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Amino acids (AAs) and ammonia are metabolic markers essential for nitrogen metabolism and cell regulation in both plants and humans. NMR provides interesting opportunities to investigate these metabolic pathways, yet lacks sensitivity, especially in case of 15 N. In this study, spin order embedded in p-H2 is used to produce on-demand reversible hyperpolarization in 15 N of pristine alanine and ammonia under ambient protic conditions directly in the NMR spectrometer. This is made possible by designing a mixed-ligand Ir-catalyst, selectively ligating the amino group of AA by exploiting ammonia as a strongly competitive co-ligand and preventing deactivation of Ir by bidentate ligation of AA. The stereoisomerism of the catalyst complexes is determined by hydride fingerprinting using 1 H/D scrambling of the associated N-functional groups on the catalyst (i.e., isotopological fingerprinting), and unravelled by 2D-ZQ-NMR. Monitoring the transfer of spin order from p-H2 to 15 N nuclei of ligated and free alanine and ammonia targets using SABRE-INEPT with variable exchange delays pinpoints the monodentate elucidated catalyst complexes to be most SABRE active. Also RF-spin locking (SABRE-SLIC) enables transfer of hyperpolarization to 15 N. The presented high-field approach can be a valuable alternative to SABRE-SHEATH techniques since the obtained catalytic insights (stereochemistry and kinetics) will remain valid at ultra-low magnetic fields. ispartof: ADVANCED SCIENCE ispartof: location:Germany status: Published online

Hyperpolarization using signal amplification by reversible exchange (SABRE) relies on target molecules and parahydrogen coordinating to a transition metal catalyst. Identification of this coordinated state becomes increasingly important, especially since bio-relevant targets such as pyruvate and amino acids exhibiting multiple binding sites are becoming compatible with SABRE. In this report, we present a fingerprinting method to discriminate and identify ligand binding sites without requiring the presence of a sensitive or isotope-labeled heteroatom. Adding a small concentration of protons to a deuterated medium, spontaneous 1H/D scrambling of exchangeable protons encodes the ligands each with an isotopological fingerprint. By use of rapid 2D zero quantum NMR, the binding sites are decoded from the hydrides in less than a minute. The new methodology is explained and demonstrated on Ir mixed complexes with pyridine, benzylamine, and ammonia as common N-functional ligands. ispartof: Journal Of Physical Chemistry Letters vol:13 issue:15 pages:3516-3522 ispartof: location:United States status: published

Hyperpolarization using signal amplification by reversible exchange (SABRE) relies on target molecules and parahydrogen coordinating to a transition metal catalyst. Identification of this coordinated state becomes increasingly important, especially since bio-relevant targets such as pyruvate and amino acids exhibiting multiple binding sites are becoming compatible with SABRE. In this report, we present a fingerprinting method to discriminate and identify ligand binding sites without requiring the presence of a sensitive or isotope-labeled heteroatom. Adding a small concentration of protons to a deuterated medium, spontaneous

Efficient, room temperature hyperpolarisation of exchangeable solvent protons combining parahydrogen (p-H2), ami-nopropyldiethoxymethylsilane (APDMS) and IrCl(COD)(IMES) to generate an active aminosilane-iridium complex, broadens the capabilities of SABRE-type hyperpolarisation of protons. A primary pool of hyperpolarised exchangeable protons transfers its hyperpolarisation to co-solutes with labile protons, partly overcoming the catalytic specificity of SABRE-type spin-transfer catalysis. The silane functionality of APDMS appears to be crucial to the improvement. Their role is unprecedented in p-H2-based hyperpolarisation of nuclear spins and promises to broaden applicability of ultra-sensitive solution-state NMR spectroscopy for the detection and elucidation of molecular behaviors otherwise unde-tectable at conventional sensitivity levels. doi: 10.1021/acs.jpcc.0c01149 Efficient, room temperature hyperpolarisation of exchangeable solvent protons combining parahydrogen (p-H2), ami-nopropyldiethoxymethylsilane (APDMS) and IrCl(COD)(IMES) to generate an active aminosilane-iridium complex, broadens the capabilities of SABRE-type hyperpolarisation of protons. A primary pool of hyperpolarised exchangeable protons transfers its hyperpolarisation to co-solutes with labile protons, partly overcoming the catalytic specificity of SABRE-type spin-transfer catalysis. The silane functionality of APDMS appears to be crucial to the improvement. Their role is unprecedented in p-H2-based hyperpolarisation of nuclear spins and promises to broaden applicability of ultra-sensitive solution-state NMR spectroscopy for the detection and elucidation of molecular behaviors otherwise unde-tectable at conventional sensitivity levels. ispartof: The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter vol:124 issue:27 pages:14541-14549 status: published

The morphology of zeolite W (MER topology) synthesized from Hydrated Silicate Ionic Liquids (HSILs) shows a distinct temperature dependence, reflected in a fundamental difference in the underlying crystal growth mechanism as revealed by Atomic Force Microscopy (AFM). Zeolite W crystals obtained at 90 °C develop in a highly supersaturated solution through birth and spread growth, whereas synthesis at 175 °C results in elongated, spiral grown zeolite W particles. Supersaturation was measured through the concentration of dissolved aluminate, being the limiting species. The evolution of the aluminum concentration during crystallization at different temperatures was monitored with 27Al Nuclear Magnetic Resonance (NMR) spectroscopy. Supersaturation conditions determine the nucleation rate, the prevailing crystal growth mechanism, and resulting crystal morphology. The morphology of zeolite W (MER topology) synthesized from Hydrated Silicate Ionic Liquids (HSILs) shows a distinct temperature dependence, reflected in a fundamental difference in the underlying crystal growth mechanism as revealed by Atomic Force Microscopy (AFM). Zeolite W crystals obtained at 90 °C develop in a highly supersaturated solution through birth and spread growth, whereas synthesis at 175 °C results in elongated, spiral grown zeolite W particles. Supersaturation was measured through the concentration of dissolved aluminate, being the limiting species. The evolution of the aluminum concentration during crystallization at different temperatures was monitored with 27Al Nuclear Magnetic Resonance (NMR) spectroscopy. Supersaturation conditions determine the nucleation rate, the prevailing crystal growth mechanism, and resulting crystal morphology. ispartof: Microporous and Mesoporous Materials vol:274 pages:379-384 status: published

