Jan-Bernd Hövener

1 month ago | analyticalsciencejournals.onlinelibrary.wiley.com | Josh Peters |Frank D. Sönnichsen |Jan-Bernd Hövener |Andrey N. Pravdivtsev

α Flip-angle αm Maximum flip-angle ADC Analog-to-digital-converter BB Broadband C Concentration d.i. Deionized dDNP Dissolution dynamic nuclear polarization FID Free induction decay GdCA Gadolinium-based contrast agent P Polarization RG Receiver gain RRT Receiver range threshold TR Repetition time Sm Maximum signal SNR Signal-to-noise-ratio 1 Introduction Nuclear magnetic resonance is a universal analytical method [1].

Dec 13, 2024 | nature.com | Lukas Kaltschnee |Andrey N. Pravdivtsev |Manuel Gehl |Gangfeng Huang |Christoph Riplinger |Frank Neese | +7 more

Hydrogenases are widespread metalloenzymes used for the activation and production of molecular hydrogen. Understanding the catalytic mechanism of hydrogenases can help to establish industrial (bio)catalytic hydrogen production and conversion. Here we show the observation of so-far undetectable intermediates of [Fe]-hydrogenase in its catalytic cycle. We observed these intermediates by applying a signal-enhancing NMR technique based on parahydrogen. Molecular hydrogen occurs as orthohydrogen or parahydrogen, depending on its nuclear spin state. We found that catalytic conversion of parahydrogen by the [Fe]-hydrogenase leads to notably enhanced NMR signals (parahydrogen-induced polarization, PHIP). The observed signals encode information about how the [Fe]-hydrogenase binds hydrogen during catalysis. Our data support models of the catalytic mechanism that involve the formation of a hydride at the iron centre. Moreover, PHIP enabled studying the binding kinetics. This work demonstrates the hitherto unexploited power of PHIP to study catalytic mechanisms of hydrogenases. The catalytic mechanism of [Fe]-hydrogenases is not well understood. Now a signal-enhanced nuclear magnetic resonance method based on parahydrogen is introduced to study [Fe]-hydrogenase under turnover conditions in situ, revealing intermediates of the catalytic cycle.

Dec 2, 2024 | nature.com | Xin Gui |Oleg Salnikov |Arne Brahms |Eduard Y Chekmenev |Rainer Herges |Simon B Duckett | +2 more

AbstractThe signal amplification by reversible exchange process (SABRE) enhances NMR signals by unlocking hidden polarization in parahydrogen through interactions with to-be-hyperpolarized substrate molecules when both are transiently bound to an Ir-based organometallic catalyst. Recent efforts focus on optimizing polarization transfer from parahydrogen-derived hydride ligands to the substrate in SABRE.

Aug 8, 2023 | nature.com | Frowin Ellermann |Arne Brahms |Rainer Herges |Jan-Bernd Hövener |Aidan Sirbu

AbstractNuclear spin hyperpolarization is a quantum effect that enhances the nuclear magnetic resonance signal by several orders of magnitude and has enabled real-time metabolic imaging in humans. However, the translation of hyperpolarization technology into routine use in laboratories and medical centers is hampered by the lack of portable, cost-effective polarizers that are not commercially available.