RESUMO
A method based on capillary electrophoresis (CE) with UV absorbance detection is presented to characterize synthetic amyloid beta (Aß) peptide preparations at different aggregation states. Aggregation of Aß (1-40) and Aß (1-42) is closely linked to Alzheimer's disease (AD), and studying how Aß peptides self-assemble to form aggregates is the focus of intense research. Developing methods capable of identifying, characterizing and quantifying a wide range of Aß species from monomers to fully formed fibrils is critical for AD research and is a major analytical challenge. Monomer and fibril samples of Aß (1-40) and Aß (1-42) were prepared and characterized for this study. The monomer-equivalent concentration for each sample was determined by HPLC-UV, and aggregate formation was confirmed and characterized by transmission electron microscopy. The same samples were studied using CE with UV absorbance detection. Analysis by mass spectrometry of collected CE fractions was used to confirm the presence of Aß for some CE-UV peaks. The CE-UV method reported here clearly indicates that monomeric and aggregated Aß were electrophoretically separated, and substantial differences in the electrophoretic profiles between samples of Aß (1-40) and Aß (1-42) were observed. This CE-UV method can differentiate between Aß monomer, oligomeric intermediates, and mature fibrils.
