Who she is
Frances Arnold grew up in Pittsburgh and trained as an engineer, not a chemist. Concerned about energy and the environment, she wanted to make fuels and chemicals in cleaner ways. That led her to enzymes, the protein catalysts that run the chemistry of living things in water, at room temperature and with little waste.
Key contributions
The problem. Enzymes are superb catalysts, lowering the activation energy of reactions so much that they can speed them up millions of times. But natural enzymes are made for the conditions inside cells, not for a chemical factory. In the 1980s chemists tried to redesign enzymes by reasoning about their structure, with little success: proteins are too complicated to predict.
Directed evolution. Arnold’s solution, first reported in 1993, was to let evolution do the design:
- Make random changes (mutations) in the gene for an enzyme.
- Produce many variants of the enzyme in bacteria.
- Test them and keep the ones that work best under the desired conditions.
- Repeat, starting from the best variant.
After a few rounds she had an enzyme that worked well in an organic solvent, where the original barely worked at all.
Key idea
Directed evolution does not need to know why a change works, only whether it works. Repeated cycles of variation and selection, the same process that shaped life, can optimize a catalyst in months.
New chemistry from enzymes. Her group has since evolved enzymes that make bonds no natural enzyme makes, such as carbon–silicon bonds (2016). Enzymes from directed evolution are now used to make medicines with fewer steps and less waste, and to turn plant sugars into fuels.
Prizes and legacy
She received half of the 2018 Nobel Prize in Chemistry “for the directed evolution of enzymes”; the other half went to George Smith and Gregory Winter for phage display. She was the fifth woman to win the Nobel Prize in Chemistry. Her approach is now a standard method in green chemistry.
Connections to your lessons
Enzymes are catalysts, so her work extends the lessons on activation energy and reaction rates, and it offers a cleaner way to carry out the organic reactions that make medicines.
Timeline
- 1956Born and raised in Pittsburgh, Pennsylvania.
- 1979Graduates in mechanical and aerospace engineering from Princeton University, with an early interest in renewable energy.
- 1985Earns her PhD in chemical engineering at the University of California, Berkeley.
- 1986Joins Caltech, where she remains for her career.
- 1993Reports the first directed evolution of an enzyme: after rounds of random mutation and selection, a protein-cutting enzyme works far better in an organic solvent.
- 2005Co-founds a company to make renewable fuels using engineered microorganisms.
- 2016Her group evolves an enzyme that makes carbon–silicon bonds, a reaction no known natural enzyme carries out.
- 2018Awarded half of the Nobel Prize in Chemistry, the fifth woman to receive the chemistry prize.
Sources and further reading
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