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Signal amplification by reversible exchange

Sören Lehmkuhl, Martin Wiese, Lukas Schubert, Mathias Held, Markus Küppers, Matthias Wessling, Bernhard Blümich
Hyperpolarization methods entail a high potential to boost the sensitivity of NMR. Even though the "Signal Amplification by Reversible Exchange" (SABRE) approach uses para-enriched hydrogen, p-H2 , to repeatedly achieve high polarization levels on target molecules without altering their chemical structure, such studies are often limited to batch experiments in NMR tubes. Alternatively, this work introduces a continuous flow setup including a membrane reactor for the p-H2 , supply and consecutive detection in a 1 T NMR spectrometer...
March 31, 2018: Journal of Magnetic Resonance
Manuel Iglesias, Luis A Oro
This review summarises the most recent advances in Ir-NHC catalysis while revisiting all the classical reactions in which this type of catalyst has proved to be active. The influence of the ligand system and, in particular, the impact of the NHC ligand on the activity and selectivity of the reaction have been analysed, accompanied by an examination of the great variety of catalytic cycles hitherto reported. The reaction mechanisms so far proposed are described and commented on for each individual process. Moreover, some general considerations that attempt to explain the influence of the NHC from a mechanistic viewpoint are presented at the end of the review...
March 20, 2018: Chemical Society Reviews
Soumya S Roy, Kate M Appleby, Elizabeth J Fear, Simon B Duckett
Signal Amplification by Reversible Exchange (SABRE) is used to switch on the latent singlet spin order of para-hydrogen (p-H2 ) so that it can hyperpolarize a substrate (sub = nicotinamide, nicotinate, niacin, pyrimidine, and pyrazine). The substrate then reacts reversibly with [Pt(OTf)2 (bis-diphenylphosphinopropane)] by displacing OTf- to form [Pt(OTf)(sub)(bis-diphenylphosphinopropane)]OTf. The 31 P NMR signals of these metal complexes prove to be enhanced when the substrate possesses an accessible singlet state or long-lived Zeeman polarization...
March 1, 2018: Journal of Physical Chemistry Letters
Wissam Iali, Peter J Rayner, Simon B Duckett
Hyperpolarization turns weak nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) responses into strong signals, so normally impractical measurements are possible. We use para hydrogen to rapidly hyperpolarize appropriate 1 H, 13 C, 15 N, and 31 P responses of analytes (such as NH3 ) and important amines (such as phenylethylamine), amides (such as acetamide, urea, and methacrylamide), alcohols spanning methanol through octanol and glucose, the sodium salts of carboxylic acids (such as acetic acid and pyruvic acid), sodium phosphate, disodium adenosine 5'-triphosphate, and sodium hydrogen carbonate...
January 2018: Science Advances
Alexandra M Olaru, Thomas B R Robertson, Jennifer S Lewis, Alex Antony, Wissam Iali, Ryan E Mewis, Simon B Duckett
Fluorinated ligands have a variety of uses in chemistry and industry, but it is their medical applications as 18 F-labelled positron emission tomography (PET) tracers where they are most visible. In this work, we illustrate the potential of using 19 F-containing ligands as future magnetic resonance imaging (MRI) contrast agents and as probes in magnetic resonance spectroscopy studies by significantly increasing their magnetic resonance detectability through the signal amplification by reversible exchange (SABRE) hyperpolarization method...
January 2018: ChemistryOpen
Peter J Rayner, Simon Duckett
Signal Amplification by Reversible Exchange (SABRE) turns typically weak magnetic resonance responses into strong signals making previously impractical measurements possible. This technique has gained significant popularity due to its speed and simplicity. This minireview tracks the development of SABRE from the initial hyperpolarization of pyridine in 2009 to the point where 50% ¹H polarization levels have be achieved in a di-dueterio-nicotinate, a key step in the pathway to potential clinical use. Simple routes to efficient ¹⁵N hyperpolarization and the creation of hyperpolarized long-lived magnetic states are illustrated...
January 6, 2018: Angewandte Chemie
Stephan Knecht, Alexey S Kiryutin, Alexandra V Yurkovskaya, Konstantin L Ivanov
We propose an explanation of the previously reported SABRE (Signal Amplification By Reversible Exchange) effect at high magnetic fields, observed in the absence of RF-excitation and relying only on "spontaneous" polarization transfer from parahydrogen (pH2 , the H2 molecule in its nuclear singlet spin state) to a SABRE substrate. We propose a detailed mechanism for spontaneous polarization transfer and show that it is comprised of three steps: (i) Generation of the anti-phase Î1z Î2z spin order of catalyst-bound H2 ; (ii) spin order conversion Î1z Î2z →(Î1z +Î2z ) due to cross-correlated relaxation, leading to net polarization of H2 ; (iii) polarization transfer to the SABRE substrate, occurring due to NOE...
