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Simultaneous monitoring of peptide aggregate distributions, structure, and kinetics using amide hydrogen exchange: Application to Aβ(1-40) fibrillogenesis

Authors

  • Wei Qi,

    1. Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904; telephone: 434-924-1351; fax: 434-982-2658
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  • Aming Zhang,

    1. Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904; telephone: 434-924-1351; fax: 434-982-2658
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  • Dhara Patel,

    1. Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, Baltimore, Maryland
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  • Sungmun Lee,

    1. Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, Baltimore, Maryland
    Current affiliation:
    1. Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332.
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  • Jamie L. Harrington,

    1. Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904; telephone: 434-924-1351; fax: 434-982-2658
    Current affiliation:
    1. Genzyme Corporation, 1 The Mountain Road, Framingham, MA 01701.
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  • Liming Zhao,

    1. Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, Baltimore, Maryland
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  • David Schaefer,

    1. Physics Department, Towson University, Towson, Maryland
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  • Theresa A. Good,

    1. Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, Baltimore, Maryland
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  • Erik J. Fernandez

    Corresponding author
    1. Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904; telephone: 434-924-1351; fax: 434-982-2658
    • Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904; telephone: 434-924-1351; fax: 434-982-2658.
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Abstract

Increasing evidence indicates that soluble aggregates of amyloid beta protein (Aβ) are neurotoxic. However, difficulty in isolating these unstable, dynamic species impedes studies of Aβ and other aggregating peptides and proteins. In this study, hydrogen–deuterium exchange (HX) detected by mass spectrometry (MS) was used to measure Aβ(1-40) aggregate distributions without purification or modification that might alter the aggregate structure or distribution. Different peaks in the mass spectra were assigned to monomer, low molecular weight oligomer, intermediate, and fibril based on HX labeling behavior and complementary assays. After 1 h labeling, the intermediates incorporated approximately ten more deuterons relative to fibrils, indicating a more solvent exposed structure of such intermediates. HX-MS also showed that the intermediate species dissociated much more slowly to monomer than did the very low molecular weight oligomers that were formed at very early times in Aβ aggregation. Atomic force microscopy (AFM) measurements revealed the intermediates were roughly spherical with relatively homogenous diameters of 30–50 nm. Quantitative analysis of the HX mass spectra showed that the amount of intermediate species was correlated with Aβ toxicity patterns reported in a previous study under the same conditions. This study also demonstrates the potential of the HX-MS approach to characterizing complex, multi-component oligomer distributions of aggregating peptides and proteins. Biotechnol. Bioeng. 2008;100: 1214–1227. © 2008 Wiley Periodicals, Inc.

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