Search

Metal dihydride dihydrogen‐derived intermediates can be short‐lived and difficult to detect despite their ubiquitous role in chemical transformations such as hydrogenation. Here, highly reactive [Ir(H)3(η2‐η2‐COD)(IMes)] forms by trapping [Ir(H)2(η2‐H2)(η2‐η2‐COD)(IMes)]X [X=Cl or MeO], resulting from reaction of the Ir(I) precatalyst [IrCl(η2‐η2‐COD)(IMes)] with a base and H2. This trihydride allows access to the unusual [Ir2(H)4(OMe)(IMes)2(pyridine)3]X, [Ir2(H)2(μ2‐H)2(η2‐η2‐COD)(IMes)2], [Ir3(H)9(IMes)3], [Ir4(H)12(IMes)4] and [Ir2(H)4(μ2‐H)2(IMes)2(pyridine)2]. A combination of 2D NMR, parahydrogen hyperpolarized NMR, MS, and XRD are used to characterise these reaction products and rationalise their formation via the moiety {Ir(H)3(IMes)}. Consequently, the results of these studies have implications for iridium‐catalyzed polarization transfer from parahydrogen via the well‐known precursor [IrCl(η2‐η2‐COD)(IMes)]. [ABSTRACT FROM AUTHOR]

Large trans‐sarcolemmal ionic shifts occur with fatiguing exercise or stimulation of isolated muscles. However, it is unknown how resting membrane potential (EM) and intracellular sodium concentration ([Na+]i) change with repeated contractions in living mammals. We investigated (i) whether [Na+]i (peak, kinetics) can reveal changes of Na+–K+ pump activity during brief or fatiguing stimulation and (ii) how resting EM and [Na+]i change during fatigue and recovery of rat soleus muscle in situ. Muscles of anaesthetised rats were stimulated with brief (10 s) or repeated tetani (60 Hz for 200 ms, every 2 s, for 30 s or 300 s) with isometric force measured. Double‐barrelled ion‐sensitive microelectrodes were used to quantify resting EM and [Na+]i. Post‐stimulation data were fitted using polynomials and back‐extrapolated to time zero recovery. Mean pre‐stimulation resting EM (layer 2–7 fibres) was −71 mV (surface fibres were more depolarised), and [Na+]i was 14 mM. With deeper fibres, 10 s stimulation (2–150 Hz) increased [Na+]i to 38–46 mM whilst simultaneously causing hyperpolarisations (7.3 mV for 2–90 Hz). Fatiguing stimulation for 30 s or 300 s led to end‐stimulation resting EM of −61 to −53 mV, which recovered rapidly (T1/2, 8–22 s). Mean end‐stimulation [Na+]i increased to 86–101 mM with both fatigue protocols and the [Na+]i recovery time‐course (T1/2, 21–35 s) showed no difference between protocols. These combined findings suggest that brief stimulation hyperpolarises the resting EM, likely via maximum Na+‐induced stimulation of the Na+–K+ pump. Repeated tetani caused massive depolarisation and elevations of [Na+]i that together lower force, although they likely interact with other factors to cause fatigue. [Na+]i recovery kinetics provided no evidence of impaired Na+–K+ pump activity with fatigue. Key points: It is uncertain how resting membrane potential, intracellular sodium concentration ([Na+]i), and sodium–potassium (Na+–K+) pump activity change during repeated muscle contractions in living mammals.For rat soleus muscle fibres in situ, brief tetanic stimulation for 10 s led to raised [Na+]i, anticipated to evoke maximal Na+‐induced stimulation of the Na+–K+ pump causing an immediate hyperpolarisation of the sarcolemma.More prolonged stimulation with repeated tetanic contractions causes massive elevations of [Na+]i, which together with large depolarisations (via K+ disturbances) likely reduce force production. These effects occurred without impairment of Na+–K+ pump function.Together these findings suggest that rapid activation of the Na+–K+ pump occurs with brief stimulation to maintain excitability, whereas more prolonged stimulation causes rundown of the trans‐sarcolemmal K+ gradient (hence depolarisation) and Na+ gradient, which in combination can impair contraction to contribute to fatigue in living mammals. [ABSTRACT FROM AUTHOR]

Plant defensins are a large family of small cationic proteins with diverse functions and mechanisms of action, most of which assert antifungal activity against a broad spectrum of fungi. The partial mechanism of action has been resolved for a small number of members of plant defensins, and studies have revealed that many act by more than one mechanism. The plant defensin Ppdef1 has a unique sequence and long loop 5 with fungicidal activity against a range of human fungal pathogens, but little is known about its mechanism of action. We screened the S. cerevisiae non-essential gene deletion library and identified the involvement of the mitochondria in the mechanism of action of Ppdef1. Further analysis revealed that the hyperpolarisation of the mitochondrial membrane potential (MMP) activates ROS production, vacuolar fusion and cell death and is an important step in the mechanism of action of Ppdef1, and it is likely that a similar mechanism acts in Trichophyton rubrum. [ABSTRACT FROM AUTHOR]

Aripiprazole has fewer metabolic side effects than other antipsychotics; however, there are some severe ones in the liver, leading to drug-induced liver injury. Repeated treatment with aripiprazole affects cell division. Since this process requires a lot of energy, we decided to investigate the impact of aripiprazole on rat liver cells and mitochondria as the main source of cellular energy production by measuring the mitochondrial membrane potential, respiration, adenosine triphosphate (ATP) production, oxidative stress, antioxidative response, and human blood haemolysis. Here, we report that mitochondrial hyperpolarisation from aripiprazole treatment is accompanied by higher reactive oxygen species (ROS) production and increased antioxidative response. Lower mitochondrial and increased glycolytic ATP synthesis demand more glucose through glycolysis for equal ATP production and may change the partition between the glycolysis and pentose phosphate pathway in the liver. The uniform low amounts of the haemolysis of erythrocytes in the presence of aripiprazole in 25 individuals indicate lower quantities of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH+H+), which is in accordance with a decreased activity of glucose 6-phosphate dehydrogenase and the lower dehydrogenase activity upon aripiprazole treatment. The lower activity of glucose 6-phosphate dehydrogenase supports a shift to glycolysis, thus rescuing the decreased mitochondrial ATP synthesis. The putative reduction in NADPH+H+ did not seem to affect the oxidised-to-reduced glutathione ratio, as it remained equal to that in the untreated cells. The effect of aripiprazole on glutathione reduction is likely through direct binding, thus reducing its total amount. As a consequence, the low haemolysis of human erythrocytes was observed. Aripiprazole causes moderate perturbations in metabolism, possibly with one defect rescuing the other. The result of the increased antioxidant enzyme activity upon treatment with aripiprazole is increased resilience to oxidative stress, which makes it an effective drug for schizophrenia in which oxidative stress is constantly present because of disease and treatment. [ABSTRACT FROM AUTHOR]

