TENSOR DETERMINATION OF N1 SITE IN DEOXYGUANOSINE

固态核磁共振谱包含大量有关 特定原子核的取向。化学位移各向异性(CSA) 可以表示为与方向相关的二阶张量 在其频率分布上。对修正案的解释 频率要求张量元素的方向 被映射到分子参照系中。脱氧鸟苷 碱基在N1位合成15N标记。张量 通过测量二维固体核磁共振进行了分析 粉末材料的PISEMA谱。一维15N 谱产生CSA张量的主要元素和 可以模拟二维谱来确定取向 15N-1H偶极耦合张量相对于CsA张量。这个 偶极张量的方向是沿着连接 两个原子核，因此是分子参照系的锚。这个 鸟苷碱基的15N CSA张量的主值为？11= 54ppm；？22=108ppm；相对于外部铵？33=201ppm 硫酸盐。模拟的二维谱表明， ？33单元与N-H键共线。主要要素？11 和？22位于嘌呤环平面上。这种关系现在可以是 用于从15N化学位移中获得结构信息 定向DNA的频率。

Solid-state NMR spectra contain a wealth of information regarding orientation of specific nuclei. The chemical shift anisotropy (CSA) can be represented as a second rank tensor with orientation dependence in its frequency distribution. The interpretation of the CSA frequency requires that the orientation of the elements of the tensor be mapped into the molecular frame of reference. The deoxyguanosine base was synthetically labeled with 15N in position N1. The tensor analysis was made by measuring the two-dimensional solid-state NMR PISEMA spectrum of the powder material. The one-dimensional 15N spectrum yields the principal elements of the CSA tensor and the two-dimensional spectrum can be simulated to determine the orientation of the 15N-1H dipolar coupling tensor relative to the CSA tensor. The orientation of the dipolar tensor is along the vector connecting the two nuclei, hence an anchor to the molecular frame of reference. The principal values of the 15N CSA tensor for the guanosine base are ?11= 54 ppm; ?22=108 ppm; and ?33=201 ppm relative to external ammonium sulfate. The simulated two-dimensional spectrum indicates that the ?33 element is colinear with the N-H bond. The principle elements ?11 and ?22 lie in the plane of the purine ring. This relation can now be used to elicit structural information from 15N chemical shift frequencies of oriented DNA.