期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 137, 期 26, 页码 8428-8434出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.5b01252
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Hyperpolarization (HP) of nuclear spins is critical for ultrasensitive nuclear magnetic resonance (NMR) and magnetic resonance imaging (Mm). We demonstrate an approach for >1500-fold enhancement of key small-molecule metabolites: 1-C-13-pyruvic acid, 1-C-13-sodium lactate, and 1-C-13-acetic acid. The C-13 solution NMR signal of pyruvic acid was enhanced 1600-fold at B = 1 T and 40 degrees C by pre-polarizing at 14 T and similar to 2.3 K. This brute-force approach uses only field and temperature to generate HP. The noted 1 T observation field is appropriate for benchtop NMR and near the typical 1.5 T of MRI, whereas high-field observation scales enhancement as 1/B. Our brute-force process ejects the frozen, solid sample from the low-T, high-B polarizer, passing it through low field (B < 100 G) to facilitate thermal mixing. That equilibrates H-1 and C-13 in hundreds of milliseconds, providing C-13 HP from H-1 Boltzmann polarization attained at high BIT. The ejected sample arrives at a room-temperature, permanent magnet array, where rapid dissolution with 40 degrees C water yields HP solute. Transfer to a 1 T NMR system yields C-13 signals with enhancements at 80% of ideal for noted polarizing conditions. High-resolution NMR of the same product at 9.4 T had consistent enhancement plus resolution of C-13 shifts and J-couplings for pyruvic acid and its hydrate. Comparable HP was achieved with frozen aqueous lactate, plus notable enhancement of acetic acid, demonstrating broader applicability for small-molecule NMR and metabolic MRI. Brute-force avoids co-solvated free-radicals and microwaves that are essential to competing methods. Here, unadulterated samples obviate concerns about downstream purity and also exhibit slow solid-state spin relaxation, favorable for transporting HP samples.
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