髮夾式去氧寡核酸三螺旋AGAXAG(X=G, C)+(TY)_3T_4(ZT)_3 (Y, Z=C, 5-methylcytidine)形成與性質之研究

Studies of the Formation and Characterization of Hairpin DNA Triples of AGAXAG (X=G, C)+(TY)_3T_4(ZT)_3 (Y, Z=C, 5-methylcytidine)

蔡欣泰(H. T. Tsay) ； 林淑萍(S. B. Lin) ； 蔡玲美(L. M. Tsay) ； 甘魯生(L. S. Kan)

《化學》 54卷1期 (1996/03) Pp. 24-32

https://doi.org/10.6623/chem.1996004

摘要

以一系列的去氧寡核酸，其鹼基序列為AGAXAG(X=G, C)和(TY)_3T_4(ZT)_3 (Y, Z = C, 5-methylC)，來研究含三個TAT及三個C^+GC共六個三鹼基組的三螺旋之形成，其中T_4是髮夾式結構要件。研究方法有紫外線混合滴定法，紫外線熔點測定法及圓二色光譜等。研究的條件事變寡核酸鏈內鹼基成分、酸鹼度(pH 4至 7)及鹽的濃度(NaCl 0.1至1M)，當X=G時可得下列之結果：(1)：含六個三鹼基組的髮夾式三螺旋的穩定性良好；(2)：5-MethylC不但可穩定Hoogsteen的氫鍵亦可穩定Watson-Crick的氫鍵；(3)：此等三螺旋在低pH值，高鹽濃度下較穩定。如X=C，則(4)：以無氫鍵之CCC三組代替一個C^+GC三組髮夾式三螺旋仍相當穩定。此類三螺旋之性質和X=G三螺旋相似。由此開啟了以此等髮夾式三螺旋來研究各種和酸鹼基衍生物形成三螺旋之能力的大門。

並列摘要

A series of oligodeoxyribonucleotides, with sequences AGAXAG (X =G, C) and (TY)_3T_4(ZT)_3(Y, Z = C, 5-methylC), were used to study the formation and properties of hairpin triplexes with a T_4 loop by uv mixing titration, uv melting point, and circular dichroism methods. For experimental conditions pH ranges from 4 to 7 and NaCl concentration ranges from 0.1 to 1 M, we concluded that (1) a very short hairpin triplex can be formed with only three TAT and three C^+GC triads (X = G); (2) 5-methylC stablizes both Hoogsteen and Watson-Crick hydroger. bonds in the triplex (X = G and C); (3) the triplexes under study are more stable in lower pH and higher NaCl concentrations (X = G and C); and most importantly, (4) triplexes formed with CCC non-hydrogen bonded triad are fairly stable, which greatly encourages further studies of triplexes containing nucleic acid base analogs.