Frances Arnold-one of just eight living individuals to have been elected to all three branches of the National Academies-pioneered directed evolution, a method of protein engineering now used in laboratories around the world. This technique, which could be imagined as a molecular analog of breeding, proved almost immediately applicable to a range of fundamental and practical problems.

Research in the Arnold group focuses on development of evolutionary design principles for engineering biological systems-enzymes, metabolic pathways, genetic regulatory circuits, and ecosystems.

Arnold's group uses directed evolution to explore enzyme functions that natural environments have never required, along with functions for which the molecular basis is poorly understood. Lab members construct synthetic families of enzymes-the protein molecules that catalyze biological processes-in order to study structure-function relationships free from constraints of natural selection. Their experiments help elucidate why nature's designs work the way they do.

The group has generated proteins with a variety of features useful in medicine and alternative energy, like improved stability and the ability to function in nonnatural environments. It has constructed new biosynthetic pathways and circuits for controlling gene expression and intercellular signaling capabilities. Group members are also refining enzymes that can break down cellulose, the key structural component of plant cell walls, which would allow the efficient production of cellulosic biofuels.