Advanced Technologies

Space Shuttle Experiment a Sweet Success

EXPERIMENTS ABOARD THE SPACE SHUTTLE may help safely satisfy the sweet tooths of diabetics and those watching their waistlines. A team of French and American scientists reports they have crystallized one of the most interesting families of intensely sweet proteins, a natural molecule called thaumatin, isolated from the African Serendipity Berry (Thaumatococcus daniellii).

In a control study, the team compared space-grown thaumatin crystals with some previously obtained from Earth in a conventional laboratory. Using otherwise similar crystallizing conditions, the space crystal showed a nearly 25-percent larger volume and yielded twice the crystalline order, compared to its Earth-grown counterparts.

The complex and costly management of human diabetes, obesity and oral health has spawned a widespread search for natural sugar substitutes that are both noncaloric and safe. The calorie-free thaumatin protein, sometimes called nature's "artificial sweetener," was analyzed by scientists from the University of California at Irvine and the Institute for Molecular Biology in Strasbourg, France.

The natural proteins as a group are the sweetest compounds ever discovered. On a scale in which 0 refers to no sweetness and 1 refers to table sugar or sucrose, thaumatin is nearly off the scale at 3,000, more than ten times sweeter than other sugar substitutes such as saccharin or aspartame. Scientists hope to use the space-grown crystals to improve the biological understanding of how these molecules work, based on detailed knowledge of their shape and exact atomic positions. According to the study, the visual quality of the space crystals "appeared virtually flawless, with no observable imperfections, striations or anomalies." The scientists found that the space crystals provided 30-percent more real information about the molecule's shape. This moves the investigation closer to revealing the biological function of these complex molecules.

According to the team's report, the space crystals reinforce the conclusion of other reports based on different macromolecules that a microgravity environment provides distinct advantages. In the best of only a few thaumatin crystals grown in microgravity, compared with many more trials conducted on Earth, the microgravity-grown crystals were consistently and significantly larger, as well as substantially more defect free. This is the first experiment to produce space crystals by multiple methods, with both methods suggesting the same conclusion: crystals grown in microgravity can be significantly improved in their x-ray diffraction properties when compared with those grown on Earth.

Thaumatin already is being marketed as a nutritional supplement in blood sugar stabilizers for childhood behavioral problems and the more than 3.5 million sufferers from attention deficit disorder. Among soft drink consumers alone, nearly 20.6 million tons of chemicals are used around the world—nearly four kilograms per capita—with a growth of about 20 percent toward the end of the decade.

For more information, contact Dr. David Noever at Marshall Space Flight Center.
Call: 205/544-7783, Fax: 205/544-2102, E-mail: david.noever@msfc.nasa.gov
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Molecular information from crystals grown on the Space Shuttle may help develop a noncaloric sweetener to help control diabetes, obesity and other health-related uses.