Protein crystallisation under microgravity conditions: What did we learn on TIM crystallisation from the Soyuz missions?

The protein Triose Phosphate Isomerase from the hyperthermophilic organism Thermotoga maritima was crystallised on board of the International Space Station in the framework of the Soyuz missions. In this paper we report on the scientific results obtained during these flights. Firstly it was shown that different crystallisation techniques and environments can result in different crystal forms for the same protein in the same crystallisation conditions, what is presumably due to a change in the rate at which supersaturation is achieved. Secondly, the X-ray quality of the crystals grown in the ISS is superior to their ground control crystals. Mimicking microgravity on ground, by adding a small amount of gel to avoid convection, also results in an improvement of X-ray quality. Nevertheless our analysis shows that the crystals obtained in this gelled ground environment are of inferior quality as compared to their space homologues. Finally we observed movement of crystals grown in the International Space Station, not only because of g-jitters but also due to residual accelerations. This has an important effect on concentration gradients of precipitants and therefore on the solubility of the protein.