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Also while in college, she read Eve Curie's biography of her Nobel Prize-winning mother, Marie Curie, which excited her about nuclear physics, a hot new field in the late 1930s. In 1939 she attended a lecture by Italian scientist Enrico Fermi on nuclear fission, which had just been discovered by Lise Meitner, Fritz Strassmann, and Otto Hahn. This made her even more excited about pursuing a career in nuclear science.
After graduating from Hunter she wanted to go to graduate school, but it was hard for a Jewish woman to get accepted to a university in 1941. At first, the best opportunity she could get was a job as a secretary to a professor at Columbia University, with the understanding that she could eventually take graduate physics courses there.
But the possible U.S. entrance into World War II was looming on the horizon, and many male graduate students were either being drafted into the military or being sent to work on secret wartime research projects. Suddenly there was a shortage of graduate students at universities in the United States, and women students were recruited to take the places of the men who were leaving. Yalow was accepted by the University of Illinois, and she arrived there in September 1941. She was the first woman graduate student in the physics department at Illinois since 1917. There she met and later married (in 1943) Aaron Yalow, who was also a graduate student in physics.
After she earned her Ph.D. in 1945, Rosalyn Yalow returned to Hunter College, this time as a teacher. World War II was now over, and her classes were filled with veterans attending college thanks to the G.I. Bill, which paid for their education. In 1947 her husband introduced her to a physicist at Columbia University named Edith Quimby, who was a specialist in the medical use of radioactive isotopes. Yalow told Quimby she was interested in working as a volunteer in her lab. Instead Quimby took Yalow to see Gioacchino Failla, an influential person in the field of medical physics. Failla made a phone call to the Veterans Administration (VA) hospital in the Bronx. Immediately Yalow was offered a part-time job as a researcher there. For the next few years, she split her time between teaching at Hunter and working at the VA, until finally going full-time at the VA in 1950.
At first at the VA hospital, Yalow had only an old janitor's closet to use as a laboratory, and since her field was so new, she often had to build her own equipment. In 1950 Solomon A. Berson, a medical doctor, came to work with her. For the next 22 years Yalow and Berson would work together using radioactive isotopes to study what happens inside the human body. The isotopes of a chemical element have the same number of protons but different numbers of neutrons. A radioactive isotope is one that gives off radiation while it decays.
In one early project Yalow and Berson studied diabetes. People with diabetes have trouble metabolizing sugar because their bodies do not make enough of a special protein called insulin. In healthy people insulin helps the body metabolize sugar. Diabetics must take injections of insulin so they can metabolize sugars properly.
Yalow and Berson wanted to look at what happened to insulin when it was injected into the body. To help trace the insulin after it was injected, the two scientists added an atom of a radioactive isotope of iodine, iodine-125, to the insulin molecule. (This is called labeling.) The radiation given off by the iodine-125 atom would help them follow the insulin molecule through the body. For example, if radiation was found coming from a patient's urine, they would know that the insulin molecule had been broken down by the body and its iodine-125 atom had been passed out of the body through the urine.
Yalow and Berson noticed that diabetics who had been taking insulin for a long time kept the labeled insulin in their bodies longer than healthy people. In those days diabetics usually used insulin taken from cattle. Cattle insulin is slightly different from human insulin, so the body saw it as a foreign substance and attacked it with antibodies. The antibodies bound to the insulin molecules so that it took longer for the labeled insulin to pass through the body. This immune response also made it harder for the body to use the insulin. Through this discovery the two scientists realized that human insulin would be better than cattle insulin for diabetics. The human body would not attack human insulin. Genetically modified bacteria were eventually engineered that could produce large amounts of human insulin. Today nearly all the insulin used to treat diabetes is produced by genetically modified bacteria.
But the most famous discovery made by Yalow and Berson was a technique called radioimmunoassay, or RIA, a method of quantifying minute amounts of biological substances in the body using radioactive-labeled material. The human body is made of chemical compounds, many of which are present in the blood in very low concentrations. Measuring the concentrations of various compounds in the body is important for diagnosing diseases and for making sure a medicine is working properly, but measuring extremely low concentrations can be difficult. RIA makes the job much easier.
The way RIA works is a bit complicated but very clever. A known quantity of the substance that the researcher wants to measure—a hormone, in Yalow’s and Berson’s case—is tagged with a radioactive isotope. Then it is mixed in solution with its naturally occurring antibody (the “immuno” part of RIA), and hormone-antibody pairs are formed. They are then added to a quantity of the patient’s blood, in which there is an unknown quantity of the hormone that the researcher wants to determine. Since antibodies prefer nonradioactive versions of the hormone to radioactive ones, they gradually separate from their radioactive partners and team up with the natural hormone. A researcher then separates out all the hormone-antibody pairs (both the radioactive and the nonradioactive ones) and measures the radioactivity of the mixture. The difference in the level of radioactivity of this mixture from the radioactivity of the original sample of tagged pairs gives a measure (“assay”) of how much natural hormone was in the sample of blood.
In 1977 Yalow received the Nobel Prize in Physiology or Medicine for her and Berson’s development of RIA as it applied to tracing hormones in the body. Since Nobel Prizes are only given to living people, Yalow received the award without Berson, who died in 1972. She shared it with two other scientists, Roger Guillemin and Andrew V. Schally, who were honored for their work on hormone production in the brain.
Yalow’s lab at the VA hospital in the Bronx, which by then was much larger than the janitor's closet where she had started out, is named after Berson. She says she did this so that his name would still be on every paper she published as long as she worked there.
Yalow and her husband had two children, Benjamin and Elanna. In addition to receiving the Nobel Prize, she was the first woman to receive the Albert Lasker Basic Medical Research Award (1976), and in 1988 she was awarded the National Medal of Science by President Ronald Reagan. She continued to conduct and direct research at her VA lab until her retirement in 1991. She is still a Distinguished Service Professor at Mount Sinai School of Medicine.
For Further Reading on the Web
The Nobel Prize in Physiology or Medicine 1977 — from NobelPrize.org.
Rosalyn Yalow: Assaying the Unknown — Yalow's life and work, from Modern Drug Discovery, a publication of the American Chemical Society.
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