A triplex forming oligonucleotide is complementary pursuant to the G/T or A/G recognition motif to a homopurine, or substantially homopurine target sequence in double stranded nucleic acids, and at least one and preferably all of the guanine bases are replaced by their pyrazolo[3,4-d]pyrimidine analog, namely by 6-amino-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-one. The oliginucleotides containing the pyrazolo[3,4-d]pyrimidine analog of guanine exhibit a lesser degree of self-association, and lack the nucleophilic nitrogen atom in the 7 position of guanine. The latter feature results in a diminished extent of self-crosslinking in ODNs which also have a covalently attached cross-linking agent.
三链体形成寡核苷酸与双链核酸中的同源
嘌呤或基本上同源
嘌呤目标序列互补,其识别基序为G/T或A/G。至少一个,最好是所有
鸟嘌呤碱基被其
吡唑并[3,4-d]
嘧啶类似物取代,即6-
氨基-1H-
吡唑并[3,4-d]
嘧啶-4(5H)-酮。含有
鸟嘌呤的
吡唑并[3,4-d]
嘧啶类似物的寡核苷酸表现出较小程度的自身组装,并且缺乏
鸟嘌呤7位的亲核氮原子。后一特征导致ODN中自交联的程度降低,同时还具有共价连接的
交联剂。