Parahydrogen induced polarisation (PHIP) is often used to enhance the sensitivity of NMR, with the purpose of extending the applicability of the technique. Nuclear spin hyperpolarisation obtained via PHIP is generally localised on the protons derived from the addition of para-enriched hydrogen to an unsaturated substrate. This limitation has been previously addressed by pulse schemes that can spread this hyperpolarised magnetisation through the entire network of J-coupled protons in the product molecule. Here, we extend this approach, by implementing 2D NMR spectroscopy on such network of hyperpolarised protons. This novel approach to 2D acquisition during parahydrogenation allows information to be gained from the entirety of a molecule, quicker and/or at lower concentrations than by conventional NMR. The efficacy of the method is exemplified by performing a 2D TOCSY experiment during hydrogenative PHIP, using 2-pentyn-1-ol as a substrate. A 2D spectrum was obtained in a few minutes at micromolar concentration, demonstrating the applicability of this methodology., (© 2025 The Author(s). Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.)

Aripiprazole has fewer metabolic side effects than other antipsychotics; however, there are some severe ones in the liver, leading to drug-induced liver injury. Repeated treatment with aripiprazole affects cell division. Since this process requires a lot of energy, we decided to investigate the impact of aripiprazole on rat liver cells and mitochondria as the main source of cellular energy production by measuring the mitochondrial membrane potential, respiration, adenosine triphosphate (ATP) production, oxidative stress, antioxidative response, and human blood haemolysis. Here, we report that mitochondrial hyperpolarisation from aripiprazole treatment is accompanied by higher reactive oxygen species (ROS) production and increased antioxidative response. Lower mitochondrial and increased glycolytic ATP synthesis demand more glucose through glycolysis for equal ATP production and may change the partition between the glycolysis and pentose phosphate pathway in the liver. The uniform low amounts of the haemolysis of erythrocytes in the presence of aripiprazole in 25 individuals indicate lower quantities of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH+H+), which is in accordance with a decreased activity of glucose 6-phosphate dehydrogenase and the lower dehydrogenase activity upon aripiprazole treatment. The lower activity of glucose 6-phosphate dehydrogenase supports a shift to glycolysis, thus rescuing the decreased mitochondrial ATP synthesis. The putative reduction in NADPH+H+ did not seem to affect the oxidised-to-reduced glutathione ratio, as it remained equal to that in the untreated cells. The effect of aripiprazole on glutathione reduction is likely through direct binding, thus reducing its total amount. As a consequence, the low haemolysis of human erythrocytes was observed. Aripiprazole causes moderate perturbations in metabolism, possibly with one defect rescuing the other. The result of the increased antioxidant enzyme activity upon treatment with aripiprazole is increased resilience to oxidative stress, which makes it an effective drug for schizophrenia in which oxidative stress is constantly present because of disease and treatment.

In this work the chemistry of yttrium complexes is exploited for small molecule capture and activation. Nuclear magnetic resonance (NMR) and density functional theory (DFT) studies were used to investigate the in situ formation of solution state ternary yttrium‐acetate, yttrium‐bicarbonate, and yttrium‐pyruvate adducts with a range of polyaminocarboxylate chelates. These studies reveal that [Y(DO3A)(H2O)2] (H3DO3A – 1,4,7,10‐tetraazacyclododecane‐1,4,7‐tricarboxylic acid) and [Y(EDTA)(H2O)q]− (H4EDTA – ethylenediaminetetraacetic acid, q = 2 and 3) are able to form ternary adducts with bicarbonate and pyruvate. In the latter, unusual decarboxylation of pyruvate to form acetic acid and CO2 was observed and further studied using SABRE‐hyperpolarised 13C NMR (SABRE – signal amplification by reversible exchange) to provide information about the reaction timescale and lifetime of intermediates involved in this conversion. The work presented demonstrates that yttrium complexes can capture and activate small molecules, which may lead to novel and useful applications of this metal in catalysis and medical imaging. [ABSTRACT FROM AUTHOR]

Utility of the pyridazine motif is growing in popularity as pharmaceutical and agrochemical agents. The detection and structural characterisation of such materials is therefore imperative for the successful development of new products. Signal amplification by reversible exchange (SABRE) offers a route to dramatically improve the sensitivity of magnetic resonance methods, and we apply it here to the rapid and cost‐effective hyperpolarisation of substituted pyridazines. The 33 substrates investigated cover a range of steric and electronic properties and their capacity to perform highly effective SABRE is assessed. We find the method to be tolerant to a broad range of electron donating and withdrawing groups; however, good sensitivity is evident when steric bulk is added to the 3‐ and 6‐positions of the pyridazine ring. We optimise the method by reference to a disubstituted ester that yields signal gains of >9000‐fold at 9.4 T (>28% spin polarisation). [ABSTRACT FROM AUTHOR]

Die Kernspinresonanz (NMR) hat sich zu einer universellen Methode für biochemische und biomedizinische Studien, einschließlich Metabolomik, Proteomik und Magnetresonanztomographie (MRT), entwickelt. Durch die Vervielfachung des NMR‐Signals ausgewählter Moleküle hat die Kernspin‐Hyperpolarisation das Anwendungsspektrum von NMR und MRT bedeutsam erweitert (z. B. hyperpolarisierte Festkörper‐NMR und metabolische Bildgebung in vivo). Parawasserstoff (pH2) erlaubt es, Moleküle schnell und kostengünstig zu hyperpolarisieren. In diesem Gebiet wurden in den letzten zehn Jahren umfangreiche Fortschritte erzielt, einschließlich der Synthese neuer Tracer, Katalysatoren und Methoden für die Polarisationsübertragung. Das Portfolio an hyperpolarisierten Molekülen umfasst nunmehr Aminosäuren, die für viele Anwendungen von großem Interesse sind. In diesem Beitrag beleuchten wir die aktuelle Literatur zur Hyperpolarisation von Aminosäuren und Peptiden. [ABSTRACT FROM AUTHOR]

