Towards uniform enhancement in solid-state cross polarization magnetic angle spinning NMR: A scheme incorporating cross polarization with rotational resonance
Towards uniform enhancement in solid-state cross polarization magnetic angle spinning NMR: A scheme incorporating cross polarization with rotational resonance
复制标题
DOI：
10.1063/1.2206787
复制
发表时间：
2006-06-21
影响因子：
4.4
通讯作者：
Ding, Shangwu
中科院分区：
文献类型：
--
作者：
Hou, Guangjin;Deng, Feng;Ding, Shangwu
描述了一种最近提出的在魔角旋转下实现固体中低γ核素均匀交叉极化增强的实验方案，称为定量交叉极化（QUCP）[侯，《化学物理快报》421，356（2006）]，并通过全面的理论分析、数值模拟以及对均匀标记和天然丰度固体的实验研究加以支持。该方法将交叉极化与偶极辅助旋转共振（DARR）[竹越，《化学物理快报》344，631（2001）]宽带同核重耦技术相结合，以在快速魔角旋转下获得定量CP谱。除了对我们在前一封信中报道的现象进行正确和系统的解释外，这项工作还提出了进行QUCP实验的一些一般性指导原则。可以确定的是，虽然QUCP中的增强因子取决于CP接触时间，但对于所有类型的碳基团仍然可以实现均匀增强。对于天然丰度样品，极化转移速率通常比标记样品慢，但在混合期间稀自旋之间总能达到准平衡，并且尽管所需的DARR照射时间可能长得多，但仍可实现均匀增强。对于标记样品，QUCP实验的时间增益几乎与常规CP相同。对于天然丰度样品，它通常比单脉冲实验好得多。使用了各种代表性系统，包括均匀的C - 13标记的DL -丙氨酸和C - 13、N - 15标记的L -酪氨酸，以及天然丰度的丙氨酸、酪氨酸和富马酸单乙酯，来验证我们的理论分析和数值模拟的有效性，并展示本方法的实用性和优势。（c）2006美国物理学会。
A recently proposed experimental scheme for achieving uniform cross polarization enhancement of low-gamma nuclear species in solids under magic angle spinning, termed quantitative cross polarization (QUCP) [Hou , Chem. Phys. Lett. 421, 356 (2006)], is described, supported with comprehensive theoretical analysis, numerical simulation, and experimental investigation with both uniformly labeled and naturally abundant solids. This method combines cross polarization with dipolar-assisted rotational resonance (DARR) [Takegoshi , Chem. Phys. Lett. 344, 631 (2001)] broadband homonuclear recoupling technique to achieve quantitative CP spectra under fast magic angle spinning. In addition to the correct and systematical interpretation on the phenomenon we reported in the previous Letter, a number of general guidelines for performing QUCP experiments are presented in this work. It is firmly established that while the enhancement factor in QUCP depends on the CP contact time, uniform enhancement can nevertheless be realized for all types of carbon group. For natural abundance samples, the polarization transfer rate is generally slower than that in labeled samples, but quasiequilibrium among dilute spins in the mixing period can always be reached and uniform enhancement can be achieved albeit the DARR irradiation time needed can be much longer. For labeled samples, the time gain of QUCP experiment is almost the same as that of conventional CP. For natural abundance samples, it is generally much better than single-pulse experiment. Various representative systems, including uniformly C-13-labeled DL-alanine and C-13, N-15 labeled L-tyrosine, as well as naturally abundant alanine, tyrosine, and monoethyl fumarate, are used to verify the validity of our theoretical analysis and numerical simulation and to demonstrate the utility and advantages of the present approach. (c) 2006 American Institute of Physics.