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Related Concept Videos

Amyloid Fibrils03:03

Amyloid Fibrils

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. 
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Amyloid Fibrils03:03

Amyloid Fibrils

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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Evaluation of the Impact of Protein Aggregation on Cellular Oxidative Stress in Yeast
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Crowding alone cannot account for cosolute effect on amyloid aggregation.

Shahar Sukenik1, Regina Politi, Lior Ziserman

  • 1Institute of Chemistry, The Fritz Haber Research Center, The Hebrew University of Jerusalem, Edmund J. Safra Campus, Jerusalem, Israel.

Plos One
|January 21, 2011
PubMed
Summary
This summary is machine-generated.

Excluded cosolutes can stabilize protein structures and alter amyloid formation. While polyols slow aggregation and increase yield, polyethylene glycols show minimal impact, suggesting crowding effects are complex.

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Area of Science:

  • Biochemistry
  • Biophysics
  • Protein Misfolding Diseases

Background:

  • Amyloid fiber formation is a key process in protein aggregation and diseases.
  • Macromolecular crowding, caused by excluded volume effects of cosolutes, is thought to influence protein aggregation.
  • Previous studies suggested excluded cosolutes reduce fibrillation times.

Purpose of the Study:

  • To investigate the effects of excluded cosolutes on the stability of a model peptide's monomeric beta-hairpin conformation.
  • To examine how these cosolutes influence the kinetics and equilibrium of amyloid fibril formation.
  • To differentiate between excluded volume effects and other potential mechanisms driving cosolute influence on amyloidogenesis.

Main Methods:

  • Circular Dichroism (CD) spectroscopy to assess protein conformation and stabilization.
  • Thioflavin T (ThT) fluorescence assays to monitor fibrillation kinetics.
  • Transmission Electron Microscopy (TEM) to visualize amyloid fibril morphology.
  • Utilized polyols (glycerol, sorbitol) and polyethylene glycols (PEGs) as model excluded cosolutes.

Main Results:

  • Excluded cosolutes, particularly polyols, stabilized the monomeric beta-hairpin conformation.
  • Polyols increased lag times and equilibrium aggregation levels in a concentration- and size-dependent manner.
  • Fibrillation rates were largely unaffected by polyethylene glycols across various molecular weights.
  • Stabilization free energy correlated linearly with cosolute concentration and molecular volume.

Conclusions:

  • Cosolutes can stabilize native protein states against aggregation.
  • The observed effects on amyloid formation are not solely explained by excluded volume interactions.
  • Other forces, beyond simple macromolecular crowding, likely contribute to cosolute-mediated modulation of amyloidogenesis.