Photo of JoAnne Stubbe

JoAnne Stubbe

  • National Medal of Science
  • Chemistry
For her ground-breaking experiments establishing the mechanisms of ribonucleotide reductases, polyester synthases, and natural product DNA cleavers compelling demonstrations of the power of chemical investigations to solve problems in biology.

JoAnne Stubbe on what sparked her interest in science

I’ve never been one who’s driven by something practical,” JoAnne Stubbe once said. “I focus on trying to understand basic biology, which I find really interesting.” ‘Really interesting’ may be something of an understatement from a woman known to her colleagues as a fiercely determined, intensely curious, and rigorously focused scientist.

In her more than 40 years of research, Stubbe has taken huge steps in explaining how enzymes have evolved over millions years to be able to carry out the chemistry necessary to sustain life as we know it.

In a long list of important insights and discoveries, her most notable contribution was the uncovering of how a class of enzymes—called ribonucleotide reductases, or RNRs—are involved in the replication and repair of DNA molecules. Stubbe was able to precisely pinpoint how RNRs use complex chemistry to convert the building blocks of RNA into the building blocks of DNA. Without RNRs, DNA wouldn’t exist, nor would it be able to repair itself.

Though Stubbe prefers to focus on the pure science of her experiments, her insights and discoveries have led to some very practical real-world innovations. Her work on RNRs led directly to the development of the drug gemcitabine, which is used to treat advanced pancreatic cancer and non-small cell lung carcinomas. Other reactions uncovered by Stubbe are being used to synthesize biodegradable plastics—a much more environmentally sound option that traditional petroleum-based plastics.

A tireless experimenter and collaborator, JoAnne still finds her work exhilarating after all these years. “I have always been fascinated by how nature has evolved over millions of years to do these very tough chemical reactions,” she says. “Enzymes do a lot of pretty cool things and I love discovering exactly how they do it.”