Catching rays with DNA

DNA nanotechnology is a field that is one part chemistry and one part architecture, but with scientists using building materials that are 50,000 times smaller than a human hair.

Imagine using coiled strands of DNA, wrapped end over end, to build tiny robots that could enter the body and deliver drugs exactly where they need to go, or nanoscale solar panels that work to provide more renewable energy. That is the promise, excitement and long-term dream of this technology.

With a $849,000 Department of Energy grant, Hao Yan, a chemist at the Biodesign Institute at Arizona State University, is exploring a more efficient way to capture and transfer solar energy, by programming DNA nanotechnology to mimic systems seen in nature.

“I was fascinated by the idea of using nature's material to build man-made systems and devices that can potentially be useful for health and energy applications,” Yan said.

Yan and collaborators Neal Woodbury and Yan Liu from Arizona State University, Mark Bathe from the Massachusetts Institute of Technology and David Whitten from the University of New Mexico, will be using a molecular scaffold to try and build a system similar to what plants use in their cells to transform sunlight into energy. As they perfect and alter the design, they also expect to learn more about how natural photosynthesis occurs.

During the past two decades, the field of DNA nanotechnology has changed from drawing flat pictures with DNA to building 3-D shapes. Since then, there has been an ever-increasing complexity, creativity and competition to discovering how these tiny structures are designed and built, and the introduction of using DNA as a scaffold to hold molecules in particular, designed arrangements.

“Science is always one thing building on top of another,” said Yan, who directs the Biodesign Center for Molecular Design and Biomimetics. “There are a lot of stepping-stones. You learn a lot of lessons and a lot of failures.”

Light-gathering molecules

In plants and bacteria that use sunlight as an energy source, molecular pigments, called chromophores, absorb energy from the sun. The energy is transferred from one chromophore to another in a row of closely packed pigments until it reaches a point where that energy can be converted into sugar, providing food for organisms to grow.

“Nature has this light-harvesting system that can arrange chromophores into closely packed arrangements,” said Yan, “That means the chromophores are touching each other. That causes the energy to efficiently be transferred from one point to another point.”

Unfortunately, the proteins that hold chromophores close together are difficult to synthesize in the lab. During the next three years, Yan will be testing a different approach.

He will be using DNA, instead of proteins, as a molecular scaffold to hold the pigments in close proximity to each other. His goal for this grant is to produce a scaffold that will hold the pigments and transfer the energy from one point in space to a different place.

By placing pigments in different spaces, shapes and distances apart, they will start to learn what properties are important for efficient-energy transfer through the pigments. These insights could lead to an easier way to build light-energy-harvesting systems that will absorb more energy and have it travel efficiently to where it is needed 

“We can control the geometry, we can control the dimensions, we can control where we put the chromophores, and then we can study how they transfer the energy,” Yan said.

This close look at nature’s machinery may lead to better understanding the mechanics of how nature captures solar energy, which may be used to improve future solar-energy technologies.