Long-lived states to sustain hyperpolarized magnetization
- 3 November 2009
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 106 (44), 18469-18473
- https://doi.org/10.1073/pnas.0908123106
Abstract
Major breakthroughs have recently been reported that can help overcome two inherent drawbacks of NMR: the lack of sensitivity and the limited memory of longitudinal magnetization. Dynamic nuclear polarization (DNP) couples nuclear spins to the large reservoir of electrons, thus making it possible to detect dilute endogenous substances in magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI). We have designed a method to preserve enhanced ("hyperpolarized") magnetization by conversion into long-lived states (LLS). It is shown that these enhanced long-lived states can be generated for proton spins, which afford sensitive detection. Even in complex molecules such as peptides, long-lived proton states can be sustained effectively over time intervals on the order of tens of seconds, thus allowing hyperpolarized substrates to reach target areas and affording access to slow metabolic pathways. The natural abundance carbon-13 polarization has been enhanced ex situ by almost four orders of magnitude in the dipeptide Ala-Gly. The sample was transferred by the dissolution process to a high-resolution magnet where the carbon-13 polarization was converted into a long-lived state associated with a pair of protons. In Ala-Gly, the lifetime T(LLS) associated with the two nonequivalent H(alpha) glycine protons, sustained by suitable radio-frequency irradiation, was found to be seven times longer than their spin-lattice relaxation time constant (T(LLS)/T(1) = 7). At desired intervals, small fractions of the populations of long-lived states were converted into observable magnetization. This opens the way to observing slow chemical reactions and slow transport phenomena such as diffusion by enhanced magnetic resonance.Keywords
This publication has 39 references indexed in Scilit:
- Diffusion Coefficients of Biomolecules Using Long-Lived Spin StatesJournal of the American Chemical Society, 2009
- Generation of hyperpolarized substrates by secondary labeling with [1,1- 13 C] acetic anhydrideProceedings of the National Academy of Sciences, 2009
- Increasing Hyperpolarized Spin Lifetimes Through True Singlet EigenstatesScience, 2009
- Singlet states open the way to longer time‐scales in the measurement of diffusion by NMR spectroscopyConcepts in Magnetic Resonance Part A, 2008
- Hyperpolarized 13 C allows a direct measure of flux through a single enzyme-catalyzed step by NMRProceedings of the National Academy of Sciences, 2007
- Hyperpolarized 89Y Offers the Potential of Direct Imaging of Metal Ions in Biological Systems by Magnetic ResonanceJournal of the American Chemical Society, 2007
- Long-lived nuclear spin states in the solution NMR of four-spin systemsJournal of Magnetic Resonance, 2006
- Real-time metabolic imagingProceedings of the National Academy of Sciences, 2006
- Adiabatic Single Scan Two-Dimensional NMR SpectrocopyJournal of the American Chemical Society, 2003
- An improved sequence for broadband decoupling: WALTZ-16Journal of Magnetic Resonance (1969), 1983