Hyperpolarized ~(89)Y Offers the Potential of Direct Imaging of Metal Ions in Biological Systems by Magnetic Resonance

摘要

Hyperpolarization of nuclear spins can produce a dramatic increase in sensitivity for NMR active nuclei. Although the idea of transferring spin polarization from electrons to nuclei by dynamic nuclear polarization (DNP) to create a hyperpolarized NMR sample has been around since the mid-1950s, applications of this technology for study of liquid samples have appeared only recently. In 2003, Ardenkjaer-Larsen et al. developed an automated method to polarize ~(13)C nuclei at low temperatures in the presence of a stable trityl radical then bring the sample to room temperature very quickly to perform NMR measurements. Obviously, this method was most practical for long T_1 ~(13)C nuclei such as non-protonated carbonyl or carboxyl carbons in rapidly tumbling small molecules, which yielded NMR signal enhancements of 10 000-fold or higher. One of the more exciting applications of this technology was reported shortly thereafter by Golman et al. who demonstrated that it is practical to do real time metabolic imaging of [1-~(13)C]pyruvate, [1-~(13)C]lactate, and [1-~(13)C]alanine in live animals using ~(13)C chemical shift imaging (lactate and alanine are quickly formed from the injected hyperpolarized pyruvate through single-enzyme catalyzed steps).