New trityl radicals for studies of biopolymers by NMR and EPR spectroscopies

核磁共振（NMR）和电子顺磁共振（EPR）光谱通常用于研究生物聚合物。NMR可以提供高分辨率的结构，但本质上是一种不敏感的技术，这限制了其应用。然而，快速出现的动态核极化（DNP）领域通过将自旋极化从电子转移到核自旋，使NMR的灵敏度提高了数百倍。该提案的主要目标是制备新的基于三芳基甲基（三苯甲基）的单自由基以及用于DNP-NMR的双自由基。螺环己醇衍生的三苯甲基自由基将解决三苯甲基的有限水溶性和它们的电子弛豫速率的缺点。除了解决三苯甲基的水溶性与单自由基的生物应用，新的双自由基，特别是氮氧自由基-三苯甲基自由基也将被制备。此外，两类新的三苯甲基为基础的自由基，三苯甲基-三苯甲基双自由基和1，3-bisdiphenylene-2-phenylallyl（BDPA）-三苯甲基双自由基将被制备。这些窄线双自由基将被制备用于增加几个低伽马核（13 C、15 N和29 Si）的极化。由于三苯甲基自由基在还原条件下具有高稳定性，因此一些新的自由基将用于细胞内DNP-NMR。马来酰亚胺和碘乙酰胺衍生的三苯甲基自由基将被制备用于蛋白质的定点自旋标记，后者也将被应用于核酸，用于EPR光谱研究。三苯甲基自由基也将连接到荧光标记的细胞穿透肽用于细胞递送。这样的肽缀合物将使得能够通过荧光显微镜观察三苯甲基自由基的细胞位置。选定的三苯甲基自由基也将用于最先进的脉冲DNP-NMR实验。提出的自由基有可能显着影响DNP-NMR领域，以及EPR。

Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies are commonly used for investigation of biopolymers. NMR can provide high-resolution structures but is an inherently insensitive technique, which limits its applications. However, the rapidly emerging field of dynamic nuclear polarization (DNP) has led to an increased sensitivity of NMR, of up to several hundred-fold, by transferring spin polarization from electrons to nuclear spins. The main goal of this proposal is the preparation of new triarylmethyl (trityl)-based mono- as well as biradicals for DNP-NMR. A spirocyclohexanolyl-derived trityl radical will address shortcomings of limited water-solubility of trityls and of their electron relaxation rates. In addition to addressing water-solubility of trityls for biological applications with monoradicals, new biradicals will also be prepared, in particular nitroxide-trityl radicals. Moreover, two new classes of trityl-based radicals will be prepared, trityl-trityl biradicals and 1,3-bisdiphenylene-2-phenylallyl (BDPA)-trityl biradicals. These narrow-line biradicals will be prepared for increased polarization of several low-gamma nuclei (13C, 15N and 29Si). Since trityl radicals possess high stability under reducing conditions, some of the new radicals will be used for in-cell DNP-NMR. Maleimide- and iodoacetamide-derived trityl radicals will be prepared for site-directed spin labeling of proteins and the latter will also be applied for nucleic acids, for studies by EPR spectroscopy. Trityl radicals will also be attached to a fluorescently-labeled, cell-penetrating peptide for cellular delivery. Such peptide conjugates will enable visualization of the cellular location of the trityl radicals by fluorescence microscopy. Selected trityl radicals will also be used for state-of-the-art pulsed DNP-NMR experiments. The proposed radicals have the potential to significantly impact the field of DNP-NMR, as well as EPR.