Light up G-quadruplex DNA with a [2.2.2]- heptamethinecyanine dye

摘要

The interactions of a triangle-shaped [2.2.2]heptamethinecyanine dye 1, namely 1,5,7-tris-[3-methyl-benzothiazol-2-yl]-[2.2.2]heptamethindiium, with quadruplex DNA were studied with photometric and fluorimetric titrations, thermal DNA denaturation, CD and ~1H-NMR spectroscopy. The ligand binds to the quadruplex DNA with moderate affinity (K= 8 × 10~5 M_(-1)), mainly by terminal π stacking. Remarkably, the ligand 1 exhibits a selectivity for quadruplex DNA relative to duplex DNA. Whereas the cyanine dye is very weakly fluorescent in aqueous solution, the emission intensity increases by a factor of >100 upon association with quadruplex DNA. Thus, it is shown that trinuclear cyanine derivatives may be employed as selective probes for the fluorimetric detection of quadruplex DNA.