The application of various action spectroscopy and absorption spectroscopy methods for studying the structure of biological molecules and their constituent fragments in an isolated state is considered. The main attention is paid to the results achieved in the study of the nucleosides which are the structural units of DNA and RNA. It has been demonstrated that modern low-temperature spectroscopy methods allow registration the vibrational spectra of isolated nucleosides in neutral or ionized form. It was shown that most of the nucleosides can be converted into the gas phase by prolonged evaporation from the Knudsen cell without thermal decomposition. Cooling molecules to cryogenic temperatures plays an important role in these studies. The conformational equilibrium of the gas phase between syn and anti subsets of nucleosides is maintained due to fast cooling when frozen in inert matrices. Within these subsets, interconversion processes between conformers can occur during cooling if the conformers are separated by low energy barriers. In inert gas matrices at 6 K, subsets of the syn-conformers of deoxyribonucleosides are mainly frozen with the C2′-endo structure of the deoxyribose ring. The structures of molecular ions of nucleosides are very different from their neutral forms. In particular protonation leads to the domination of the enol forms of thymidine, as well as syn-conformations of adenosine, stabilized by the intramolecular hydrogen bond N3H⁺•••O5.

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低温下分离出的核苷的分子结构和振动光谱（综述文章）

考虑了各种作用光谱和吸收光谱方法在研究处于分离状态的生物分子及其组成片段的结构中的应用。主要关注于在核苷（DNA和RNA的结构单元）的研究中获得的结果。已经证明，现代的低温光谱方法允许以中性或离子化形式记录分离的核苷的振动光谱。结果表明，通过长时间从Knudsen细胞蒸发而不会发生热分解，大多数核苷都可以转化为气相。在这些研究中，将分子冷却至低温温度起着重要作用。之间的气相的构象平衡顺式和当在惰性基质中冷冻时，由于快速冷却，可以维持抗核苷的抗亚群。在这些子集中，如果构象异构体之间被低能垒隔开，则在冷却过程中可能会发生构象异构体之间的相互转化过程。在6 K的惰性气体基质中，脱氧核糖核苷的顺式构象的子集主要以脱氧核糖环的C2'-内切结构冷冻。核苷分子离子的结构与其中性形式有很大不同。特别地，质子化导致胸苷的烯醇形式以及由分子内氢键N3H ⁺ ••O5稳定的腺苷的顺式构象占优势。