Storage of nuclear magnetization as long-lived singlet order in low magnetic field.

Storage of nuclear magnetization as long-lived singlet order in low magnetic field.

MedLine Citation:	PMID: 20855584 Owner: NLM Status: MEDLINE
Abstract/OtherAbstract:	Hyperpolarized nuclear states provide NMR signals enhanced by many orders of magnitude, with numerous potential applications to analytical NMR, in vivo NMR, and NMR imaging. However, the lifetime of hyperpolarized magnetization is normally limited by the relaxation time constant T(1), which lies in the range of milliseconds to minutes, apart from in exceptional cases. In many cases, the lifetime of the hyperpolarized state may be enhanced by converting the magnetization into nuclear singlet order, where it is protected against many common relaxation mechanisms. However, all current methods for converting magnetization into singlet order require the use of a high-field, high-homogeneity NMR magnet, which is incompatible with most hyperpolarization procedures. We demonstrate a new method for converting magnetization into singlet order and back again. The new technique is suitable for magnetically inequivalent spin-pair systems in weak and inhomogeneous magnetic fields, and is compatible with known hyperpolarization technology. The method involves audio-frequency pulsed irradiation at the low-field nuclear Larmor frequency, employing coupling-synchronized trains of 180° pulses to induce singlet-triplet transitions. The echo trains are used as building blocks for a pulse sequence called M2S that transforms longitudinal magnetization into long-lived singlet order. The time-reverse of the pulse sequence, called S2M, converts singlet order back into longitudinal magnetization. The method is demonstrated on a solution of (15)N-labeled nitrous oxide. The magnetization is stored in low magnetic field for over 30 min, even though the T(1) is less than 3 min under the same conditions.

Authors:	Giuseppe Pileio; Marina Carravetta; Malcolm H Levitt
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Publication Detail:	Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2010-09-20
Journal Detail:	Title: Proceedings of the National Academy of Sciences of the United States of America Volume: 107 ISSN: 1091-6490 ISO Abbreviation: Proc. Natl. Acad. Sci. U.S.A. Publication Date: 2010 Oct
Date Detail:	Created Date: 2010-10-06 Completed Date: 2010-11-16 Revised Date: 2011-07-27
Medline Journal Info:	Nlm Unique ID: 7505876 Medline TA: Proc Natl Acad Sci U S A Country: United States
Other Details:	Languages: eng Pagination: 17135-9 Citation Subset: IM
Affiliation:	School of Chemistry, Southampton University, Hampshire SO17 1BJ, United Kingdom.
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MeSH Terms
Descriptor/Qualifier:	Magnetic Resonance Spectroscopy / instrumentation, methods* Magnetics* Nitrous Oxide / chemistry
Chemical
Reg. No./Substance:	10024-97-2/Nitrous Oxide
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