HIGH-RESOLUTION SEPARATION OF AMYLOID BETA-PEPTIDES - STRUCTURAL VARIANTS PRESENT IN ALZHEIMERS-DISEASE AMYLOID

In Alzheimer's disease (AD), one of the cardinal neuropathological sig ns is deposition of amyloid, primarily consisting of the amyloid beta- peptide (A beta). Structural variants of AD-associated A beta peptides have been difficult to purify by high-resolution chromatographic tech niques. We therefore developed a novel chromatographic protocol, enabl ing high-resolution reverse-phase liquid chromatography (RPLC) purific ation of A beta variants displaying very small structural differences, By-using a combination of size-exclusion chromatography and the novel RPLC protocol, A beta peptides extracted From AD amyloid were purifie d and subsequently characterized. Structural analysis by microsequenci ng and electrospray-ionization mass spectrometry revealed that the RPL C system-resolved a complex mixture of A beta variants terminating at either residue 40 or 42. A beta variants differing by as little as one amino acid residue could be purified rapidly to apparent homogeneity. The resolution of the system was further illustrated by its ability t o separate structural isomers of A beta(1-40). The present chromatogra phy system might provide Further insight into the role of N-terminally and posttranslationally modified A beta variants, because each varian t can now be studied individually.