J. Fraser Stoddart, a former professor of chemistry and biochemistry, received the Nobel Prize on Oct. 5 for building the world’s smallest machines, including molecular elevators, artificial muscles and molecule-sized computer chips.
Stoddart powered the machines with a chemical structure he built called rotaxane, which contains a circular molecule ringed onto a molecular axle, or rod. The chemical energy contained within the structure can then be harnessed for mechanical work or be transformed into electrical signals.
Kendall Houk, who co-authored nine papers with Stoddart, said he and Stoddart used mathematical methods to predict how Stoddart’s molecular machinery would react to different stimuli.
Houk, the Saul Winstein Chair in Organic Chemistry, said Stoddart’s machine works through coupled reduction and oxidation reactions, or reactions that involve the loss and gain of electrons. That transferal of energy spurs the mechanical motion.
“When you change the charge of a molecule from neutral to positive, for example, it can change the interactions between the molecules,” Houk said. “Our computations could calculate the change in strength of the interactions when you switch stuff around and explain reactions that we observed.”
He said rotaxane was used to build molecular muscles that stretch or compress, just like their life-size counterparts. He added Stoddart’s technology was also used to build molecular elevators, or four-legged molecules whose legs can change length to toggle their height.
“The dream is to have control over little machines that can repair things and so forth,” Houk said. “Artificial muscles and elevators are not useful yet, but basic research isn’t necessarily to solve a practical problem; it’s to discover things others things can then build upon.”
Houk added the molecular machines may later be used for drug delivery.
“Say you want to release a drug in a specific way,” Houk said. “When you remove the ‘cork’ – the organic molecule that plugs up the bottle opening – via electrical stimulation, the drug is released.”
Jeffrey Zink, a professor of chemistry and biochemistry who collaborated with Stoddart to build the drug delivery mechanism, said the device can deliver anti-cancer drugs in a controlled manner that current methods cannot achieve.
“With chemotherapy, the drugs enter the bloodstream and cause widespread liver damage and hair loss,” Zink said. “When the (drug delivery) valve is closed, the drug doesn’t come out until it’s needed. This is on-command release that’s highly localized to only the tumor.”
He added Stoddart also repurposed the molecular machines to build electrical switches and miniature electronics.
“(Stoddart) was an outstanding synthetic chemist; he was very imaginative and very creative,” Zink said.
Catherine Clarke, chair of the chemistry and biochemistry department, said Stoddart’s Nobel Prize win mirrored those of other Nobel laureates in the chemistry department at UCLA.
She said she compares Stoddart’s work on circular rotaxane to Paul Boyer and Donald Cram’s Nobel Prize-winning work. Boyer identified ATP synthase, the protein motor that generates energy in a cell and Kram helped build crown ethers, large circular chemicals.
Clarke said although Stoddart now teaches at Northwestern University he continues to be an active presence at UCLA. Each year, Stoddart presents the Norma Stoddart Prize to a chemistry graduate student who both conducted exemplary research and was an active member of the department. The prize is named after his late wife, a biochemist who Clarke said was almost like a mother figure for Stoddart’s laboratory.
At Northwestern, Stoddart is refining the uses for his molecular machines.
Stoddart will officially receive the prize in December in Stockholm, Sweden. He will share the Nobel Prize with two other researchers; Jean-Pierre Sauvage, a professor emeritus at the University of Strasbourg, France and Bernard L. Feringa at the University of Groningen in the Netherlands.