Biomolecular solid-state NMR spectroscopy at 1200\xa0MHz: the gain in resolution

Morgane Callon,Alexander A Malär,Alexander Däpp,Sara Pfister,Marco E Weber,Anja Böckmann,Matías Chávez,Václav Římal,Dawid Zyla,Andreas Hunkeler,Lauriane Lecoq,Marie‐Laure Fogeron ,Rajdeep Deb,Rudolf Glockshuber,Anahit Torosyan,Steven Jonas ,Matthias Ernst,Riccardo Cadalbert,Michael Nassal,Thomas Wiegand,Johannes Zehnder,Beat H Meier

doi:10.1007/s10858-021-00373-x

Abstract

Progress in NMR in general and in biomolecular applications in particular is driven by increasing magnetic-field strengths leading to improved resolution and sensitivity of the NMR spectra. Recently, persistent superconducting magnets at a magnetic field strength (magnetic induction) of 28.2 T corresponding to 1200 MHz proton resonance frequency became commercially available. We present here a collection of high-field NMR spectra of a variety of proteins, including molecular machines, membrane proteins, viral capsids, fibrils and large molecular assemblies. We show this large panel in order to provide an overview over a range of representative systems under study, rather than a single best performing model system. We discuss both carbon-13 and proton-detected experiments, and show that in 13C spectra substantially higher numbers of peaks can be resolved compared to 850 MHz while for 1H spectra the most impressive increase in resolution is observed for aliphatic side-chain resonances.

Highlights

New technologies have often stood at the beginning of new spectroscopic techniques and NMR is a good example: Microcomputers have enabled Fourier spectroscopy (Ernst and Anderson 1965) and multidimensional NMR (Aue et al 1976), high and stable magnetic fields generated by persistent superconducting magnets have been instrumental for the first protein structure determinations (Williamson et al 1985; Wüthrich 2003) and the structural and dynamic investigation of increasingly larger proteins (Pervushin et al 1997; Fiaux et al 2002; Rosenzweig and Kay 2014)
We attribute this observation to the offset dependence of the CP step caused by the limited rf-field strength available at the 1200 MHz spectrometer on the 13C channel of the probe
Since the magic-angle spinning (MAS) frequency of the 1200 MHz 3.2 mm probe is currently limited to 20 kHz, corresponding to ~ 66 ppm, some rotational-resonance (Colombo et al 1988; Raleigh et al 1988) line-broadening effects are present at 1200 MHz between the carbonyl and aliphatic resonances

Summary

Introduction

New technologies have often stood at the beginning of new spectroscopic techniques and NMR is a good example: Microcomputers have enabled Fourier spectroscopy (Ernst and Anderson 1965) and multidimensional NMR (Aue et al 1976), high and stable magnetic fields generated by persistent superconducting magnets have been instrumental for the first protein structure determinations (Williamson et al 1985; Wüthrich 2003) and the structural and dynamic investigation of increasingly larger proteins (Pervushin et al 1997; Fiaux et al 2002; Rosenzweig and Kay 2014). Reliable magic-angle sample spinning probes together with high magnetic fields have enabled biomolecular solid-state NMR spectroscopy (McDermott et al 2000). The first solid-state NMR protein-structure determination used a magnetic-field strength of 17.6 T (proton resonance frequency 750 MHz) (Castellani et al 2002), and the first prion fibril structure was determined at 850 MHz (Wasmer et al 2008). Since 1000 MHz proton Larmor frequency is the present limit of what could be achieved with low-temperature superconducting (LTS) wire (such as Nb3Sn and NbTi), persistent magnetic fields exceeding 1000 MHz required solenoid coils made out of high-temperature superconducting (HTS) wire (e.g. REBCO) (Maeda and Yanagisawa 2019). Persistent hybrid superconducting magnets combining both, LTS and HTS, have been developed by Bruker Switzerland AG generating magnetic-field strengths up to 28.2 T corresponding to 1200 MHz proton Larmor frequency

Methods

Results

Conclusion