Experimental observations and numerical modelling of diffusion-driven crystallisation processes

Abstract

This paper reports experimental results and modelling on the crystallisation processes induced by counter diffusion method of a precipitant agent in a lysozyme protein solution. Comparison between experimental observations and numerical simulations in the presence of convection and sedimentation and without them (suppressed using gel) provides a validation of the model. Different values of the initial protein concentration are used, in order to investigate the effects of supersaturation conditions on the process, and in particular on nucleation. The model and the experimental approach may represent a useful methodology for the determination of the parameters and conditions that may lead to protein crystallisation. A Mach-Zehnder interferometer is used to monitor the transport dynamics in situ in the fluid phase by observing the compositional field. The effect of the solute transport gives rise to a "nucleation front" that propagates inside the protein solution. The crystal formation, caused by progressing of the front, results in a modulation in time and in space (similar to Liesegang patterns), due to the non-linear interplay among transport, crystal nucleation and growth. Both experimental observation and numerical modelling show spatial and size distributions of crystals that demonstrate comparable evidences of the phenomena.

On the variety of particle accumulation structures under the effect of g-jitters

“…Beyond practical applications, it is rather clear that these problems also exert an appeal on researchers and scientists as a consequence of the complexity of the possible stages of evolution, of the non-linear behavior and because these organized particle structures are aesthetically and philosophically pleasing as well as irresistible to theoretical physicists (Balkovsky et al, 2001;Saw et al, 2008;Di Carlo et al, 2009). Moreover, the fact that strikingly well-ordered and similar phenomena are found also in other systems (not just physical, but also chemical and biological systems; see, e.g., Carotenuto et al, 2002;Lappa, 2003b and2011), indicates that these subjects really stand at the intersection of many scientific branches (which make them a multi-domain field of investigations and a truly interdisciplinary science).…”

Femtosecond laser-induced nucleation of protein in agarose gel

“…At 24 h after the laser irradiation, some crystals were observed around the irradiated area, where some long-lasting bubbles remained. On the other hand, crystals nucleating spontaneously in a control sample still appeared up to the distance of about 8 mm from the end, suggesting that, in the region farther than 8 mm, the degree of supersaturation was insufficient to nucleate spontaneously [28]. It is also worth noting that the number and size of crystals decreased in both directions away from the irradiated area.…”

“…It is also worth noting that the number and size of crystals decreased in both directions away from the irradiated area. The observed distributions of size and number of crystals cannot be explained from the point of view of spontaneous nucleation [27][28][29][30], because supersaturation in the agarose gel drops the further the distance is from the end. Thus, these results strongly indicate that femtosecond laser irradiation induces nucleation in agarose gel in a metastable region, where spontaneous nucleation does not occur.…”

“…T-7638), and was used without further purification. A counterdiffusion method was adopted for crystallization in agarose gel [27][28][29][30]. A thaumatin solution at a concentration of 20 mg/ml was prepared in 0.1 M N-[2-acetamido]-2-iminodiacetic acid (ADA) adjusted to pH 6.5 with NaOH.…”

On the nature, formation and diversity of particulate coherent structures in microgravity conditions and their relevance to materials science and problems of astrophysical interest

“…In many industrial processes involving particle formation or solids handling, particles have a tendency to stick together or to accumulate in specific regions of the physical space. In protein crystallisation processes, macromolecules attach one another due to the supersaturated environment they are in (Carotenuto et al 2002, Lappa 2011. Suspension polymerisation processes go through a "sticky-phase" with significant agglomeration levels (Yuan et al 1991).…”