Enzyme crystals growing in the microgravity of the International Space Station will help scientists develop improved antidotes for toxic nerve agents.

In June, samples of a human enzyme called acetylcholinesterase (AChE) journeyed to the space station aboard the SpaceX CRS-11 Dragon capsule as part of the Countermeasures Against Chemical Threats (CounterACT) project, which is an initiative led by the National Institutes of Health.

Organophosphates (OPs), a group of chemicals that includes several pesticides as well as sarin and VX nerve agents, block the activity of AChE enzymes, which allow muscles to relax after being stimulated by the nervous system. When the activity of AChE is blocked by OPs, muscles can't relax, which, in turn, can lead to paralysis and eventually death, according to a statement from the National Institute of Neurological Disorders and Stroke (NINDS). [6 Coolest Space Shuttle Science Experiments]

"With increasing worldwide concern about the use of chemical weapons, there is significant interest in developing better counteragents," David A. Jett, director of the CounterACT program, said in the statement.

Using the AChE enzyme samples sent to the space station, astronauts are growing large crystals of pure enzyme. Thanks to the microgravity conditions of space, astronauts are able to grow larger, more uniform crystals than scientists can on Earth, officials said in the statement.

Those large-scale crystals can help researchers better understand the structure of the AChE enzyme. Once the crystals are grown to a size that's large enough, they will be returned to Earth for further study. Scientists plan to investigate the crystals using a method called neutron diffraction, which can provide an atomic-level view of the enzyme.

"Using this technique, we will be able to get a closer look at how the enzyme interacts with pesticides and nerve agents and learn about how the bond between the two can be chemically reversed," Zoran Radić, a researcher from the University of California, said in the statement. "This method would not work on the smaller enzyme crystals that can be grown here."

Because OP exposure blocks the AChE enzyme, the antidotes that are used to counteract this type of poisoning work because they directly break the chemical bond between AChE and OP, which reactivates the AChE enzyme. However, current antidotes are too slow to be fully effective. Using the large-scale samples grown on the space station, scientist hope to develop an oral antidote that can break the AChE-OP bond more quickly.

"Developing better countermeasures against these sorts of nerve agents is a major thrust of our overall program," Jett said in the statement. "This project is the kind of cutting-edge science we envisioned when we established the CounterACT program."

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