How Do Gyrating Beads Accelerate Amyloid Fibrillization?

Area of Science:

• Biochemistry
• Materials Science
• Biophysics

Background:

• Amyloid fibrillization is central to neurodegenerative diseases.
• High-throughput screening assays are crucial for drug discovery but require optimization.
• Mechanisms driving bead-accelerated fibrillization in microtiter plates remain unclear.

Purpose of the Study:

• To elucidate the physical and chemical mechanisms by which gyrating beads influence superoxide dismutase-1 (SOD1) fibrillization rates.
• To identify bead material properties that correlate with changes in SOD1 aggregation kinetics.
• To optimize bead-based assays for enhanced control and reduced variability in amyloid formation.

Main Methods:

• Investigated the effect of 12 different beads (varying in hydrophobicity, mass, stiffness, topology) on D90A apo-SOD1 fibrillization.
• Assayed fibril elongation rates and nucleation (lag times) under gyrating conditions.
• Correlated bead properties with measured kinetic parameters and analyzed forces (buoyant, contact) and surface characteristics (hydrophobicity, contact angle).

Main Results:

• Bead mass showed a strong linear correlation (R²=0.7) with SOD1 fibril elongation rate; heavier beads led to faster rates.
• Nucleation rates correlated with bead mass for non-polymeric beads (glass, ceramic, metallic).
• For polymeric beads, both hydrophobicity (contact angle) and contact forces influenced lag times, while non-polymeric beads' kinetics were explained by contact forces alone.

Conclusions:

• Bead mass, through buoyant and contact forces, is a primary driver of SOD1 fibrillization kinetics.
• Surface hydrophobicity plays a significant role for polymeric beads but not non-polymeric ones.
• Optimized bead-based assays can achieve faster nucleation and reduced stochasticity for SOD1 aggregation studies.