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Fluid Physics and Macromolecular Crystal Growth in MicrogravityThe molecular structure of biological macromolecules is important in understanding how these molecules work and has direct application to rational drug design for new medicines and for the improvement and development of industrial enzymes. In order to obtain the molecular structure, large, well formed, single macromolecule crystals are required. The growth of macromolecule crystals is a difficult task and is often hampered on the ground by fluid flows that result from the interaction of gravity with the crystal growth process. One such effect is the bulk movement of the crystal through the fluid due to sedimentation. A second is buoyancy driven convection close to the crystal surface. On the ground the crystallization process itself induces both of these flows. Buoyancy driven convection results from density differences between the bulk solution and fluid close to the crystal surface which has been depleted of macromolecules due to crystal growth. Schlieren photograph of a growing lysozyme crystal illustrating a 'growth plume' resulting from buoyancy driven convection. Both sedimentation and buoyancy driven convection have a negative effect on crystal growth and microgravity is seen as a way to both greatly reduce sedimentation and provide greater stability for 'depletion zones' around growing crystals. Some current crystal growth hardware however such as those based on a vapor diffusion techniques, may also be introducing unwanted Marangoni convection which becomes more pronounced in microgravity. Negative effects of g-jitter on crystal growth have also been observed. To study the magnitude of fluid flows around growing crystals we have attached a number of different fluorescent probes to lysozyme molecules. At low concentrations, less than 40% of the total protein, the probes do not appear to effect the crystal growth process. By using these probes we expect to determine not only the effect of induced flows due to crystal growth hardware design but also hope to optimize crystallization hardware so that destructive flows are minimized both on the ground and in microgravity.
Document ID
Document Type
Conference Paper
Pusey, M.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Snell, E.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Judge, R.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Chayen, N.
(Imperial Coll. of Science, Technology and Medicine London, United Kingdom)
Boggon, T.
(Manchester Univ. United Kingdom)
Date Acquired
August 20, 2013
Publication Date
December 1, 2000
Publication Information
Publication: Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference
Subject Category
Fluid Mechanics And Thermodynamics
Distribution Limits
Work of the US Gov. Public Use Permitted.

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