The HH-DTC is a sophisticated apparatus designed to let scientists
take a close look at how liquids diffuse into each other. The individual
cells comprise a chamber with a rotating center section so sections of the
fluid can be isolated from each other until the start of the experiment
and after the end.
The cells are made from optical-quality plastic so they can be photographed during the experiment. Each cell has a small light-emitting diode and lens to back-light the solution.
Diffusion is what happens when molecules and atoms elbow their way from the source, where they are concentrated, into an area where they are absent. The effect is most noticeable when a person wearing a strong cologne enters a room and soon everyone can smell it.
In protein crystal growth experiments, the diffusion can be altered by using a solution, such as salt water, that will absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules join to form crystals.
With the HH-DTC, pictured above, scientists will investigate different solutions and mixtures as they look for the best recipe for crystallizing different proteins. HH-DTC actually is the forerunner of a more advanced Observable Protein Crystal Growth Apparatus planned for use aboard International Space Station.
Operation of HH-DTC is simple. Eight cells are carried in an assembly, and three assemblies will be aboard the Shuttle. An astronaut will use a hand crank to rotate the center shaft of each cell 90 degrees to form a single, straight volume. Two HH-DTC assemblies will be in a temperature-controlled locker, and a third will be in the cabin so the crew can photograph what happens as the three fluids in each cell meet.
The principal investigator for the HH-DTC is Dr. Alexander McPherson of the University of California at Riverside Biochemistry Department. The project scientist is Bill Witherow of Marshall's Space Sciences Laboratory.
Author: Dave
Dooling
Curator: Bryan Walls
NASA Official: John M. Horack