This study has found that the Maltose binding protein A beta 42 fusion protein (MBP-A beta 42) forms soluble oligomers while the shorter MBP-A beta 16 fusion and control MBP did not. MBP-A beta 42, but neither MBP-A beta 16 nor control MBP, was toxic in a dose-dependent manner in both yeast and primary cortical neuronal cells. This study demonstrates the potential utility of MBP-A beta 42 as a reagent for drug screening assays in yeast and neuronal cell cultures and as a candidate for further A beta 42 characterization. Crown Copyright (C) 2011 Published by Elsevier Inc. All rights reserved.