Measurements of the persistent singlet state of N<sub>2</sub>O in blood and other solvents—Potential as a magnetic tracer

Ghosh, Rajat K.; Kadlecek, Stephen; Ardenkjær‐Larsen, Jan Henrik; Pullinger, Benjamin; Pileio, Giuseppe; Levitt, Malcolm H.; Kuzma, N. N.; Rizi, Rahim R.

doi:10.1002/mrm.23119

Cited by 37 publications

(46 citation statements)

References 14 publications

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

2013

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“…The same issue also arises during the infusion of hyperpolarized molecules into the blood stream, during the time lag before reaching the targeted organs for in vivo applications, as well as during the signal acquisition. Multiple strategies have been explored and developed in the last years for minimizing losses of polarization, such as the use of fast fluid transfer devices [19], the rapid elimination of the free radicals [20][21][22], or the storage of hyperpolarization in the form of long-lived states (LLS) [23][24][25][26][27][28].…”

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Optimizing dissolution dynamic nuclear polarization

Bornet

2016

Journal of Magnetic Resonance

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“…6−9 In previous work, we reported the potential of doubly 15 N-labeled nitrous oxide, 15 N 2 O. 10,11 The ordinary T 1 lifetime of the spin order is 30 s for 15 N 2 O dissolved in human blood. The singlet decay constant in blood, ∼7 min, is 15 times longer.…”

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Direct Enhancement of Nuclear Singlet Order by Dynamic Nuclear Polarization

et al. 2012

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Hyperpolarized singlet order is available immediately after dissolution DNP, avoiding need for additional preparation steps. We demonstrate this procedure on a sample of [1,2− 13 C 2 ]pyruvic acid.T he large signal improvement provided by spin hyperpolarization methods has dramatically extended the in vivo potential of NMR spectroscopy.1 Hyperpolarized nuclear spin order permits tracing of both endogenous and nonendogenous substances as they are transported through the blood vessels and organs and participate in metabolism.2−4 A limitation of these techniques is the often short observation time scale imposed by nuclear spin relaxation. Hyperpolarized magnetization typically decays with the longitudinal relaxation time T 1 , which is typically between a fraction of a second and 1 min and can be particularly short in vivo because of the presence of paramagnetic species and high concentrations of other magnetic nuclei. Short decay times hinder the use of hyperpolarized substrates for imaging metabolism in vivo because of the relatively long times taken for substrates to reach the tissue of interest from the point of injection. For instance, while hyperpolarized 129 Xe can be used as a lung imaging agent in gas-phase magnetic resonance imaging (MRI) because its relaxation time is several hours in the gas phase, its potential as a tracer in blood is very limited because the T 1 relaxation time of 129 Xe is reduced to only a few seconds upon dissolution. 5A potential remedy for the limited hyperpolarization lifetime is the use of nuclear singlet states involving coupled spin-1 / 2 pairs. The lifetime of the nuclear singlet state (|αβ⟩ − |βα⟩)/ √2 is capable of exceeding T 1 in some circumstances, since many common relaxation mechanisms are symmetric with respect to spin exchange and cannot induce singlet−triplet transitions. 6−9 In previous work, we reported the potential of doubly 11In some cases, substances exhibiting hyperpolarized singlet order are accessible directly by chemical reactions of hydrogen enriched with the para-hydrogen spin isomer.12−14 An alternative approach is to prepare hyperpolarized magnetization using a method such as dynamic nuclear polarization (DNP) 15,16 and then to convert it into singlet order. Several conversion methods are available:• application of resonant radiofrequency pulses in a high magnetic field to excite a "precursor state", 7 which is transformed into singlet order upon adiabatic transport to a low field; 17,18• preparation of singlet order in a high magnetic field using a radiofrequency pulse sequence;19−21• application of an audio-frequency pulse sequence in a low magnetic field on a prepolarized sample; 22• exploitation of chemical symmetry-switching reactions. 23All of these rely upon manipulations in addition to spin hyperpolarization. In certain cases they may be difficult to implement, require extra hardware, or take up valuable time during an experiment.In this communication, we show that these preparations may be circumvented by the availability of sing...

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Measurements of the persistent singlet state of N₂O in blood and other solvents—Potential as a magnetic tracer

Cited by 37 publications

References 14 publications

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

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

Optimizing dissolution dynamic nuclear polarization

Direct Enhancement of Nuclear Singlet Order by Dynamic Nuclear Polarization

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Measurements of the persistent singlet state of N2O in blood and other solvents—Potential as a magnetic tracer

Cited by 37 publications

References 14 publications

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

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

Optimizing dissolution dynamic nuclear polarization

Direct Enhancement of Nuclear Singlet Order by Dynamic Nuclear Polarization

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Product

Resources

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Measurements of the persistent singlet state of N₂O in blood and other solvents—Potential as a magnetic tracer