The School of Biology at the University of St Andrews is inviting applications from outstanding visionary Research Fellow and Future Leader candida...

Heat shock protein 90 (Hsp90) serves as a crucial regulator of cellular proteostasis by stabilizing and regulating the activity of numerous substrates, many of which are oncogenic proteins. Therefore,...

We herein demonstrate the synthesis of a pair of enantiomerically pure YbIII complexes by post-functionalisation of the parent YbIII complex via condensation with an enantiomerically pure chiral amine...

Nuclear magnetic resonance (NMR) plays a central role in the elucidation of chemical structures but is often limited by low sensitivity. Dissolution dynamic nuclear polarization (dDNP) emerges as a transformative methodology for both solution-state NMR and metabolic NMR imaging, which could overcome this limitation. Typically, dDNP relies on combining a stable radical with the analyte within a uniform glass under cryogenic conditions. The electron polarization is then transferred through microwave irradiation to the nuclei. The present study explores the use of radicals introduced via γ-irradiation, as bearers of the electron spins that will enhance 1H or 13C nuclides. 1H solid-state NMR spectra of γ-irradiated powders at 1–5 K revealed, upon microwave irradiation, signal enhancements that, in general, were higher than those achieved through conventional glass-based DNP. Transfer of these samples to a solution-state NMR spectrometer via a rapid dissolution driven by a superheated water provided significant enhancements of solution-state 1H NMR signals. Enhancements of 13C signals in the γ-irradiated solids were more modest, as a combined consequence of a low radical concentration and of the dilute concentration of 13C in the natural abundant samples examined. Nevertheless, ca. 700–800-fold enhancements in 13C solution NMR spectra of certain sites recorded at 11.7 T could still be achieved. A total disappearance of the radicals upon performing a dDNP-like aqueous dissolution and a high stability of the samples were found. Overall, the study showcases the advantages and limitations of γ-irradiated radicals as candidates for advancing spectroscopic dDNP-enhanced NMR.

This study discusses a potential route for enhancing 1H NMR signals in the liquid phase at high magnetic fields for samples on the 100 μL volume scale using dynamic nuclear polarization (DNP). The approach involves dispersing an inert powder that is both rich in protons and capable of undergoing DNP with good efficiency at noncryogenic temperatures, and letting the solid 1H polarization thus enhanced pass from the dispersed particles onto the surrounding liquid via spontaneous cross relaxation effects. To this end, BDPA-doped polystyrene (PS) particles in the μm range were suspended in 30 μL of heptane, loaded into 3.2 mm sapphire rotors, and spun at ≈500 Hz for homogeneity purposes in a 14.1 T magnet. Irradiation with ≈13 W at 395 GHz while maintaining temperature in the 185–220 K range thus enhanced the PS proton polarization ≈12-fold within ≈2 s; after ca. 6 s of irradiation, this resulted in ca. 3-fold enhancements of the heptane proton resonances, while preserving their ≤2 Hz line widths. The conditions over which such particle-mediated transfer occurs were explored over a range of sample composition, deuteration and molecular weight; best results were obtained when polarizing a ball-milled powder made of deuterated-PS/PS/BDPA = 86.4/9.6/4.0 suspended on perdeuterated heptane-d16. While the solution-state enhancements provided by this approach are still relatively modest, its generality could open new avenues in DNP-enhanced 1H NMR that do not sacrifice on the volumes, on the high-resolution conditions, or on the multiscan averaging that is customary in contemporary applications.

Oulu, Finland – July 7, 2025 – The 2025 Richard R. Ernst Prize in Magnetic Resonance has been awarded to Professor Thomas Prisner of Goethe University Frankfurt, in recognition of his outstanding cont...

Centre of Magnetic Resonance CMR

PhD Project - Harnessing Bacterial Viruses to Combat Antibiotic-Resistant Infections at University of St Andrews, listed on FindAPhD.com

PhD Project - Synthesis of Shielded Molecular Radicals for Quantum Information Technologies at University of Edinburgh, listed on FindAPhD.com

Climate models predict that the number of heat-related deaths could soar in cities over the coming century, even when efforts are made to keep people safe.

Cyclodipeptide oxidases are filamentous enzymes. Here, the authors dissect the mechanism of a promiscuous flavoenzyme from the biosynthesis of cyclodipeptide natural products, unveiling fast catalysis...

The [1,2]-rearrangement of allylic ammonium ylides is traditionally observed as a competitive minor pathway alongside the thermally allowed [2,3]-sigmatropic rearrangement. Concerted [1,2]-rearrangements are formally forbidden, with these processes believed to proceed through homolytic C–N bond fission of the ylide, followed by radical–radical recombination. The challenges associated with developing a catalytic enantioselective [1,2]-rearrangement of allylic ammonium ylides therefore lie in biasing the reaction pathway to favor the [1,2]-reaction product, alongside controlling a stereoselective radical–radical recombination event. Herein, a Lewis basic chiral isothiourea facilitates catalytic [1,2]-rearrangement of prochiral aryl ester ammonium salts to generate unnatural α-amino acid derivatives with up to complete selectivity over the [2,3]-rearrangement and with good to excellent enantiocontrol. Key factors in favoring the [1,2]-rearrangement include exploitation of disubstituted terminal allylic substituents, cyclic N-substituted ammonium salts, and elevated reaction temperatures. Mechanistic studies involving 13C-labeling and crossover reactions, combined with radical trapping experiments and observed changes in product enantioselectivity, are consistent with a radical solvent cage effect, with maximum product enantioselectivity observed through promotion of “in-cage” radical–radical recombination. Computational analysis indicates that the distribution between [1,2]- and [2,3]-rearrangement products arises predominantly from C–N bond homolysis of an intermediate ammonium ylide, followed by recombination of the α-amino radical at either the primary or tertiary site of an intermediate allylic radical. Electrostatic interactions involving the bromide counterion control the facial selectivity of the [1,2]- and [2,3]-rearrangements, while the sterically hindered tertiary position of the allylic substituent disfavors the formation of the [2,3]-product. These results will impact further investigations and understanding of enantioselective radical–radical reactions.