title: Amyloid beta-protein: monomer structure and early aggregation states of Abeta42 and its Pro19 alloform.
abstract: The amyloid beta-protein (Abeta) is a seminal neuropathic agent in Alzheimer's disease (AD). Recent evidence points to soluble Abeta oligomers as the probable neurotoxic species. Among the naturally occurring Abeta peptides, the 42-residue form Abeta42 is linked particularly strongly with AD, even though it is produced at approximately 10% of the levels of the more abundant 40-residue form Abeta40. Here, we apply mass spectrometry and ion mobility to the study of Abeta42 and its Pro19 alloform. The Phe19 --> Pro19 substitution blocks fibril formation by [Pro19]Abeta42. Evidence indicates that solution-like structures of Abeta monomers are electrosprayed and characterized. Unfiltered solutions of Abeta42 produce only monomers and large oligomers, whereas [Pro19]Abeta42 solutions produce abundant monomers, dimers, trimers, and tetramers but no large oligomers. When passed through a 10,000 amu filter and immediately sampled, Abeta42 solutions produce monomers, dimers, tetramers, hexamers, and an aggregate of two hexamers that may be the first step in protofibril formation. These results are consistent with recently published photochemical cross-linking data and lend support to recent aggregation mechanisms proposed by Bitan, Teplow, and co-workers [J. Biol. Chem. 2003, 278, 34882-34889].
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106-9501, USA.
authors.forename: Summer L
authors.initials: SL
authors.lastname: Bernstein
authors.forename: Thomas
authors.initials: T
authors.lastname: Wyttenbach
authors.forename: Andrij
authors.initials: A
authors.lastname: Baumketner
authors.forename: Joan-Emma
authors.initials: JE
authors.lastname: Shea
authors.forename: Gal
authors.initials: G
authors.lastname: Bitan
authors.forename: David B
authors.initials: DB
authors.lastname: Teplow
authors.forename: Michael T
authors.initials: MT
authors.lastname: Bowers
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); D014867:Water; D011392:Proline