Tb^(3+)荧光离子探针检测三链DNA的形成

Ion Fluorescence Probe Detecting the Formation of Triplex DNA

Tb3 + 本身具有荧光 ,Tb3 + 和DNA结合后仍具有荧光 ,荧光强度不仅与DNA中碱基的种类有关 ,而且还与DNA是单链、双链还是三链有关。文章用Tb3 + 离子作为荧光探针 ,检测了三链DNA的形成。实验结果表明 :polydA和Tb3 + 结合后的荧光强度大于 polydT和Tb3 + 结合后的荧光强度。说明荧光强度和碱基的种类有关。实验结果还显示Tb3 + 在与三链DNA作用后的荧光光谱的谱峰位置与单链及双链DNA的荧光光谱的谱峰位置基本相同 ,但是其强度差异明显。Tb3 + 与单链DNA作用后的荧光强度最大 ,三链次之 ,Tb3 + 与双链DNA作用后的荧光强度最弱。通过测定荧光强度的变化研究了三链DNA的形成和pH、金属离子对形成三链DNA的影响。pH中性和高价阳离子的存在有利于三链DNA的形成。

The fluorescence of Tb3+ is not quenched after the rare earth ion is combined with DNA. The fluorescence intensity is related not only to the kinds of bases of DNA but also to the kinds of DNA. The rare earth ion Tb3+ was used as the fluorescence probe to detect the formation of triplex DNA. The results show that the fluorescence intensity of Tb3+ combined with polydA is much stronger than that of Tb3+ combined with polydT, which testifies that the fluorescence intensity is related to the kinds of bases combined with Tb3+. The results also demonstrate that the rare earth ion can be used to detect those three forms of DNA though their fluorescence peak positions are similar when Tb3+ as a fluorescence probe is combined with single strand DNA (ssDNA), double helix DNA (dsDNA), and triple helix DNA (tsDNA), respectively. However, their intensities are quite different. The fluorescence intensity of Tb3+ combined with ssDNA-Tb3+ is the largest. And the fluorescence intensity of Tb3+ combined with tsDNA-Tb3+ takes the second place. The minimum peak intensity belongs to the contribution of Tb3+ coupled with dsDNA-Tb3+. The reason is that the capability of energy transference of ssDNA, dsDNA and tsDNA is different. The different degree of energy transference influences the intensities of Tb3+. The influences of pH and the metal ion on the formation of triplex DNA were also studied. The authors found that the neutral pH and high valence metal ion are beneficial to the formation of ts-DNA.