title: High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification.
abstract: Alzheimer's disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling (1)H-(1)H NMR experiments to overcome many of these limitations. Using (1)H-(1)H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time (1)H-(1)H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5-15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils.
authors.affiliation: Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Kotler
authors.affiliation: 1] Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A [2] Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Brender
authors.affiliation: Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Subramanian
authors.initials: S
authors.lastname: Vivekanandan
authors.affiliation: Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: 1] Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A [2] Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: Bruker BioSpin Ltd., Bruker Corporation, 555 E Steeles Ave, Milton, ON, Canada.
authors.forename: Martine
authors.initials: M
authors.lastname: Monette
authors.affiliation: 1] Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A [2] Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Janarthanan
authors.initials: J
authors.lastname: Krishnamoorthy
authors.affiliation: 1] Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A [2] Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Patrick
authors.initials: P
authors.lastname: Walsh
authors.affiliation: Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Meagan
authors.initials: M
authors.lastname: Cauble
authors.affiliation: 1] Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A [2] Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Mark M Banaszak
authors.initials: MM
authors.lastname: Holl
authors.affiliation: Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: E Neil G
authors.initials: EN
authors.lastname: Marsh
authors.affiliation: 1] Biophysics, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A [2] Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109, U.S.A.
authors.forename: Ayyalusamy
authors.initials: A
authors.lastname: Ramamoorthy
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D006801:Humans; D046911:Macromolecular Substances / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry; D066263:Protein Aggregation, Pathological / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D046911:Macromolecular Substances; D010446:Peptide Fragments