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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Physico-chemical studies of a DNA triplex containing a new ferrocenemethyl-thymidine residue in the third strand.
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Physico-chemical studies of a DNA triplex containing a new ferrocenemethyl-thymidine residue in the third strand.

机译：在第三链中包含新的二茂铁甲基-胸苷残基的DNA三链体的物理化学研究。

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摘要

The stability of a 16-mer DNA triple helix containing a 3-N(ferrocenemethyl)-thymidine residue in the third strand has been investigated in comparison with the unmodified triplex of the same sequence. A complete physico-chemical characterization of the two triple helices on changing the pH by means of calorimetry, circular dichroism and molecular modeling is therefore reported. The thermodynamic parameters were obtained in the pH range 5.5-7.2 by differential scanning calorimetry (DSC). For both triplexes the T(m) and DeltaH degrees (T(m)) values increase on decreasing the pH. In the pH range 7.2-6.0 the triplex containing the ferrocenemethyl nucleoside is less stable than the unmodified one, whereas the modified triplex becomes more stable at pH 5.5. Such difference in stability at each pH value is overwhelmingly enthalpic in origin. CD spectra show conformational changes on decreasing the pH for both the triplexes. By spectroscopic pH titration the apparent pK(a) values of the cytosines in the two triplexes could be estimated, with the cytosines in the TFO containing the ferrocenemethyl residue having lower apparent pK(a) values. These results are consistent with the calorimetric data, showing a decrease of the thermodynamic parameters in the pH range 7.2-6.0 and an increase at pH 5.5 for the ferrocenylated triplex with respect to the unmodified one. The thermodynamic and spectroscopic data are also discussed in relation to molecular models.
机译：与相同序列的未修饰三链体相比，已经研究了在第三链中包含3-N（二茂铁甲基）-胸苷残基的16-mer DNA三链螺旋的稳定性。因此，据报道，通过量热法，圆二色性和分子模型对pH值进行改变时，两个三重螺旋的完整物理化学特征得以报道。通过差示扫描量热法（DSC）在5.5-7.2的pH范围内获得热力学参数。对于两个三元组，T（m）和DeltaH度（T（m））值都随着pH的降低而增加。在pH 7.2-6.0范围内，含有二茂铁甲基核苷的三联体比未修饰的三联体不稳定，而经修饰的三联体在pH 5.5下变得更稳定。在每个pH值下，这种稳定性差异在很大程度上是焓变的。 CD光谱显示两个三联体在降低pH时的构象变化。通过光谱pH滴定，可以估计两个三元组中胞嘧啶的表观pK（a）值，而TFO中的二甲基茂铁残基的胞嘧啶具有较低的表观pK（a）值。这些结果与量热数据一致，表明相对于未修饰的二茂铁基三聚体，在7.2-6.0的pH范围内热力学参数降低，在pH 5.5下的热力学参数升高。还讨论了与分子模型有关的热力学和光谱数据。

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