In addition to the familiar duplexDNA, certain G-rich DNA sequences can fold into a variety of four-stranded structures, which are called G-quadruplexes.
富含鸟嘌呤碱基的DNA序列能够通过鸟嘌呤环的互联作用形成四链螺旋结构，这种结构被称为G-四链体。
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It revealed that imide derivative 4, a potent binder of HIV-1 DNA, had the higher binding affinity with the duplexDNA among six DNA-recognizing mole-cules.
The stability of these triple helixes is so high that homopyrimidine PNA targeted to purine tracts of dsDNA invades the duplex by displacing one of the DNA strands.