¹⁷O MAS NMR Correlation Spectroscopy at High Magnetic Fields

Area of Science:

• Biophysical Chemistry
• Structural Biology
• Solid-State NMR Spectroscopy

Background:

• Solid-state Nuclear Magnetic Resonance (NMR) is crucial for determining biomolecular structures.
• Oxygen-17 (¹⁷O) NMR has potential for structural studies but requires advanced techniques.

Purpose of the Study:

• To investigate the structure of FMOC-protected amino acids and a dipeptide using ¹⁷O solid-state NMR.
• To demonstrate the utility of ¹⁷O NMR for probing atomic environments and interatomic distances in biomolecules.

Main Methods:

• Utilized one- and two-dimensional ¹⁷O magic-angle spinning (MAS) NMR at high magnetic fields.
• Performed various double-resonance correlation experiments (¹⁵N-¹⁷O, ¹³C-¹⁷O, ¹H-¹⁷O) on uniformly labeled samples.
• Employed REAPDOR and ZF-TEDOR techniques to measure interatomic distances.

Main Results:

• Determined ¹⁷O chemical shift and quadrupolar parameters for oxygen sites in FMOC-l-leucine, FMOC-l-valine, and N-acetyl-l-valyl-l-leucine (N-Ac-VL).
• Quantitated ¹⁵N-¹⁷O and ¹³C-¹⁷O distances within 15% of known values.
• Investigated through-space hydrogen bonding in the dipeptide using ¹H-detected ¹⁷O NMR.

Conclusions:

• ¹⁷O NMR is a viable and powerful probe for detailed structural investigations of biomolecular solids.
• The study validates ¹⁷O NMR for quantitating interatomic distances and characterizing hydrogen bonding in peptides.