Abstract Fentanyl, also known as ‘jackpot’, is a synthetic opiate that is 50–100 times more potent than morphine. Clandestine laboratories produce analogues of fentanyl, known as fentalogues to circumvent legislation regarding its production. Three pyridyl fentalogues were synthesized and then hyperpolarized by signal amplification by reversible exchange (SABRE) to appraise the forensic potential of the technique. A maximum enhancement of ‐168‐fold at 1.4 T was recorded for the ortho pyridyl 1H nuclei. Studies of the activation parameters for the three fentalogues revealed that the ratio of ligand loss trans to hydride and hydride loss in the complex [Ir(IMes)(L)3(H)2]+ (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazole‐2‐ylidene) ranged from 0.52 to 1.83. The fentalogue possessing the ratio closest to unity produced the largest enhancement subsequent to performing SABRE at earth's magnetic field. It was possible to hyperpolarize a pyridyl fentalogue selectively from a matrix that consisted largely of heroin (97 : 3 heroin:fentalogue) to validate the use of SABRE as a forensic tool.

Die Hyperpolarisation von Atomkernen bietet einen Weg, die NMR‐Empfindlichkeit erheblich zu steigern. Durch Anwendung dieses leistungsstarken Hilfsmittels wurden niedermolekulare Verbindungen mit stabilen Isotopen für die hochempfindliche biomedizinische Bildgebung genutzt. Die jüngste Entwicklung molekularer Sonden für die hyperpolarisierte In‐vivo‐Analyse hat gezeigt, dass diese Technik in der Lage ist, einzigartige metabolische und physiologische Informationen zu liefern. Dieser Aufsatz bietet eine kurze Einführung in die Technik der Hyperpolarisation, Ansätze zum rationalen Design molekularer Sonden für die hyperpolarisierte NMR‐Bildgebung und Beispiele von Molekülen, die erfolgreich in vitro oder in vivo für diesen Zweck genutzt wurden. [ABSTRACT FROM AUTHOR]

Hyperpolarisationsverstärkte Magnetresonanztomographie kann zur Untersuchung biomolekularer Prozesse im Körper verwendet werden, erfordert aber die Verwendung von Hetero‐Kernen wie 13C, 15N oder 129Xe. Hier stellen wir eine neue Art der Hyperpolarisierten Protonen Bildgebung vor, bei der die hyperpolarisierte Spinordnung in einem nicht magnetischen und langlebigen korrelierten (Singulett‐) Zustand eingeschlossen ist und nur durch eine spezifische biochemische Reaktion für die Bildgebung freigesetzt wird. In dieser Arbeit erzeugen wir hyperpolarisiertes Fumarat durch chemische Reaktion eines Eduktes mit para‐angereichertem Wasserstoffgas. Der Singulettzustand der Fumarat Protonen wird als Antiphasen‐NMR‐Signale durch enzymatische Umwandlung zu Malat in D2O freigesetzt. Anhand dieses Modellsystems zeigen wir zwei Pulssequenzen, um die NMR‐Signale für die Bildgebung zu rephasieren und die Hintergrundsignale von Wasser zu unterdrücken. Die hier vorgestellte hyperpolarisationsverstärkte Protonen Bildgebungstechnik ermöglicht eine hyperpolarisierte Bildgebung, ohne dass hierfür Hetero‐Kerne mit ihrer niedrigen natürlichen Häufigkeit und geringen Empfindlichkeit benötigt werden. [ABSTRACT FROM AUTHOR]

Objectives: To enhance detection of the products of hyperpolarized [2-13C]dihydroxyacetone metabolism for assessment of three metabolic pathways in the liver in vivo. Hyperpolarized [2-13C]DHAc emerged as a promising substrate to follow gluconeogenesis, glycolysis and the glycerol pathways. However, the use of [2-13C]DHAc in vivo has not taken off because (i) the chemical shift range of [2-13C]DHAc and its metabolic products span over 144 ppm, and (ii) 1H decoupling is required to increase spectral resolution and sensitivity. While these issues are trivial for high-field vertical-bore NMR spectrometers, horizontal-bore small-animal MR scanners are seldom equipped for such experiments. Methods: Real-time hepatic metabolism of three fed mice was probed by 1H-decoupled 13C-MR following injection of hyperpolarized [2-13C]DHAc. The spectra of [2-13C]DHAc and its metabolic products were acquired in a 7 T small-animal MR scanner using three purpose-designed spectral-spatial radiofrequency pulses that excited a spatial bandwidth of 8 mm with varying spectral bandwidths and central frequencies (chemical shifts). Results: The metabolic products detected in vivo include glycerol 3-phosphate, glycerol, phosphoenolpyruvate, lactate, alanine, glyceraldehyde 3-phosphate and glucose 6-phosphate. The metabolite-to-substrate ratios were comparable to those reported previously in perfused liver. Discussion: Three metabolic pathways can be probed simultaneously in the mouse liver in vivo, in real time, using hyperpolarized DHAc. [ABSTRACT FROM AUTHOR]

Die Bildgebung von Gasen stellt eine große Herausforderung dar, ob per MRT oder mit anderen Methoden. NMR‐ und MRT‐Signale sind direkt proportional zur Kernspindichte und zur Kernspinpolarisation (Ausrichtungsgrad der Kernspins bzgl. eines angelegten Magnetfeldes). Die Kernspinpolarisation ist unter typischen Bedingungen sehr niedrig, z. B. ist die Polarisation bei 1.5 T und einer physiologisch relevanten Temperatur nur ein hunderttausendstel der maximal erreichbaren Polarisation. Daher wird MRT in erster Linie zur Bildgebung von Wasser, welches in Gewebe in hoher Konzentration vorliegt, herangezogen. Hyperpolarisationsmethoden erhöhen vorübergehend die Kernspinpolarisation bis zu einem Polarisationsgrad von maximal eins, was eine Signalverstärkung von mehreren Größenordnungen bedeutet. Dies ermöglicht 3D‐Bildgebung von weniger konzentrierten Analyten, wie etwa Biomolekülen oder Gasen. Parawasserstoff‐induzierte Polarisation (PHIP) kann sehr schnell erzielt werden. Zudem sind die verwendeten Verfahren leicht skalierbar und relativ kostengünstig. In diesem Kurzaufsatz fassen wir ausgewählte Neuerungen im Bereich der Parawasserstoff‐induzierten Polarisation zusammen, die in Zukunft zu neuen, inhalierbaren Kontrastmitteln führen können. [ABSTRACT FROM AUTHOR]

