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Related Experiment Videos

Gold nanoparticles as a colorimetric sensor for protein conformational changes.

Soonwoo Chah1, Matthew R Hammond, Richard N Zare

  • 1Department of Chemistry, Stanford University, CA 94305, USA.

Chemistry & Biology
|March 31, 2005
PubMed
Summary

Researchers developed gold nanoparticles with bound yeast cytochrome c (Cyt c) that change color with pH. This indicates potential for simple colorimetric sensors detecting protein conformational changes.

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Area of Science:

  • Biophysics
  • Nanotechnology
  • Biochemistry

Background:

  • Yeast iso-1-cytochrome c (Cyt c) is a protein that undergoes conformational changes with pH.
  • Gold nanoparticles and films offer unique optical properties for sensing applications.

Purpose of the Study:

  • To investigate the use of gold nanoparticles and films functionalized with Cyt c as a sensor for protein conformational changes.
  • To correlate optical changes with pH-induced unfolding and refolding of Cyt c.

Main Methods:

  • Covalent immobilization of Cyt c onto gold nanoparticles and flat gold films via a thiol group at cysteine 102.
  • Monitoring color shifts in nanoparticle solutions using UV-VIS absorption spectroscopy.
  • Measuring changes in refractive index of gold films using surface plasmon resonance (SPR) spectroscopy.

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Main Results:

  • Bound Cyt c demonstrated reversible unfolding at low pH and refolding at high pH.
  • UV-VIS spectroscopy showed measurable color shifts in nanoparticle solutions corresponding to Cyt c conformational changes.
  • SPR spectroscopy detected corresponding changes in refractive index for Cyt c on flat gold films.

Conclusions:

  • The pH-dependent conformational changes of Cyt c are accurately detected by both UV-VIS and SPR spectroscopy.
  • Protein-covered gold nanoparticles show promise as a simple and effective colorimetric sensor for monitoring protein conformational changes.