Deaths elsewhere

Last update: November 2, 2009 - 9:24 PM

Mildred Cohn, 96, a chemist who overcame both religious and sexual prejudice to make major contributions in applying physics to problems of biology, died Oct. 12 in Philadelphia. Refusing to accept the limitations imposed on her, Cohn worked with four Nobel laureates over the course of her career, eventually earning the nation's highest science award, the National Medal of Science.

She pioneered the use of stable isotopic tracers to study the mechanisms of enzymes, which are the proteins that carry out chemical reactions within the cell. Stable isotopes, such as carbon-13 and oxygen-18, have the same chemical properties as their more common sisters -- in this case, carbon-12 and oxygen-16 -- but they do not disintegrate radioactively. When stable isotopes are incorporated into molecules in the cell, their heavier weight allows them to be traced, providing insights into biochemical reactions. She also did critical work in nuclear magnetic resonance, or NMR, an imaging technique that enables chemists to examine the structure of proteins and other molecules.

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