Dipolar truncation in magic-angle spinning NMR recoupling experiments

Abstract

Quantitative solid-state NMR distance measurements in strongly coupled spin systems are often complicated due to the simultaneous presence of multiple noncommuting spin interactions. In the case of zeroth-order homonuclear dipolar recoupling experiments, the recoupled dipolar interaction between distant spins is attenuated by the presence of stronger couplings to nearby spins, an effect known as dipolar truncation. In this article, we quantitatively investigate the effect of dipolar truncation on the polarization-transfer efficiency of various homonuclear recoupling experiments with analytical theory, numerical simulations, and experiments. In particular, using selectively 13 C-labeled tripeptides, we compare the extent of dipolar truncation in model three-spin systems encountered in protein samples produced with uniform and alternating labeling. Our observations indicate that while the extent of dipolar truncation decreases in the absence of directly bonded nuclei, two-bond dipolar couplings can generate significant dipolar truncation of small, long-range couplings. Therefore, while alternating labeling alleviates the effects of dipolar truncation, and thus facilitates the application of recoupling experiments to large spin systems, it does not represent a complete solution to this outstanding problem.

Spinning proteins, the faster, the better?

“…PDSD, [32,33] DARR [34], MIRROR [35], PARIS [36], CHHC [37], PAR [38]) due to their more favorable behavior with respect to dipolar truncation [39].…”

A Proton‐Detected 4D Solid‐State NMR Experiment for Protein Structure Determination

“…In such samples, even the closest 1 H neighbour often corresponds to a long-range contact and dipolar truncation [9] is not an issue, allowing highly-efficient first-order dipolar-recoupling experiments to be used to obtain distance information. Here we use the dipolar recoupling enhanced by amplitude modulation (DREAM) [10] mixing scheme ( Figure 1) that provides particularly high polarization-transfer efficiencies due to its adiabatic nature.…”

Proton-driven spin diffusion in rotating solids via reversible and irreversible quantum dynamics

“…In addition, PDSD does not suffer from the dipolar truncation effect, where polarization transfer between weakly coupled nuclei is obstructed by the presence of strongly coupled nuclei. 30,31 The combination of these two features makes PDSD particularly promising for providing information on a wide range of interatomic distances. However, due to the lack of an accurate theoretical description of these experiments, the quantitative relationship between molecular structure and the observed spin diffusion has remained obscure.…”