PROTEIN CRYSTAL GROWTH-ENHANCED GASEOUS NITROGEN DEWAR (PCG-EGN), THIRTY
INVESTIGATIONS
Research Area: Macromolecular Crystal Growth
Expedition(s): 0-2 and 4
Principal Investigator(s): ● Alexander McPherson, PhD, University of California at Irvine,
Irvine, California
RESEARCH OBJECTIVES
The Protein Crystal Growth-Enhanced Gaseous Nitrogen
Dewar (PCG-EGN) experiment tests proteins and protein
solutions to determine if they can tolerate the freeze-thaw
mechanism used to initiate protein crystal experiments.
Understanding these results can lead to a better selection
process for later protein crystal experiments on the
International Space Station (ISS).
EARTH BENEFITS
Knowledge of precise 3-D molecular structure is a key
component in biotechnology fields such as protein
engineering and pharmacology. In order to obtain accurate
data on the 3-D structure of protein crystals or other macromolecules, scientists employ a
process called X-ray Crystallography. Crystallographers construct computer models that reveal
the complex structures of a protein molecule. However, in order to generate accurate
computer models crystallographers must first crystallize the protein and analyze the resulting
crystals by a process called X-ray diffraction. Precise measurements of thousands of diffracted
intensities from each crystal help scientists map the probable positions of the atoms within
each protein molecule. This complex process requires several months to several years to
complete.
On Earth, the crystallization process is hindered by forces of sedimentation and convection
since the molecules in the crystal solution are not of uniform size and weight. This leads to
many crystals of irregular shape and small size that are unusable. However, the microgravity
environment aboard the ISS is relatively free from the effects of sedimentation and convection
and provides an exceptional environment for crystal growth.
SPACE BENEFITS
Hardware that provides low-cost and low-crew maintenance crystal production in the
microgravity environment is extremely beneficial to scientific studies on Earth. The crystals that
are grown in microgravity grow larger and are better organized than those grown on Earth. The
research that is done on these crystals may further human space exploration efforts by
technological and biological advancements developed as a direct result of this research.
Electron density map of thaumatin
crystal grown on the International
Space Station on Increment 2. NASA
Marshall Space Center image.