Capillary electrophoresis for the analysis of the effect of sample preparation on early stages of Aβ1-40 aggregation.

Abstract

Aggregation of the amyloid-β protein (Aβ) contributes to the neurodegeneration characteristic of Alzheimer's disease. Of particular importance are the early stages of aggregation, which involve the formation of soluble oligomers and protofibrils. In these studies, we demonstrate the potential for CE with UV detection using a polyethylene oxide separation matrix to identify the evolution of various oligomeric species of Aβ1-40 . To demonstrate the efficacy of this technique, UV-CE was utilized to compare two methods commonly used to prepare Aβ for aggregation experiments and their effect on the formation of early aggregates. SEC-purified Aβ1-40 initially contained more small species, including monomer, than did freshly dissolved Aβ1-40 pretreated with hexafluoroisopropanol. Strikingly, the lag time to oligomer formation for SEC-isolated Aβ1-40 samples was ∼23 h shorter compared to freshly dissolved Aβ1-40 samples. Furthermore, oligomers formed from the aggregation of SEC-purified Aβ1-40 persisted within solution for a longer period of time. These results indicate that the initial sample preparation has a drastic influence on the early stages of Aβ1-40 aggregation. This is the first report of the use of UV-CE with a separation matrix to study the effect of sample preparation on early aggregation of Aβ1-40 . UV-CE was also used in parallel with dot blot analysis and inhibitory compounds to discern structural characteristics of individual oligomer peaks, demonstrating the capacity of UV-CE as a complimentary technique to further understand the aggregation process.