Lycksell P O, Gräslund A, Claesens F, McLaughlin L W, Larsson U, Rigler R
Department of Biophysics, University of Stockholm, Arrhenius Laboratory, Sweden.
Nucleic Acids Res. 1987 Nov 11;15(21):9011-25. doi: 10.1093/nar/15.21.9011.
Studies of 1H NMR selective saturation recovery were performed to determine the imino proton exchange with solvent water of the base pairs in the Eco RI endonuclease recognition sequence GAATTC, placed at the center of self-complementary decamer and dodecamer oligonucleotides. In one oligonucleotide the innermost adenine was replaced by the fluorescent base analogue 2-aminopurine (2AP). From the measurements at different concentrations of TRIS buffer acting as proton exchange catalyst, base pair lifetimes were evaluated. The results at 25 degrees show that the AT base pairs have lifetimes of the order of a few ms, whereas the surrounding GC base pairs in a dodecamer have lifetimes of about 100 ms. The (2AP)T base pair has a shorter lifetime than the corresponding AT base pair. The temperature dependent optical absorption, and for the 2AP containing oligonucleotide fluorescence, were used to study the single strand-duplex equilibrium of the decamers. The results indicate that NMR and the optical techniques, although applied at very different concentrations, monitor the same conformational transition of the oligonucleotide.
进行了1H NMR选择性饱和恢复研究，以确定位于自互补十聚体和十二聚体寡核苷酸中心的Eco RI核酸内切酶识别序列GAATTC中碱基对的亚氨基质子与溶剂水的交换。在一种寡核苷酸中，最里面的腺嘌呤被荧光碱基类似物2-氨基嘌呤（2AP）取代。通过在不同浓度的作为质子交换催化剂的TRIS缓冲液中的测量，评估了碱基对的寿命。25摄氏度时的结果表明，AT碱基对的寿命约为几毫秒，而十二聚体中周围的GC碱基对的寿命约为100毫秒。(2AP)T碱基对比相应的AT碱基对寿命更短。利用温度依赖性光吸收以及含2AP寡核苷酸的荧光，研究了十聚体的单链-双链平衡。结果表明，NMR和光学技术虽然应用于非常不同的浓度，但监测的是寡核苷酸相同的构象转变。
