By Marie Claire Chelini

Despite decades of effort, humans still struggle to efficiently convert one source of energy into another.

Steam motors, gasoline combustion and solar panels all convert less than half their fuel’s potential energy into energy we can use. By comparison, mitochondria, tiny power plants inside cells, convert almost 100 percent of the energy they receive into usable energy.

Now a $1 million award from the W. M. Keck Foundation will help a Duke University research team take a crucial step towards replicating and improving upon one of the energy conversion processes that happens inside cells.

“In the long run, this may allow us to make higher-efficiency solar energy conversion systems,” said David Beratan, the R.J. Reynolds Distinguished Professor of Chemistry and Physics at Duke. “It could give us a way to transfer the energy captured by solar panels into the power grid or into chemical forms with very limited waste.”

The Keck-supported work will be led by Beratan, Michael Therien, the William R. Kenan, Jr. distinguished professor of chemistry at Duke, and William DeGrado, professor of pharmaceutical chemistry at the University of California, San Francisco.

Understanding the team’s work starts with taking a closer look at mitochondria, which help generate a cell’s energy.

Mitochondria rearrange electric charges—electrons and protons—to turn glucose and oxygen into ATP, which cells can then use as fuel. To do this, mitochondria rely on enzymes called bifurcases, which move electric charges around and send electrons into two different pathways. This process is known as electron bifurcation.

Electron bifurcation can be thought of like two cars on a roller coaster. The first car gets a signal, and launches forward, dragging the second car behind along curves, twists, and turns and gains momentum as it goes. At a crucial moment, the cars separate from one another. The first car takes a sharp right, falling on a downward slope and gently returning to the point of origin. The second car, propelled by all the momentum gathered along the ride, shoots up ahead, rising to a new level of energy.

In nature, this is not a perfectly efficient process. Sometimes the separation of the charges is reversed, and the electrons lose momentum and return backward to the point of origin. Sometimes they simply fall off the track, a process known as short-circuiting. Despite these hiccups, this intracellular energy-conversion machinery is still far more efficient than anything a human can make.

The team intends to design and manufacture proteins that mimic this process. They will use light pulses to trigger electron bifurcation and record the electrons’ wild ride with extremely fast spectroscopy that enables them to track the motion of each electron’s charge separately.

By grounding their new work in their own recent theoretical discoveries, the team aims to strip biology’s logic to the bare bones. If their designed enzymes can suppress short-circuiting processes and other typical failures in the natural system, it would have a groundbreaking impact on the ability to design energy conversion devices and next-generation energy catalysts.

No team has ever been able to build synthetic proteins with these high-efficiency electron bifurcation capabilities, but Therien, Beratan, and DeGrado’s combined expertise, paired with the Keck Foundation support, puts the team in position to be the first.

“This funding provides us the means to test theory and to make new predictions that we would really be hamstrung to do if we were to just rely on Mother Nature’s examples,” Therien said.

Beratan agreed. “We’re very pleased that the Keck Foundation supports this kind of idea,” he said. “It is super ambitious but has huge potential.”

The W. M. Keck Foundation was established in 1954 in Los Angeles by William Myron Keck, founder of The Superior Oil Company.  One of the nation’s largest philanthropic organizations, the W. M. Keck Foundation supports outstanding science, engineering and medical research.  The Foundation also supports undergraduate education and maintains a program within Southern California to support arts and culture, education, health and community service projects.