Slideshow: Folded Proteins Get Gold Standard

credit Courtesy of Matthew R. Hammond/Stanford University
The image shows visual evidence of the effect of pH on a gold nanoparticle solution. "A" shows the color of gold nanoparticle solutions, "B" shows the color of cytochrome-c coated nanoparticle solutions at different pHs right after mixing. The pH values for vials, reading from left to right, are 4.0, 5.0, 5.5, 6.2, 6.7, 7.2, 8.3, 9.2, and 10.1. "C" shows the color of cytochrome c-coated nanoparticle solutions at different pHs after 24 hours.

credit Courtesy of Matthew R. Hammond/Stanford University
When cytochrome c attaches to gold nanoparticles (Au cyt-c), the pH is lowered, causing a color change. Shown are three vials of Au cyt-c at different pH values. Superimposed in each vial is the corresponding transmission electron microscopy image of the nanoparticles.