Tsay L M, Lin S B, Tsay H T, Chen H H, Kan L S
Institute of Chemistry, Academia Sinica, Taipei, Taiwan.
J Biomol Struct Dyn. 1995 Jun;12(6):1235-45. doi: 10.1080/07391102.1995.10508809.
The UV mixing titration, gel electrophoresis, and CD measurements indicate that oligomers with a basic sequence of 5'-d-T-(C-T-)2C-(T-)4C-(T-C-)2T form a hairpin type triplex with the target 5'-d-A-(G-A-)2G. The stability, measured UV melting temperatures, were studied in aqueous solution as functions of mC (5-methylcytidine) replacement of C, pH (4 to 7), and salt concentrations (up to 1 M). The order of stability is 5'-d-A-(G-A-)2G + 5'-d-T-(C-T-)2C-(T-)4C-(T-C-)2T < 5'-d-A-(G-A-)2G + 5'-d-T-(mC-T-)2mC-(T-)4C-(T-C-)2T approximately 5'-d-A-(G-A-)2G + 5'-d-T-(C-T-)2C-(T-)4 mC-(T-mC-)2T < 5'-d-A-(G-A-)2G + 5'-d-T-(mC-T-)2mC-(T-)4mC-(T-mC-)2T at pH 4. These results indicate that (a) a stable triplex is formed with three T.A.T and three C+.G.C base triads and (b) mC is more effective than C to stablize the triplex formation in acidic condition. Thus, this provides a simple system for further studies of triplex.
紫外混合滴定、凝胶电泳和圆二色测量表明，具有5'-d-T-(C-T-)2C-(T-)4C-(T-C-)2T基本序列的寡聚物与靶标5'-d-A-(G-A-)2G形成发夹型三链体。在水溶液中，以5-甲基胞嘧啶（mC）取代胞嘧啶（C）、pH值（4至7）和盐浓度（高达1 M）为变量，研究了以紫外熔解温度衡量的稳定性。在pH值为4时，稳定性顺序为5'-d-A-(G-A-)2G + 5'-d-T-(C-T-)2C-(T-)4C-(T-C-)2T < 5'-d-A-(G-A-)2G + 5'-d-T-(mC-T-)2mC-(T-)4C-(T-C-)2T ≈ 5'-d-A-(G-A-)2G + 5'-d-T-(C-T-)2C-(T-)4 mC-(T-mC-)2T < 5'-d-A-(G-A-)2G + 5'-d-T-(mC-T-)2mC-(T-)4mC-(T-mC-)2T。这些结果表明：（a）由三个T.A.T和三个C+.G.C碱基三联体形成了稳定的三链体；（b）在酸性条件下，mC比C更有效地稳定三链体的形成。因此，这为进一步研究三链体提供了一个简单的系统。
