Forces that control triple helix stability

2 Forces that control triple helix stability 

Correspondingly G in the third strand binds to G in the duplex [21,22,23], The second motif often requires high divalent cation concentrations, and the third strand being G-rich, is prone to form self-associated structures involving G-quartets [24]. This is particularly pronounced when the third strand is a triplexforming oligonucleotide (TFO) [25,26]. Another competing structure, a G-A parallel duplex, can also interfere with triplex formation [27]. 

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