Radio amplification by stimulated emission of radiation (RASER) was recently discovered in a low‐field NMR spectrometer incorporating a highly specialized radio‐frequency resonator, where a high degree of proton‐spin polarization was achieved by reversible parahydrogen exchange. RASER activity, which results from the coherent coupling between the nuclear spins and the inductive detector, can overcome the limits of frequency resolution in NMR. Here we show that this phenomenon is not limited to low magnetic fields or the use of resonators with high‐quality factors. We use a commercial bench‐top 1.4 T NMR spectrometer in conjunction with pairwise parahydrogen addition producing proton‐hyperpolarized molecules in the Earth's magnetic field (ALTADENA condition) or in a high magnetic field (PASADENA condition) to induce RASER without any radio‐frequency excitation pulses. The results demonstrate that RASER activity can be observed on virtually any NMR spectrometer and measures most of the important NMR parameters with high precision. [ABSTRACT FROM AUTHOR]

This perspective article describes the concept of a long-lived nuclear spin state and some of its applications. Classes of molecular environments for which nuclear spin order can be stored for extended periods of time are described, and applications to studies of molecular dynamics and interactions, diffusion NMR and hyperpolarisation are presented. Some of the opportunities and challenges in the field are discussed. [ABSTRACT FROM AUTHOR]

Nuclear Magnetic Resonance (NMR) techniques display an inherently low sensitivity due to a small equilibrium magnetisation. Nowadays this issue is easily overcome through the use of hyperpolarisation methods. This however raises the question as to what precisely do we mean by "hyperpolarisation". Recently a formal definition of hyperpolarisation has been given based on the von Neumann entropy of a system. Ideally this definition should conform with the general usage in the magnetic resonance community, where hyperpolarisation is often used synonymously with "larger" NMR signals. Within this article I show that an entropy-based hyperpolarisation criterion does not always conform with the general usage. Based on this observation I introduce an alternative hyperpolarisation criterion utilising the concept of latent polarisation, where latent polarisation is a measure of the highest possible amount of polarisation that may be extracted from a system. I show that a hyperpolarisation criterion based on latent polarisation correlates more strongly with the general usage within the magnetic resonance community. Ultimately however our results show that there are several possible notions of hyperpolarisation, and the choice depends upon the questions of interest. [Display omitted] • Discussion of several different notions of hyperpolarisation. • Introduction of latent polarisation as a measure of hyperpolarised spin systems. • Graphical representations of hyperpolarised regions of Liouville space. [ABSTRACT FROM AUTHOR]

In recent years the NMR hyperpolarisation method signal amplification by reversible exchange (SABRE) has been applied to multiple substrates of potential interest for in vivo investigation. Unfortunately, SABRE commonly requires an iridium-containing catalyst that is unsuitable for biomedical applications. This report utilizes inductively coupled plasma-optical emission spectroscopy (ICP-OES) to investigate the potential use of metal scavengers to remove the iridium catalytic species from the solution. The most sensitive iridium emission line at 224.268 nm was used in the analysis. We report the effects of varying functionality, chain length, and scavenger support identity on iridium scavenging efficiency. The impact of varying the quantity of scavenger utilized is reported for the three scavengers with the highest iridium removed from initial investigations: 3-aminopropyl (S1), 3-(imidazole-1-yl)propyl (S4), and 2-(2-pyridyl) (S5) functionalized silica gels. Exposure of an activated SABRE sample (1.6 mg mL−1 of iridium catalyst) to 10 mg of the most promising scavenger (S5) resulted in

Silanols and silanes are key precursors and intermediates for the synthesis of silicon‐based materials. While their characterization and quantification by 29Si NMR spectroscopy has received significant attention, it is a technique that is limited by the low natural abundance of 29Si and its low sensitivity. Here, we describe a method using p‐H2 to hyperpolarize 29Si. The observed signal enhancements, approaching 3000‐fold at 11.7 T, would take many days of measurement for comparable results under Boltzmann conditions. The resulting signals were exploited to monitor the rapid reaction of tris(tert‐butoxy)silanol with triflic anhydride in a T1‐corrected process that allows for rapid quantification. These results demonstrate a novel route to quantify dynamic processes and intermediates in the synthesis of silicon materials. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is a well-established modality for assessing renal morphology and function, as well as changes that occur during disease. However, the significant metabolic changes associated with renal disease are more challenging to assess with MRI. Hyperpolarized carbon-13 MRI is an emerging technique which provides an opportunity to probe metabolic alterations at high sensitivity by providing an increase in the signal-to-noise ratio of 20,000-fold or more. This review will highlight the current status of hyperpolarised 13C-MRI and its translation into the clinic and how it compares to metabolic measurements provided by competing technologies such as positron emission tomography (PET). [ABSTRACT FROM AUTHOR]

Herein, we demonstrate "direct" 13C hyperpolarization of 13C‐acetate via signal amplification by reversible exchange (SABRE). The standard SABRE homogeneous catalyst [Ir‐IMes; [IrCl(COD)(IMes)], (IMes=1,3‐bis(2,4,6‐trimethylphenyl), imidazole‐2‐ylidene; COD=cyclooctadiene)] was first activated in the presence of an auxiliary substrate (pyridine) in alcohol. Following addition of sodium 1‐13C‐acetate, parahydrogen bubbling within a microtesla magnetic field (i.e. under conditions of SABRE in shield enables alignment transfer to heteronuclei, SABRE‐SHEATH) resulted in positive enhancements of up to ≈100‐fold in the 13C NMR signal compared to thermal equilibrium at 9.4 T. The present results are consistent with a mechanism of "direct" transfer of spin order from parahydrogen to 13C spins of acetate weakly bound to the catalyst, under conditions of fast exchange with respect to the 13C acetate resonance, but we find that relaxation dynamics at microtesla fields alter the optimal matching from the traditional SABRE‐SHEATH picture. Further development of this approach could lead to new ways to rapidly, cheaply, and simply hyperpolarize a broad range of substrates (e.g. metabolites with carboxyl groups) for various applications, including biomedical NMR and MRI of cellular and in vivo metabolism. [ABSTRACT FROM AUTHOR]

