一种新的测定寡糖链中糖体亚谱的NMR方法

报道一种新的测定寡糖链糖体亚谱的NMR方法, 称为MMDY混合脉冲梯度选择一维HOHAHA法. 本方法采用MMDY混合脉冲与双梯度自旋回波脉冲相结合, 为解决高度重叠的¹H NMR谱图分析困难提供了有力手段. 本方法的主要特点是: 采用双梯度自旋回波脉冲进行选择激发, 与差谱为基础的选择激发方法相比不但可节省测定时间, 而且谱图干净, 没有差谱伪峰; MMDY混合脉冲的磁化接力相干转移非常有效, 远程磁化转移信号的灵敏度高, 对于偶合常数大约为1 Hz的微弱偶合自旋体系, 如阿拉伯糖和鼠李糖, 也能够得到完整的亚谱; 梯度脉冲只是用于相干路径选择, 灵敏度比较高, 并且纯吸收形的高质量亚谱不经过复杂的Z-滤波步骤就可以快速得到, 因此比较适用于常规样品分析. 以苷类化合物为例讨论本方法的特点以及在谱峰高度的寡糖结构测定中的应用.

A New NMR Method for Extracting Subspectra of Individ-ualComponents of Sugar Chains

A new pulse sequence is proposed for extracting subspectra of individual components of sugar chains. The method uses a combination of the MMDY composite pulse and the double pulsed field gradient spin-echo and is shown to be useful in the analysis of complex spectra with many overlapped signals. The main advantages of this method are: (i) a significant decrease in experiment acquisition times; (ii) the magnetization transfer is especially efficient, for example, for sugar residues such as Ara and Rha, which have one of the coupling of ca. 1 Hz around the sugar rings, complete subspectra can be quickly obtained; (iii) high-quality pure-absorption phase subspectra can be recorded without the use of the Z-filter technique; (iv) since the gradients merely serve to suppress unwanted signals, they are not subject to the sensitivity losses associated with gradient coherence pathway selection. Its application to the separation of severely overlapping spin systems is illustrated using glycoside sample.