Sowers L C, Shaw B R, Sedwick W D
Department of Medicine, Duke University, Durham, N.C.
Biochem Biophys Res Commun. 1987 Oct 29;148(2):790-4. doi: 10.1016/0006-291x(87)90945-4.
Substitution of a methyl group in the 5-position of pyrimidines increases melting temperatures and modifies biological properties of DNA. Increased DNA stability is often attributed to hydrophobic interactions between water and the methyl group. However, we present evidence that the major effect of methyl substitution is to increase the molecular polarizability of the pyrimidine, thereby increasing the base stacking. Experimentally determined base stacking interaction constants for free bases in water are shown to correlate well with calculated molecular polarizability and DNA melting temperatures.
嘧啶5位上甲基的取代增加了DNA的解链温度并改变了其生物学特性。DNA稳定性的增加通常归因于水与甲基之间的疏水相互作用。然而，我们提供的证据表明，甲基取代的主要作用是增加嘧啶的分子极化率，从而增强碱基堆积。实验测定的水中游离碱基的碱基堆积相互作用常数与计算得到的分子极化率和DNA解链温度具有良好的相关性。
