Combined zero-quantum and spin-diffusion mixing for efficient homonuclear correlation spectroscopy under fast MAS: broadband recoupling and detection of long-range correlations

Abstract

Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35–40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD–RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD–RFDR sequences experimentally on a U-13C,15N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD–RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD–RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD–RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD–RFDR experiment is beneficial in a broad range of conditions, including both high and moderate MAS frequencies and magnetic fields.

Molecular architecture of fungal cell walls revealed by solid-state NMR

“…To assign the NMR resonances of cell wall polysaccharides, we measured 2D 13 C– 13 C correlation spectra using 53-ms CORD mixing 38 , 39 for through-space correlations (Fig. 1a ) and refocused 13 C INADEQUATE pulse sequence 40 , 41 for through-bond correlations (Fig.…”

Improving dipolar recoupling for site-specific structural and dynamics studies in biosolids NMR: windowed RN-symmetry sequences

“…24, 50 We have examined two samples, nanocrystalline U- 13 C, 15 N-LC8 and the same preparation but doped with 5 mM Cu(II)-EDTA. The latter sample was studied by us previously in the context of experiments combining nonuniform sampling and paramagnetically assisted condensed data collection (NUS-PACC).…”

Structural biology of supramolecular assemblies by magic-angle spinning NMR spectroscopy

“…Under these conditions, DREAM and fpRFDR (finite pulse rf driven recoupling (Ishii, 2001)) are efficient for recording one- and two-bond correlations. Another family of experiments that is particularly useful for recording long-range 13 C- 13 C distance restraints is COmbined R2 n ν -Driven (CORD) dipolar recoupling sequences, where the magnetization transfer is driven by rotor-synchronized R2 n ν symmetry based recoupling (Hou et al, 2011a; Hou et al, 2013a; Lu et al, 2015b). The R2 n ν and CN n ν symmetry recoupling schemes were originally presented by Levitt and co-workers (Carravetta et al, 2000).…”