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Frances Arnold's Directed Evolution

The Proteins Evolve, and So Does She
Frances Arnold's Directed Evolution
Photograph by Kyle Johnson for Bloomberg Businessweek

For a person who invented something called directed evolution, Frances Arnold has followed quite a meandering career path. As the highly intelligent daughter of a nuclear physicist, she seemed destined to become a scientist. In her teens she instead became an activist and hitchhiked from her Pittsburgh home to Washington, D.C., to protest the war in Vietnam. In her 20s, she worked on a solar project in South America and learned to get by on about $1 a day and tolerate flea-ridden beds before heading to the University of California-Berkeley for her PhD. “In the ’70s it was the thing to do,” she laughs. “I was looking for what I was and who I was.”

That’s an indulgence she doesn’t allow the proteins in her lab. Arnold, 56, is a professor of chemical engineering, bioengineering, and biochemistry at the California Institute of Technology. In the early 1990s, she pioneered a method to evolve proteins not found in nature. She starts by mutating DNA, the genetic blueprints for building proteins, by mixing it with molecules that cause it to copy itself with mistakes. The DNA with the mutations that seem most promising are inserted into living organisms, which translate the genes into proteins. This process is repeated over and over—sometimes up to 50 times—to get the desired characteristics.