Fentanyl, also known as 'jackpot', is a synthetic opiate that is 50–100 times more potent than morphine. Clandestine laboratories produce analogues of fentanyl, known as fentalogues to circumvent legislation regarding its production. Three pyridyl fentalogues were synthesized and then hyperpolarized by signal amplification by reversible exchange (SABRE) to appraise the forensic potential of the technique. A maximum enhancement of ‐168‐fold at 1.4 T was recorded for the ortho pyridyl 1H nuclei. Studies of the activation parameters for the three fentalogues revealed that the ratio of ligand loss trans to hydride and hydride loss in the complex [Ir(IMes)(L)3(H)2]+ (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazole‐2‐ylidene) ranged from 0.52 to 1.83. The fentalogue possessing the ratio closest to unity produced the largest enhancement subsequent to performing SABRE at earth's magnetic field. It was possible to hyperpolarize a pyridyl fentalogue selectively from a matrix that consisted largely of heroin (97 : 3 heroin:fentalogue) to validate the use of SABRE as a forensic tool. [ABSTRACT FROM AUTHOR]

For the first time, a 1H solid-state photo-CIDNP effect is reported. The effect is observed in frozen solution of cyclohexanone in 1,4-dioxane-d8 under magic-angle spinning and continuous irradiation by the full spectrum of a xenon arc lamp. The spectral features show close similarity with those observed by 1H liquid-state photo-CIDNP NMR. [ABSTRACT FROM AUTHOR]

Diazirine moieties are chemically stable and have been incorporated into biomolecules without impediment of biological activity. The 15N2 labeled diazirines are appealing motifs for hyperpolarization supporting relaxation protected states with long‐lived lifetimes. The (‐CH15N2) diazirine groups investigated here are analogues to methyl groups, which provides the opportunity to transfer polarization stored on a relaxation protected (‐CH15N2) moiety to 1H, thus combining the advantages of long lifetimes of 15N polarization with superior sensitivity of 1H detection. Despite the proximity of 1H to 15N nuclei in the diazirine moiety, 15N T1 times of up to (4.6±0.4) min and singlet lifetimes Ts of up to (17.5±3.8) min are observed. Furthermore, we found terminal diazirines to support hyperpolarized 1H2 singlet states in CH2 groups of chiral molecules. The singlet lifetime of 1H singlets is up to (9.2±1.8) min, thus exceeding 1H T1 relaxation time (at 8.45 T) by a factor of ≈100. [ABSTRACT FROM AUTHOR]

Hyperpolarisation methods that premagnetise agents such as pyruvate are currently receiving significant attention because they produce sensitivity gains that allow disease tracking and interrogation of cellular metabolism by magnetic resonance. Here, we communicate how signal amplification by reversible exchange (SABRE) can provide strong 13C pyruvate signal enhancements in seconds through the formation of the novel polarisation transfer catalyst [Ir(H)2(η2‐pyruvate)(DMSO)(IMes)]. By harnessing SABRE, strong signals for [1‐13C]‐ and [2‐13C]pyruvate in addition to a long‐lived singlet state in the [1,2‐13C2] form are readily created; the latter can be observed five minutes after the initial hyperpolarisation step. We also demonstrate how this development may help with future studies of chemical reactivity. [ABSTRACT FROM AUTHOR]

Hyperpolarized magnetic resonance spectroscopy enables quantitative, non‐radioactive, real‐time measurement of imaging probe biodistribution and metabolism in vivo. Here, we investigate and report on the development and characterization of hyperpolarized acetylsalicylic acid (aspirin) and its use as a nuclear magnetic resonance (NMR) probe. Aspirin derivatives were synthesized with single‐ and double‐13C labels and hyperpolarized by dynamic nuclear polarization with 4.7 % and 3 % polarization, respectively. The longitudinal relaxation constants (T1) for the labeled acetyl and carboxyl carbonyls were approximately 30 seconds, supporting in vivo imaging and spectroscopy applications. In vitro hydrolysis, transacetylation, and albumin binding of hyperpolarized aspirin were readily monitored in real time by 13C‐NMR spectroscopy. Hyperpolarized, double‐labeled aspirin was well tolerated in mice and could be observed by both 13C‐MR imaging and 13C‐NMR spectroscopy in vivo. [ABSTRACT FROM AUTHOR]

Benchtop NMR spectrometers with sub-ppm spectral resolution have opened up new opportunities for performing NMR outside of the standard laboratory environment. However, the relatively weak magnetic fields of these devices (1–2 T) results in low sensitivity and significant peak overlap in 1H NMR spectra. Here, we use hyperpolarised 13C{1H} NMR to overcome these challenges. Specifically, we demonstrate the use of the signal amplification by reversible exchange (SABRE) parahydrogen-based hyperpolarisation technique to enhance the sensitivity of natural abundance 1D and 2D 13C{1H} benchtop NMR spectra. We compare two detection methods for SABRE-enhanced 13C NMR and observe an optimal 13C{1H} signal-to-noise ratio (SNR) for a refocused INEPT approach, where hyperpolarisation is transferred from 1H to 13C. In addition, we exemplify SABRE-enhanced 2D 13C benchtop NMR through the acquisition of a 2D HETCOR spectrum of 260 mM of 4-methylpyridine at natural isotopic abundance in a total experiment time of 69 min. In theory, signal averaging for over 300 days would be required to achieve a comparable SNR for a thermally polarised benchtop NMR spectrum acquired of a sample of the same concentration at natural abundance. [ABSTRACT FROM AUTHOR]

