Color Change Marks Protein Folding

Protein chemists have developed a colorimetric assay that allows immediate detection of changes in the three-dimensional structure of protein molecules.

Investigators at Stanford University (Palo Alto, CA, USA) covalently attached microscopic gold particles to molecules of the protein cytochrome c via a thiol group in the cysteine-102 residue. They found that raising or lowing the pH of solutions of the protein caused it to fold or unfold. The alteration in shape changed the refractive index of the bound gold particles, and the solution changed from blue to purple and back again, depending on the pH.

Writing in the March 2005 issue of Chemistry and Biology, the investigators said, "We chose gold nanoparticles because they are simple to prepare, easy to control, and cost effective. To the best of our knowledge, however, gold nanoparticles have not been previously used to investigate the folding and unfolding of proteins.”

Senior author Dr. Richard Zare, professor of chemistry at Stanford University, said, "What we have developed is a simple and inexpensive sensor for determining when a protein changes its conformation. The new sensor may eventually provide biomedical researchers a fast, affordable method for detecting antibodies and other disease-related proteins.”



Related Links:
Stanford University