Moody M R, van Genderen M H, Buck H M
Department of Organic Chemistry, Eindhoven University of Technology, The Netherlands.
Biopolymers. 1990;30(5-6):609-18. doi: 10.1002/bip.360300513.
Phosphate-methylated (P.M.) DNA possesses a very high affinity for complementary natural DNA, as a result of the absence of interstrand electrostatic repulsions. In this study, a model system phosphate-methylated d[Cn] with natural d(Gk) (n less than k) is chosen for an investigation of the thermodynamic properties that determine duplex stability. The enthalpy change of a melting transition is shown to be considerably larger than is observed for corresponding natural DNA duplexes. It is found that delta Hn0 of GG/CC nearest neighbor pairwise interaction equals -15.6 kcal/mol, compared to -11.0 kcal/mol for the natural analog. The entropy change is strongly dependent on the length of the natural DNA strand and the number of phosphate-methylated DNA oligomers hybridized. The results are explained by means of a model in which a cooperative effect for subsequent hybridizations of phosphate-methylated DNA oligomers is assumed, thus giving additional stability.
磷酸甲基化（P.M.）DNA对互补的天然DNA具有非常高的亲和力，这是由于链间不存在静电排斥作用。在本研究中，选择了一个磷酸甲基化的d[Cn]与天然d(Gk)（n小于k）的模型系统，来研究决定双链稳定性的热力学性质。结果表明，熔解转变的焓变比相应的天然DNA双链体观察到的焓变大得多。研究发现，GG/CC最近邻碱基对相互作用的ΔHn0等于-15.6千卡/摩尔，而天然类似物为-11.0千卡/摩尔。熵变强烈依赖于天然DNA链的长度以及杂交的磷酸甲基化DNA寡聚物的数量。这些结果通过一个模型来解释，该模型假设磷酸甲基化DNA寡聚物的后续杂交存在协同效应，从而赋予额外的稳定性。
