Tuning the activity of an enzyme for unusual environments: Sequential random mutagenesis of subtilisin E for catalysis in dimethylformamide.

Arnold introduced a biochemical molecule manipulating technique to mimic the process of natural selection in creating new enzymes adapted to a specific catalytic reaction. She directed evolution of subtilisin E to obtain an enzyme variant which was active in a highly unnatural (denaturing) environment. In 2018 Arnold received half of the Nobel Prize in Chemistry "for the directed evolution of enzymes."

(Thanks to Juan Weiss for this reference and its interpretation.)