Lysozyme crystal growth kinetics in microgravity

Abstract

Mach-Zehnder interferometry is applied to quantitatively characterize growth of lysozyme crystals in microgravity. Experiments were performed by the Free Interface Diffusion technique into APCF FID reactors using large seeds. Tracking of the experiments using interferometry allowed to monitor the onset of supersaturation and the seed growth. A large and stable concentration depletion zone around the growing crystal developed, whose time evolution was analyzed. The interferograms were analyzed taking into account finite thickness of the cell by integrating the concentration over the straight lines through the optical path. It was concluded that there may be a quasi-steady state growth mode at the stage when the spacial concentration distribution did not change but its absolute value over all the cell was slowly diminishing. From this portion of the data, an estimate was made of the dimensionless parameter beta R/D where beta is the face kinetic coefficient, R is the effective crystal size and D is the lysozyme diffusivity in solution, as followed from the steady state model. For the assumed quasi steady state data portion, the parameter varies between 0.7 and 0.9 suggesting mixed diffusion-interface kinetic controlled growth.

Crystallization in Gels

“…These improvements in the crystal quality are attributed to the gel-growth method for the following reasons: (1) within the hydrogel, mass transport is essentially controlled by diffusion; and (2) the protein concentration gradient (depletion zone) generated by each crystal during its growth is not destroyed by density-driven convective flow or by sedimentation [24][25][26]. These improvements in the crystal quality are attributed to the gel-growth method for the following reasons: (1) within the hydrogel, mass transport is essentially controlled by diffusion; and (2) the protein concentration gradient (depletion zone) generated by each crystal during its growth is not destroyed by density-driven convective flow or by sedimentation [24][25][26].…”

On the Quality of Protein Crystals Grown under Diffusion Mass-transport Controlled Regime (I)

“…The formation of a stable depletion zone in diffusive setups minimizes and stabilizes the supersaturation at the crystal/solution interface, reducing and making constant the growth rate, which kinetically favors the arrangement of molecules at the crystal surface and allows for efficient transport of impurities out of it. This is generally accepted as a factor enabling crystal perfection [17][18][19][20]. Therefore, it was concluded that the diffusive mass-transport conditions created during microgravity experiments are a key factor in obtaining good quality protein crystals [21,22].…”

Discrete layers of interacting growing protein seeds: Convective and morphological stages of evolution

“…The procedure usually employed in these studies consists in growing a very limited number ͑N͒ of "seeds" ͑see, for instance, the excellent works of Otálora et al ͓4,5͔,Lee and Chernov ͓6͔,etc.͒. In practice, multiple-nucleation events are obtained in gel ͓N = O͑100͔͒ usually by a counter diffusion technique ͑for further details about this technique and its models see, e.g., Refs.…”