The aqueous phase of Alzheimer's disease brain contains assemblies built from similar to 4 and similar to 7 kDa A beta species

Introduction: Much knowledge about amyloid beta (A beta) aggregation and toxicity has been acquired using synthetic peptides and mouse models, whereas less is known about soluble Ab in human brain. Methods: We analyzed aqueous extracts from multiple A beta brains using an array of techniques. Results: Brains can contain at least four different A beta assembly forms including: (i) monomers, (ii) a similar to 7kDa Ab species, and larger species (iii) from similar to 30-150 kDa, and (iv)>160 kDa. High molecular weight species are by far the most prevalent and appear to be built from similar to 7 kDa A beta species. The similar to 7 kDa A beta species resist denaturation by chaotropic agents and have a higher A beta 42/A beta 40 ratio than monomers, and are unreactive with antibodies to Asp1 of Ab or APP residues N-terminal of Asp1. Discussion: Further analysis of brain-derived similar to 7 kDa Ab species, the mechanism by which they assemble and the structures they form should reveal therapeutic and diagnostic opportunities. (C) 2015 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.