February 2018: Journal of Magnetic Resonance
Stephan Knecht, Alexey S Kiryutin, Alexandra V Yurkovskaya, Konstantin L Ivanov
A method is proposed for significant improvement of NMR pulse sequences used in high-field SABRE (Signal Amplification By Reversible Exchange) experiments. SABRE makes use of spin order transfer from parahydrogen (pH2 , the H2 molecule in its singlet spin state) to a substrate in a transient organometallic Ir-based complex. The technique proposed here utilizes "re-polarization", i.e., multiple application of an NMR pulse sequence used for spin order transfer. During re-polarization only the form of the substrate, which is bound to the complex, is excited by selective NMR pulses and the resulting polarization is transferred to the free substrate via chemical exchange...
February 2018: Journal of Magnetic Resonance
Philip Norcott, Michael J Burns, Peter J Rayner, Ryan E Mewis, Simon B Duckett
By introducing a range of2 H labels into pyridine and the para-substituted agents, methyl isonicotinate and isonicotinamide, we significantly improve their NMR detectability in conjunction with the signal amplification by reversible exchange process. We describe how the rates of T1 relaxation for the remaining1 H nuclei are increased and show how this leads to a concomitant increase in the level of1 H and13 C hyperpolarization that can ultimately be detected.
December 23, 2017: Magnetic Resonance in Chemistry: MRC
Anand Manoharan, Peter J Rayner, Wissam Iali, Michael J Burns, V Hugh Perry, Simon B Duckett
Production of a biocompatible hyperpolarized bolus for signal amplification by reversible exchange (SABRE) could open the door to simple clinical diagnosis via magnetic resonance imaging. Essential to successful progression to preclinical/clinical applications is the determination of the toxicology profile of the SABRE reaction mixture. Herein, we exemplify the cytotoxicity of the SABRE approach using in vitro cell assays. We conclude that the main cause of the observed toxicity is due to the SABRE catalyst...
February 20, 2018: ChemMedChem
Alexey S Kiryutin, Alexandra V Yurkovskaya, Herbert Zimmermann, Hans-Martin Vieth, Konstantin L Ivanov
Signal amplification by reversible exchange (SABRE) is a promising hyperpolarization technique, which makes use of spin-order transfer from parahydrogen (the H2 molecule in its singlet spin state) to a to-be-polarized substrate in a transient organometallic complex, termed the SABRE complex. In this work, we present an experimental method for measuring the magnetic field dependence of the SABRE effect over an ultrawide field range, namely, from 10 nT to 10 T. This approach gives a way to determine the complete magnetic field dependence of SABRE-derived polarization...
December 12, 2017: Magnetic Resonance in Chemistry: MRC
Peter M Richardson, Scott Jackson, Andrew J Parrott, Alison Nordon, Simon B Duckett, Meghan E Halse
Signal amplification by reversible exchange (SABRE) is a hyperpolarisation technique that catalytically transfers nuclear polarisation from parahydrogen, the singlet nuclear isomer of H2 , to a substrate in solution. The SABRE exchange reaction is carried out in a polarisation transfer field (PTF) of tens of gauss before transfer to a stronger magnetic field for nuclear magnetic resonance (NMR) detection. In the simplest implementation, polarisation transfer is achieved by shaking the sample in the stray field of a superconducting NMR magnet...
November 28, 2017: Magnetic Resonance in Chemistry: MRC
Soumya S Roy, Gabriele Stevanato, Peter J Rayner, Simon B Duckett
Signal Amplification by Reversible Exchange (SABRE) is an attractive nuclear spin hyperpolarization technique capable of huge sensitivity enhancement in nuclear magnetic resonance (NMR) detection. The resonance condition of SABRE hyperpolarization depends on coherent spin mixing, which can be achieved naturally at a low magnetic field. The optimum transfer field to spin-1/2 heteronuclei is technically demanding, as it requires field strengths weaker than the earth's magnetic field for efficient spin mixing...
December 2017: Journal of Magnetic Resonance
K Buckenmaier, M Rudolph, C Back, T Misztal, U Bommerich, P Fehling, D Koelle, R Kleiner, H A Mayer, K Scheffler, J Bernarding, M Plaumann
Ultra-low-field (ULF) nuclear magnetic resonance (NMR) is a promising spectroscopy method allowing for, e.g., the simultaneous detection of multiple nuclei. To overcome the low signal-to-noise ratio that usually hampers a wider application, we present here an alternative approach to ULF NMR, which makes use of the hyperpolarizing technique signal amplification by reversible exchange (SABRE). In contrast to standard parahydrogen hyperpolarization, SABRE can continuously hyperpolarize 1 H as well as other MR-active nuclei...
