In one experiment, the team put a drop of vodka on a yeast cell. It "screamed."
"It really doesn't like it. It's probably trying to react in some way to move the alcohol out," Gimzewski said.
In another experiment, the team listened to the yeast cell at different temperatures.
"It's like a difference between a cold day and hot day," Gimzewski explained. "[Raising the temperature] doubles the frequency, doubles the pitch.
"And that is the tendency we'd expect when it's related to the metabolism of something that's very sensitive to temperature."
In a final experiment, the researchers shut off the fuel supply to the yeast cell, essentially killing it. Its response was the sound of death, a hissing sound like the white noise of a television with no reception.
The experiments convinced Gimzewski's team that the sounds of living cells are made by organized protein motors communicating with one another and moving around nutrients.
"There's a kind of cooperation between them, between the protein motors," Gimzewski said. "It's a bit like having an orchestra—all the [people playing instruments] isn't random."
Human Application
Gimzewski and colleagues first reported this discovery in August 2004 in the research journal Science.
Now the team is developing a meter to measure the movement in human cells. Their collaborator is Veeco Instruments, a Woodbury, New York-based company that makes tools for measuring at the nanoscale. (For kids: Nanomaterials)
Yeast cells are rigid enough to move the atomic force microscope's needle up and down, Gimzewski explained, but human cells are more like water balloons: too soft to move the needle.
A new device developed by the team uses a laser to record a cell's movements. The device can be moved from cell to cell with magnets.
Researchers hope that by using these meters on different parts of the body, they will be able to listen for ailments. For example, they are currently determining the sound difference between cancerous breast cells and normal breast cells.
Gimzewski says he expects cancerous cells to resonate at a lower pitch than healthy cells, because cancer cells are softer. The softness allows the cells to spread more easily through the body.
"It's a different approach to medicine, an approach in which we listen to our bodies at the cell level," he said.
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