Protein Growth Facilities on Board the ISS

Although there have been some intriguing successes from the experiments carried out to date, at least as many crystals were lost before they could be returned to Earth-based laboratories for study. This is because in the past, most microgravity experiments were consigned to the middeck lockers of the Space Shuttle. Generally, fewer than a hundred crystallizations per flight were attempted, and most were allowed to run for only a week or less.

It should be different when the ISS is completed and in full operation swing. Regular Space Shuttle flights to and from the ISS will allow for considered planning of crystallization experiments. Improvement and standardization of the crystallization hardware will allow laboratory scientists to optimize crystallization procedures for the specialized hardware, maximizing the chances for success.

On board the ISS, experiments will be carried out in dedicated racks in the sciences modules. Many more crystallizations will be set up and allowed to proceed for weeks or months, with periodic visual monitoring both on the ISS and from the ground. In addition, it will be possible to automate the process of crystal growth, monitoring, mounting, and freezing, and of obtaining diffraction data in microgravity.

For example, the X-ray Crystallography Facility (XCF) is a multipurpose facility designed to provide and coordinate all elements of protein crystal growth experiments on board the ISS, including sample growth, monitoring, mounting, freezing, and X-ray diffraction. A module for the growth phase is designed to house vapor diffusion experiments. The visualization unit uses magnified still photographs of samples that have completed growth to determine whether the resulting crystals are worth preserving. The Crystal Preparation Prime Item (CPPI) is a robotic system that mounts the crystals on hair loops for cryopreservation or on hair loops inside a capillary, unfrozen. Finally, the X-ray Diffraction Module employs a low-power (24 W) X-ray source and has a maximum resolution of 1.1 A. The various modules are controlled remotely from the ground; crew time is only required to move samples from unit to unit.

The incorporation of microscopic examination, a crucial element of successful crystallization in space, means that the crystallization process can be monitored and successful crystallization recognized when it occurs. The coupling of microscopic examination with automated procedures for crystal recovery and freezing will dramatically improve the ability of scientists to bring back high-quality crystals from space.

Figure 8-10. Astronaut Donald R. Pettit, during his spare time on board the ISS, built a small laboratory to experiment and obsene the behavior of fluids and ctystals in microgravity. This activity used simple materials that would not impact the programmatic supplies and was dubbed "Saturday Morning Science". In this photograph, he is shown looking closely at a water bubble within a 50-millimeter metal loop. Photo courtesy of NASA. Source: http://spaceflight.nasa.gov/station/crew/exp6/spacechroniclesl8.html

Figure 8-10. Astronaut Donald R. Pettit, during his spare time on board the ISS, built a small laboratory to experiment and obsene the behavior of fluids and ctystals in microgravity. This activity used simple materials that would not impact the programmatic supplies and was dubbed "Saturday Morning Science". In this photograph, he is shown looking closely at a water bubble within a 50-millimeter metal loop. Photo courtesy of NASA. Source: http://spaceflight.nasa.gov/station/crew/exp6/spacechroniclesl8.html

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