PROTEIN CRYSTAL GROWTH MONITORING BY DIGITAL HOLOGRAPHIC MICROSCOPE FOR THE
INTERNATIONAL SPACE STATION (PROMISS-1, -2, -3 AND -4), FOUR INVESTIGATIONS
Research Area: Macromolecular Crystal Growth
Expedition(s): 5, 7-9, 12
Principal Investigator(s): ● Juan M. Garcia-Ruiz, PhD, University of Granada,
Granada, Spain
● Fermin Otalora Munoz, University of Granada, Granada, Spain
● Ingrid Zegers, PhD, Free University, Brussels, Belgium
RESEARCH OBJECTIVES
The major objective of the Protein Crystal Growth Monitoring by Digital Holographic
Microscope for the International Space Station (PROMISS-1,-2,-3,-4) experiments is to produce
a detailed analysis and a quantitative interpretation of the relationship between the quality of
the obtained crystals and the environment in which they are produced by the method of digital
holography. The experiment aims to investigate the protein growth processes in weightless
conditions using the counter diffusion technique in order to measure the parameters of the
growing protein crystals and to measure the composition changes (depletion zone) of liquid
around the growing protein crystals.
RESULTS
The following results are based on the first 3
series of PromlSS experiments, which were
performed on 6 proteins: the complex of the
variable domain of a camelid heavy chain
antibody with Iysozyme (cablys3*lysozyme),
Thermotoga marirtima triose phosphate
isomerase (TIM), pike parvalbumin, hen egg
white Iysozyme, equine spleen ferritin, and
lumazine synthase. For 12 out of the 18
reactors flown (6 reactors per mission),
crystals were obtained in the right time frame.
The results showed that counter diffusion experiments can be useful not only for producing
crystals of higher quality, but also in cases where one wants to obtain a different crystal form
with improved (diffraction) properties. The effect of diffusive conditions was very extensively
investigated for the proteins TIM and cablys31ysozyme. For TIM, more than 100 datasets were
collected from crystals grown either in non-convective environments (in microgravity or in gels on
the ground) or by conventional techniques prone to convection. The results show that there is a
clear effect of diffusion, and the crystal perfection was higher for crystals grown in a non-
convective environment. Analysis of crystal growth rates and mass transport showed that the
depletion zone model cannot explain this, as TIM crystals essentially grew in a regime controlled
by surface growth rates. Diffusion is not rate-limiting and no depletion zone was formed. For
other proteins like cablys3lysozyme the influence of a diffusive environment was negligible.
Images of the activated reactors at their return to
Brussell’s. ESA image.