Long-lived states to sustain hyperpolarized magnetization

Vasos, Paul R.; Sarkar, Riddhiman; Ahuja, Puneet; Jannin, Sami; Ansermet, Jean-Philippe; Konter, J. A.; Hautle, P.; Brandt, B. van den; Bodenhausen, Geoffrey

doi:10.1073/pnas.0908123106

Cited by 183 publications

(215 citation statements)

References 40 publications

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“…Magnetic inequivalence, however, may require that additional steps are taken to suppress the singlet-triplet interconversion during storage periods. Current methods include applying radiofrequency spin locking fields (5,8,9), performing a chemical reaction (10), or rapidly shuttling the sample into a region of low magnetic field (3,4).…”

Section: Introductionmentioning

confidence: 99%

Hyperpolarized singlet NMR on a small animal imaging system

Laustsen

Pileio

Tayler

et al. 2012

Magnetic Resonance in Med

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Nuclear spin hyperpolarization makes a significant advance toward overcoming the sensitivity limitations of in vivo magnetic resonance imaging, particularly in the case of low-gamma nuclei. The sensitivity may be improved further by storing the hyperpolarization in slowly relaxing singlet populations of spin-1/2 pairs. Here, we report hyperpolarized 13 C spin order transferred into and retrieved from singlet spin order using a small animal magnetic resonance imaging scanner. For spins in sites with very similar chemical shifts, singlet spin order is sustained in high magnetic field without requiring strong radiofrequency irradiation. The demonstration of robust singlet-to-magnetization conversion, and vice versa, on a small animal scanner, is promising for future in vivo and clinical deployments. Magn Reson Med 000:000-000, 2012. V C 2012 Wiley Periodicals, Inc.

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Section: Introductionmentioning

confidence: 99%

Hyperpolarized singlet NMR on a small animal imaging system

Laustsen

Pileio

Tayler

et al. 2012

Magnetic Resonance in Med

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“…So far, combinations of hyperpolarization with singlet states have therefore involved conventional hyperpolarization of 13 C magnetization, followed by conversion to singlet order at a later stage (13) or the participation of chemical reactions (10).…”

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confidence: 99%

“…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. long-lived spin states | low-field NMR | singlet states T he NMR of long-lived-spin states is an emerging technique with potential applications to the transport of hyperpolarized spin order and to the investigation of molecular geometry and dynamics (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The long lifetime of long-lived singlet states (in some cases, almost 30 min; ref.…”

mentioning

confidence: 99%

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

Pileio

Carravetta

Levitt

2010

Proc. Natl. Acad. Sci. U.S.A.

176

216

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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.

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“…For example, in liquid state experiments singlet states in nuclear spin pairs can exhibit lifetimes much longer than the single-spin polarization lifetime (T 1 ) [1][2][3][4][5][6][7][8][9][10][11][12]. In addition, nuclear spin singlet states can be used as a resource for spectroscopic interrogation of couplings within many-spin systems, including J-couplings, dipolar, and hyperfine couplings in both organic molecules and spin networks in solids [13][14][15].…”

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confidence: 99%

Preparation of Nuclear Spin Singlet States Using Spin-Lock Induced Crossing

2013

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We introduce a broadly applicable technique to create nuclear spin singlet states in organic molecules and other many-atom systems. We employ a novel pulse sequence to produce a spin-lock induced crossing (SLIC) of the spin singlet and triplet energy levels, which enables triplet/singlet polarization transfer and singlet state preparation. We demonstrate the utility of the SLIC method by producing a long-lived nuclear spin singlet state on two strongly-coupled proton pairs in the tripeptide molecule phenylalanine-glycine-glycine dissolved in D2O, and by using SLIC to measure the J-couplings, chemical shift differences, and singlet lifetimes of the proton pairs. We show that SLIC is more efficient at creating nearly-equivalent nuclear spin singlet states than previous pulse sequence techniques, especially when triplet/singlet polarization transfer occurs on the same timescale as spin-lattice relaxation.There is great current interest in the controlled preparation and coherent manipulation of singlet states for nuclear spin pairs in molecules and other many-atom systems (e.g., spin networks in solids), as spin singlet states are largely decoupled from environmental perturbations that limit the spin state lifetime. For example, in liquid state experiments singlet states in nuclear spin pairs can exhibit lifetimes much longer than the single-spin polarization lifetime (T 1 ) [1][2][3][4][5][6][7][8][9][10][11][12]. In addition, nuclear spin singlet states can be used as a resource for spectroscopic interrogation of couplings within many-spin systems, including J-couplings, dipolar, and hyperfine couplings in both organic molecules and spin networks in solids [13][14][15]. Such singlet states exist naturally when nuclear spins are strongly J-coupled relative to their resonance frequency differences, ∆ν, i.e., J >> ∆ν. However, due to the differences in spin singlet and triplet state symmetries, it is not possible to transfer polarization from the triplet to the singlet state by directly driving a radiofrequency transition, which limits the control of singlet state preparation and manipulation. Tayler and Levitt demonstrated that triplet/singlet polarization transfer can instead be acheived using a series of π-pulse trains in which the pulse timing is synchronized to the J-coupling strength between nuclei [5]. This "M2S" sequence takes advantage of the small amount of mixing between singlet and triplet states that is present when- * devience@fas.harvard.edu † rwalsworth@cfa.harvard.edu ‡ mrosen@cfa.harvard.edu ever ∆ν > 0. Feng and Warren also showed that the M2S sequence can create singlet states in certain heteronuclear systems even when ∆ν = 0 [12]. These results hold promise for creating hyperpolarized singlet states without the need for a symmetry-breaking chemical reaction or continuous spin-locking [11]. However, in all results to date, the polarization transfer to the spin singlet state only occurs during the final third of the M2S sequence time, and before this stage the spin polarization occupies states subj...

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Long-lived states to sustain hyperpolarized magnetization

Cited by 183 publications

References 40 publications

Hyperpolarized singlet NMR on a small animal imaging system

Hyperpolarized singlet NMR on a small animal imaging system

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

Preparation of Nuclear Spin Singlet States Using Spin-Lock Induced Crossing

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