Substituted 2-(phenylamino)-5-phenyl-1,3,4-oxadiazoles were studied by 15N NMR spectroscopy. All signals were assigned on the basis of HMQC and HMBC experiments. Chemical shifts values were correlated with empirical Hammett parameters as well as with calculated electron densities and chemical shieldings.
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http://dx.doi.org/10.1002/mrc.1928 | DOI Listing |
J Am Chem Soc
January 2025
Institute of Organic Chemistry, University Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany.
In ion-pair catalysis, the last intermediate structures prior to the stereoselective transition states are of special importance for predictive models due to the high isomerization barrier between - and -substrate double bonds connecting ground and transition state energies. However, in prior experimental investigations of chiral phosphoric acids (CPA) solely the early intermediates could be investigated while the key intermediate remained elusive. In this study, the first experimental structural and conformational insights into ternary complexes with CPAs are presented using a special combination of low temperature and relaxation optimized N HSQC-NOESY NMR spectroscopy to enhance sensitivity.
View Article and Find Full Text PDFCarbohydr Polym
March 2025
Department of Molecular Sciences, Swedish University of Agricultural Sciences, Almas Allé 5, Uppsala 75651, Sweden. Electronic address:
Chitin is the second most abundant biopolymer in nature after cellulose and is composed of N-acetylglucosamine (GlcNAc) connected via β(1 → 4)-glycosidic bonds. Despite its prominence in nature and diverse roles in pharmaceutical and food technological applications, there is still a need to develop methods to study structure and function of chitin and its corresponding oligomers. Efforts have been made to analyse chitin oligomers by NMR spectroscopy, but spectral overlap has prevented any differentiation between the interior residues.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
University of Pittsburgh School of Medicine, Structural Biology, 3501 5th Ave., Biomedical Science Tower 3, Room 2044, 15261, Pittsburgh, UNITED STATES OF AMERICA.
Bacterial biofilms are major contributors to persistent infections and antimicrobial resistance, posing significant challenges to treatment. However, obtaining high-resolution structural information on native bacterial biofilms has remained elusive due to the methodological limitations associated with analyzing complex biological samples. Solid-state NMR (ssNMR) has shown promise in this regard, but its conventional application is hindered by sensitivity constraints for unlabeled native samples .
View Article and Find Full Text PDFJ Phys Chem Lett
January 2025
Centre for Hyperpolarization in Magnetic Resonance, University of York, Heslington YO10 5NY, United Kingdom.
This research uses perfluorocarbons (PFCs) as effective alternatives to traditional toxic solvents in reversible -hydrogen-induced polarization (PHIP) for NMR signal enhancement. Hydrogen solubility in PFCs is shown here to be an order of magnitude higher than in typical organic solvents by determination of Henry's constants. We demonstrate how this high H solubility enables the PFCs to deliver substantial polarization transfer from -hydrogen, achieving up to 2400-fold signal gains for H NMR detection and 67,000-fold (22% polarization) for N NMR detection at 9.
View Article and Find Full Text PDFBiomol NMR Assign
January 2025
Department of Chemistry and Chemical Biology, TU Dortmund University, Dortmund, Germany.
Cyclic GMP-AMP synthase (cGAS) is a DNA-sensing enzyme that is a member of the nucleotidyltransferase (NTase) family and functions as a DNA sensor. The protein is comprised of a catalytic NTase core domain and an unstructured hypervariable N-terminal domain (NTD) that was reported to increase protein activity by providing an additional DNA-binding surface. We report nearly complete H, N, and C backbone chemical-shift assignments of mouse cGAS NTD (residues 5-146), obtained with a set of 3D and 4D solution NMR experiments.
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