Abstract

Alzheimer's disease is associated with the abnormal deposits of amyloid beta protein (Ab) that occurs as fibrils within the cerebral neuropil. To characterize the way in which these fibrils assemble under different pH conditions, we have performed transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) on synthetic full-length Ab peptides as well as various Ab peptides with truncated sequences. TEM images of negatively stained preparations provide information about the fibril width and morphology, and STEM analysis of unstained preparations provides a quantitative determination of the mass-per-length (MPL) and thus the numbers of beta-sheets within fibrils. Taken together the results reveal how the structure of fibrils grown from Alzheimer-related Ab peptides depend on the growth conditions, including protein concentration and pH. MPL measurements reveal the existence of fundamental fibrillizing units, or """"""""protofilaments,"""""""" consisting of well-defined numbers of cross-beta sheets. Variations in fibril morphology at the EM level are being used by scientists in NIDDK to correlate with atomic-level information about the peptide backbone conformation obtained from NMR spectroscopy. STEM measurements have shown that Ab(1-40) fibrils grown by several generations of seeding the monomer under quiescent conditions are composed of triple beta sheets whereas fibrils grown in agitated medium contain double beta sheet structures.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
Office of The Director, National Institutes of Health (OD)
Type
Intramural Research (Z01)
Project #
1Z01OD011017-07
Application #
7146056
Study Section
(BEPS)
Project Start
Project End
Budget Start
Budget End
Support Year
7
Fiscal Year
2005
Total Cost
Indirect Cost

  Institution

Name
Office of the Director, NIH
Department
Type
DUNS #
City
State
Country
United States
Zip Code

  Publications

Petkova, Aneta T; Leapman, Richard D; Guo, Zhihong et al. (2005) Self-propagating, molecular-level polymorphism in Alzheimer's beta-amyloid fibrils. Science 307:262-5
Petkova, A T; Buntkowsky, G; Dyda, F et al. (2004) Solid state NMR reveals a pH-dependent antiparallel beta-sheet registry in fibrils formed by a beta-amyloid peptide. J Mol Biol 335:247-60
Antzutkin, Oleg N; Leapman, Richard D; Balbach, John J et al. (2002) Supramolecular structural constraints on Alzheimer's beta-amyloid fibrils from electron microscopy and solid-state nuclear magnetic resonance. Biochemistry 41:15436-50
Petkova, Aneta T; Ishii, Yoshitaka; Balbach, John J et al. (2002) A structural model for Alzheimer's beta -amyloid fibrils based on experimental constraints from solid state NMR. Proc Natl Acad Sci U S A 99:16742-7
Antzutkin, O N; Balbach, J J; Leapman, R D et al. (2000) Multiple quantum solid-state NMR indicates a parallel, not antiparallel, organization of beta-sheets in Alzheimer's beta-amyloid fibrils. Proc Natl Acad Sci U S A 97:13045-50
Balbach, J J; Ishii, Y; Antzutkin, O N et al. (2000) Amyloid fibril formation by A beta 16-22, a seven-residue fragment of the Alzheimer's beta-amyloid peptide, and structural characterization by solid state NMR. Biochemistry 39:13748-59