Grupo de Espectroscopía Molecular (GEM), Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain.
Phys Chem Chem Phys. 2010 Nov 14;12(42):14128-34. doi: 10.1039/c0cp00665c. Epub 2010 Sep 27.
The complexes uracil-water and thymine-water have been investigated using laser ablation molecular-beam Fourier transform microwave (LA-MBFTMW) spectroscopy. Only one conformer of each complex has been observed. The spectra of the parent and several isotopically enriched species with (15)N at uracil moiety and D or (18)O at water have been measured. For uracil-water the spectra are characterized by the hyperfine structure of two (14)N nuclei. For thymine-water only the parent and (18)O-water enriched species have been observed. Their spectra are characterized by the hyperfine structure of two (14)N nuclei with an additional doubling due to the A and E states of the torsion of the methyl group. The barrier to internal rotation of the methyl group has been determined from the analysis of the spectrum. Investigation of the structure of the adducts from the rotational constants of the different isotopologues shows that the observed conformers correspond to the most stable forms in which water closes a cycle with the nucleic acid bases forming N-H(NB)...O(w) and H(W)...O=C(2) hydrogen bonds.
已使用激光烧蚀分子束傅里叶变换微波（LA-MBFTMW）光谱法研究了尿嘧啶-水和胸腺嘧啶-水复合物。仅观察到每个复合物的一种构象。已经测量了母体和几种同位素丰度的物种的光谱，其中尿嘧啶部分具有（15）N 且水具有 D 或（18）O。对于尿嘧啶-水，光谱的特征在于两个（14）N 核的超精细结构。对于胸腺嘧啶-水，仅观察到母体和（18）O-水丰富的物种。它们的光谱的特征在于两个（14）N 核的超精细结构，由于甲基的扭转的 A 和 E 态，存在额外的倍增。通过对光谱的分析，确定了甲基内旋转的势垒。从不同同位素异构体的旋转常数研究加合物的结构表明，观察到的构象对应于最稳定的形式，其中水与核酸碱基形成 N-H（NB）...O（w）和 H（W）...O=C（2）氢键，形成一个环。
