Kanehara H, Nishi M, Makino K
Department of Polymer Science and Engineering, Kyoto Institute of Technology, Japan.
Nucleic Acids Symp Ser. 1995(34):53-4.
Duplex stability measured by the melting temperature (Tm) of the duplex between oligodeoxynucleotide whose one phosphate linkage is replaced by thiophosphate and its complementary DNA/RNA. The resultant Tm values were higher for Sp isomer than Rp isomer when DNA was a target. When RNA was a target, however, Rp isomers of 5'-dGCTsTCG-3' and 5'-dGCAsTCG-3' had higher stability than Sp isomers. NMR and CD spectra obtained for the duplexes of such isomers exhibited only small difference for the base protons around the phosphorothioate linkage and could not account for the difference in Tm. Temperature dependent NMR spectra showed broadening for the AH8 proton signal of Rp and for the TH6 proton resonance of Sp. This characteristic broadening may be indicative of the different melting behavior of the duplexes of the isomers.
通过硫代磷酸酯取代一个磷酸键的寡脱氧核苷酸与其互补DNA/RNA之间双链体的解链温度（Tm）来测量双链体稳定性。当DNA为靶标时，Sp异构体的所得Tm值高于Rp异构体。然而，当RNA为靶标时，5'-dGCTsTCG-3'和5'-dGCAsTCG-3'的Rp异构体比Sp异构体具有更高的稳定性。此类异构体双链体的NMR和CD光谱显示，硫代磷酸酯键周围碱基质子的差异很小，无法解释Tm的差异。温度依赖性NMR光谱显示，Rp的AH8质子信号和Sp的TH6质子共振出现展宽。这种特征性展宽可能表明异构体双链体具有不同的解链行为。
