Spinning-rate encoded chemical shift correlations from rotational resonance solid-state NMR experiments

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy
• Biophysical chemistry
• Structural biology

Background:

• Magic-angle-spinning (MAS) solid-state NMR is crucial for structural measurements, relying on carbon-13 (13C) to 13C distance restraints.
• Broadbanded recoupling methods offer many cross-peaks but suffer from precision limitations and weak signals due to relaxation and dipolar truncation.
• Frequency-selective methods, like rotational resonance (R(2)), improve precision but yield limited cross-peaks, complicating constraint extraction.

Purpose of the Study:

• To develop a more time-efficient method for obtaining 2D-like spectra in solid-state NMR.
• To enable precise, simultaneous, long-distance 13C-13C constraint measurements.
• To facilitate the setup and implementation of R(2) and R(2)-width (R(2)W) experiments.

Main Methods:

• A novel approach combining 1D R(2)W experiments with chemical shift information encoded in MAS rates.
• Acquisition of 2D-like spectra by analyzing R(2) matching conditions across a range of MAS rates.
• Utilizing R(2)-mediated polarization transfer to observe long-distance 13C-13C cross-peaks.

Main Results:

• A time-efficient experiment yielding 2D-like spectra with benefits of multidimensional R(2)W measurements.
• Successful observation of long-distance 13C-13C cross-peaks via R(2)-mediated polarization transfer.
• Demonstration of efficient setup and targeted implementation of traditional R(2) or R(2)W experiments.

Conclusions:

• The presented method offers a significant improvement in time efficiency for acquiring structural constraints in solid-state NMR.
• This technique enhances the precision and accuracy of distance measurements, particularly for long-range interactions.
• The approach is adaptable for other variable-MAS and frequency-selective solid-state NMR experiments, broadening its applicability.