Effect of convective disturbances induced by g-jitter on the periodic precipitation of lysozyme |
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Authors: | Email author" target="_blank">Marcello?LappaEmail author L?Carotenuto |
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Affiliation: | (1) MARS Center, Via Gianturco 31, 80146 Napoli, Italy |
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Abstract: | Numerical simulations are carried out to investigate the crystallization process of a protein macromolecular substance under
two different conditions: pure diffusive regime and microgravity conditions present on space laboratories. The configuration
under investigation consists of a protein reactor and a salt chamber separated by an “interface”. The interface is strictly
related to the presence of agarose gel in one of the two chambers. Sedimentation and convection under normal gravity conditions
are prevented by the use of gel in the protein chamber (pure diffusive regime). Under microgravity conditions periodic time-dependent
accelerations (g-jitter) are taken into account. Novel mathematical models are introduced to simulate the complex phenomena
related to protein nucleation and further precipitation (or resolution) according to the concentration distribution and in
particular to simulate the motion of the crystals due to g-jitter in the microgravity environment. The numerical results show
that gellified lysozyme (crystals “locked” on the matrix of agarose gel) precipitates to produce “spaced deposits”. The crystal
formation results modulated in time and in space (Liesegang patterns), due to the non-linear interplay among transport, crystal
nucleation and growth. The propagation of the nucleation front is characterized by a wavelike behaviour. In microgravity conditions
(without gel), g-jitter effects act modifying the phenomena with respect to the on ground gellified configuration. The role
played by the direction of the applied sinusoidal acceleration with respect to the imposed concentration gradient (parallel
or perpendicular) is investigated. It has a strong influence on the dynamic behaviour of the depletion zones and on the spatial
distribution of the crystals. Accordingly the possibility to obtain better crystals for diffraction analyses is discussed. |
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