Since reaching the clinic, magnetic resonance imaging (MRI) has become an irreplaceable radiological tool because of the macroscopic information it provides across almost all organs and soft tissues within the human body, all without the need for ionising radiation. The sensitivity of MR, however, is too low to take full advantage of the rich chemical information contained in the MR signal. Hyperpolarisation techniques have recently emerged as methods to overcome the sensitivity limitations by enhancing the MR signal by many orders of magnitude compared to the thermal equilibrium, enabling a new class of metabolic and molecular X-nuclei based MR tracers capable of reporting on metabolic processes at the cellular level. These hyperpolarised (HP) tracers have the potential to elucidate the complex metabolic processes of many organs and pathologies, with studies so far focusing on the fields of oncology and cardiology. This review presents an overview of hyperpolarisation techniques that appear most promising for clinical use today, such as dissolution dynamic nuclear polarisation (d-DNP), parahydrogen-induced hyperpolarisation (PHIP), Brute force hyperpolarisation and spin-exchange optical pumping (SEOP), before discussing methods for tracer detection, emerging metabolic tracers and applications and progress in preclinical and clinical application. [ABSTRACT FROM AUTHOR]

Abstract: Hyperpolarization techniques are key to extending the capabilities of MRI for the investigation of structural, functional and metabolic processes in vivo. Recent heterogeneous catalyst development has produced high polarization in water using parahydrogen with biologically relevant contrast agents. A heterogeneous ligand‐stabilized Rh catalyst is introduced that is capable of achieving 15N polarization of 12.2±2.7 % by hydrogenation of neurine into a choline derivative. This is the highest 15N polarization of any parahydrogen method in water to date. Notably, this was performed using a deuterated quaternary amine with an exceptionally long spin‐lattice relaxation time (T1) of 21.0±0.4 min. These results open the door to the possibility of 15N in vivo imaging using nontoxic similar model systems because of the biocompatibility of the production media and the stability of the heterogeneous catalyst using parahydrogen‐induced polarization (PHIP) as the hyperpolarization method. [ABSTRACT FROM AUTHOR]

By introducing a range of 2H 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 remaining 1H nuclei are increased and show how this leads to a concomitant increase in the level of 1H and 13C hyperpolarization that can ultimately be detected. [ABSTRACT FROM AUTHOR]

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. Although convenient, this method suffers from limited reproducibility and cannot be used with NMR spectrometers that do not have appreciable stray fields, such as benchtop instruments. Here, we use a simple hand‐held permanent magnet array to provide the necessary PTF during sample shaking. We find that the use of this array provides a 25% increase in SABRE enhancement over the stray field approach, while also providing improved reproducibility. Arrays with a range of PTFs were tested, and the PTF‐dependent SABRE enhancements were found to be in excellent agreement with comparable experiments carried out using an automated flow system where an electromagnet is used to generate the PTF. We anticipate that this approach will improve the efficiency and reproducibility of SABRE experiments carried out using manual shaking and will be particularly useful for benchtop NMR, where a suitable stray field is not readily accessible. The ability to construct arrays with a range of PTFs will also enable the rapid optimisation of SABRE enhancement as function of PTF for new substrate and catalyst systems. [ABSTRACT FROM AUTHOR]

Abstract: Tailoring the physical features and the porous network architecture of silica‐based hyperpolarizing solids containing TEMPO radicals, known as HYPSO (hybrid polarizing solids), enabled unprecedented performance of dissolution dynamic nuclear polarization (d‐DNP). High polarization values up to P(1H)=99 % were reached for samples impregnated with a mixture of H2O/D2O and loaded in a 6.7 T polarizer at temperatures around 1.2 K. These HYPSO materials combine the best performance of homogeneous DNP formulations with the advantages of solid polarizing matrices, which provide hyperpolarized solutions free of any—potentially toxic—additives (radicals and glass‐forming agents). The hyperpolarized solutions can be expelled from the porous solids, filtered, and rapidly transferred either to a nuclear magnetic resonance (NMR) spectrometer or to a magnetic resonance imaging (MRI) system. [ABSTRACT FROM AUTHOR]

Abstract: Signalverstärkung durch reversiblen Austausch (SABRE) wandelt typischerweise schwache Kernresonanz‐Aussagen in starke Signale um, wodurch sonst nicht durchführbare Messungen möglich werden. Aufgrund ihrer Geschwindigkeit und Einfachheit hat die Methode erhebliche Beliebtheit gewonnen. Dieser Kurzaufsatz beschreibt die Entwicklung von SABRE ausgehend von der ursprünglichen Hyperpolarisation von Pyridin im Jahr 2009 bis zu dem Punkt, bei dem 50‐prozentige 1H‐Polarisationsgrade für ein Dideuterionicotinat erzielt wurden, womit ein Schlüsselschritt des Wegs zu einer denkbaren klinischen Anwendung erreicht war. Einfache Wege zur hocheffizienten 15N‐Hyperpolarisation und zur Generierung langlebiger hyperpolarisierter magnetischer Zustände werden aufgezeigt. Abschließend beschreiben wir, wie das kürzlich berichtete SABRE‐RELAY‐Verfahren Parawasserstoff einen Weg bietet, einen viel größeren Umfang molekularer Baugruppen wie Amide, Alkohole, Carbonsäuren und Phosphate zu hyperpolarisieren, als dies früher für möglich gehalten wurde. Schon heute ist vorauszusehen, dass SABRE aufgrund dieser gebündelten Entwicklungen erhebliche Auswirkungen sowohl auf die chemische Analyse als auch auf die Diagnose von Krankheiten haben wird. [ABSTRACT FROM AUTHOR]

Benchtop NMR spectrometers with sub-ppm spectral resolution have opened up new opportunities for performing NMR outside of the standard laboratory environment. However, the relatively weak magnetic fields of these devices (1–2 T) results in low sensitivity and significant peak overlap in 1H NMR spectra. Here, we use hyperpolarised 13C{1H} NMR to overcome these challenges. Specifically, we demonstrate the use of the signal amplification by reversible exchange (SABRE) parahydrogen-based hyperpolarisation technique to enhance the sensitivity of natural abundance 1D and 2D 13C{1H} benchtop NMR spectra. We compare two detection methods for SABRE-enhanced 13C NMR and observe an optimal 13C{1H} signal-to-noise ratio (SNR) for a refocused INEPT approach, where hyperpolarisation is transferred from 1H to 13C. In addition, we exemplify SABRE-enhanced 2D 13C benchtop NMR through the acquisition of a 2D HETCOR spectrum of 260 mM of 4-methylpyridine at natural isotopic abundance in a total experiment time of 69 min. In theory, signal averaging for over 300 days would be required to achieve a comparable SNR for a thermally polarised benchtop NMR spectrum acquired of a sample of the same concentration at natural abundance.

