APCF-PPG10 (ZAGARI)
Early published results have come out for crystals of (Pro-Pro Gly) 10 (PPG10). PPG10 is a
collagen protein found in many tissues. This collagen is particularly concentrated in the skin,
joints, and bones. Video that was collected during
Expedition 3 showed the small movements within the
crystallizing solutions. A direct correlation between crystal
motion and acceleration from events on station (such as
docking, venting, and crew movement) was determined for
the first time. The PPG10 crystals were independently
studied by X-ray diffraction in various labs; the best
resolution attained for microgravity-grown crystals from
ISS was 1.5A, superior to the 1.7A obtained on the ground.
The teams of APCF scientists are combining data from
previous spaceflights, the ground, and the station to get
the best possible information on protein structures for
applications in pharmaceutical and physiological research
(Vergara 2005).
PPG10 crystals grown aboard the ISS were observed to
move coherently and followed parallel trajectories, which was different from movements
observed aboard the shuttle. These movements have been linked to large-scale acceleration
events such as the undocking of the shuttle, change in ISS attitude, and the venting of water
and air. Final distribution of the crystals in solution was strongly affected by this motion. Crystal
appearance time and growth rate was comparable in all crystal environments (agarose gel in
microgravity, solution on Earth and agarose gel on Earth). These observations suggest that the
crystal growth mechanism is kinetically controlled (Vergara 2002, Berisio 2002).
Using 2 other experiment aboard ISS Microgravity Acceleration Measurement System
(MAMS)—which measured residual gravity on the experiment—and Space Acceleration
Measurement System (SAMS )—which measured acceleration caused by space craft docking
and undocking, change in ISS attitude, venting, and crew movement—a direct correlation
between crystal motion and acceleration was determined for the first time. However, this
paper reports that there is no apparent correlation between the resulting crystal motions and
crystal quality.
APCF-RHODOPSIN (DE GRIP)
Even though the reactors successfully produced small crystals on Earth, they did not perform
well during their stay on ISS Expedition 3. Apparently, slight technical problems developed that
lead to minor leakage of the protein chamber. Slow destabilization of the rhodopsin protein
occurred that prevented formation of suitable crystals (One Year Postflight Report).
PUBLICATION(S)
Vergara A, Lorber B, Sauter C, Giege R, Zagari A. Lessons from crystals grown in the Advanced
Protein Crystallisation Facility for conventional crystallization applied to structural biology.
Biophysical Chemistry. 2005;118(2-3):102-112. doi: 10.1016/j.bpc.2005.06.014.
PPG10 crystals grown in microgravity,
in reactor number 612 containing
agarose gel. NASA image.