AsianScientist (Mar. 24, 2016) – Sometimes, distance can lend a new perspective to a problem. For Japanese researchers studying protein crystal growth, that distance was 250 miles up—the altitude at which the International Space Station (ISS) orbits the Earth.
To better isolate the growth of protein crystals from the effects of gravity, the group of Katsuo Tsukamoto in Tohoku University’s Department of Earth and Planetary Science and the Japan Aerospace Exploration Agency grew crystals in a specially-designed chamber onboard the ISS. Their work was published in Review of Scientific Instruments.
The researchers monitored the very slow growth and dissolution rate—approximately one centimeter per second—of the crystals by laser interferometry. This was the first time the technique had been used onboard the ISS to measure the growth rate of the crystals at various temperatures. To observe this, Yamazaki and his colleagues developed unique growth cells suitable for long-term projects, for about six months.
“We are interested in the growth mechanisms of a 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 Mr. Tomoya Yamazaki, a PhD student in Tsukamoto’s lab.
The experimental process, known as NanoStep, was performed in the Japanese Experimental Module, or KIBO, of the International Space Station in 2012. Tsukamoto and his colleagues had previously measured the growth rates of protein crystals under simulated microgravity by using a Russian recoverable satellite and aircraft in parabolic flights.
The researchers took precise measurements of the growth rate of the lysozyme crystals versus their driving force, supersaturation—the natural logarithm of the protein’s concentration divided by its solubility—with measurements of the solution’s refractive index distribution obtained through interferometry. This also yielded crucial information about the growth mechanism.
While the researchers expected growth rates of the crystal solution to be slower because of the suppression of solution convection, the results instead showed an increased growth rate. This may be due to the suppression of transport speed of impurity molecules with larger diameter to the growing crystal.
Extended projects for the researchers using the same apparatus to test the growth of different crystals, such as glucose isomerase crystals, are currently in preparation.
The article can be found at: Yamazaki et al. (2016) Development of Compartment for Studies on the Growth of Protein Crystals in Space.
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Source: American Institute of Physics; Photo: Charles Knowles/Flickr/CC.
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