Cryogenic electron microscopy of amyloid-beta oligomers
Abstract
Oligomers of the amyloid-beta peptide are thought to be one of the causes of the most abundant form of dementia: Alzheimer's disease. In spite of their relevance for the disease, their structure is debated and several conflicting models have been proposed mainly based on solution and solid state NMR. In our research we have established the preparation of amyloid-beta oligomers of three different sizes (~20 kDa, ~60 kDa, and 75-150 kDa) according to blue native polyacrylamide gel electrophoresis and Western blotting. All oligomers show well-defined beta-sheet bands in infrared spectra and also well-defined infrared bands of single, site-specifically 13C, 15N-labeled residues. The well-defined bands testify to their structural homogeneity, which prompted us to study the two larger oligomers with cryogenic electron microscopy (cryo EM) at SciLifeLab in Stockholm. The aim here is either to obtain an atomic structure of each of the two larger oligomers or shape constraints for structural modeling in combination with our infrared data. An initial cryo EM screening made us change the preparation method to increase the oligomer concentration. The screening of the improved preparations was judged by the cryo EM specialist to be promising for structural studies because of the homogeneity of the aggregates and of the sufficient number of particles. After having obtained a grant for 300 h of expert support, we will shortly start evaluating these data for which we here apply for storing resources.
