Gersanovski D, Colson P, Houssier C, Fredericq E
Biochim Biophys Acta. 1985 Apr 19;824(4):313-23. doi: 10.1016/0167-4781(85)90037-5.
At low ionic strength, Tb3+ binding strongly alters the secondary structure of DNA. Circular dichroism and electro-optical techniques are more sensitive than fluorescence to study these alterations in double-stranded DNA, at low Tb3+/DNA phosphate (I/P) ratios. Both techniques yield the following conclusion: as I/P is increased, native and sonicated DNA undergo a transition from the B- to psi-form, the latter being a compact structure characteristic of aggregated DNA. Our study of alkylated DNA establishes that the accessibility of N-7 guanine to Tb3+ is clearly required for structural alterations in an aggregated state to occur. The chelation of the phosphate group and of the N-7 guanine by Tb3+ simultaneously alters the geometry of the sugar-phosphate backbone and the stacking interaction between the bases in double-stranded DNA.
在低离子强度下，Tb3+ 的结合会强烈改变 DNA 的二级结构。在低 Tb3+/DNA 磷酸根（I/P）比率时，圆二色性和电光技术比荧光技术更灵敏，可用于研究双链 DNA 中的这些变化。两种技术都得出以下结论：随着 I/P 的增加，天然 DNA 和超声处理的 DNA 会从 B 型转变为 psi 型，后者是聚集态 DNA 的一种紧密结构特征。我们对烷基化 DNA 的研究表明，聚集态发生结构改变显然需要 N-7 鸟嘌呤对 Tb3+ 具有可及性。Tb3+ 对磷酸基团和 N-7 鸟嘌呤的螯合会同时改变糖-磷酸主链的几何形状以及双链 DNA 中碱基之间的堆积相互作用。
