Dynamic nuclear polarization (DNP) has shown great promise as a tool to enhance the nuclear magnetic resonance signals of proteins in the cellular environment. As sensitivity increases, the ability to select and efficiently polarize a specific macromolecule over the cellular background has become desirable. Herein, we address this need and present a tetrazine-based DNP agent that can be targeted selectively to proteins containing the unnatural amino acid (UAA) norbornene-lysine. This UAA can be introduced efficiently into the cellular milieu by genetic means. Our approach is bio-orthogonal and easily adaptable to any protein of interest. We illustrate the scope of our methodology and investigate the DNP transfer mechanisms in several biological systems. Our results shed light on the complex polarization-transfer pathways in targeted DNP and ultimately pave the way to selective DNP-enhanced NMR spectroscopy in both bacterial and mammalian cells.

中文翻译：

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用于生物系统的基于四嗪的靶向动态核极化剂。

动态核极化（DNP）作为增强细胞环境中蛋白质核磁共振信号的工具已显示出巨大的前景。随着灵敏度的提高，在细胞背景上选择并有效极化特定大分子的能力变得越来越理想。在此，我们满足了这一需求，并提出了一种基于四嗪的 DNP 试剂，该试剂可以选择性地靶向含有非天然氨基酸 (UAA) 降冰片烯赖氨酸的蛋白质。这种 UAA 可以通过遗传手段有效地引入细胞环境中。我们的方法是生物正交的，并且可以轻松适应任何感兴趣的蛋白质。我们阐述了我们方法的范围，并研究了几种生物系统中的 DNP 转移机制。我们的结果揭示了目标 DNP 中复杂的偏振转移途径，并最终为细菌和哺乳动物细胞中选择性 DNP 增强 NMR 光谱铺平了道路。