Simultaneous 15N polarization of several biocompatible substrates in ethanol–water mixtures by signal amplification by reversible exchange (SABRE) method,Magnetic Resonance in Chemistry

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Simultaneous 15N polarization of several biocompatible substrates in ethanol–water mixtures by signal amplification by reversible exchange (SABRE) method
Magnetic Resonance in Chemistry ( IF 1.9 ) Pub Date : 2021-06-04 , DOI: 10.1002/mrc.5184
Alexey S Kiryutin _{1,

2} , Alexandra V Yurkovskaya _{1,

2} , Pavel A Petrov ₃ , Konstantin L Ivanov _{1,

2}

Affiliation

Signal amplification by reversible exchange (SABRE) is a popular method for generating strong signal enhancements in nuclear magnetic resonance (NMR). In SABRE experiments, the source of polarization is provided by the nonthermal spin order of parahydrogen (pH₂, the H₂ molecule in its nuclear singlet spin state). Polarization formation requires that both pH₂ and a substrate molecule bind to an Ir-based complex where polarization transfer occurs. Subsequently, the complex dissociates and free polarized substrate molecules are formed. In this work, we present approaches towards biocompatible SABRE, meaning that several small biomolecules are simultaneously polarized by using the SABRE method in water–ethanol solutions at room temperature. We are able to demonstrate significant ¹⁵N-NMR signal enhancements in water–ethanol solutions for biomolecules like nicotinamide, metronidazole, adenosine-5′-monophosphate, and 4-methylimidazole and found that the first three substrates are polarized at the same level as a well-known pyridine. We show that simultaneous polarization of several molecules is indeed feasible when the reactions are carried out at an ultralow field of about 400–500 nT. The achieved enhancements are between 100-fold and 15,000-fold. The resulting ¹⁵N polarization (maximal value about 4% achieved for metronidazole and pyridine at 45°C) strongly depends on the sample temperature, pH₂ bubbling pressure, and pH₂ flow. One more parameter, which is important for optimizing the enhancement, is the solvent pH. Hence, this study presents a step in developing biocompatible SABRE polarization and gives a clue on how such SABRE experiments should be optimized to achieve the highest NMR signal enhancement.

中文翻译：

通过可逆交换 (SABRE) 方法的信号放大对乙醇-水混合物中的几种生物相容性底物同时进行 15N 极化

通过可逆交换 (SABRE) 进行信号放大是在核磁共振 (NMR) 中产生强信号增强的常用方法。在 SABRE 实验中，极化源由仲氢的非热自旋顺序（p H ₂，处于其核单重态自旋状态的 H ₂分子）提供。极化形成要求p H ₂底物分子与发生极化转移的基于 Ir 的复合物结合。随后，复合物解离并形成自由极化的底物分子。在这项工作中，我们提出了实现生物相容性 SABRE 的方法，这意味着在室温下使用 SABRE 方法在水-乙醇溶液中同时极化几个小生物分子。我们能够证明重要的¹⁵N-NMR 信号在水-乙醇溶液中对烟酰胺、甲硝唑、5'-单磷酸腺苷和 4-甲基咪唑等生物分子的信号增强，发现前三种底物的极化水平与众所周知的吡啶相同。我们表明，当反应在约 400-500 nT 的超低场下进行时，几个分子的同时极化确实是可行的。实现的增强在 100 倍到 15,000 倍之间。产生的¹⁵ N 极化（甲硝唑和吡啶在 45°C 时的最大值约为 4%）很大程度上取决于样品温度、p H ₂起泡压力和p H ₂流动。另一个对优化增强很重要的参数是溶剂的 pH 值。因此，本研究提出了开发生物相容性 SABRE 极化的一个步骤，并为如何优化此类 SABER 实验以实现最高 NMR 信号增强提供了线索。

更新日期：2021-06-04

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