The Aggregation Potential of the 1-15-and 1-16-Fragments of the Amyloid β Peptide and Their Influence on the Aggregation of Aβ40

The aggregation of amyloid beta (A beta) peptide is important in Alzheimer's disease. Shorter A beta fragments may reduce A beta's cytotoxicity and are used in diagnostics. The aggregation of A beta 16 is controversial; Liu et al. (J. Neurosci. Res. 75:162-171, 2004) and Liao et al. (FEBS Lett. 581:1161-1165, 2007) find that A beta 16 does not aggregate and reduces A beta's cytotoxicity, Du et al. (J. Alzheimer's Dis. 27:401-413, 2011) reports that A beta 16 aggregates and that A beta 16 oligomers are toxic to cells. Here the aggregation potential of two shorter fragments, A beta 15 and A beta 16, and their influence on A beta 40 is measured by electron paramagnetic resonance (EPR) spectroscopy and the ThioT fluorescence assay (ThioT). Continuous-wave, 9 GHz EPR measurements and ThioT results reveal that neither A beta 15 nor A beta 16 aggregate by themselves and that they do not affect A beta 40 aggregation.