Characterization of intrinsically disordered regions through scalar coupling-based solid-state NMR experiments

Abnormal amyloid fibrils are characteristic features and common pathological mechanisms of various neurodegenerative diseases, often found in disease-related brain regions, leading to neuroinflammation and neuronal apoptosis. Many disease-associated amyloid fibrils consist of a rigid fibril core primarily composed of cross-β sheets, surrounded by a fuzzy coat formed by intrinsically disordered regions (IDR). Over the past two decades, substantial structural knowledge of the rigid fibril core has been accumulated through cryo-electron microscopy (cryo-EM) and solid-state nuclear magnetic resonance (ssNMR) based on cross-polarization. In contrast, the highly disordered conformations of the fuzzy coats have hindered their structural characterization. Here, we describe the application of two-dimensional (2D) heteronuclear single quantum coherence (HSQC) and three-dimensional (3D) HNCO, HNCA, and HN(CO)CA spectra, utilizing the scalar coupling-based ¹H detection magic angle spinning (MAS) ssNMR techniques for backbone assignment of the IDR in amyloid fibrils, with the aim of further elucidating the conformational changes of the IDR during ligand binding processes.