"Almost all [communication] within our brains is the result of vesicles being released one at a time," Scheller says. "Different responses are elicited from vesicles with different contents. So it's very important to know the contents of the individual vesicles."
But the vesicles that transmit messages between brain neurons are too tiny to manipulate and examine. Instead, Zare and Scheller chose to work with the vesicles that regulate egg-laying in sea slugs. These vesicles are about 1,000 times larger than those the brain uses large enough to analyze with Zare's new technique. "Snails don't have many cells, but the cells they have are large and juicy," Zare explains.
Daniel Chiu, a graduate student, and Sheri Lillard, a postdoc in Zare's lab, developed the technique, which captures one vesicle at a time, pops it open and analyzes its contents.
The first step in this process is to trap a single vesicle and introduce it into a tiny chamber, where Chiu and Lillard can manipulate it. This step is not as simple as it may sound. Because the vesicle is so small, the researchers have to use delicate procedures.
The chemists trap the tiny package using a laser. The vesicle moves to the most intense area of the laser beam and stops there. Once the vesicle is immobilized, the researchers move a minuscule tube next to the vesicle. A slight electric current slides the vesicle into the tube.
Next, the researchers add chemicals that tear open the package and label its contents with a dye. This dye, which attaches only to specific molecules, glows when light hits it. The dye transforms the vesicle's chemicals into beacons.
The dye fa
'"/>
Contact: David F. Salisbury
salisbury@stanford.edu
650-725-1944
Stanford University
28-May-1998