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Related Experiment Videos

Do protein molecules unfold in a simple shear flow?

Juan Jaspe1, Stephen J Hagen

  • 1Department of Physics, University of Florida, Gainesville, 32611-8440, USA.

Biophysical Journal
|August 8, 2006
PubMed
Summary

Shear forces from fluid flow do not significantly denature small globular proteins. Even at high shear rates, horse cytochrome c showed no measurable unfolding, suggesting extreme forces are needed for shear denaturation.

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Area of Science:

  • Biochemistry
  • Protein dynamics
  • Fluid mechanics

Background:

  • Proteins are sensitive to environmental changes like heat and pH, often leading to denaturation.
  • Shear forces from fluid flow are hypothesized to destabilize proteins, but quantitative evidence is scarce.
  • Understanding protein stability under mechanical stress is crucial for various applications.

Purpose of the Study:

  • To investigate the quantitative effect of high shear rates on protein stability.
  • To determine if shear forces can induce measurable denaturation in a small globular protein.
  • To assess the threshold shear rate required for protein unfolding.

Main Methods:

  • Studied horse cytochrome c, a small globular protein with fluorescence sensitive to unfolding.
  • Applied high shear rates (up to ~2 x 10^5 s^-1) by forcing the protein solution through a silica capillary at high speeds (~10 m/s).
  • Monitored protein unfolding via fluorescence changes using ultraviolet laser illumination, capable of detecting <1% unfolding.

Main Results:

  • No significant destabilization or denaturation of horse cytochrome c was observed even at the highest applied shear rates.
  • The study could detect stability shifts as small as ~0.01 kJ/mol, indicating high sensitivity.
  • A theoretical model suggests shear rates around 10^7 s^-1 are necessary to denature typical small globular proteins.

Conclusions:

  • High shear rates encountered in typical fluid flow conditions do not appear to cause significant denaturation of small globular proteins like horse cytochrome c.
  • The phenomenon of shear denaturation may require much higher shear rates than previously assumed or commonly encountered.
  • Further research is needed to fully elucidate the relationship between shear stress and protein stability across different protein types and conditions.

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