PNA-DNA Chimeras Containing 5-Alkynyl-pyrimidine PNA Units. Synthesis, Binding Properties, and Enzymatic Stability
作者:Zoltán Bajor、Gyula Sági、Zsuzsanna Tegyey†、Ferenc Kraicsovits
DOI:10.1081/ncn-120025243
日期:2003.10.1
Three chimeric dimer synthons (oeg_t(NH)T, oeg_up(NH)T and oeg_uh(NH)T) containing thymine (t), 5-(1-propynyl)-uracil (up) and 5-(1-hexyn-1-yl)-uracil (uh) PNA units with N-(2-hydroxyethyl)glycine (oeg) backbone were synthesized in solution and incorporated into T-20 oligonucleotide analogues, using standard P-amidite chemistry. Insertion of dimer blocks led to destabilization of duplexes with dA(20) target. The smallest T-m drops were found for chimeras containing oeg_up(NH)T dimers. Incorporation of the chimeric synthons into the 3'-end of T-20 brought about growing resistance to 3'-exonucleolytic (SV PDE) cleavage in the order of oeg_t(NH)T < oeg_up(NH)T < oeg_uh(NH)T. Due to different endonuclease activities of 3'- and 5'-exonucleases applied, placing of five consecutive dimers at the 5'-terminus resulted in a relatively smaller, but also side-chain dependent, stabilization towards the hydrolysis by 5'-exonuclease (BS PDE). Neither exonucleases (SV and BS PDE) nor an endonuclease (Nuclease P-1) could hydrolyse the unnatural phosphodiester bond linking the 3'-OH of thymidine to the terminal OH of N-(2-hydroxyethyl)glycine PNA backbone.