Atomic Structure of GNNQQNY Nanocrystals: A Validated Approach for Polymorphic Amyloids

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Amyloid fibrils are crucial in diseases but difficult to study due to polymorphism.
• Traditional MAS NMR faces challenges with low signal-to-noise ratios and spectral overlap.

Purpose of the Study:

• To develop and validate advanced MAS NMR methods for high-resolution structural analysis of amyloid fibrils.
• To address spectral degeneracy and improve distance measurements in complex biological systems.

Main Methods:

• Utilized specific 13C, 15N-labeling to resolve spectral degeneracy in the GNNQQNY peptide.
• Employed frequency-selective rotational echo double resonance (FSR) and z-filtered transfer echo double resonance (ZF-TEDOR) experiments.
• Introduced a novel FSR-RFDR pulse sequence for deconvoluting overlapped resonances.

Main Results:

• Achieved high-precision distance restraints for the GNNQQNY peptide.
• Calculated a high-resolution MAS NMR structure of GNNQQNY nanocrystals, validating the approach against X-ray crystallography.
• Demonstrated the effectiveness of the FSR-RFDR sequence in complex spectra.

Conclusions:

• The validated MAS NMR approach provides a robust pipeline for studying heterogeneous amyloid fibrils.
• Advances understanding of amyloid polymorphism at the atomic level.
• Enables precise structural determination of challenging biological macromolecules.