October 18, 2017: Scientific Reports
Kirill V Kovtunov, Larisa M Kovtunova, Max E Gemeinhardt, Andrey V Bukhtiyarov, Jonathan Gesiorski, Valerii I Bukhtiyarov, Eduard Y Chekmenev, Igor V Koptyug, Boyd M Goodson
The hyperpolarization of heteronuclei via signal amplification by reversible exchange (SABRE) was investigated under conditions of heterogeneous catalysis and microtesla magnetic fields. Immobilization of [IrCl(COD)(IMes)], [IMes=1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD=cyclooctadiene] catalyst onto silica particles modified with amine linkers engenders an effective heterogeneous SABRE (HET-SABRE) catalyst that was used to demonstrate a circa 100-fold enhancement of (15) N NMR signals in (15) N-pyridine at 9...
August 21, 2017: Angewandte Chemie
Wissam Iali, Alexandra M Olaru, Gary G R Green, Simon B Duckett
Signal amplification by reversible exchange (SABRE) is shown to allow access to strongly enhanced1 H NMR signals in a range of substrates in aqueous media. To achieve this outcome, phase-transfer catalysis is exploited, which leads to less than 1.5×10-6  mol dm-3 of the iridium catalyst in the aqueous phase. These observations reflect a compelling route to produce a saline-based hyperpolarized bolus in just a few seconds for subsequent in vivo MRI monitoring. The new process has been called catalyst separated hyperpolarization through signal amplification by reversible exchange or CASH-SABRE...
August 4, 2017: Chemistry: a European Journal
Danila A Barskiy, Roman V Shchepin, Christian P N Tanner, Johannes F P Colell, Boyd M Goodson, Thomas Theis, Warren S Warren, Eduard Y Chekmenev
Nuclear spin hyperpolarization techniques are revolutionizing the field of13 C molecular MRI. While dissolution dynamic nuclear polarization (d-DNP) is currently the leading technique, it is generally slow (requiring ≈1 h) and costly (≈$USD106 ). As a consequence of carbon's central place in biochemistry, tremendous progress using13 C d-DNP bioimaging has been demonstrated to date including a number of clinical trials. Despite numerous attempts to develop alternatives to d-DNP, the competing methods have faced significant translational challenges...
June 20, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Marianna Fekete, Peter J Rayner, Gary G R Green, Simon B Duckett
The signal amplification by reversible exchange (SABRE) approach has been used to hyperpolarise the substrates indazole and imidazole in the presence of the co-ligand acetonitrile through the action of the precataysts [IrCl(COD)(IMes)] and [IrCl(COD)(SIMes)].2 H-labelled forms of these catalysts were also examined. Our comparison of the two precatalysts [IrCl(COD)(IMes)] and [IrCl(COD)(SIMes)], coupled with2 H labelling of the N-heterocyclic carbene and associated relaxation and polarisation field variation studies, demonstrates the critical and collective role these parameters play in controlling the efficiency of signal amplification by reversible exchange...
October 2017: Magnetic Resonance in Chemistry: MRC
Johannes F P Colell, Meike Emondts, Angus W J Logan, Kun Shen, Junu Bae, Roman V Shchepin, Gerardo X Ortiz, Peter Spannring, Qiu Wang, Steven J Malcolmson, Eduard Y Chekmenev, Martin C Feiters, Floris P J T Rutjes, Bernhard Blümich, Thomas Theis, Warren S Warren
Signal amplification by reversible exchange (SABRE) is an inexpensive, fast, and even continuous hyperpolarization technique that uses para-hydrogen as hyperpolarization source. However, current SABRE faces a number of stumbling blocks for translation to biochemical and clinical settings. Difficulties include inefficient polarization in water, relatively short-lived (1)H-polarization, and relatively limited substrate scope. Here we use a water-soluble polarization transfer catalyst to hyperpolarize nitrogen-15 in a variety of molecules with SABRE-SHEATH (SABRE in shield enables alignment transfer to heteronuclei)...
June 14, 2017: Journal of the American Chemical Society
Johannes F P Colell, Angus W J Logan, Zijian Zhou, Roman V Shchepin, Danila A Barskiy, Gerardo X Ortiz, Qiu Wang, Steven J Malcolmson, Eduard Y Chekmenev, Warren S Warren, Thomas Theis
Signal Amplification by Reversible Exchange (SABRE) is a fast and convenient NMR hyperpolarization method that uses cheap and readily available para -hydrogen as a hyperpolarization source. SABRE can hyperpolarize protons and heteronuclei. Here we focus on the heteronuclear variant introduced as SABRE-SHEATH (SABRE in SHield Enables Alignment Transfer to Heteronuclei) and nitrogen-15 targets in particular. We show that 15 N-SABRE works more efficiently and on a wider range of substrates than 1 H-SABRE, greatly generalizing the SABRE approach...
March 30, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
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