Most of the more than 100,000 3D protein structures that scientists have collected to date have come from X-ray scans. However, these X-ray scans cannot detect hydrogen atoms, which make up about 50 percent of the atoms in these proteins and may play important roles in the protein’s activity. Neutron scans can determine the precise locations of these hydrogen atoms, but these require large protein crystals, which are difficult to grow. As such, fewer than 100 3D protein structures have been determined using neutron beams, said study lead author Joseph Ng, a biochemist and director of the Biotechnology Science and Engineering Program at the University of Alabama in Huntsville and president of HudsonAlpha associate company iXpressGenes.

Previous research found that growing large pure crystals of protein is difficult on Earth because of effects arising from the planet’s gravity. In gravity, heavierfluids sink and lighter fluids rise, driving convection or churning that can interfere with crystal formation. Previous work has long suggested that in the microgravity experienced in orbit around Earth, such problems with crystal growth would largely vanish, the researchers wrote in a paper describing the new experiments. (This new experiment is not the first time scientists havegrown protein crystals in space. Cost and logistics are also barriers to carrying out these kinds of experiments).

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