There's Gold In Them Thar Mercury Detectors (Gold Nanoparticles That Is)

This is really neat. Previously when scientists wanted to check a body of water for mercury contamination they would have to take samples back to the lab for analysis by sophisticated lab instruments. These scientists at Northwestern University in Evanston, IL, near where I grew up in Rogers Park, have discovered a way to use nanoparticles of gold, and some specially crafted DNA to create a simple "litmus test" for mercury.

It sounds sort of simple but I can gaurantee if you read this full article from EurekAlert you'll realize how ingenious this was. An excerpt follows.

The Northwestern method takes advantage of gold's intense color when the metal is measured on the scale of atoms. Mirkin and his team started with gold nanoparticles, each just 15 nanometers in diameter, held together by complementary strands of DNA. Because they are held together within a certain critical distance, the gold nanoparticles -- and the solution they are in -- are blue. When the solution is heated, the DNA breaks apart, and the gold nanoparticles, no longer in close proximity to each other, are now bright red.

Knowing that mercuric ion binds selectively to the bases of a thymidine-thymidine (T-T) mismatch, the researchers designed each strand of DNA, which is attached to a gold nanoparticle, to have a single thymidine-thymidine (T-T) mismatch. If mercury is present in the solution it binds tightly to the T-T mismatch site.

The key to the technology is that the blue to red color change occurs at 46 degrees Celsius if the solution has no mercury, and it occurs at a higher temperature if mercury is present.

"When mercury binds to the T-T mismatch site it is like adding some superglue -- the gold nanoparticles are now held together even more tightly," said Mirkin. "The mercury creates a stronger bond that requires a higher temperature to break apart the DNA strands."

See, I told you it was simple. Yeah, right.