Girl Scientist Magazine

Rosalyn Yalow, a Nobel Prize-winning scientist who co-developed the laboratory technique of radioimmunoassay that permits measurement of once immeasurably small quantities of hormones and other biological molecules, died May 30 in the Bronx. She was 89.

Dr. Yalow, the second woman to win the Nobel in physiology or medicine, had been partially disabled in recent years from a series of strokes. No cause of death was given. She had lived in the Bronx for all but four years of her life.

Dr. Yalow’s measurement method — an “assay,” in scientific parlance — initially transformed the study of hormones, and in particular insulin, which regulates the concentration of sugar in the bloodstream. She and her scientific partner, Solomon A. Berson, who died in 1972, used the technique to make pathfinding observations about diabetes.

The power of the technique was immediately recognized by scientists in other fields.

Radioimmunoassay, or RIA, became an essential tool in diagnostic and research labs and transformed blood banks, where it was used to detect pathogens such as the hepatitis B virus that had been unwittingly passed on to people getting transfusions.

“The technique revolutionized medicine,” said William A. Bauman, a physician and researcher at the Mount Sinai School of Medicine in New York. “Before them, there was a lot of guesswork in medicine. They took away the guesswork.”

“Her method contributed enormously not only to endocrinology but to all the biological sciences,” said Andrew V. Schally, a researcher at the Veterans Affairs hospital in Miami who shared the 1977 Nobel Prize for physiology or medicine with Dr. Yalow and Roger Guillemin. Her co-winners used radioimmunoassay to study the action of hormones produced by the brain. (The first woman to win the Nobel in physiology or medicine was Gerty Cori, in 1947.)

Like Schally, Dr. Yalow did her most important work in the VA medical system, in her case at the Bronx VA Hospital. Schally recalled Thursday that when they won the Nobel Prize, murmurs in Congress about shutting down the VA system came to an abrupt end.

Radioimmunoassay depends on the ability of antibodies, which are Y-shaped proteins produced by the immune system, to bind with other molecules. For example, a molecule of an antibody against insulin will bind and hold a molecule of insulin.

However, another insulin molecule can knock the first one off and replace it, like children competing in a game of musical chairs. That competition between radioactively “labeled” and unlabeled molecules is the basis for the test.

In their original experiment, Dr. Yalow and Berson labeled insulin with radioactive iodine atoms and mixed it with a solution containing antibodies to insulin. The researchers then added a sample of human plasma that contained an unknown quantity of insulin.

Some of the insulin molecules then competed with the radiolabeled insulin for attachment to the antibody. Measuring the amount of free radiolabeled insulin by a Geiger counter or some other method gives an indirect but precise estimate of the amount of insulin in the plasma sample.