Calderone D M, Mantilla E J, Hicks M, Huchital D H, Murphy W R, Sheardy R D
Department of Chemistry, Seton Hall University, South Orange, New Jersey 07079-2694, USA.
Biochemistry. 1995 Oct 24;34(42):13841-6. doi: 10.1021/bi00042a016.
The interaction specificities of cobalt(III) ammines with the self-complementary eight-base pair DNA oligomer (5medC-dG)4 have been investigated. Standard protocol for preparing DNA samples calls for heat annealing the DNA oligomer in phosphate buffer in the absence or presence of cobalt(III) ammine complex for 2 min at 80 degrees C, followed by slow cooling to 25 degrees C. An alternative method for DNA preparation is incubation of the oligomer in the presence of the cobalt(III) complex at 37 degrees C followed by exhaustive dialysis. The conformational properties of the thus-treated DNA oligomer were determined by inspection of the UV and CD spectra at 25 and 95 degrees C and thermal denaturation studies. With heat annealing in the absence of any cobalt(III) complex, (5medC-dG)4 assumes a double-stranded, right-handed B conformation at 25 degrees C. Upon heat annealing in the presence of 200 microM [Co(NH3)6]3+, (5medC-dG)4 assumes a double-stranded, left-handed Z conformation at 25 degrees C. In contrast, the CD and UV spectra of (5medC-dG)4 heat annealed in the presence of 200 microM [Co(NH3)5(OH2)]3+ are consistent with a distorted B-like conformation at 25 degrees C. Incubation of the oligomer in the presence of [Co(NH3)5(OH2)]3+ results in modification of the conformational properties of the oligomer at both 25 and 95 degrees C relative to the untreated oligomer. The extent of modification depends upon the incubation concentration of [Co(NH3)5-(OH2)]3+ and the reaction time. Atomic absorption (AA) analyses of these treated DNA samples indicate a high degree of cobalt association to the oligomer.(ABSTRACT TRUNCATED AT 250 WORDS)
已对钴（III）氨配合物与自互补八碱基对DNA寡聚物（5 - 甲基胞嘧啶 - 鸟嘌呤）4的相互作用特异性进行了研究。制备DNA样品的标准方案要求在不存在或存在钴（III）氨配合物的情况下，将DNA寡聚物在磷酸盐缓冲液中于80℃加热退火2分钟，然后缓慢冷却至25℃。另一种DNA制备方法是在37℃下将寡聚物与钴（III）配合物一起孵育，随后进行彻底透析。通过检查25℃和95℃下的紫外光谱和圆二色光谱以及热变性研究，确定了如此处理后的DNA寡聚物的构象性质。在不存在任何钴（III）配合物的情况下进行热退火时，（5 - 甲基胞嘧啶 - 鸟嘌呤）4在25℃时呈现双链右手B构象。在存在200μM [Co(NH3)6]3 + 的情况下进行热退火时，（5 - 甲基胞嘧啶 - 鸟嘌呤）4在25℃时呈现双链左手Z构象。相比之下，在存在200μM [Co(NH3)5(OH2)]3 + 的情况下进行热退火的（5 - 甲基胞嘧啶 - 鸟嘌呤）4的圆二色光谱和紫外光谱与25℃时扭曲的类B构象一致。在[Co(NH3)5(OH2)]3 + 存在下孵育寡聚物会导致寡聚物在25℃和95℃时相对于未处理的寡聚物的构象性质发生改变。改变程度取决于[Co(NH3)5(OH2)]3 + 的孵育浓度和反应时间。对这些处理后的DNA样品进行的原子吸收（AA）分析表明钴与寡聚物有高度的结合。（摘要截于250字）
