Scientists are using CD players to do a lot more than just play the latest top-40 hits. A paper published online this week by the journal Organic and Biomolecular Chemistry describes a method of using the machines to detect molecules in solution by monitoring their interactions with a modified CD. The researchers hope the innovation will lead to less expensive medical diagnostic tests.

Many laboratory tests rely on laser light to detect molecules. Recognizing that CD players also utilize laser light to read information, James J. La Clair and Michael D. Burkart of the University of California at San Diego decided to take advantage of this relatively inexpensive set up. They first developed a procedure to attach specific molecules to the face of a CD. These molecules are chosen based on their ability to react with compounds of interest in samples being tested. After the altered CD reacts with the sample solution, it is placed in the player. The presence of extra molecules attached to the disc introduces errors into the readout of the data. Comparing how the modified CD plays before and after interacting with the sample can reveal the presence or absence of the target molecules. "Thats the novelty of this," Burkart says. "We are actually using the error to get our effect."

Although the technique holds promise for medical testing, it cannot yet quantify the amount of a particular molecule in a sample. Instead, Burkart hopes to utilize it as a screening method in his chemistry lab, because compared to a $100,000 protein chip reader, a CD player is a bargain. Plus, La Clair notes, "how many people on this planet can actually hear a molecule attached to another molecule?"