Mining for proteins  pg. 2

Electrospray ionization, developed by John Fenn, Ph.D., and his colleagues at Yale University, is a method of squirting a protein solution through an intense electrical field in order to create a fine spray of charged droplets. The liquid evaporates, sending relatively large proteins into the mass spectrometer for analysis.

Another method, called matrix-assisted laser desorption/ionization or “MALDI,” was developed independently by researchers in Germany and Japan. Protein or tissue samples are mixed with a matrix, a material that can absorb laser energy, and applied to a target probe or plate. When struck by a laser, the matrix is partially vaporized, and electrically charged proteins are jettisoned into the mass spectrometer.

“It’s like hitting a golf ball out of a sand trap,” explains Vanderbilt mass spectrometry expert Richard Caprioli, Ph.D. “You hit the sand around it.”

“X-ray crystallography, as the core technique of structural biology and structural genomics, is providing a paradigm shift in the ability of scientists to understand, control and design new biomedical activities.”
Walter Chazin, Ph.D. Director of Vanderbilt’s Center for Structural Biology
Photo by Dana Johnson
For their contributions to mass spectrometry, Fenn and Japanese researcher Koichi Tanaka were awarded the Nobel Prize in Chemistry last fall. They shared the award with Kurt Wüthrich, Ph.D.

Detecting protein interactions

In the late 1980s, researchers at the State University of New York at Stony Brook pioneered a technique for studying protein interactions called the “yeast two-hybrid system.”

They broke apart a yeast protein that binds to and turns on a gene essential for cell growth. One half was attached to a known protein, or “bait,” and the other half was attached to the “prey,” the protein being studied. If the bait and prey interact, the two halves of the original protein will be brought back together, the gene will be turned on, and yeast cells will grow.

The technique does not pick up all of the interactions that occur in nature, but it has helped researchers construct “maps” of protein-protein interactions in organisms like the H. pylori bacterium, the major cause of ulcers. This information may lead to new ways to treat the infection.

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