Broadband adiabatic inversion cross‐polarization to integer‐spin nuclei with application to deuterium NMR
Broadband adiabatic inversion cross‐polarization to integer‐spin nuclei with application to deuterium NMR
复制标题
宽带绝热反演交叉极化到整数自旋核及其在氘核磁共振中的应用
DOI：
10.1002/mrc.5145
复制
发表时间：
2021
影响因子：
2
通讯作者：
Schurko, Robert W.
中科院分区：
文献类型：
--
作者：
Altenhof, Adam R.;Wi, Sungsool;Schurko, Robert W.
整数自旋四极核的固态核磁共振（SSNMR）光谱对于各种材料和生物固体的分子水平表征非常重要；在整数自旋中，2H (S= 1) 是迄今为止研究最广泛的，因为它在探测动态运动中很有用。整数自旋核的 SSNMR 谱通常具有非常广泛的粉末图案，这些图案主要来自一阶四极相互作用的影响；因此，获取高质量光谱仍然是一个挑战。宽带绝热反演交叉极化 (BRAIN-CP) 脉冲序列能够在大带宽上进行交叉极化 (CP) 增强，已成功采集整数自旋核的 SSNMR 谱，包括 14N (S= 1)，特别是与具有扫频 WURST 脉冲 (WURST-CPMG) 的 Carr-Purcell/Meiboom-Gill 脉冲序列结合使用，用于基于 T2 的信号增强。然而，迄今为止，还没有对 BRAIN-CP 基础的自旋动力学进行系统研究，也没有任何具体的理论模型来帮助其参数化以应用于整数自旋核。此外，BRAIN-CP/WURST-CPMG 方案尚未被证明可广泛应用于宽线或超宽线 (UW)2H SSNMR。在此，我们提供了静态条件下自旋-1/2 → 自旋-1 CP 的 BRAIN-CP 脉冲序列的理论描述，包括一组描述 Hartmann-Hahn 匹配条件的解析方程和阐明涉及偏振转移、相干交换和绝热反演的 CP 机制的数值模拟。提出了几个实验示例，用于与理论模型和先前开发的整数自旋 CP 方法进行比较，证明了从高效宽带 CP 中快速获取 2 H NMR 谱。
Solid‐state NMR (SSNMR) spectroscopy of integer‐spin quadrupolar nuclei is important for the molecular‐level characterization of a variety of materials and biological solids; of the integer spins,2H (S= 1) is by far the most widely studied, due to its usefulness in probing dynamical motions. SSNMR spectra of integer‐spin nuclei often feature very broad powder patterns that arise largely from the effects of the first‐order quadrupolar interaction; as such, the acquisition of high‐quality spectra continues to remain a challenge. The broadband adiabatic inversion cross‐polarization (BRAIN‐CP) pulse sequence, which is capable of cross‐polarization (CP) enhancement over large bandwidths, has found success for the acquisition of SSNMR spectra of integer‐spin nuclei, including14N (S= 1), especially when coupled with Carr–Purcell/Meiboom–Gill pulse sequences featuring frequency‐swept WURST pulses (WURST‐CPMG) forT2‐based signal enhancement. However, to date, there has not been a systematic investigation of the spin dynamics underlying BRAIN‐CP, nor any concrete theoretical models to aid in its parameterization for applications to integer‐spin nuclei. In addition, the BRAIN‐CP/WURST‐CPMG scheme has not been demonstrated for generalized application to wideline or ultra‐wideline (UW)2H SSNMR. Herein, we provide a theoretical description of the BRAIN‐CP pulse sequence for spin‐1/2 → spin‐1 CP under static conditions, featuring a set of analytical equations describing Hartmann–Hahn matching conditions and numerical simulations that elucidate a CP mechanism involving polarization transfer, coherence exchange, and adiabatic inversion. Several experimental examples are presented for comparison with theoretical models and previously developed integer‐spin CP methods, demonstrating rapid acquisition of2H NMR spectra from efficient broadband CP.