Professor Witus instructs student Malik Mays '19 in her lab.

 “Some chemists trace their academic genealogy back hundreds of years.”
— Professor Cao

When this year’s Nobel Prize in Chemistry was announced, the news spread quickly. The American winner, one of three, is Sir Fraser Stoddart, who was advisor and mentor to Macalester professors Leah Witus and Dennis Cao during their time at Northwestern University. Stoddart was Cao’s PhD advisor from 2010 to 2014 and Witus was a postdoctoral scholar in his lab from 2012 to 2015.

The Nobel honors Stoddart for his work in the design and synthesis of molecular machines. With his research group, he created mechanically interlocked molecules such as rotaxanes, which consist of a ring encircling an axle. In rotaxanes, the ring can be made to move to specific locations along the axle much like a molecular shuttle.

“Our work synthesizing these molecules was inspired by biology,” says Witus. “There are proteins that act as molecular-scale biological machines. As synthetic chemists, we were working to create rotaxanes that could contract and expand on demand, like muscles do. Eventually, this could be used to make artificial molecular muscles for applications such as advanced prosthetic devices.”

During Cao’s PhD, he worked on making molecular gates for drug-loaded nanoparticles that open and close on command and on organizing molecular switches in three dimensions. “Some of these interlocked molecules are good at accepting and releasing electrons and can be made to switch between multiple states,” says Cao. Think 0s and 1s, accept and release, open and close. “Computer chips based on single molecular switches would be tiny compared to the silicon transistors in today’s computer chips and could potentially revolutionize computing, reducing our use of heavy metals and their associated environmental costs.”

“Fraser was very supportive, but also tough,” says Cao. “You could exchange 30 drafts of a manuscript with him and it would still come back covered in red ink.”

“That’s something I want to bring to my students here,” says Witus, “the practice of revising until the details are perfect.”

Professor Stoddart is known for being very devoted to this research. “Fraser was a ‘work 20 hours, sleep four hours kind of guy,” adds Cao, who noted that the lab brought together people from all over the world. Cao and Witus met at the lab and are believed to be the sixth marriage to come out of Stoddart’s lab over the years.

Chemists are often interested in their academic genealogy—who you worked with and learned from, who your thesis advisor was. “Some chemists trace their academic genealogy back hundreds of years,” says Cao.

Both Cao and Witus mentored Mac students in their chemistry labs over the summer. “Students in my Young Researchers group heard me talk about my previous advisors, including Fraser Stoddart,” says Witus, “so they were very excited when the Nobel was announced.  Our students are now the ‘academic grandchildren’ of a Nobel Laureate.”

October 17 2016

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