A physico-chemical study of triple helix formation by an oligodeoxythymidylate with N3′→P5′ phosphoramidate linkages

摘要

Non-denaturing gel retardation assay, DNA melting experiments and FTIR spectroscopy were used to characterize the triple helix formed by a 15mer 2′-deoxythymidylate with N3′→P5′ phosphoramidate linkages with its target sequence. The results indicate that: (i) the pentadecadeoxythymidylate with phosphoramidate linkages [dT₁₅(np)] is highly potent to form a triple helix with a dT₁₅·dA₁₅ target duplex through Hoogsteen base-pairing; (ii) it forms a dT₁₅(np)·dA₁₅xdT₁₅(np) triplex with the single-stranded oligo-2′-deoxyadenylate (dA₁₅) without detectable double-helical intermediate; (iii) it does not only form a triple helix on the dT₁₅·dA₁₅ target duplex, but also partially displaces the dT₁₅ strand from the dT₁₅·dA₁₅ duplex to form a dT₁₅(np)·dA₁₅xdT₁₅(np) complex.