Imagine growing crystals - in space. Scientists have examined a space-grown protein crystal to better understand how zero gravity impacts the growth of crystals.
In this latest study, researchers aboard the International Space Station monitored the very slow growth and dissolution rate of the growth of protein crystals.
"We are interested in the growth mechanisms of space-grown protein crystal-a lysozyme crystal-as a model crystal to understand why space-grown crystals sometimes do show better quality than the Earth-grown crystals," said Tomoya Yamazaki, one of the researchers working on the project.
The experiment was performed on the ISS in 2012. The researchers took precise measurements of the growth rate of the lysozyme crystals versus their driving force. In this case, that force was supersaturation. The researchers also looked at measurements of the solution's refractive index distribution.
The researchers modified the supersaturation of the solution by increasing and decreasing the growth cell's temperature. This meant that the scientists had to create a closed growth cell that would withstand the stresses of this temperature fluctuation. The researchers attached tubes made of elastomer to help relieve thermal stress on the glass.
The researchers expected growth rates of the crystal solution to be slower due to the suppression of solution convection. Instead, the researchers found that there was an increased growth rate in this case.
The researchers had several theories as to why this was. It could be due to the suppression of transport speed of impurity molecules with a larger diameter to the growing crystal.
While the researchers have found out a little bit more about how crystals grow in space, they have also created a growth cell that could be used in the future. This cell could be used to fine tune the measurements of small growth or dissolution rates of insoluble minerals. As an example, it may be able to measure calcium carbonate crystals and be able to predict the dissolution of clay minerals surrounding nuclear waste.
The findings reveal that experiments on the ISS not only tell researchers more about the effects of space but may also help drive experiments on Earth.
The findings are published in the March 2016 journal Review of Scientific Instruments.
