Development of Novel Spin-labeled Nucleosides which detect base-pairing

我们设计了一种新型的自旋标记核苷，其中一个自旋源，一个N-叔丁基氨氧基自由基，直接连接到核碱基。合成了2-N-叔丁基氨基腺苷、2-N-叔丁基氨基羟肌苷、8-N-叔丁基氨基羟肌苷和5-N-叔丁基氨基胞嘧啶衍生物，并用电子顺磁共振（EPR）研究了它们的稳定性和性质。研究N-叔丁基氨基胍核苷与互补碱基形成氢键后的EPR谱是否发生变化是一个有趣的问题。在CH_2Cl_2溶液中，O-硅基-5-N-叔丁基氨基胞嘧啶核苷的EPR谱发生了变化。在寡核苷酸中引入2-N-叔丁基氨基腺苷，测定了其EPR谱。所得寡核苷酸的EPR谱在磷酸盐缓冲液中显示三条谱线。当与互补链形成双链体时，高谱线消失，表明EPR谱可能提供有用的寡核苷酸结构信息。2-N-叔丁胺氧肌苷的EPR谱显示了pH依赖性，这是由于嘌呤结构的改变

We designed novel spin-labeled nucleosides, in which a spin source, an N-tert-butylaminoxyl radical, was directly attached to nucleobase. 2-N-tert-Butylaminoxyladenosine, 2-N-tert-butylaminoxylinosine, and 8-N-tert-butylaminoxylinosine, and 5-N-tert-butylaminoxylcytidine derivative were synthesized and thier stabilities and properties were studied by using electron peramagnetic resonance(EPR). It was of interest to investigate if EPR spectra of N-tert-butylaminoxylnucleosides changed upon formation of hydrogen bonding with complementary base. EPR spectra of O-silylated-5-N-tert-butylaminoxylcytidine in CH_2Cl_2 changed upon addition of O-silylated guanosine, which might form hydrogen bonds with the aminoxyl cytidine. 2-N-tert-Butylaminoxyladenosine was introduced into oligoncleotide and its EPR spectra were measured. The EPR spectrum of the obtained oligonucleotide showed three lines in phosphate buffer. The high line disappeared upon duplex formation with the complementary strand to show that the EPR spectra might give useful information on the structure of oligonucleotide. EPR spectra of 2-N-tert-butylaminoxylinosine showed pH dependency due to structural change of purine moiety