Thomas R
Laboratoire de Génétique, Faculté des Sciences, Université Libre de Bruxelles, Rhode-St-Genèse, Belgium.
Gene. 1993 Dec 15;135(1-2):77-9. doi: 10.1016/0378-1119(93)90051-4.
Nucleic acids display a very characteristic ultraviolet absorption spectrum with a maximum near 260 nm and a minimum near 230 nm. It was discovered in 1950 that the spectrum of native DNA is much lower than the spectrum calculated from its constituent nucleotides (nt). The observed absorbance strongly increases (hyperchromic effect), not only following hydrolysis, but also following mild treatments, known to respect the phosphoester bonds between nt (and to have little effect on the molecular weight). These results show that DNA has a secondary structure made of secondary valence interactions between the nitrogen bases, and that this secondary structure collapses (DNA denaturation) following mild treatments (low pH, high temperature or, even simply, low salt concentration).
核酸呈现出非常独特的紫外吸收光谱，在260nm附近有最大值，在230nm附近有最小值。1950年发现，天然DNA的光谱比由其组成核苷酸（nt）计算出的光谱低得多。观察到的吸光度不仅在水解后会显著增加（增色效应），而且在已知能保留nt之间磷酸酯键（且对分子量影响很小）的温和处理后也会增加。这些结果表明，DNA具有由氮碱基之间的次级价键相互作用构成的二级结构，并且这种二级结构在温和处理（低pH、高温或甚至仅仅是低盐浓度）后会瓦解（DNA变性）。
