1H detected 1H,15N correlation spectroscopy in rotating solids

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy
• Structural Biology
• Biophysics

Background:

• Determining long-range distances in solid-state proteins is crucial for understanding their global fold.
• Proton-proton (1H-1H) dipolar couplings broaden spectra, complicating analysis in solid-state NMR.
• Existing methods often compromise sensitivity or are limited by dipolar truncation.

Purpose of the Study:

• To develop novel correlation experiments for measuring long-range 1H-1H distances in solid-state peptides and proteins.
• To overcome limitations of existing techniques, particularly broadening and dipolar truncation.
• To enhance sensitivity and spectral resolution in 1H magic angle spinning (MAS) NMR.

Main Methods:

• Utilizing perdeuteration and back-substitution of exchangeable protons in 2H,15N-labeled samples.
• Employing 1H detection with full labeling of exchangeable sites to maximize sensitivity.
• Designing pulse schemes that leverage the dispersion of amide 15N resonances.
• Demonstrating the experiments on a uniformly labeled dipeptide (N-Ac-Val-Leu-OH).

Main Results:

• Achieved significant attenuation of strong 1H-1H dipolar couplings.
• Demonstrated a sensitivity gain of >5 compared to 15N-detected experiments.
• Observed improved 1H amide linewidths, indicating enhanced spectral resolution.
• Circumvented the issue of dipolar truncation in 1H-1H spin systems.

Conclusions:

• The new correlation experiments enable accurate measurement of long-range 1H-1H distances in uniformly labeled solid-state proteins.
• These methods offer improved sensitivity and resolution for structural analysis.
• The approach is expected to be valuable for constraining the global fold of proteins using solid-state NMR.