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Updated: Aug 16, 2026

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Characterization of pH-Dependent Reversible Self-Assembly of Amyloid Beta 1-40-Coated Gold Colloids
Published on: March 21, 2025
Poly-(L-alanine) expansions form core beta-sheets that nucleate amyloid assembly
Leonid M Shinchuk1, Deepak Sharma, Sylvie E Blondelle
1Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467-3811, USA.
Proteins
|August 23, 2005
Summary
Expanded polyalanine (polyAla) stretches in PABPN1 cause oculopharyngeal muscular dystrophy (OPMD). This study shows polyAla peptide length critically influences self-assembly into stable, amyloid-like fibrils, explaining disease pathology.
Area of Science:
- Biochemistry
- Molecular Biology
- Neuroscience
Background:
- Oculopharyngeal muscular dystrophy (OPMD) is linked to expanded polyalanine (polyAla) tracts in PABPN1.
- These expansions lead to intranuclear fibrillar inclusions in affected neurons and muscle cells.
Purpose of the Study:
- To investigate the role of polyAla homopolymer length in protein misfolding and fibril formation.
- To understand the self-assembly properties of synthetic polyAla peptides.
Main Methods:
- Analysis of synthetic poly-(L-alanine) peptides with varying lengths (3-20 residues).
- Studied conformational transitions and assembly structures under different conditions (concentration, temperature, time).
- Utilized X-ray diffraction to determine fibril structure.
Main Results:
- PolyAla assembly is dependent on peptide length, concentration, temperature, and incubation time.
- Peptides with >15 residues formed complete beta-sheet complexes.
- PolyAla fibrils exhibited cross-beta arrangement similar to amyloid but lacked typical amyloid staining properties.
- Fibrils demonstrated high stability across a wide range of temperatures, pH, and resistance to denaturants and proteases.
Conclusions:
- PolyAla homopolymer length is a critical determinant of self-assembly into stable beta-sheet structures.
- These findings suggest that stabilized expanded polyAla stretches mediate the formation of fibrillar inclusions in OPMD.
- The study provides a molecular basis for understanding PABPN1-related myopathies.
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Amyloid fibrils are aggregates of misfolded proteins. Under most circumstances, misfolded proteins are either refolded by chaperone proteins or degraded by the proteasome. However, in the case of a mutation or a disease, these proteins can accumulate to form large clusters and often further assemble to form elongated fibers, called fibrils.
Amyloid deposits were observed as early as 1639 in the liver and the spleen. In 1854, Rudolph Virchow performed iodine staining, normally used to...
Amyloid deposits were observed as early as 1639 in the liver and the spleen. In 1854, Rudolph Virchow performed iodine staining, normally used to...
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Amyloid fibrils are aggregates of misfolded proteins. Under most circumstances, misfolded proteins are either refolded by chaperone proteins or degraded by the proteasome. However, in the case of a mutation or a disease, these proteins can accumulate to form large clusters and often further assemble to form elongated fibers, called fibrils.
Amyloid deposits were observed as early as 1639 in the liver and the spleen. In 1854, Rudolph Virchow performed iodine staining, normally used to...
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The primary structure of a protein is its amino acid sequence.
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