- 作者: Ono, Akira ; 甘魯生
- 作者服務機構: Dept. of Chemistry, Tokyo Metropolitan Univ., Tokyo, Japan
- 中文摘要: The influence of 5-bromo and 2'-O-methyl substitution of pyrimidine bases on nucleic acid triplex formation was examined by thermal denaturation and circular dichroism spectra with the following oligomers: 5'-(U/sub m/)/sub 15/T(I, U/sub m/=2'-O- methyluridine), 5'-(/sup B/U/sub m/)/sub 15/T (II, /sup B/U/sub m/=5-bromo-2'-O-methyluridine), 5'-(C/sub m/U/sub m/)/sub 6/C/sub m/-T (III, C/sub m/=2'-O- methylcytidine), and 5'-(C/sub m//sup B/U/sub m/)/sub 6/ C/sub m/T (IV). Both I and II form triplexes with dA/sub 16/ (A) or 5'-d(C/sub 2/A/sub 16/C/sub 2/)-5'- d(G/sub 2/T/sub 16/G/sub 2/) (D), but III and IV form triplexes with 5'-d(AG)/sub 8/ (G). Triplex formation involving two unmodified oligomers, dT/sub 16/ (T) and 5'- d(CT)/sub 7/ ( C), was used for comparison. The orders of melting temperatures (T/sub m/) of triplexes were II.bcdot.A.bcdot.II (T/sub m/=48.degree.C)>I.bcdot.A.bcdot.I(34.degree.C)>T.bcdot.A.bcdot.T (22.degree.C);II.bcdot.D(T/sub m/=30.degree.C)>I.bcdot.D (22. degree.C)>T.bcdot.D(12.degree.C); and IV.bcdot.G.bcdot.IV (T/sub m/=82.degree.C)>III.bcdot.G.bcdot.III (72.degree.C)>C.bcdot.G.bcdot.C (55.degree.C). The pKa of IV.bcdot.G.bcdot.IV, III.bcdot.G.bcdot.III, and C.bcdot.G.bcdot.C were determined by CD to be 6.5, 6.3, and 6.2, respectively. Triplexes formed by oligonucleotides containing both 2'-O-methyl and 5-bromo substitutions are more stable and have a greater pKa than those formed by oligonucleotides with 2'-O-methyl substitution only; which in turn are more stable and have a greater pKa than those formed by unmodified oligonucleotides.
- 英文摘要: --
- 中文關鍵字: Triplex; Oligonucleotide; Pyrimidine Base; Circular Dichroism; Modification
- 英文關鍵字: 寡核酸;嘧啶鹼;圓二分法;修飾