Orekhov Vladislav Yu, Ibraghimov Ilghiz, Billeter Martin
Swedish NMR Centre, Göteborg University, Box 465, 40530 Göteborg, Sweden.
J Biomol NMR. 2003 Oct;27(2):165-73. doi: 10.1023/a:1024944720653.
Resolution depends on the number of points sampled in a FID; in indirectly detected dimensions it is an important determinant of the total experiment time. Based on the high redundancy present in NMR data, we propose the following timesaving scheme for three-dimensional spectra. An extensive grid of discrete t1- and t2-values is used, which increases resolution while preserving the spectral width. Total experiment time is reduced by avoiding the recording of t3-FIDs for selected pairs of t1 and t2; typically the recording is omitted for about 75% of the (t1,t2) combinations. These data sets are referred to as sparse, and post-experimental processing making optimal use of spectral redundancy provides the missing, non-recorded data. We have previously shown that three-way decomposition (TWD) within the MUNIN approach provides a practical way to process dense NMR data sets. Here, a novel TWD algorithm [Ibraghimov, (2002) Numer. Linear Algebra Appl. 9, 551-565] is used to complement a sparsely recorded time-domain data set by providing the missing FIDs for all (t1,t2) combinations omitted in the experiment. A necessary condition is that for each t1-value at least a few FIDs are recorded, and similar for each t2-value. The method is demonstrated on non-uniformly sampled (15)N-NOESY-HSQC data sets recorded for the 14 kD protein azurin. The spectra obtained by TWD, reconstruction and ordinary transform to frequency-domain are, in spite of the large number of signals and the high dynamic range typical for NOESYs, highly similar to a corresponding reference spectrum, for which all (t1,t2) combinations were recorded.
分辨率取决于在自由感应衰减（FID）中采样的点数；在间接检测维度中，它是总实验时间的一个重要决定因素。基于核磁共振（NMR）数据中存在的高冗余性，我们针对三维谱图提出了以下节省时间的方案。使用了一个广泛的离散t1和t2值网格，这在保持谱宽的同时提高了分辨率。通过避免记录选定的t1和t2对的t3-FID，总实验时间得以减少；通常约75%的（t1,t2）组合的记录被省略。这些数据集被称为稀疏数据集，实验后利用谱冗余进行的最佳处理可提供缺失的未记录数据。我们之前已经表明，MUNIN方法中的三向分解（TWD）为处理密集的NMR数据集提供了一种实用方法。在此，一种新颖的TWD算法[伊布拉吉莫夫，（2002年）《数值线性代数及其应用》9，551 - 565]被用于通过为实验中省略的所有（t1,t2）组合提供缺失的FID来补充稀疏记录的时域数据集。一个必要条件是对于每个t1值至少记录几个FID，对于每个t2值也是如此。该方法在为14 kD蛋白质天青蛋白记录的非均匀采样（15）N - NOESY - HSQC数据集上得到了验证。尽管存在大量信号以及典型的NOESY高动态范围，但通过TWD、重建并常规转换到频域得到的谱图与相应的参考谱图高度相似，参考谱图记录了所有（t1,t2）组合。
