ATLANTA--Dr. Gary Hastings, a professor in the Department of Physics and Astronomy at Georgia State University, has received a two-year, $400,000 federal grant to study solar energy conversion in photosynthesis.
The goal of this project, which is funded by the U.S. Department of Energy's Office of Basic Energy Sciences, is to determine how plants and other organisms capture solar energy efficiently in photosynthesis. This information could be used to help scientists design more efficient artificial solar cells and allow humans to take better advantage of natural energy from the sun.
In this project, Hastings will seek to gain a molecular-level understanding of how replacing the pigment that plays a key role in photosynthesis with pigments of varying structures changes the rate at which electrons travel across the cell membrane during solar energy conversion.
Electron transfer occurs naturally in photosynthesis. During photosynthesis in plants, light energy from the sun hits a pigment and causes an electron to rapidly move across the cell membrane, but the electron doesn't come back, which makes solar energy capture in plants very efficient. In artificial systems, on the other hand, the electron goes back much of the time, making these systems much less efficient.
"This is an ultra-efficient reaction," Hastings said. "The question is what is it about these pigments that makes that happen? If we know how this works, we can make cheaper, simpler solar energy capture systems that can do essentially the same thing. You want to know how this works so you can mimic it."
The project will study photosynthesis in cyanobacteria, often called blue-green algae, using time-resolved infrared spectroscopy. Photosynthesis in cyanobacteria works in exactly the same way as it does in plants. In cyanobacteria, the pigment phylloquinone (also known as vitamin K1) functions as an intermediary in electron transfer in photosynthesis. Phylloquinone is embedded in a protein and gains some unique properties when it interacts with this protein structure. The research team will replace this phylloquinone pigment with other pigments, modifying the photosynthesis system. They will use laser beams to initiate photosynthesis in the cyanobacteria and then use infrared light to follow how molecular bonds of the incorporated pigment and the surrounding protein vary due to electron transfer activity.
"Taking out one pigment and putting in another pigment changes the rates of how the electron gets across this membrane," Hastings said. "We're monitoring how molecular bonds of pigments change as electrons arrive and then leave. The nature of these changes tells us about the structure the pigment adopts in the protein. This information will help us to design modified pigment-protein systems that will or will not have certain structural aspects and allow us to control how fast an electron moves from point A to B."
Knowledge about electron transfer and the relationship between pigments and proteins can also be applied to other fields because this is the heart of much of biochemistry, Hastings said.
The research team will use Georgia State's High Performance Computing facilities to simulate experimental data, with the goal of building a predictive algorithm for efficient solar converters. Data obtained through computation would allow them to more easily find the pigment structure that offers the best electron transfer and solar energy conversion and make further predictions, rather than having to do actual experiments, simplifying work to improve artificial solar cells.