Crystal Quality Versus Crystal Size: Results of Short Duration Versus Long Duration Crystal Growth of Bacteriorhodopsin in Space Shuttle (CPCF) and MIR Station (DCAM) Experiments

Christian Zörb, Andrea Weisert, Katja Brunner, and Gottfried Wagner

Department of Biology, Chemistry, and Geological Sciences, Justus-Liebig-University, Senckenbergstr. 17, D-35390 Gießen, Germany


Two crystal habits of bacteriorhodopsin were grown in a Space Shuttle and a MIR station liquid-liquid-diffusion experiment, namely individual needle-shaped crystals with lengths of up to 1.9 mm and clustered bunches of multi-nucleated needles with lengths of up to 4.9 mm. As shown earlier, morphology of the individual needles had improved in micro-gravity in terms of sharp needle edges and compact needle packing, compared to the ground controls.

For DCAM on MIR, the average values of length of individual needles, of length of needle clusters and of needle cluster compactness varied inconsistently with the gravity conditions: e.g., needle clusters on average were longer in micro-gravity than on ground, while compactness of the clusters, i.e. the average ratio of clustered length to clustered width, had improved on ground compared to micro-gravity. Slow diffusion in DCAM produced some exceptionally large individual needles, almost twice the size of the largest CPCF needles.

For CPCF in micro-gravity of the Space Shuttle, size and shape of the individual needles turned out of even quality superior to that of the ground controls and the results in DCAM. Evenness and efficiency of the crystals grown in micro-gravity were little affected by variation of the gradient of crystallising agent used, i.e. crystallant AmSO4, but had considerable effect in the parallel ground controls. Cluster compactness had significantly improved, depending on the equilibrium crystallant concentration, either in favour of the ground control or the micro-gravity experiment. In CPCF, average volume of the individual type of needles in suspension was increased by 50 % in micro-gravity compared to the ground control.