Volume 4, Number 2 May/June 1996
Proteins are large, complicated molecules that play critical roles in all of our biological functions; every disease involves the action of proteins. Knowledge about the detailed structure of certain proteins allows researchers to use structure-based drug design (SBDD) to develop new drugs to block undesired effects. SBDD requires the growth of high quality protein crystals, and the X-ray diffraction of those crystals to determine their three-dimensional structural.
Since 1984, protein crystals grown on more than thirty Shuttle missions have shown that space-grown crystals can be significantly larger, or with higher internal order (quality), than Earth-grown crystals. Microgravity is very important for commercial SBDD as it accelerates or often enables the growth of the high quality crystals needed. However, most protein crystals are fragile and easily degraded by factors such as temperature change, mechanical shock, or even time; so space-grown crystals need to be analyzed while they are still fresh.
Directed by NASA's Office of Space Access and Technology, the Center for Macromolecular Crystallography (CMC) at the University of Alabama at Birmingham has completed a design study for the X-Ray Crystallography Facility (XCF) for the International Space Station (ISS). The XCF system provides a capability for the ISS to grow, harvest and mount crystals, and obtain structural data, and then downlink the data to researchers on the ground. Also, crystal quality can be assessed before completing data collection in order to determine if new attempts are needed to grow better crystals. In that way, the XCF will provide timely and effective operations to meet the needs of commercial research.
The XCF includes a rack of equipment with three major subsystems. One subsystem provides for collecting, examining, selecting and mounting crystals, in preparation for obtaining the X-ray diffractions. Crystallographers will perform these operations remotely from the ground with minimal crew assistance. A "snap" freezer will allow cryopreservation of selected crystals.
Another subsystem includes an advanced, efficient means of generating, focusing, and detecting X-rays to obtain the diffraction data. A device will orient the crystals, and can maintain a crystal cryofrozen. A third subsystem performs command and control functions, acquires and stores data, and handles all communications with the crew and the ground. The XCF will be supported by a second rack outfitted for the growth and storage of crystals.
The XCF design is feasible, and can be fully operational onboard the ISS by the end of 2001 to provide an early demonstration of a highly effective and efficient use of ISS capabilities. The XCF holds the clear promise of being a leading producer of the benefits expected from the Nation's investment in the Space Station.
The X-Ray Crystallography Facility (XCF) design concept consists of two racks, a crystal growth rack and a diffraction rack.
For more information on the XCF, contact Bill McDonald at the CMC. Phone: 205/975-8797. Please mention that you read about it in Innovation.
