- 作者: 魏明財,林淑萍,林維政,甘魯生
- 作者服務機構: Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C.
- 中文摘要: A more elaborate sequence-independent triple-helix formation viability study was carried out and extended from a recombination-like triple-helical DNA motif of a previous study (J. Mol. Recognition 14, 122-139 (2001)). The intended triple-helix was formed by mixing one part of a DNA hairpin duplex and one part of a single (or third) strand identical to one of the duplex strands and complementary to the other strand. In contrast to the common purine and pyrimidine motifs in triple-stranded DNA, the strands of the recombination-like motif are not monotonously built from pyrimidine only, or purine only, in the sequence. The stability of the recombination-like motif triplexes with varying sequences was monitored by UV thermal melting curves. The results showed that the order of the stability of the R-form DNA base triads (J. Mol. Biol., 239, 181-200 (1994)) is G*(G B C) > C*(C B G) > A*(A B T) > T*(T B A) (the Watson-Crick base pair is denoted in the parentheses) in 200 mM NaCl, at pH 7. In an attempt to increase the stability of the triplex in the recombination-like motif, we replaced cytidine by 5-methylcytidine (mC) of the third strand. There is a general trend that mC modification stabilizes the complex (< 2 °C per mC). The complex is furthermore stabilized by Mg2+ ion. The Tm increases from 7 to 2 °C from less stable to highly stable triplex by 20 mM Mg2+ ion in solution.
- 英文摘要: --
- 中文關鍵字: DNA triplex; Recombination-like motif; Parallel homologous strands; Base modification; Thermal melting.
- 英文關鍵字: --