Proton Detected Solid-State NMR of Membrane Proteins at 28 Tesla (1.2 GHz) and 100 kHz Magic-Angle Spinning

Abstract

The available magnetic field strength for high resolution NMR in persistent superconducting magnets has recently improved from 23.5 to 28 Tesla, increasing the proton resonance frequency from 1 to 1.2 GHz. For magic-angle spinning (MAS) NMR, this is expected to improve resolution, provided the sample preparation results in homogeneous broadening. We compare two-dimensional (2D) proton detected MAS NMR spectra of four membrane proteins at 950 and 1200 MHz. We find a consistent improvement in resolution that scales superlinearly with the increase in magnetic field for three of the four examples. In 3D and 4D spectra, which are now routinely acquired, this improvement indicates the ability to resolve at least 2 and 2.5 times as many signals, respectively.

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

“…We herein present first results obtained on a 1200 MHz spectrometer for a set of biomolecular samples that we have already investigated at 850 MHz, and compare sensitivity and resolution in 1 H- and 13 C-detected NMR spectra. Proton-detected spectra at 1200 MHz are also under investigation in other labs and a preprint has become available during the submission process as (Nimerovsky et al 2021 ). We avoided the temptation to select one “typical” sample, i.e.…”

Proton-phosphorous connectivities revealed by high-resolution proton-detected solid-state NMR

“…These protons are in a stronger coupling regime and their resolution is expected to show the steepest improvement with an increase in MAS frequency or external magnetic field strength. 7,8,67,70,86 For instance the use of the recently installed 28.2 T (1200 MHz) magnet 67,86 allows to push the resolution for such resonances even further as it becomes evident by comparing the better peak separation and line narrowing in the 1 H-MAS spectra of compound 1 between 850 MHz and 1200 MHz in Fig. S2 (ESI †).…”

“…Note that also Redfield-type relaxation processes might contribute to the homogeneous linewidth in presence of large dynamic motions, for a detailed discussion of the different contributions to the proton linewidth, see references 65,66 . Another important contribution to the proton linewidth, the so-called inhomogeneous contribution, is caused by an imperfect magneticfield homogeneity (the magnet "shim"), magic-angle instabilities 67 , structural disorder or anisotropic bulk magnetic susceptibility effects 61,[68][69][70][71] and is not dependent on the MAS frequency 66 . Besides fast MAS to achieve narrow proton resonances, homonuclear decoupling [72][73][74] eventually also combined with double-quantum spectroscopy 75 or the removal of the homogeneous broadening in constant-time experiments 74 has been reported.…”

Solid-state NMR study of structural heterogeneity of the apo WT mouse TSPO reconstituted in liposomes

“…The field of membrane proteins within lipid bilayers by solid-state nuclear magnetic resonance (ssNMR) has also seen a continuous and important progress during the last decades with various biologically and medically relevant systems investigated: ABC transporter BmrA [5,6], -barrel AlkL [7], BamC lipoprotein [8], envelope protein E of the SARS-CoC-2 [9], human VDAC [10] to give just few examples. The access to magnetic fields as high as 1.2 GHz and ultra-fast (above 100 kHz) spinning CPMAS probes fostered even more the investigation of such challenging biological systems [11,12]. Most of membrane protein structures determined by NMR were for systems in detergent and only few in membrane lipids [13][14][15][16].…”