds all the other polynucleotide studied biphasically, with affinities ranging from <106 Mâ 1 to >108 Mâ 1. The ITC data reveals that for both compounds thermodynamic signatures for binding are dependent on the sequence being bound. In both cases, the data for Poly(dA).poly(dT) is particularly anomalous. An analysis of the data shows that binding is selective, with affinities at flexible sequences being several orders of magnitude higher than those at more rigid sequences.
报告合成了两种水溶性二吡啶-[3,2-a:2â²,3â²-c]-吩嗪类似物,其中含有一个或两个附加氨基/酰胺链。对这两种新化合物进行的稳态光学研究显示,它们在水和非水溶剂中具有基于 dppz 的高能发光特性。用双链 DNA 进行光学滴定显示,加入 DNA 后,发光被淬灭。根据吸收和发射变化构建的结合曲线表明,其中一种化合物的结合特性可以忽略不计,而另一种化合物与 DNA 的结合亲和力相对较高(>105 Mâ 1)。为了更详细地研究这种结合力较高的化合物而进行的等温量热实验表明,它与 CT-DNA 的相互作用实际上是双相的,一个结合点紧密(>105 Mâ 1),另一个结合点较弱(â¼105 Mâ 1)。在这两种情况下,结合都是由熵驱动的。我们还对新化合物与各种多核苷酸的相互作用进行了进一步的量热研究。为了便于比较,我们还对之前报道的 dppz 的双吡啶鎓衍生物进行了类似的实验。这些研究表明,双吡啶鎓衍生物能以相对较低的亲和力(§¼104 Mâ 1)单相结合所有这些序列。不过,虽然氨基/酰胺链附加衍生物与聚(dA).聚(dT)单相结合的亲和力相对较低,但它与所研究的所有其他多核苷酸都是双相结合,亲和力从<106 Mâ 1到>108 Mâ 1不等。ITC 数据显示,这两种化合物的结合热力学特征都取决于所结合的序列。在这两种情况下,Poly(dA).poly(dT)的数据尤其异常。对数据的分析表明,结合具有选择性,与柔性序列的亲和力比与刚性序列的亲和力高出几个数量级。