Influence of Charged Polypeptides on Nucleation and Growth of CaCO₃ Evaluated by Counterdiffusion Experiments

Abstract

Many mineralization processes occur in convection-free conditions. Understanding these processes requires knowledge of crystal nucleation and growth processes in gels or high viscous sol systems. In this work, the crystallization parameters of calcium carbonate in an agarose viscous sol using counterdiffusion crystallization were monitored as a function of time. Additionally, by comparing the precipitation parameters in the high viscous sol entrapping charged polypeptides, namely, poly-L-lysine (pLys), poly-Laspartate (pAsp), and poly-L-glutamate (pGlu), it was possible to establish the polypeptide capability to inhibit, or eventually promote, the calcium carbonate nucleation and/or crystal growth processes. The polymorphism and morphology of the precipitates indicate that pLys only influences the growth mechanism of calcium carbonate without affecting the nucleation process. On the contrary, pAsp and, to a minor extent, pGlu affect both nucleation and growth. The application of this analysis can be extended to other additives and macromolecules able to affect crystallization processes.

Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate: Implications for their use as paleoclimatic proxy

“…However, the large crystal size reached by silica hydrogel precipitates is an important advantage that allows for hand-picking of selected CaCO 3 polymorphs. Recent efforts that were aimed at resolving the evolution of physicochemical conditions within silica hydrogel systems prior and during crystallization (Sancho-Tomás et al, 2013;Gebrehiwet et al, 2014) have greatly facilitated a more accurate timing and spatial understanding of the conditions needed for initiation of crystallization, further allowing to implement simple algorithms in geochemical codes (PHREEQC, Parkhurst and Appelo, 1999). However, despite these improvements, it is still not possible to give a quantitative account of their evolution once the first crystals start to grow and new crystals simultaneously form in other places of the precipitation region.…”

Effects of Mg and Hydrogel Solid Content on the Crystallization of Calcium Carbonate in Biomimetic Counter-diffusion Systems

“…Differences in threshold supersaturation between experiments can be qualitatively estimated by considering changes in the waiting time for the first visible crystal (t w ). 12,44 Since the longer the mass transfer operates, higher amounts of reagent are delivered to the region of the hydrogel where crystallization takes place, higher t w values amount to higher threshold supersaturations. Nindiyasari et al have recently shown that an increase in the solid content of gelatin hydrogels results in a more complex porosity, with smaller pores and thicker pore walls, and leads to higher threshold supersaturation values.…”

Crystallization of Calcium Carbonate in Alginate and Xanthan Hydrogels

“…The initial supersaturation was defined as relative supersaturation, S = (Π/K sp ) 1/2 , where Π is the ion activity product, Π = a(Ca 2+ )·a(CO 3 2− ), and K sp is the thermodynamic solubility product of calcite (K sp = 3.313 × 10 −9 ), vaterite (K sp = 1.221 × 10 −8 ) or amorphous calcium carbonate (ACC) (K sp = 3.976 × 10 −7 ) [37] at 25 • C. Detailed calculation procedure, which considers the respective protolytic equilibria and equilibrium constants, as well as the charge and mass balance equations, was shown previously [56,57]. However, it should be emphasized that in the case of precipitation in gels, the presence of the respective polysaccharide was not considered so the calculated initial supersaturation is given only for comparison with bulk precipitation experiments.…”

“…Double-diffusion of calcium and carbonate ions into the polyacrylamide hydrogels of different polymer content has been investigated and a correlation between morphology of precipitate and hydrogel concentration was found [35]. A similar experimental setup was also applied in the agarose hydrogel system in order to estimate the impact of porosity on the properties of mineral phase and to correlate it with supersaturation profile and presence of additives [36,37]. Besides the above-mentioned two-step protocols, simultaneous gel and CaCO 3 formation has also been described.…”