DNA BENDING EFFECT OF REPLACING ADENINE W/ GUANINE NMR & COMPUTER EXPERIMENTS

小凹槽的宽度按下式确定 三个密切相关的I I-mer B-DNA双链，代号为AAA、GAA和 GGA C-C-T-C-A-C-T-C-C G-G-A-G-T-G-A-G-G-G AAA C-C-T-C-A-C-T-C-C-G-G-A-G-T-G-A-G-C-T-C-A-C-T-C-T-C-C-C G-G-A-G-T-G-A-G-G-G GGA III通过监测链间NOE 在腺嘌呤的H2和3‘-相邻残基的H1’之间 500兆赫的互补链。已经表明，该宽度 在富含GC的寡核苷酸中，小槽的宽度很窄 狭窄的小凹槽不是A-道DNA特有的东西。 凹槽的宽度由局部序列上下文和 不依赖于邻近的A-道DNA。我们还知道，DNA 折弯与假定反式的核苷酸单位有关 A区5‘端C4’-C5‘构象和异构体 A-道3‘端的结构。鉴于我们之前的 观察到富含GC的低聚物中也存在DNA弯曲和扭曲 GAA和GGA，我们已经进行了一系列的‘H-H，’H-“P和‘H-13C 用COSY核磁共振实验确定‘H-’H，‘H_31p，31p_i 3C，3 债券联结。糖磷酸盐的各种偶合常数 GAA和GGA中的主干正在沿着双工的每个链 通过计算机模拟提取。除了提取 耦合常数，我们还记录了GaA的NOESY谱 和GGA在不同的混合时间。耦合数据与NOESY 关于这些低聚物的距离数据将被用来推导出 均衡的空间构型。据认为，这些数据 将有助于更好地理解DNA弯曲问题。

The width of the minor groove was determined in the following three closely related I I-mer B-DNA duplexes code named AAA, GAA and GGA C-C-T-C-A-A-A-C-T-C-C G-G-A-G-T-T-T-G-A-G-G AAA C-C-T-C-A-A-A-C-T-C-C G-G-A-G-T-T-T-G-A-G-G GAA C-C-T-C-A-A-A-C-T-C-C G-G-A-G-T-T-T-G-A-G-G GGA III by monitoring the interstrand NOE between the H2 of adenine and Hl' of the 3'-neighboring residue from the complementary strand at 500 MHz. It has been shown that the width of the minor groove was narrow in the GC rich oligonucleotides and that the narrow minor groove was not something endemic to A-tract DNA. The width of the groove is dictated by local sequence contexts and independent of neighboring A-tract DNA. It is also known that DNA bending is associated with nucleotidyl units assuming trans conformation about C4'-C5' at the 5' end of A-tract, and heteronomous structures at the 3' end of the A-tract. In view of our previous observation that DNA bends and kinks also occur in GC rich oligomers GAA and GGA, we have carried out a series of 'H-H, 'H-"P and 'H- 13C COSY NMR experiments to determine 'H-'H, 'H_31 p, 31 p_ I 3C, three bond couplings. The various coupling constants of the sugar phospahte backbone in GAA and GGA along each chain of the duplex are being extracted using computer simulation. In addition to extracting the coupling constants, we have also recorded the NOESY spectra for GAA and GGA at various mixing times. The coupling data and the NOESY distance data on these oligomers will be used to derive an ensemble of spatial configurations in equilibrium. It is believed that these data will lead to a better understanding of the DNA bending problem.