Non‐Pairwise Interactions in Parahydrogen Experiments: Nuclear Exchange of Single Protons Enables Bulk Water Hyperpolarization

Emondts, Meike; Schikowski, Daniel; Klankermayer, Jürgen; Schleker, P. Philipp M.

doi:10.1002/cphc.201800521

Cited by 13 publications

(12 citation statements)

References 50 publications

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“… [112] Although this polarization is achieved by the coherent redistribution of polarization (SABRE mechanism), it is also possible that an exchange pathway involving single proton spins is feasible. [113] Consequently, there are several ways in which the successful hyperpolarization of AAs and peptides can be brought about using SABRE‐RELAY.…”

Section: Phip Of Amino Acidsmentioning

confidence: 99%

Parahydrogen‐Induced Polarization of Amino Acids

et al. 2021

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Nuclear magnetic resonance (NMR) has become a universal method for biochemical and biomedical studies, including metabolomics, proteomics, and magnetic resonance imaging (MRI). By increasing the signal of selected molecules, the hyperpolarization of nuclear spin has expanded the reach of NMR and MRI even further (e.g. hyperpolarized solid‐state NMR and metabolic imaging in vivo). Parahydrogen (pH2) offers a fast and cost‐efficient way to achieve hyperpolarization, and the last decade has seen extensive advances, including the synthesis of new tracers, catalysts, and transfer methods. The portfolio of hyperpolarized molecules now includes amino acids, which are of great interest for many applications. Here, we provide an overview of the current literature and developments in the hyperpolarization of amino acids and peptides.

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Section: Phip Of Amino Acidsmentioning

confidence: 99%

Parahydrogen‐Induced Polarization of Amino Acids

et al. 2021

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“…Indeed, chemical exchange involving complex-bound substrates in SABRE has been reported before in the case of coordinated water. 47,48 We can account for this process, by adding appropriate terms to equation (4):…”

Section: A Sabre-relay Via Chemical Exchangementioning

confidence: 99%

Theoretical description of hyperpolarization formation in the SABRE-relay method

Knecht

Barskiy

Buntkowsky

et al. 2020

The Journal of Chemical Physics

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SABRE (Signal Amplification By Reversible Exchange) has become a widely used method for hyperpolarizing nuclear spins, thereby enhancing their Nuclear Magnetic Resonance (NMR) signals by orders of magnitude. In SABRE experiments, non-equilibrium spin order is transferred from parahydrogen to a substrate in a transient organometallic complex. Applicability of SABRE is expanded by the methodology of SABRE-relay, in which polarization can be relayed to a second substrate either by direct chemical exchange of hyperpolarized nuclei or by polarization transfer between two substrates in a second organometallic complex. To understand the mechanism of the polarization transfer and study the transfer efficiency, we propose a theoretical approach to SABRE-relay, which can treat both spin dynamics and chemical kinetics as well as the interplay between them. The approach is based on a set of equations for the spin density matrices of the spin systems involved (i.e., SABRE substrates and complexes), which can be solved numerically. Using this method, we perform a detailed study of polarization formation and analyse in detail the dependence of attainable polarization level on various chemical kinetic and spin dynamic parameters. We foresee applications of the present approach for optimizing SABRE-relay experiments with the ultimate goal of achieving maximal NMR signal enhancements for substrates of interest.

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“…% ZULF Spectrum of ethanol (simplified SABRE-relay process) % Magnetic field and spectral parameters B0 = 1e-9; % detection field (T) In systems using dichloromethane as solvent, [Ir(IMes)(COD)]Cl as the precatalyst, benzylamine, and methanol, we have observed increased SABRE efficiency at transfer fields above those expected from currently accepted SABRE-relay theory (39). Two possible mechanisms could be active in addition to the traditional SABRE mechanism modeled by an AA'X three spin system: A) NEPTUN (Nuclear Exchange Polarization by Transposing Unattached Nuclei), is based on direct hydride transfer from the catalyst to an axially bound substrate which has a labile proton (46); B) Magnetic field dependence complicated by the presence of a heteronucleus, such as 15 N. A single heteronucleus present in the active SABRE complex can split a single maximum in the magnetic field dependence into two (32,47).…”

Section: Materials and Methods Optimizationmentioning

confidence: 79%

“…The nature of the second peak is still under investigation, but may have two possible explanations. First, this maximum may originate from an asymmetric Ir complex operating under a mechanism similar to the one described by Emondts et al This mechanism, called NEPTUN (Nuclear Exchange Polarization by Transposing Unattached Nuclei), is based on direct hydride transfer from the catalyst to an axially bound substrate which has a labile proton (Figure S12) (46). This requires formation of an asymmetric complex where the chemical equivalence of the bound hydrides is broken forming an AB spin system which then evolves magnetization that can be detected in the substrate following hydride transfer.…”

Section: Mechanism Of Sabre-relay Polarization Transfer Via Benzylaminementioning

confidence: 98%

Relayed Hyperpolarization for Zero-Field Nuclear Magnetic Resonance

Dyke

Eills

Picazo‐Frutos

et al. 2022

Preprint

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Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) is a rapidly developing form of spectroscopy that drastically reduces the size and expense of portable devices with NMR capabilities. However, signal acquisition still requires a mechanism for orienting nuclear spins (e.g., generating a bulk magnetic moment for detection), and the currently employed methods only apply to a limited pool of chemicals or come at prohibitively high cost. Here, we demonstrate that the parahydrogen-based SABRE-relay method (SABRE = Signal Amplification by Reversible Exchange) can be used as a more general means of generating hyperpolarized analytes for ZULF NMR. This method is applicable to a wide range of small molecules possessing exchangeable protons, as we demonstrate here by observing zero-field J-spectra of [13C]-methanol, [1-13C]-ethanol, and [2-13C]-ethanol. We also explore the magnetic-field dependence of the proton hyperpolarization efficiency in SABRE-relay, and show the existence of a second, previously unexplored maximum at 19 mT. We further demonstrate that water does not significantly diminish SABRE-relay performance using benzylamine as polarization-transfer agent and use this to hyperpolarize ethanol extracted from a store-bought sample of vodka (1H polarization of ~0.1%). Applications for detecting trace chemical impurities and measuring J-spectra from natural extracts are also discussed.

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Non‐Pairwise Interactions in Parahydrogen Experiments: Nuclear Exchange of Single Protons Enables Bulk Water Hyperpolarization

Cited by 13 publications

References 50 publications

Parahydrogen‐Induced Polarization of Amino Acids

Parahydrogen‐Induced Polarization of Amino Acids

Theoretical description of hyperpolarization formation in the SABRE-relay method

Relayed Hyperpolarization for Zero-Field Nuclear Magnetic Resonance

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