NASA - National Aeronautics and Space Administration

Fact sheet number: FS-2001-04-80-MSFC
Release date: 04/01

Protein Crystal Growth (PCG) Single-locker Thermal Enclosure System (STES) housing the Protein Crystallization Apparatus for Microgravity (PCAM)

Experiment Location on ISS: U.S. Lab EXPRESS Rack 2

Principal Investigators: Dr. Daniel Carter and Dr. Craig Kundrot

Project Manager: Todd Holloway, NASAs Marshall Space Flight Center in Huntsville, Ala.

Structural biological experiments conducted in the Single-locker Thermal Enclosure System (STES) may provide a basis for understanding the function of important macromolecules and possibly contribute to the development of new macromolecules. The scope of biological macromolecules includes proteins, polysaccharides and other carbohydrates, lipids and nucleic acids of biological origin, or those expressed in plant, animal, fungal, or bacteria systems.

The fundamental goal for growing biological macromolecular crystals is to determine their structure and the biological processes in which they are involved. Scientists select macromolecules, crystallize them, and analyze the atomic details often by using X-ray crystallography. By sending an intense X-ray beam through a crystal, scientists try to determine the 3-dimensional atomic structure of the macromolecule. Understanding these structures may impact the studies of medicine, agriculture, the environment and other biosciences. Every chemical reaction essential to life depends on the function of these compounds.

Microgravity the near weightlessness of space offers an environment which sometimes allows the growth of macromolecular structures crystals that show greater detail when exposed to X-ray diffraction than those crystals grown on Earth.

The International Space Station will provide for longer-duration experiments in a more research-friendly, acceleration-free, dedicated laboratory, than provided by the Space Shuttle. Mission 6A is a pathfinder flight to characterize the use of the Space Station for this type of research.

Experiment Operations

The Single-locker Thermal Enclosure System for the structural biology experiment is an incubator/refrigerator module that can house different devices for growing biological crystals in microgravity. On the Shuttle STS-100 mission to the International Space Station, scheduled for launch in April 2001, two of these STES units will be flown. Once on board the International Space Station, the units will be located in the U.S. Lab EXPRESS Rack 2. The experiments are scheduled to return to Earth aboard the Shuttle STS-104 Mission in May.

Each STES unit houses six Protein Crystallization Apparatuses for Microgravity (PCAM) designed to grow crystals using the sitting drop method of vapor diffusion.

A solution of water containing the biological material is surrounded by a solution that attracts water called a precipitant and usually is composed of salts, a polymer, or an organic solvent. As the precipitant attracts water away from the solution containing the biological material, crystals may begin to grow.

These crystals are grown inside each of the six PCAM cylinders.

Each cylinder is 15.2 inches (38.61 centimeters) long and 3.2 inches (8.128 centimeters) in diameter. In each cylinder, there are nine plastic growth trays. Each tray has seven sample wells, or chambers, covered by a synthetic rubber seal. The six PCAM cylinders house a total of 378 biological crystal experiments. A total of 756 biological crystal experiments will be housed in the two STES units.

Samples are prepared on Earth by placing a drop of the biological sample solution and precipitant solution together in the sample well. The sample well is surrounded by a donut-shaped reservoir that holds absorbent material similar to that of a disposable diaper. The material in the reservoir is used to absorb the evaporating component as crystallization occurs. A synthetic rubber seal placed on the tray isolates the sample drop from the reservoir until the start of the experiment in microgravity and keeps the crystals from forming on Earth or bouncing out of their sample chambers.

Once the experiments are taken aboard the Space Station, a crewmember will open the front of each STES unit and rotate a shaft on the end of each cylinder with a socket wrench. This loosens the seals and allows evaporation to begin. Once all cylinders are activated, the STES units are closed and the samples left to crystallize. Near the end of the mission, the procedure is reversed to deactivate the experiments and reseal the chambers for the return to Earth.

Flight History

Mission: STS-63
Days in Space: 8.27
No. of Samples: 378

Mission: STS-67
Days in Space: 16.63
No. of Samples: 378

Mission: STS-73
Days in Space: 15.91
No. of Samples: 756

Mission: STS-83
Days in Space: 3.23
No. of Samples: 630

Mission: STS-85
Days in Space: 11.85
No. of Samples: 630

Mission: STS-95
Days in Space: 8.91
No. of Samples: 378

Benefits

With science being performed on the International Space Station, scientists are no longer restricted to relatively short-duration flights to conduct structural biology experiments. This research will enable the more accurate mapping of the 3-dimensional structure of macromolecules. Once the structure of a particular macromolecule is known, it may become much easier to determine how these compounds function. Every chemical reaction essential to life depends on the function of these compounds.

More Information

Additional information on structural biology and crystal growth in microgravity is available at:

http://crystal.nasa.gov/
http://www.microgravity.nasa.gov/

A photo of a PCAM experiment tray is available at:

http://www.ssl.msfc.nasa.gov/msl1/images/pcambig.jpg

Additional information on expedition experiments is available at:

http://www.scipoc.msfc.nasa.gov/
http://www.spaceflight.nasa.gov/