Elliott Stuart J, Stern Quentin, Cala Olivier, Jannin Sami
Univ. Lyon, CNRS, ENS Lyon, UCBL, Université de Lyon, CRMN UMR 5280, 69100, Villeurbanne, France.
Univ. Lyon, CNRS, ENS Lyon, UCBL, Université de Lyon, CRMN UMR 5280, 69100, Villeurbanne, France.
Solid State Nucl Magn Reson. 2021 Dec;116:101762. doi: 10.1016/j.ssnmr.2021.101762. Epub 2021 Oct 16.
A strategy of dipolar order mediated nuclear spin polarization transfer has recently been combined with dissolution-dynamic nuclear polarization (dDNP) and improved by employing optimized shaped radiofrequency pulses and suitable molecular modifications. In the context of dDNP experiments, this offers a promising means of transferring polarization from high-gamma H spins to insensitive C spins with lower peak power and lower energy compared with state-of-the-art cross-polarization schemes. The role of local molecular groups and the glassing matrix protonation level are both postulated to play a key role in the polarization transfer pathway via an intermediary reservoir of dipolar spin order. To gain appreciation of the mechanisms involved in the dipolar order mediated polarization transfer under dDNP conditions, we investigate herein the influence of the pivotal characteristics of the sample makeup: (i) revising the protonation level for the constituents of the DNP glass; and (ii) utilizing deuterated molecular derivatives. Experimental demonstrations are presented for the case of [1-C]sodium acetate. We find that the proton sample molarity has a large impact on both the optimal parameters and the performance of the dipolar order mediated cross-polarization sequence, with the C signal build-up time drastically shortened in the case of high solvent protonation levels. In the case of a deuterated molecular derivative, we observe that the nearby H substituted methyl group is deleterious to the H→C transfer phenomenon (particularly at low levels of sample protonation). Overall, increased solvent protonation makes the dipolar order governed polarization transfer significantly faster and more efficient. This study sheds light on the influential sample formulation traits which govern the dipolar order-controlled transfer of polarization and indicates that the polarization transfer efficiencies of deuterated molecules can be boosted and reach high performances simply by adequate solvent protonation.
一种由偶极序介导的核自旋极化转移策略最近已与溶解动态核极化（dDNP）相结合，并通过采用优化的整形射频脉冲和适当的分子修饰得到改进。在dDNP实验的背景下，与现有技术的交叉极化方案相比，这提供了一种将极化从高γ氢自旋转移到低灵敏度碳自旋的有前景的方法，且具有更低的峰值功率和能量。据推测，局部分子基团和玻璃化基质的质子化水平在通过偶极自旋序中间库的极化转移途径中都起着关键作用。为了深入了解dDNP条件下偶极序介导的极化转移所涉及的机制，我们在此研究样品组成的关键特性的影响：（i）改变DNP玻璃成分的质子化水平；（ii）使用氘代分子衍生物。给出了[1-C]醋酸钠情况的实验演示。我们发现质子样品摩尔浓度对偶极序介导的交叉极化序列的最佳参数和性能都有很大影响，在高溶剂质子化水平的情况下，碳信号建立时间会大幅缩短。在氘代分子衍生物的情况下，我们观察到附近的氢取代甲基对氢→碳转移现象有害（特别是在低样品质子化水平时）。总体而言，溶剂质子化程度的提高使偶极序控制的极化转移明显更快且更有效。这项研究揭示了控制偶极序控制的极化转移的有影响的样品配方特征，并表明通过适当的溶剂质子化可以提高氘代分子的极化转移效率并达到高性能。
