Zheng Zeyu, Peng Qiwei, Sun Huijun, Wang Xinchang, Chen Zhong
Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Department of Electronic Science, Xiamen University, Xiamen, 361005, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, 361005, China.
Magn Reson Lett. 2024 May 24;5(1):200137. doi: 10.1016/j.mrl.2024.200137. eCollection 2025 Feb.
Enhancing the sensitivity of nuclear magnetic resonance (NMR) technology has been the focus of NMR research for decades, which offers the potential to significantly expand its applications in chemistry, biology, and medical imaging. Parahydrogen-induced polarization (PHIP) emerges as a cost-effective approach to substantially enhance the sensitivity of NMR. Nevertheless, the amplification of the H signal in PHIP is susceptible to interference from the thermal polarization state H NMR signal. Employing RASER (radiofrequency amplification by stimulated emission of radiation) proves effective in mitigating such interference, which can reduce the linewidth and increase the sensitivity at the same time. In this work, we utilized PHIP and RASER to enhance the signal-to-noise ratio (SNR) of a series of biocompatible alkynyl organic acid molecules. The alkynyl acid with the highest enhancement factor was first identified through PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) experiments. Subsequently, RASER experiments were carried out through hyperpolarization of 5-hexynoic acid, exploring its signal characteristics under varying flow rates and pressures. The SNR of proton signals of 5-hexynoic acid surpassed 150,000, an 18.62-fold improvement compared with traditional hyperpolarized signals in PASADENA, and a markedly narrowed linewidth of 0.06 Hz.
几十年来，提高核磁共振（NMR）技术的灵敏度一直是NMR研究的重点，这为显著扩展其在化学、生物学和医学成像中的应用提供了潜力。仲氢诱导极化（PHIP）作为一种经济高效的方法出现，可大幅提高NMR的灵敏度。然而，PHIP中H信号的放大易受热极化态H NMR信号的干扰。采用RASER（受激辐射射频放大）被证明可有效减轻此类干扰，它能同时减小线宽并提高灵敏度。在这项工作中，我们利用PHIP和RASER提高了一系列生物相容性炔基有机酸分子的信噪比（SNR）。首先通过帕萨迪纳（仲氢与合成使核排列显著增强，PASADENA）实验确定了增强因子最高的炔基酸。随后，通过对5-己炔酸进行超极化开展了RASER实验，探索其在不同流速和压力下的信号特征。5-己炔酸质子信号的SNR超过150,000，与帕萨迪纳传统超极化信号相比提高了18.62倍，线宽显著变窄至0.06 Hz。
