Growth of organic crystals in a microgravity environment

Precipitant-Controlled Growth of Lysozyme Crystals in Sodium Thiocyanate

“…2,5 The microgravity environment of space often dramatically decreases the rate of growth of crystals, and many investigators conjecture that this slow, diffusion-limited growth rate is the primary reason for improved quality in space grown crystals. [6][7][8] In mass transfer limited growth we can assume a simple film model for the mass transfer 9 :…”

“…To easily adapt the temperature control protocols to precipitant control, some simplifying assumptions are made about the system. First, it is assumed that slow growth rates are advantageous and lead to improved crystal quality. , The microgravity environment of space often dramatically decreases the rate of growth of crystals, and many investigators conjecture that this slow, diffusion-limited growth rate is the primary reason for improved quality in space grown crystals. − In mass transfer limited growth we can assume a simple film model for the mass transfer: where m is the mass of the crystal, k f is the film coefficient, A is the surface area of the crystal, C is the concentration of protein in the liquid phase, and C sat is the solubility of the protein under the particular thermodynamic conditions of the system at that moment in time. The mass and surface area of the crystal can be related to its size ( L ) via the crystal density (ρ = mass of protein per volume of crystal), volume shape factor ( k V = 8 for a cube), and area shape factor ( k A = 24 for a cube): Using these definitions and eq 1, the growth rate expression ( G ) can be related to the film model expression for a cube: Using the approach that proved successful in temperature-based CSC, it is assumed that only one crystal will form during the experiment resulting in a simple mass balance on the system:…”