ISS Research Results: Protein Crystal Growth-Enhanced Gaseous Nitrogen (PCG-EGN) Dewar

Results

PCG-EGN
dewar was delivered by the Shuttle Atlantis on April 10, 2002. Students
participating in the Student Access
to Space program loaded and froze the samples during workshops held
in January and February 2002. This
will be PCG-EGN’s fourth trip to the Station.

The
first flight of PCG-EGN, during Increment 0 while the Station underwent
initial construction, was meant to be a risk mitigation flight to test
the dewar’s performance and to map out the hanging drop crystallization
method to be used in future flights. Bubbles spanning the diameter of
the sample tubes had formed in all the tubes. Such bubbles tend to interrupt
the liquid-liquid diffusion, but despite this, crystals grew in 9 of the
30 tubes. The researchers reported large crystals, including some as large
as 2.0 x 1.1 x 1.0 mm³. 

Shuttle
experiments suggest that the dewar system combined with long-duration
flights made possible by the ISS,
which allow much longer equilibration times,
will help researchers avoid difficulties faced by other protein crystal
growth systems.  Previous experiments using the Dewar have resulted
in larger crystals with improved resolution of 0.5 to 1.0 Å (i.e.,
better-ordered, higher-quality) over crystals grown from the same solution
on Earth.

Applications

Crystals
grown in space are usually larger and better-ordered than those grown on
Earth, allowing researchers to examine them using a variety of methods,
including X-ray diffraction, electron microscopy, and atomic force microscopy. 
Mapping the three-dimensional and chemical structures of proteins, viruses,
and nucleic acids help researchers to design drugs and medical treatments,
create more effective pesticides, as well as to better understand the basic
biochemical processes of plants and animals. 

PCG-EGN
is one of several systems being tested on the ISS.  The wide range
of crystal-growth experiments being conducted in different systems will
allow researchers to determine the best and most economical methods for
growing each type of protein crystal.  The PCG-EGN dewar is a low-cost
platform that requires minimal Station space, resources, and crew time,
making it a desirable research option for a wide range of protein crystal
growth experiments.

PCG-EGN
is also one of the experiments flown on Station to offer students hands-on
access to science being conducted in space. Since its first flight in
1999, the PCG-EGN has housed biological samples mixed by students from
across the United States. The program, Student Access to Space, is sponsored
by the Microgravity Research Program Office at NASA Marshall Space Flight
Center, NASA’s Office of Biological and Physical Research, as well as
educational and corporate institutions. Student Access to Space offers
lesson plans and experiment kits that help students conduct crystal growth
experiments in the classroom. Based on their in-class studies, students
may enter the essay contest, which determines the teams that will go to
Marshall Space Flight Center and participate in a workshop led by the
PCG-EGN principal investigator, Alexander McPherson, and help mix protein
solutions to fly in the dewar. The newest feature provided by the program
is a Web site that allows students to monitor the in-flight results of
the experiment. "Involving students in the first Space Station experiment
is a great way to teach them biochemistry and show them how our first
permanent outpost in space can be used for research," stated McPherson.
The student participants in the last flight of the PCG-EGN dewar were
also invited to Kennedy Space Center to watch their experiments be launched
on STS-98. "We really try to make it a very special experience for
them," said Greg Jenkins, student project manager for the EGN Dewar
experiments, "because they’ve overcome peer pressure in doing science,
and we’d really like for it to get back that these students are receiving
something good from science."

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