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本文应用镧系离子作为核磁共振探针的方法,研究了5′-CMP,5-AMP以及5′-IMP三种核苷酸在酸性水溶液中的构象分布。将实验测得的~1H NMR谱的镧系诱导假接触位移、纵向弛豫速率增强以及邻位自旋耦合常数等数据用计算机进行分析处理。结果表明,核苷酸分子在水溶液中的构象以一组构象异构体平衡共存。与晶态相比,分子中绕单键旋转的二面角以及戊糖环的折叠形式均有一定的变化,但碱基仍以稳定的反式存在。用镧系离子核磁共振探针法作溶液中分子构象分析是一种定量化的方法。同时对镧系诱导假接触位移、顺磁弛豫加强数据以及邻位自旋耦合常数、NOE数据进行综合分析可以得出可靠的结果。通常,分子在溶液中以一系列构象异构体平衡共存。
In this paper, we have studied the conformational distribution of 5’-CMP, 5’-IMP and 5’-IMP nucleotides in acidic aqueous solution using lanthanide ions as NMR probes. The experimentally measured ~ 1H NMR spectra of lanthanide-induced false contact displacement, longitudinal relaxation rate enhancement and ortho-spin coupling constants and other data were analyzed by computer. The results show that the conformation of nucleotide molecules in aqueous solution coexist in equilibrium with a set of conformers. Compared with the crystalline state, the dihedral angles around the single bond in the molecule and the folding form of the pentose ring have some changes, but the base still exists in a stable trans. Lanthanide ion NMR probe method for the solution of molecular conformation analysis is a quantitative method. At the same time, reliable results can be obtained by synthetically analyzing Lanthanoid induced false contact displacement, paramagnetic relaxation enhancement data and ortho-spin coupling constants and NOE data. In general, molecules coexist in equilibrium in a series of conformers.