Florida Tech untangles findings from the SABOL experiment performed on the International Space Station
Sam Durrance remembers being nervous last spring as he removed the tape from the foam crate that arrived at his Florida Institute of Technology lab via FedEx. Inside was a shoebox-sized experiment featuring nine test tubes, wires and electrodes that not long ago had been cargo inside a SpaceX Dragon capsule that arrived in a more spectacular fashion – splashing down in the Pacific Ocean, fresh off the International Space Station.
It would be a few more weeks until Durrance, a professor of physics and space sciences, could determine if the experiment worked and what he and his colleagues might learn from it about the way some proteins can self-assemble into long, thin structures called fibrils. Such knowledge could have implications on researching neurological diseases such as Alzheimer’s, where strings of protein mysteriously form into tangles affecting brain function.
But good science often requires patience as much as it does calculations. And sometimes science throws in a surprise or two, as turned out to be the case with the metal box Durrance had unpacked.
That box was technically known as Self-Assembly in Biology and the Origin of Life, or SABOL. It was developed by Durrance and Florida Tech colleagues Daniel Kirk, professor of aerospace engineering, Hector Gutierrez, professor of mechanical engineering, and several students. The experiment utilized the microgravity environment of the space station to study how protein fibrils form and grow, a fundamental biological process.
Durrance, the lead scientist on the team (who, as a former astronaut, has spent time in space aboard space shuttles Columbia and Endeavor), said the inspiration came from growing lysozyme protein fibrils in his Florida Tech lab. In such an environment, these protein fibers make long chains in solution until gravity pulls them down to the bottom of a growth chamber, which limits how long and complex they can get for research purposes. Durrance predicted that the same growth process carried out in microgravity would allow for longer, possibly more complex self-assembly of protein structures consisting of multiple fibers wrapped in helical form around each other. Such a construct would be useful for studying propagation over a longer period and perhaps revealing more about the fibers’ nature.
During its time in space, the experiment designed and built by Florida Tech faculty and students managed to grow protein fibrils in three of the nine vials where a liquid solution and protein powder made contact via an automatic plunger and then heated to create the right growing environment. But a closer look at the fibers under a microscope was needed to see what form the fibers took.
“When we looked at the first images, we were blown away,” Durrance said.
The fibers looked completely different than the control group grown on Earth under the same conditions but minus the microgravity environment. Instead of long and tangled, the microgravity-grown fibrils were very short and much thicker.
“Pretty much the opposite of what we thought would happen,” Durrance said.
After Durrance and his graduate student, Dylan Bell, ruled out that the surface structure inside the tube influenced the growth patterns, they had to conclude that microgravity affected the morphology in an unexpected way.
Bell is now trying to replicate how the fibril-growing process proceeded in space here on the ground, which may yield fundamental insight on how the assembly process works and could lead to further development in the science of self-organizing biological molecules. His guess is the ability of proteins to flow through the solution like they do on Earth was hindered by the lack of natural buoyant convection, which isn’t present in microgravity.
Instead of the protein molecules being moved quickly to the growing end of the fibrils by buoyant forces, Bell thinks the slower process of diffusion was the only avenue to grow outward when the vials in space were heated to begin the self-assembly process.
“I think it’s fair to say that the project has shown that self assembly is much more of a mystery because the results blew away the science team,” said Daniel Batcheldor, head of the Department of Physics and Space Sciences. “This is what we love as scientists, because results we don’t understand means we are going to learn something.”