The structural heterogeneity of water-extractable arabinoxylan (WE-AX) impacts wheat flour functionality. 1H diffusion-ordered (DOSY) nuclear magnetic resonance (NMR) spectroscopy revealed structural heterogeneity within WE-AX fractions obtained via graded ethanol precipitation. Combination with high-resolution 1H-1H correlation NMR spectroscopy (COSY) allowed identifying the relationship between the xylose substitution patterns and diffusion properties of the subpopulations. WE-AX fractions contained distinct subpopulations with different diffusion rates. WE-AX subpopulations with a high self-diffusivity contained high levels of monosubstituted xylose. In contrast, those with a low self-diffusivity were rich in disubstituted xylose, suggesting that disubstitution mainly occurs in WE-AX molecules with large hydrodynamic volumes. In general, WE-AX fractions precipitating at higher and lower ethanol concentrations had higher and lower self-diffusivity and more and less complex substitution patterns. Although 1H DOSY NMR, as performed in this study, was valuable for elucidating WE-AX structural heterogeneity, physical limitations arose when studying WE-AX populations with high molecular weight dispersions. ispartof: Journal Of Agricultural And Food Chemistry vol:69 issue:13 pages:3912-3922 ispartof: location:United States status: published

Arabinoxylan oligosaccharides (AXOS) are a complex mixture of cereal derived, water soluble prebiotics, obtained by enzymatic hydrolysis of arabinoxylan, a group of dietary fibers exerting numerous nutritional and health-beneficial effects. Such complex biomolecular mixtures are notoriously difficult to characterize without initial physical fractiona-tion. Here we present the in-situ analysis of AXOS using a variety of state-of-the-art sensitivity-enhanced 13C-DOSY methods, enabling virtual separation and identification of the components. Three dimensional correlation plots dis-playing 13C diffusivity (DOSY: Diffusion Ordered SpectroscopY), relaxation parameters (TOSY: raTe of relaxation Or-dered SpectrscopY) and chemical shift offer a unique way to elucidate the composition of mixtures. We have demon-strated this multifaceted 13C probed correlation strategy in standard mixtures of aliphatic and aromatic compounds, before implementing it on AXOS. These 3D-DOSY-TOSY plots in combination with 2D-NMR correlation experiments offer unprecedented clarity for assigning chemical functions, molecular size distribution and dynamics of oligosaccha-ride mixtures. doi: 10.1021/acs.jafc.9b06442 Arabinoxylan oligosaccharides (AXOS) are a complex mixture of cereal derived, water soluble prebiotics, obtained by enzymatic hydrolysis of arabinoxylan, a group of dietary fibers exerting numerous nutritional and health-beneficial effects. Such complex biomolecular mixtures are notoriously difficult to characterize without initial physical fractiona-tion. Here we present the in-situ analysis of AXOS using a variety of state-of-the-art sensitivity-enhanced 13C-DOSY methods, enabling virtual separation and identification of the components. Three dimensional correlation plots dis-playing 13C diffusivity (DOSY: Diffusion Ordered SpectroscopY), relaxation parameters (TOSY: raTe of relaxation Or-dered SpectrscopY) and chemical shift offer a unique way to elucidate the composition of mixtures. We have demon-strated this multifaceted 13C probed correlation strategy in standard mixtures of aliphatic and aromatic compounds, before implementing it on AXOS. These 3D-DOSY-TOSY plots in combination with 2D-NMR correlation experiments offer unprecedented clarity for assigning chemical functions, molecular size distribution and dynamics of oligosaccha-ride mixtures. ispartof: Journal Of Agricultural And Food Chemistry vol:68 issue:10 pages:3250-3259 ispartof: location:United States status: published

Symmetry breaking of parahydrogen using iridium catalysts converts singlet spin order into observable hyperpolarization. In this contribution, iridium catalysts are designed to exhibit asymmetry in their hydrides, regulated by in situ generation of deuterated ammonia governed by ammonium buffers. The concentrations of ammonia (N) and pyridine (P) provide a handle to generate a variety of stereo-chemically asymmetric N-heterocyclic carbene iridium complexes, ligating either [3xP], [2xP;N], [P;2xN] or [3xN] in an octahedral SABRE type configuration. The non-equivalent hydride positions, in correspondence with the ammonium buffer solutions, enables to extend singlet-triplet or | ⟩ → | ⟩ mixing at high magnetic field and experimentally induce prolonged generation of non-equilibrium longitudinal two-spin order. This long-lasting magnetization can be exploited in hyperpolarized 2D-OPSY-COSY experiments providing direct structural information on the catalyst using a single contact with parahydrogen. Separately, field cycling revealed hyperpolarization properties in low-field conditions. Controlling catalyst stereochemistry by introducing small and deuterated ligands, such as deuterated ammonia, simplifies the spin-system. This is shown to unify experimental and theoretically derived field-sweep experiments for four-spin systems. ispartof: Chemphyschem vol:22 issue:12 pages:1170-1177 ispartof: location:Germany status: Published online