Radaelli Alice, Yoshihara Hikari A I, Nonaka Hiroshi, Sando Shinsuke, Ardenkjaer-Larsen Jan Henrik, Gruetter Rolf, Capozzi Andrea
Laboratory for Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland 1015.
Department of Chemistry and Biotechnology, The University of Tokyo, Tokyo, Japan 113-8656.
J Phys Chem Lett. 2020 Aug 20;11(16):6873-6879. doi: 10.1021/acs.jpclett.0c01473. Epub 2020 Aug 10.
SA-BDPA is a water-soluble, narrow-line width radical previously used for dynamic nuclear polarization (DNP) signal enhancement in solid-state magic angle spinning NMR spectroscopy. Here, we report the first study using SA-BDPA under dissolution DNP conditions (6.7 T and 1.15 K). Longitudinal-detected (LOD)-electron spin resonance (ESR) and C DNP measurements were performed on samples containing 8.4 M [C]urea dissolved in 50:50 water:glycerol (v/v) doped with either 60 or 120 mM SA-BDPA. Two distinct DNP mechanisms, both "pure" thermal mixing and a well-resolved solid effect could clearly be identified. The radical's ESR line width (30-40 MHz), broadened predominantly by dipolar coupling, excluded any contribution from the cross effect. Microwave frequency modulation increased the enhancement by DNP at the lower radical concentration but not at the higher radical concentration. These results are compared to data acquired with trityl radical AH111501, highlighting the unusual C DNP properties of SA-BDPA.
SA - BDPA是一种水溶性、窄线宽自由基，以前用于固态魔角旋转核磁共振光谱中的动态核极化（DNP）信号增强。在此，我们报告了在溶解态DNP条件（6.7 T和1.15 K）下使用SA - BDPA的首次研究。对含有溶解于50:50水:甘油（v/v）中的8.4 M [C]尿素且掺杂有60或120 mM SA - BDPA的样品进行了纵向检测（LOD） - 电子自旋共振（ESR）和碳DNP测量。两种不同的DNP机制，即“纯”热混合和清晰分辨的固体效应都能被明确识别。该自由基的ESR线宽（30 - 40 MHz）主要因偶极耦合而变宽，排除了交叉效应的任何贡献。微波频率调制在较低自由基浓度下增加了DNP增强效果，但在较高自由基浓度下未增加。将这些结果与用三苯甲基自由基AH111501获得的数据进行比较，突出了SA - BDPA不同寻常的碳DNP特性。
