Publications

Hyperpolarized (HP) 13C nuclear magnetic resonance (NMR) spectroscopy enables real-time observation of metabolic fluxes but is typically limited to single-shot measurements due to complex preparation procedures and low experimental throughput. Here, we established a rapid and experimentally accessible workflow for temporally controlled HP measurements in living cells. Using SABRE-SHEATH at 0.4 & micro;T, we achieved 7.7% +/- 0.2% 13C polarization of 50 mM [1-13C]pyruvate within 60 s. Simple 1:50 dilution with phosphate-buffered D2O yielded cell-compatible solutions that retained 5.3% +/- 0.4% polarization of 1.3 mM pyruvate without multi-step purification. Combined with a simplified agarose bead immobilization approach, this enabled four injections of HP pyruvate into the same HeLa cell population within 7 min. Under rapid (approximate to 2 min) reinjection intervals, the pyruvate-to-lactate conversion progressively declined, whereas stable metabolic conversion was maintained at 20 min intervals with intermittent cell medium perfusion. These findings demonstrate that rapid repeated substrate delivery can transiently exhaust cellular metabolic conversion capacity. This experimentally accessible operating mode enables the study of short-term metabolic dynamics that remain obscured in conventional single-shot HP-NMR or long timescale thermally polarized NMR measurements.

JTD Keywords: Bioreactor, Carbon-13, Culture, Glucose, Hyperpolarization, Metabolism, Para-hydrogen, Parahydrogen, Polarization, Pyruvate, Sabre

Hyperpolarized nuclear spins in molecules exhibit high magnetization that is unachievable by classical polarization techniques, making them widely used as sensors in physics, chemistry, and medicine. The state of a hyperpolarized material, however, is typically only studied indirectly and with partial destruction of magnetization, due to the nature of conventional detection by resonant-pickup NMR spectroscopy or imaging. Here, we establish atomic magnetometers with sub-pT sensitivity as an alternative modality to detect in real time the complex dynamics of hyperpolarized materials without disturbing or interrupting the magnetogenesis process. As an example of dynamics that are impossible to detect in real time by conventional means, we examine parahydrogen-induced H-1 and C-13 magnetization during adiabatic eigenbasis transformations at mu mu T-field avoided crossings. Continuous but nondestructive magnetometry reveals previously unseen spin dynamics, fidelity limits, and magnetization backaction effects. As a second example, we apply magnetometry to observe the chemical-exchange-driven C-13 hyperpolarization of [1-C-13]-pyruvate-the most important spin tracer for clinical metabolic imaging. The approach can be readily combined with other high-sensitivity magnetometers and is applicable to a broader range of general observation scenarios involving production, transport, and systems interaction of hyperpolarized compounds.

JTD Keywords: Adiabaticity, Dnp, Field, Hyperpolarization, Nmr, Nuclear spins, Optical magnetometry, Order, Para-hydrogen, Parahydrogen, Polarimetry, Polarization transfer

The combination of a powerful and broadly applicable nuclear hyperpolarization technique with emerging (near-)zero-field modalities offers novel opportunities in a broad range of nuclear magnetic resonance spectroscopy and imaging applications, including biomedical diagnostics, monitoring catalytic reactions within metal reactors and many others. These are discussed along with a roadmap for future developments.

JTD Keywords: Couplings, Hyperpolarization, Nmr, Parahydrogen, Phase, Radicals, Time

Photochemically induced dynamic nuclear polarization (photo-CIDNP) enables nuclear spin ordering by irradiating samples with light. Polarized spins are conventionally detected via high-field chemical-shift-resolved NMR (above 0.1 T). In this Letter, we demonstrate in situ low-field photo-CIDNP measurements using a magnetically shielded fast-field-cycling NMR setup detecting Larmor precession via atomic magnetometers. For solutions comprising mM concentrations of the photochemically polarized molecules, hyperpolarized 1H magnetization is detected by pulse-acquired NMR spectroscopy. The observed NMR line widths are about 5 times narrower than normally anticipated in high-field NMR and are systematically affected by light irradiation during the acquisition period, reflecting a reduction of the transverse relaxation time constant, T2*, on the order of 10%. Magnetometer-detected photo-CIDNP spectroscopy enables straightforward observation of spin-chemistry processes in the ambient field range from a few nT to tens of mT. Potential applications of this measuring modality are discussed.

JTD Keywords: field-dependence, mechanism, nmr, parahydrogen, photo-cidnp, polarization, quinone, spin-hyperpolarization, Radical-pair

Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.

JTD Keywords: electron-paramagnetic-resonance, high-resolution nmr, hydrogen-induced polarization, level anti-crossings, long-lived states, parahydrogen-induced polarization, photosynthetic reaction-center, reversible exchange catalysis, solid-state nmr, Dynamic-nuclear-polarization