Sensitivity optimized HCN and HCNCH experiments for 13C/15N labeled oligonucleotides
Sensitivity optimized HCN and HCNCH experiments for 13C/15N labeled oligonucleotides
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DOI：
10.1023/a:1008369515755
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发表时间：
1998-10-01
影响因子：
2.7
通讯作者：
Sklenái, V
中科院分区：
文献类型：
--
作者：
Fiala, R;Jiang, F;Sklenái, V
C-13/N-15 标记寡核苷酸研究中使用的三重共振 HCN 和 HCNCH 实验包括延长的进化周期（通常长达 100 ms），以允许通过复杂的异核自旋网络进行相干转移。不幸的是，由于单键 H-1-C-13 偶极相互作用主导的快速自旋-自旋弛豫，大部分磁化强度在演化过程中丢失。最近证明，通过将自旋系统保持在不受强偶极耦合影响的质子-碳多量子相干状态，可以显着提高实验的灵敏度。然而，多量子相干性对同核以及长程异核相互作用非常敏感。由于这些相互作用而产生的不需要的磁化转移可以将灵敏度降低回单量子实验的水平，对于某些自旋部分，甚至完全消除信号。在本文中，我们表明，与非选择性实验相比，重新聚焦干扰相干性的改进 HCN 方案通常可将灵敏度提高 1.5 至 4 倍。此外，还提出了灵敏度大幅提高的新型多量子 2D 和 3D HCNCH 实验。
Triple resonance HCN and HCNCH experiments used in studies of C-13/N-15 labeled oligonucleotides include extended evolution periods (typically up to 100 ms) to allow coherence transfer through a complex heteronuclear spin network. Unfortunately, most of the magnetization is lost during the evolution due to fast spin-spin relaxation dominated by one-bond H-1-C-13 dipolar interaction. As demonstrated recently, the sensitivity of the experiments can be dramatically improved by keeping the spin system in a state of proton-carbon multiple-quantum coherence which is not affected by the strong dipolar coupling. However, the multiple-quantum coherence is very sensitive to homonuclear as well as long-range heteronuclear interactions. Unwanted magnetization transfer due to these interactions can reduce the sensitivity back to the level of a single-quantum experiment and, for some spin moieties, even eliminate the signal completely. In the present paper we show that a modified HCN scheme that refocuses the interfering coherences improves sensitivity routinely by a factor of 1.5 to 4 over a nonselective experiment. In addition, novel multiple-quantum 2D and 3D HCNCH experiments with substantially enhanced sensitivity are presented.