Parahydrogen-induced polarization is a hyperpolarization method for enhancing nuclear magnetic resonance signals by chemical reactions/interactions involving the para spin isomer of hydrogen gas. This method has allowed for biomolecules to be hyperpolarized to such a level that they can be used for real time in vivo metabolic imaging. One particularly promising example is fumarate, which can be rapidly and efficiently hyperpolarized at low cost by hydrogenating an acetylene dicarboxylate precursor molecule using parahydrogen. The reaction is relatively slow compared to the timescale on which the hyperpolarization relaxes back to thermal equilibrium, and an undesirable 2nd hydrogenation step can convert the fumarate into succinate. To date, the hydrogenation chemistry has not been thoroughly investigated, so previous work has been inconsistent in the chosen reaction conditions in the search for ever-higher reaction rate and yield. In this work we investigate the solution preparation protocols and the reaction conditions on the rate and yield of fumarate formation. We report conditions to reproducibly yield over 100 mM fumarate on a short timescale, and discuss aspects of the protocol that hinder the formation of fumarate or lead to irreproducible results. We also provide experimental procedures and recommendations for performing reproducible kinetics experiments in which hydrogen gas is repeatedly bubbled into an aqueous solution, overcoming challenges related to the viscosity and surface tension of the water.

仲氢诱导的极化是通过涉及化学反应/相互作用增强核磁共振信号的超极化方法对氢气的自旋异构体。这种方法允许生物分子超极化到可以用于实时体内代谢成像的水平。一个特别有前途的例子是富马酸盐，它可以通过使用仲氢氢化乙炔二羧酸盐前体分子以低成本快速有效地超极化。与超极化松弛回到热平衡的时间尺度相比，该反应相对缓慢，并且不希望的第二氢化步骤可以将富马酸盐转化为琥珀酸盐。迄今为止，氢化化学还没有得到彻底的研究，因此以前的工作在选择的反应条件方面不一致，以寻求更高的反应速率和产率。在这项工作中，我们研究了溶液制备方案和对富马酸盐形成速率和产率的反应条件。我们报告了在短时间内可重复产生超过 100 mM 富马酸盐的条件，并讨论了阻碍富马酸盐形成或导致不可重现结果的协议方面。我们还提供实验程序和建议，用于执行可重复的动力学实验，其中氢气反复鼓泡到水溶液中，克服与水的粘度和表面张力相关的挑战。