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A H anisotropic-isotropic chemical shift correlation experiment which employs symmetry-based recoupling sequences to reintroduce the chemical shift anisotropy in ν and ultrafast MAS to resolve H sites in ν is described. This experiment is used to measure H shift parameters for L-ascorbic acid, a compound with a relatively complex hydrogen-bonding network in the solid. The H CSAs of hydrogen-bonded sites with resolved isotropic shifts can be extracted directly from the recoupled lineshapes. In combination with DFT calculations, hydrogen positions in crystal structures obtained from X-ray and neutron diffraction are refined by comparison with simulations of the full two-dimensional NMR spectrum. The improved resolution afforded by the second dimension allows even unresolved hydrogen-bonded sites H to be assigned and their shift parameters to be obtained.
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http://dx.doi.org/10.1016/j.ssnmr.2017.02.002 | DOI Listing |
J Am Chem Soc
September 2025
Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of Korea.
The thermodynamic equilibrium assumption often invoked in modeling ion migration in solid-state materials remains insufficient to capture the true migration behavior of Li ions, particularly in less-crystalline superionic conductors that exhibit anomalously high Li ion conductivity. Such materials challenge classical frameworks and necessitate a lattice dynamics-based perspective that explicitly accounts for nonequilibrium phonon interactions and transient structural responses. Here, we uncover a phonon-governed Li ion migration mechanism in garnet-structured superionic conductors by comparing Ta-doped LiLaZrTaO (LLZTO4) to its undoped analogue, LiLaZrAlO (LLZO).
View Article and Find Full Text PDFJ Am Chem Soc
June 2025
Centre de RMN à Très Hauts Champs de Lyon (UMR 5082), CNRS, Ecole Normale Supérieure de Lyon and Université Clade Bernard Lyon 1, Villeurbanne 69100, France.
We present ultrafast magic-angle spinning (MAS) at 160 kHz in solid-state nuclear magnetic resonance (NMR), demonstrating unprecedented spectral quality and coherence lifetimes in proton-detected experiments on biomolecular systems. By optimizing experimental and sample conditions and utilizing advanced filling and handling tools, we achieve superior resolution on both microcrystalline and membrane-reconstituted proteins, paving the way for new applications in structural biology.
View Article and Find Full Text PDFBiochemistry
March 2025
Institute for Chemistry, Technical University of Berlin, Str. des 17. Juni 135, Berlin D-10623, Germany.
Phytochromes are red-light-sensitive biliprotein photoreceptors that control a variety of physiological processes in plants, fungi, and bacteria. Lately, greater attention has been paid to these photoreceptors due to their potential as fluorescent probes for deep-tissue microscopy. Such fluorescing phytochromes have been generated by multiple amino acid substitutions in weakly fluorescent wild-type (WT) proteins.
View Article and Find Full Text PDFPhys Chem Chem Phys
March 2025
Department of Chemistry, McGill University, Montreal, QC, Canada.
The properties of materials containing azobenzene depend strongly on the dynamics of and isomerization which in turn are influenced by the presence of different possible tautomers. Two commonly used food azo dyes, Allura Red (ALR) and Amaranth (AMA), were studied by NMR spectroscopy to experimentally determine their tautomeric forms and then theoretically rationalized. Variable temperature 2D H-N HMBC NMR provided a direct measure of the hydrazone percentage of the dyes in solution which was complimented by H ultrafast magic-angle spinning (MAS) and C CPMAS solid state NMR to characterize the structures of the solid dyes alone and incorporated into chitosan films designed to disassemble upon exposure to light and water.
View Article and Find Full Text PDFJ Am Chem Soc
February 2025
National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, C
Proton-detected solid-state nuclear magnetic resonance (ssNMR) under ultrafast magic-angle spinning (MAS) has become a powerful tool for elucidating the structures of proteins with sub-milligram quantities, where establishing C-N correlations is essential. However, traditional C-N cross-polarization (CP), effective at lower MAS frequencies, suffers diminished efficiency under ultrafast MAS conditions. To overcome this limitation, we developed a robust method for selective polarization between insensitive nuclei (SPINE).
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