An Investigation of the Perfection of Lysozyme Protein Crystals Grown in Microgravity and on Earth

摘要

Lysozyme has been used to investigate the effect of microgravity crystallisa-tion on protein crystal perfection. Crystals were grown in the European Space Agency's Advanced Protein Crystallisation Facility onboard the NASA Space Shuttle. Two missions of differing duration took place, Spacehab-1 and IML-2. The microgravity crystallisation time in each was 7 days and 10 hours, and 12 days and 11 hours respectively. The IML-2 crystals had grown much larger than the Spacehab-1 crystals (2.5 mm versus 0.8 mm at maximum). The earth grown control crystals, in each case, reached a size of 0.8 mm at maximum. The perfec-tion of the crystals was evaluated with collimated, intense, synchrotron radiation. This was done using the Laue method, via the spot size, and by monochromatic rocking widths directly. For the Spacehab-1 crystals spot size measurements were carried out on station 9.5 of the SRS, along with an analysis of intensity to sigma ratio, immediately after the mission. Five months later rocking widths were measured at LURE. The IML-2 crystals were evaluated at the ESRF, on BL3 three months after their return to earth and also a further three months later on the joint Swiss-Norwegian beamline. Both the Spacehab-1 and IML-2 crystals were of exceptional perfection with the crystal mosaicity reaching val- ues as small as 0.0010° and 0.0017° respectively. Earth-grown control crystals had values as small as 0.0032° and 0.007° respectively. There is no evidence of 'shelf-life' ageing of the crystals, at least over a period of 6 months, since there is close agreement of the mosaicity values from the Spacehab-1 crystals tested within weeks of that mission and the IML-2 crystals tested 6 months after that mission. The perfect mosaic block size has evidently increased over that realised in the earth-grown controls.