Manual and automatic assignment of two different Aβ40 amyloid fibril polymorphs using MAS solid-state NMR...

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Alzheimer's disease is characterized by amyloid-beta (Aβ) peptide aggregation into fibrils.
• Aβ40 peptide exhibits significant structural polymorphism, with 14 fibril structures already determined.
• The underlying mechanisms driving Aβ40 fibril polymorphism remain poorly understood.

Purpose of the Study:

• To assign the NMR chemical shifts for two distinct Aβ40 fibril polymorphs, designated P1 and P2.
• To investigate the structural differences between these Aβ40 fibril polymorphs using solid-state NMR.
• To evaluate the utility of automated software (ARTINA) for chemical shift assignment in fibrillar systems.

Main Methods:

• Solid-state NMR spectroscopy, specifically 13C-detected 3D NCACX and NCOCX experiments.
• Preparation of Aβ40 fibril polymorphs using an extensive seeding protocol.
• Sample preparation in the presence and absence of the small heat shock protein αB-crystallin.
• Manual chemical shift assignment and comparison with automated assignment using ARTINA software.

Main Results:

• Successful assignment of NMR chemical shifts for the P1 and P2 Aβ40 fibril polymorphs.
• Analysis of secondary chemical shifts revealed distinct structural features between P1 and P2.
• Comparison of manual and automated assignment strategies highlighted the performance of ARTINA software.

Conclusions:

• The study provides crucial structural insights into Aβ40 fibril polymorphism.
• NMR chemical shift assignments facilitate further investigation into the structural basis of Alzheimer's disease.
• Automated NMR assignment tools like ARTINA show promise for analyzing complex fibrillar structures.