Cryo-EM structure determination of amyloid fibrils: Methodology, insights, and practical tools.

Amyloid fibrils are central to many neurodegenerative and systemic diseases, and cryo-electron microscopy (cryo-EM) has become the primary method for determining their structures at near-atomic resolution. At the same time, amyloid fibrils pose specific experimental and computational challenges. In this chapter, we describe a practical cryo-EM workflow for amyloid fibrils, covering sample preparation, grid vitrification, filament picking, separation of polymorphs, helical reconstruction, and model building. We focus on practical choices, common problems, and solutions that have worked well in our own experience. The aim is to provide a hands-on guide for researchers working on amyloid fibrils and to support further method development in amyloid cryo-EM.