Magic-angle-spinning NMR techniques for measuring long-range distances in biological macromolecules

Area of Science:

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

Background:

• Solid-state NMR is crucial for molecular structure determination via nuclear-spin dipole-dipole couplings.
• Transverse relaxation (T2) limits the measurement of weak dipolar couplings and long distances, hindering structural analysis.

Purpose of the Study:

• To develop and apply advanced magic-angle-spinning (MAS) solid-state NMR techniques for measuring distances up to 20 Å.
• To overcome limitations imposed by nuclear spin relaxation times.

Main Methods:

• Utilized high gyromagnetic ratios of hydrogen-1 ((1)H) and fluorine-19 ((19)F) spins.
• Employed multispin effects to accelerate dipolar dephasing and (1)H/(19)F spin diffusion for nanometer-range distance probing.
• Applied third-spin heteronuclear detection, the HARDSHIP pulse sequence, and rotational-echo double-resonance (REDOR) technique.
• Leveraged relayed magnetization transfer (spin diffusion) for long-distance measurements.

Main Results:

• Successfully measured distances in the 15-20 Å range.
• Determined hydrogen-bond lengths, torsion angles, protein conformational distributions, and oligomeric assembly.
• Measured crystallite thicknesses in biological nanocomposites.
• Provided insights into peptide-lipid bilayer structures and protein-ligand binding site geometry.
• Elucidated oligomeric structures of membrane peptides using (19)F spin diffusion.

Conclusions:

• Developed novel MAS solid-state NMR techniques to extend distance measurement capabilities.
• These methods effectively probe molecular structures, interactions, and dynamics at the nanoscale.
• Advanced NMR approaches provide critical structural information for complex biological systems.