Magic angle spinning dynamic nuclear polarization solid-state NMR spectroscopy of γ-irradiated molecular organic solids
Magic angle spinning dynamic nuclear polarization solid-state NMR spectroscopy of γ-irradiated molecular organic solids
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DOI：
10.1016/j.ssnmr.2022.101785
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发表时间：
2022-04-08
影响因子：
3.2
通讯作者：
Rossini, Aaron J.
中科院分区：
文献类型：
--
作者：
Carnahan, Scott L.;Chen, Yunhua;Rossini, Aaron J.
在过去的15年里，魔角旋转（MAS）动态核极化（DNP）已经成为一种提高高分辨率固态NMR光谱实验灵敏度的方法。最近，伽马辐照已被用于在各种固体中产生显著浓度的均匀分布的自由基，包括石英、葡萄糖和纤维素。伽马辐照的石英和葡萄糖先前都显示出显着的MAS DNP增强。在这里，γ-照射施加到12个小的有机分子，以测试γ-照射作为一种通用的方法，创造稳定的自由基的MAS DNP实验的有机固体和药物的适用性。在辐照的葡萄糖、组氨酸、苹果酸和丙二酸中观察到自由基浓度在0.25 mM-10 mM范围内，并且通过H-1 -> C-13 CPMAS实验测量，H-1 DNP分别显着增强32、130、19和11。然而，通常在含有芳环的有机分子中观察到低于0.05 mM的自由基浓度，从而阻止了相当大的DNP增强。DNP灵敏度增益的几个照射的化合物超过了可以得到的中继DNP的方法，使用外源性极化剂的解决方案和浸渍程序。在几种情况下，在室温下实现了显着的H-1 DNP增强。这项研究表明，在许多情况下，γ-辐照是一个可行的替代稳定的外源性自由基的DNP实验有机固体。
In the past 15 years, magic angle spinning (MAS) dynamic nuclear polarization (DNP) has emerged as a method to increase the sensitivity of high-resolution solid-state NMR spectroscopy experiments. Recently, gamma-irradiation has been used to generate significant concentrations of homogeneously distributed free radicals in a variety of solids, including quartz, glucose, and cellulose. Both gamma-irradiated quartz and glucose previously showed significant MAS DNP enhancements. Here, gamma-irradiation is applied to twelve small organic molecules to test the applicability of gamma-irradiation as a general method of creating stable free radicals for MAS DNP experiments on organic solids and pharmaceuticals. Radical concentrations in the range of 0.25 mM-10 mM were observed in irradiated glucose, histidine, malic acid, and malonic acid, and significant H-1 DNP enhancements of 32, 130, 19, and 11 were obtained, respectively, as measured by H-1 -> C-13 CPMAS experiments. However, concentrations of free radicals below 0.05 mM were generally observed in organic molecules containing aromatic rings, preventing sizeable DNP enhancements. DNP sensitivity gains for several of the irradiated compounds exceed that which can be obtained with the relayed DNP approach that uses exogeneous polarizing agent solutions and impregnation procedures. In several cases, significant H-1 DNP enhancements were realized at room temperature. This study demonstrates that in many cases gamma-irradiation is a viable alternative to addition of stable exogenous radicals for DNP experiments on organic solids.