Nucleation dynamics in amyloid-beta dimerization revealed by single-molecule fingerprinting

Area of Science:

• Biophysics
• Neurodegenerative Diseases
• Molecular Biology

Background:

• Amyloid-beta (Aβ) peptide aggregation is central to Alzheimer's disease (AD) pathology.
• Soluble Aβ oligomers are the primary neurotoxic species, but their formation kinetics are poorly understood.
• Understanding the earliest stages of Aβ aggregation is crucial for developing therapeutic strategies.

Purpose of the Study:

• To construct and characterize the first oligomers formed during Aβ aggregation: parallel and antiparallel Aβ(1-40) dimers.
• To investigate the dynamic structural evolution and misfolding kinetics of these dimers at single-amino-acid resolution.
• To explore the inhibitory effect of rosmarinic acid on Aβ(1-40) dimerization.

Main Methods:

• Bottom-up construction of Aβ(1-40) dimers.
• Single-molecule mechanical unfolding using optical tweezers.
• Single-molecule fingerprinting to identify molecular interactions.

Main Results:

• Successfully constructed parallel and antiparallel Aβ(1-40) dimers.
• Observed three intermediates during dimer association and dissociation, with the diphenylalanine (Aβ(19-20)) dimer showing the highest formation probability.
• Demonstrated that rosmarinic acid inhibits Aβ(1-40) dimerization by binding to the Aβ(19-20) site.

Conclusions:

• The study provides the first detailed characterization of Aβ dimer formation kinetics.
• The developed single-molecule tool is effective for studying amyloid aggregation dynamics.
• Rosmarinic acid shows potential as an inhibitor of early-stage Aβ aggregation relevant to Alzheimer's disease.