Diffusion-ordered NMR spectroscopy (DOSY) is a powerful approach for the analysis of molecular mixtures, yet its application range is limited by the relatively low sensitivity of NMR. We show here that spectrally resolved 13C DOSY data can be collected, in a single scan, for substrates hyperpolarised by dissolution dynamic nuclear polarisation (D-DNP), which provides signal enhancements of several orders of magnitude. For this we use a convection-compensation pulse scheme, which we also analyse by numerical simulation. The proposed method further allows the acquisition of several consecutive DOSY spectra in a single D-DNP experiment. [ABSTRACT FROM AUTHOR]

Diazirines are an attractive class of potential molecular tags for magnetic resonance imaging owing to their biocompatibility and ease of incorporation into a large variety of molecules. As recently reported, 15N2-diazirine can be hyperpolarized by the SABRE-SHEATH method, sustaining both singlet and magnetization states, thus offering a path to long-lived polarization storage. Herein, we show the generality of this approach by illustrating that the diazirine tag alone is sufficient for achieving excellent signal enhancements with long-lasting polarization. Our investigations reveal the critical role of Lewis basic additives, including water, on achieving SABRE-promoted hyperpolarization. The application of this strategy to a 15N2-diazirine-containing choline derivative demonstrates the potential of 15N2-diazirines as molecular imaging tags for biomedical applications. [ABSTRACT FROM AUTHOR]

We recently reported a pump-probe method that uses a single laser pulse to introduce para hydrogen ( p -H 2 ) into a metal dihydride complex and then follows the time-evolution of the p -H 2 -derived nuclear spin states by NMR. We present here a theoretical framework to describe the oscillatory behaviour of the resultant hyperpolarised NMR signals using a product operator formalism. We consider the cases where the p -H 2 -derived protons form part of an AX, AXY, AXYZ or AA′XX′ spin system in the product molecule. We use this framework to predict the patterns for 2D pump-probe NMR spectra, where the indirect dimension represents the evolution during the pump-probe delay and the positions of the cross-peaks depend on the difference in chemical shift of the p -H 2 -derived protons and the difference in their couplings to other nuclei. The evolution of the NMR signals of the p -H 2 -derived protons, as well as the transfer of hyperpolarisation to other NMR-active nuclei in the product, is described. The theoretical framework is tested experimentally for a set of ruthenium dihydride complexes representing the different spin systems. Theoretical predictions and experimental results agree to within experimental error for all features of the hyperpolarised 1 H and 31 P pump-probe NMR spectra. Thus we establish the laser pump, NMR probe approach as a robust way to directly observe and quantitatively analyse the coherent evolution of p -H 2 -derived spin order over micro-to-millisecond timescales. [ABSTRACT FROM AUTHOR]

We evaluated the influence of K+ channels (i.e., Ca2+-activated K+ (KCa), ATP-sensitive K+ (KATP), and voltage-gated K+ (KV) channels) and key enzymes (nitric oxide synthase (NOS) and cyclooxygenase (COX)) on nicotine-induced cutaneous vasodilation and sweating. Using intradermal microdialysis, we evaluated forearm cutaneous vascular conductance (CVC) and sweat rate in 2 separate protocols. In protocol 1 ( n = 10), 4 separate sites were infused with ( i) lactated Ringer (Control), ( ii) 50 mmol·L−1 tetraethylammonium (KCa channel blocker), ( iii) 5 mmol·L−1 glybenclamide (KATP channel blocker), and ( iv) 10 mmol·L−1 4-aminopyridine (KV channel blocker). In protocol 2 ( n = 10), 4 sites were infused with ( i) lactated Ringer (Control), ( ii) 10 mmol·L−1 Nω-nitro- l-arginine (NOS inhibitor), ( iii) 10 mmol·L−1 ketorolac (COX inhibitor), or ( iv) a combination of NOS+COX inhibitors. At all sites, nicotine was infused in a dose-dependent manner (1.2, 3.6, 11, 33, and 100 mmol·L−1; each for 25 min). Nicotine-induced increase in CVC was attenuated by the KCa, KATP, and KV channel blockers, whereas nicotine-induced increase in sweat rate was reduced by the KCa and KV channel blockers ( P ≤ 0.05). COX inhibitor augmented nicotine-induced increase in CVC ( P ≤ 0.05), which was absent when NOS inhibitor was co-administered ( P > 0.05). In addition, our secondrary experiment ( n = 7) demonstrated that muscarinic receptor blockade with 58 μmol·L−1 atropine sulfate salt monohydrate abolished nicotine-induced increases in CVC (1.2-11 mmol·L−1) and sweating (all doses). We show that under a normothermic resting state: ( i) KCa, KATP, and KV channels contribute to nicotinic cutaneous vasodilation, ( ii) inhibition of COX augments nicotinic cutaneous vasodilation likely through NOS-dependent mechanism(s), and ( iii) KCa and KV channels contribute to nicotinic sweating. [ABSTRACT FROM AUTHOR]

This perspective article reviews some of the recent developments in the field of hyperpolarisation, with a focus on solution-state NMR spectroscopy of small molecules. Two techniques are considered in more detail, dissolution dynamic nuclear polarisation (D-DNP) and signal amplification by reversible exchange (SABRE). Some of the opportunities and challenges for applications of hyperpolarised solution-state magnetic resonance in chemistry are discussed. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A prerequisite for tissue electrolyte homeostasis is highly regulated ion and water transport through kidney or intestinal epithelia. In the present work, we monitored changes in the cell and luminal volumes of type II Madin-Darby canine kidney (MDCK) cells grown in a 3D environment in response to drugs, or to changes in the composition of the basal extracellular fluid. Using fluorescent markers and high-resolution spinning disc confocal microscopy, we could show that lack of sodium and potassium ions in the basal fluid (tetramethylammonium chloride (TMACl) buffer) induces a rapid increase in the cell and luminal volumes. This transepithelial water flow could be regulated by inhibitors and agonists of chloride channels. Hence, the driving force for the transepithelial water flow is chloride secretion, stimulated by hyperpolarization. Chloride ion depletion of the basal fluid (using sodium gluconate buffer) induces a strong reduction in the lumen size, indicating reabsorption of water from the lumen to the basal side. Lumen size also decreased following depolarization of the cell interior by rendering the membrane permeable to potassium. Hence, MDCK cells are capable of both absorption and secretion of chloride ions and water; negative potential within the lumen supports secretion, while depolarizing conditions promote reabsorption. [ABSTRACT FROM AUTHOR]

