Concentration Dependence Of Aggregation Pathways During Aβ42 Aggregation Revealed By Single Molecule FRET Imaging And Deep Learning

Document Type

Poster Session

Publication Date

2-8-2024

Published In

Biophysical Journal

Abstract

Protein aggregation into amyloid fibrils is the hallmark of several devasting neurodegenerative diseases. Understanding disease etiology hinges on our ability to uncover the molecular mechanics of how soluble monomers assemble to form insoluble fibrils consisting of thousands of constituent monomers. Although amyloid fibril formation is a highly specific self-assembly process, growth patterns and resultant fibril morphologies are highly dependent on solution conditions. Bulk biophysical methods are unable to fully characterize these mixtures of fibril polymorphs. Here, we develop and implement Förster resonance energy transfer (FRET) imaging to monitor the entire aggregation pathway of the Alzheimer’s Disease related peptide amyloid-β 42 (Aβ42) at the single fibril level in real-time. We incubated a mixture of donor-labeled, acceptor-labeled, and unlabeled Aβ42 monomers, which resulted in the formation of fibrils with diverse FRET efficiency values, indicating structural heterogeneity. FRET images reveal that increasing monomer concentration promotes the formation of a predominant fibril assembly, while fibrils formed at lower concentrations assemble via highly heterogeneous pathways. Deep learning methods enable segmentation of single fibrils within images of highly overlapping fibrils, allowing for quantitative analysis of the aggregation process. Fibrils corresponding to two major FRET efficiencies emerge from the single-fibril image data. Photon recoloring simulations support the assignment of these observed FRET populations as fibrils with parallel and anti-parallel structures.

Conference

Biophysical Society Annual Meeting 2024

Conference Dates

February 10-14, 2024

Conference Location

Philadelphia, PA

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