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Identifying cells' chemical personalities.

Identifying cells' chemical personalities

These days, sophisticated tools often become the inspiration for experiments that earlier researchers might never have dreamed of doing. Two chemists have developed such a tool for taking chemical inventories of individual cells and other liquid samples so small that millions of them could fill a thimble.

"The idea is to be able to look on a cell-by-cell basis at the chemical contents of cells," says James W. Jorgenson, who developed the technique with Robert T. Kennedy at the University of North Carolina at Chapel Hill. In the March 1 ANALYTICAL CHEMISTRY, they report using the technique--open tubular liquid chromatography (OTLC) -- to distinguish among individual neurons by their chemical makeup. They say OTLC also could help biologists demystify the chemistry underlying cellular behaviors such as responding to drugs, manufacturing neurotransmitters and differentiating into muscle, blood or brain cells.

In less time than it takes to watch a movie, the researchers can determine the chemical personality of an individual cell, in this case from the escargot's cousin -- the land snail. After isolating and homogenizing a specific neuron, the researchers inject tiny samples of the cell's watery chemical brew into a specially coated glass capillary tube to separate the sample's components. As the mixture travels down the thinner-than-hair tube, the coating hinders each component's motion to a different degree. At the tube's other end, an electrode detects many of the now separated neurotransmitters, amino acids and even unknown chemicals by measuring how much voltage it takes to oxidize each one as it exits.

A plot of the resulting data looks like a range of steep, pointy mountains. Each peak corresponds to a different cellular chemical; peak heights indicate amounts of the chemicals. In two of three types of cells the researchers analyzed, dopamine and serotonin (neurotransmitters), tyrosine and tryptophan (amino acids) and other chemicals showed up as identifiable peaks. In the third type, the neurotransmitter peaks were absent. One cell type consistently produced a prominent peak that the researchers are still trying to identify.

At this week's Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, held in Atlanta, Jorgenson plans to report data from even newer OTLC experiments in which he measured the cellular amounts of 18 amino acids that he chemically modified to be more easily oxidized by the detector electrode. At the same conference, Andrew G. Ewing, a chemist at Pennsylvania State University at University Park, and his co-workers, who have developed another technique for studying neuronal chemistry, will present data on the distribution of dopamine in different regions of single neurons.
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Author:Amato, Ivan
Publication:Science News
Date:Mar 11, 1989
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