Detection of small structural changes of DNA under physiological conditions by a combination of site-selective deuteration and Raman difference spectroscopy

通过位点选择性同位素标记和紫外共振拉曼（UVRR）光谱学的组合，即同位素编辑的拉曼光谱学，已经检测到DNA中选定的鸟嘌呤残基的微小结构变化。在251 nm光激发下，测量[8-^2H]鸟嘌呤标记和未标记寡核苷酸的UVRR光谱。在未标记和标记的DNA之间的差谱中，拉曼信号来自标记位置处的残基，并且其他组分被抵消。为了获得将同位素编辑拉曼光谱应用于鸟嘌呤残基的基本数据，通过检查七种同位素取代（2-^<13>C、2-^<15>N、6-^<18>O、7-^<15>N、8-^<13>C、9-^<15>N和1 '-^<13>C）的波数位移来研究C8-氘代鸟嘌呤环的UVRR带的振动模式。通过比较研究了拉曼谱带的氢键灵敏度， ...更多信息 ng的拉曼光谱记录在几种不同的氢键性质的溶剂。在1525 cm ~ 2附近的负峰、<-1>1485/1465 cm ~ 2附近的强正/负峰对<-1>和1025/1040 cm ~ 2附近的弱正/负峰对<-1>分别作为鸟嘌呤环上N_7、C_6 =O和N_1-H/C_2-NH_2上氢键的标记。在不存在和存在cAMP受体蛋白（CRP）的情况下测量标记和未标记寡聚体的UVRR光谱，已知CRP与双链DNA的鸟嘌呤残基形成氢键。同位素编辑谱图显示CRP与鸟嘌呤残基的C6=O形成强氢键，而与N7原子没有形成强氢键。同位素编辑的拉曼光谱可以为生理条件下的DNA-药物系统提供所选鸟嘌呤残基的结构信息。少

Small structural changes of selected guanine residues in DNA have been detected by a combination of site-selective isotope labeling and ultraviolet resonance Raman (UVRR) spectroscopy, I.e. isotope-edited Raman spectroscopy. UVRR spectra were measured for [8-^2H]guaninelabeled and unlabeled oligonucleotides excited at 251nm light. In the difference spectrum between the unlabeled and labeled DNA, Raman signals arise from the residue at the labeled position and the other components were canceled out. Thus, it becomes possible to extract the Raman signals of the selected guanine in olinonucleotides.To obtain basic data for applying isotope-edited Raman spectroscopy to guanine residues, vibrational modes of UVRR bands of the C8-deuterated guanine ring were studied by examining the wavenumber shifts upon seven isotopic substitutions (2-^<13>C, 2-^<15>N, 6-^<18>O, 7-^<15>N, 8-^<13>C, 9-^<15>N and 1'-^<13>C). The hydrogen bond sensitivities of the Raman bands were also investigated by compari … More ng the Raman spectra recorded in several solvents of different hydrogen bonding properties. Some of the Raman bands have been found to be hydrogen bonding markers at specific donor or acceptor sites on the guanine ring, A negative peak around 1525 cm^<-1> a strong positive/negative peak pair around 1485/1465 cm^<-1>, and a weak positive/negative peak pair around 1025/1040cm^<-1> serve as markers of hydrogen bonding at N7, C6=O, and N1-H/C2-NH_2, respectively.The applicability of isotopeedited Raman spectroscopy has been tested by using a 22-mer oligonucleotide duplex. UVRR spectra of the labeled and unlabeled oligomers were measured in the absence and presence of cAMP receptor protein (CRP),Which is Known to hydrogen-bonded to guanine residues of duplex DNA. The isotope-edited spectra showed that CRP is hydrogen-bonded strongly to C6=O of guanine residues but not N7 atom. Isotope-edited Raman spectroscopy can provide structural information of a selected guanine residue for DNA-drug systems under physiological conditions. Less