Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
Cluster for Pioneering Research, RIKEN, RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
J Phys Chem Lett. 2021 Mar 18;12(10):2645-2650. doi: 10.1021/acs.jpclett.1c00294. Epub 2021 Mar 10.
Triplet dynamic nuclear polarization (triplet-DNP) achieves nuclear spin polarization at moderate temperatures by using spin polarization of photoexcited triplet electrons. The applications of triplet-DNP for biomolecules have been hampered because acenes, the only polarizing agents used so far, tend to aggregate and lose their polarization in biomolecular matrices. Here, we report for the first time use of porphyrins as polarizing agents of triplet-DNP and propose a new concept of aggregation-tolerant polarizing agents. Sodium salts of tetrakis(4-carboxyphenyl)porphyrin (TCPPNa) can be dispersed in amorphous as well as crystalline biomolecular matrices, and importantly, it can generate polarized triplet electrons even in a slightly aggregated state. Triplet-DNP of crystalline erythritol containing slightly aggregated TCPPNa can achieve more than 120-fold signal enhancement. Because TCPPNa is also the first biocompatible triplet-DNP polarizing agent, this work provides a crucial step forward for the biological and medical applications of triplet-DNP.
三重态动态核极化（triplet-DNP）通过利用光激发三重态电子的自旋极化来实现中等温度下的核自旋极化。由于到目前为止仅使用的并五苯类物质容易聚集并在生物分子基质中失去极化，因此三重态-DNP 在生物分子中的应用受到了阻碍。在这里，我们首次报告了将卟啉类化合物用作三重态-DNP 的极化剂，并提出了一种新的聚集容忍性的极化剂概念。四(4-羧基苯基)卟啉钠盐（TCPPNa）可以在无定形和结晶生物分子基质中分散，并且重要的是，即使在稍微聚集的状态下，它也可以产生极化的三重态电子。含有略微聚集的 TCPPNa 的结晶赤藓糖醇的三重态-DNP 可以实现超过 120 倍的信号增强。由于 TCPPNa 也是第一个生物相容的三重态-DNP 极化剂，因此这项工作为三重态-DNP 的生物学和医学应用迈出了关键的一步。
