PCAM is one of several devices developed to grow large numbers
of protein crystals for evaluation on Earth. Little crew involvement is
required with PCAM, and the specimens are completely mixed before they are
loaded aboard the Space Shuttle.
The basic PCAM hardware is a small plastic tray molded with seven sample
wells surrounded by moats and covered by a synthetic rubber seal.
The sample wells (shown at right, next to a U.S. quarter - click for
a larger image) hold a drop of protein solution and precipitant mixed together.
The moat holds a reservoir (using much the same material as a disposable
diaper) that absorbs water as it evaporates from the solution. To keep the
crystals from forming on Earth, or bouncing out of their wells, the rubber
seal is pressed onto the lip of the wells.
Nine PCAM trays are
carried in a cylinder (shown at left), and six cylinders are carried in
a temperature-controlled locker. Once in orbit, the astronauts use a wrench
to retract metal cams that hold the rubber seals in place. Near the end
of the mission, the cams are cranked back into place until the PCAMs are
returned to Marshall and then to the principal investigators for study.
Principal investigator for the PCAM experiment is Dr. Dan Carter of Marshall's
Space Sciences Laboratory.
Author: Dave
Dooling
Curator: Bryan Walls
NASA Official: John M. Horack