Protein Crystal Growth (PCG) GN2 Dewar

Objectives

The objective of this experiment was to grow a large variety of protein and virus crystals in microgravity. This experiment was designed to establish the optimal conditions for crystallization for a wide spectrum of protein molecules and obtain large crystals to compare to crystals grown on the ground. Finally, this experiment evaluated the effectiveness of flash-frozen batch and liquid-liquid diffusion techniques.

Shuttle-Mir Missions
STS-71, STS-74, STS-76, STS-79, STS-81, STS-84, STS-89

Approach
Protein samples were placed in capillary tubing, the tubing was sealed, and the samples were frozen with liquid nitrogen. Individual protein samples, held in capillary tubes, were placed in the Dewar freezer which were designed to keep the protein samples frozen from the time of space vehicle loading to orbit. Each sample consisted of a protein solution (i.e. enzymes, hormones, viruses, etc. ) and a precipitating solution, used to induce crystallization. The Dewar was carried up to the Mir Space Station during the Shuttle flights. It was moved to the Kvant module where it was left for the duration of the mission. The Dewar has a two-week period before the samples start to thaw. Once the samples thaw in orbit, a liquid-liquid diffusion takes place between the protein solution and the precipitating solution. Protein and precipitant solutions, concentrations, volumes, pH and aspect ratios were varied per each sample to develop the best combinations. Resultant protein crystals were analyzed post-mission at various laboratories. Below is a summary of the Dewar flight history:

Flight, date # of samples # of proteins
STS-71 (6-27-95) 183 19
STS-74 (11-5-95) 166 16
STS-76 (3-22-96) 275 20 (2 units flown)
STS-79 (9-16-96) 285 11
STS-81 (1-12-97) 220 8
STS-84 (5-15-97) 107 11
STS-89 (1-22-98) 150 16

Results
Approximately 80% success in terms of obtaining crystals of different macromolecule samples. Significant size and/or X-ray quality enhancement for approximately 15% of macromolecules flown.

The Liquid-Liquid Diffusion and Batch Techniques for PCG are well suited to long-duration missions remaining stable for months. A very large number or volume of experiments can be performed with minimal hardware or on-orbit resources.

Earth Benefits
Scientists have discovered that growing some protein crystals in microgravity result in better quality crystals than on the ground. Protein crystals are used in the process for the development of therapeutic drugs. By growing protein crystals in space that cannot be grown on the ground, scientists can develop new drugs to treat diseases.

Publications
Koszelak, S., Leja, C. and McPherson, A. Crystallization of biological macromolecules from flash frozen samples on the Russian Space Station Mir. Biotechnology and Bioengineering 52, 449-458 (1996).

McPherson, A. Macromolecular crystal growth in microgravity. Crystallography Reviews, 6(2) 157-308 (1996).

McPherson, A. Recent Advances in the Microgravity Crystallization of Biological Macromolecules. Trends in Biotechnology TIBTECH. 15 No. 6(161), pp. 197-237 (1997).

Principal Investigators
Alexander McPherson, Ph.D.
University of California at Irvine

Co-Investigators
Stan Koszelak, Ph.D.

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Page last updated: 07/16/1999

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