Hey, I'm Floral Lichtman, and you're listening to Science Friday. In nature, enzymes are the

catalysts that make much of biology work. They jumpstart chemical reactions that either wouldn't

happen or would happen super slowly. They do a lot of basic biological jobs, breaking down food,

building other molecules, extracting energy. But what if we could harness evolution to engineer designer enzymes that do other jobs,

specific jobs that benefit us? Putting that idea into practice changed the game for chemistry and earned Dr. Francis Arnold

the Nobel Prize in 2018. She called it directed evolution. And this is really big. Today,

thousands of labs use these methods to coax enzymes into doing things no one had ever thought of. Dr. Francis Arnold

is a professor at Caltech, and we'll hear about where she sees this approach going in the future

and her own personal evolution, the evolution that brought her into science. Welcome to Science Friday,

Dr. Arnold. Oh, thank you so much, Flore. I'm thrilled to be here. Okay, in our intro, we

described enzymes as catalysts that make biology work. I know they're near and dear to you. Do you have a

more poetic way of thinking about them? Poetic. Well, I think about them as the transformation

agents of the whole natural world.

It's enzymes that take carbon dioxide and sunlight and simple starting materials

and build trees and human beings and flowers and birds.

They're amazing.

They're the best chemists on the planet.

When we talk about directed evolution, should I be thinking about this like enzyme breeding?

But like instead of a chihuahua, you're making, you know, a tiny adorable protein?

Well, I think of it that way. It is a way to explain that we have been modifying the biological world at the level of DNA for ages, making strange things like chihuahuas that wouldn't be found naturally.

But for some reason, human beings find them charming or useful.

So why not use that same very powerful process of directing the evolution,

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