Incomplete knowledge of the longitudinal relaxation time constant ( T1) leads to incorrect assumptions in quantitative kinetic models of cellular systems, studied by hyperpolarized real-time NMR. Using an assay that measures the intracellular signal of small carboxylic acids in living cells, the intracellular T1 of the carboxylic acid moiety of acetate, keto-isocaproate, pyruvate, and butyrate was determined. The intracellular T1 is shown to be up to four-fold shorter than the extracellular T1. Such a large difference in T1 values between the inside and the outside of the cell has significant influence on the quantification of intracellular metabolic activity. It is expected that the significantly shorter T1 value of the carboxylic moieties inside cells is a result of macromolecular crowding. An artificial cytosol has been prepared and applied to predict the T1 of other carboxylic acids. We demonstrate the value of this prediction tool. [ABSTRACT FROM AUTHOR]

The γ-glutamyl transpeptidase (GGT) enzyme plays a central role in glutathione homeostasis. Direct detection of GGT activity could provide critical information for the diagnosis of several pathologies. We propose a new molecular probe, γ-Glu-[1-13C]Gly, for monitoring GGT activity in vivo by hyperpolarized (HP) 13C magnetic resonance (MR). The properties of γ-Glu-[1-13C]Gly are suitable for in vivo HP 13C metabolic analysis since the chemical shift between γ-Glu-[1-13C]Gly and its metabolic product, [1-13C]Gly, is large (4.3 ppm) and the T1 of both compounds is relatively long (30 s and 45 s, respectively, in H2O at 9.4 T). We also demonstrate that γ-Glu-[1-13C]Gly is highly sensitive to in vivo modulation of GGT activity induced by the inhibitor acivicin. [ABSTRACT FROM AUTHOR]

Die gegenwärtig verfügbaren Techniken der molekularen Bildgebung, die atomare Auflösung erzielen, benötigen extreme Arbeitsbedingungen wie niedrige Temperaturen, Vakuum sowie große Probenvolumina. Quantensensoren, die auf der spinabhängigen Photolumineszenz von Stickstoff ‐ Fehlstellen(NV) ‐ Zentren basieren, haben ein großes Potenzial für die Detektion einzelner Moleküle mit atomarer Auflösung bei Raumtemperatur. In Diamant ‐ Nanopartikeln können NV ‐ Zentren gezielt implantiert werden, sodass einzigartige Nanosensoren entstehen, die in lebende biologische Systeme eindringen können. Aus diesen Gründen könnte die Diamant ‐ Sensorik einen noch nie dagewesenen Einblick in die Struktur und Funktion von einzelnen Biomolekülen unter physiologischen Bedingungen liefern, sodass sich biologische Prozesse bis auf das Quantenniveau und mit atomarer Auflösung beobachten ließen. Die theoretischen Grundlagen der Diamant ‐ Quantensensoren und die aktuellen Entwicklungen von ihrer Herstellung bis zu den verschiedenen Sensor ‐ Techniken werden in diesem Kurzaufsatz erörtert. Quantensensoren auf Basis der spinabhängigen Photolumineszenz von Stickstoff ‐ Fehlstellen(NV) ‐ Zentren in Diamant ermöglichen eine Bildgebung mit atomarer Auflösung unter Umgebungsbedingungen, die sich zu einer revolutionären Technik für das Verständnis von Biomolekülen in deren natürlicher Umgebung entwickeln könnte. Die jüngsten Entwicklungen dieser Technik, ihr Potenzial und ihre Herausforderungen werden kritisch diskutiert. [ABSTRACT FROM AUTHOR]

A scalable and versatile methodology for production of vinylated carboxylic compounds with 13C isotopic label in C1 position is described. It allowed synthesis of vinyl acetate-1-13C, which is a precursor for preparation of 13C hyperpolarized ethyl acetate-1-13C, which provides a convenient vehicle for potential in vivo delivery of hyperpolarized acetate to probe metabolism in living organisms. Kinetics of vinyl acetate molecular hydrogenation and polarization transfer from para-hydrogen to 13C via magnetic field cycling were investigated. Nascent proton nuclear spin polarization (% PH) of ca. 3.3 % and carbon-13 polarization (% P13C) of ca. 1.8 % were achieved in ethyl acetate utilizing 50 % para-hydrogen corresponding to ca. 50 % polarization transfer efficiency. The use of nearly 100% para-hydrogen and the improvements of % PH of para-hydrogen-nascent protons may enable production of 13C hyperpolarized contrast agents with % P13C of 20-50 % in seconds using this chemistry. [ABSTRACT FROM AUTHOR]

Studies of hyperpolarized xenon-129 (hp-129Xe) in media such as liquid crystals and cell suspensions are in demand for applications ranging from biomedical imaging to materials engineering but have been hindered by the inability to bubble Xe through the desired media as a result of viscosity or perturbations caused by bubbles. Herein a device is reported that can be reliably used to dissolve hp-129Xe into viscous aqueous and organic samples without bubbling. This method is robust, requires small sample volumes (<60 μL), is compatible with existing NMR hardware, and is made from readily available materials. Experiments show that Xe can be introduced into viscous and aligned media without disrupting molecular order. We detected dissolved xenon in an aqueous liquid crystal that is disrupted by the shear forces of bubbling, and we observed liquid-crystal phase transitions in (MBBA). This tool allows an entirely new class of samples to be investigated by hyperpolarized-gas NMR spectroscopy. [ABSTRACT FROM AUTHOR]