Kinetics of Calcite Nucleation onto Sulfated Chitosan Derivatives and Implications for Water–Polysaccharide Interactions during Crystallization of Sparingly Soluble Salts

Description:

Anionic macromolecules are found at sites of CaCO3 biomineralization in diverse organisms, but their roles in crystallization are not well-understood. We prepared a series of sulfated chitosan derivatives with varied positions and degrees of sulfation, DS(SO3 -), and measured calcite nucleation rate onto these materials. Fitting the classical nucleation theory model to the kinetic data reveals the interfacial free energy of the calcite -polysaccharide -solution system, γ net , is lowest for nonsulfated controls and increases with DS(SO3 -). The kinetic prefactor also increases with DS(SO3 -). Simulations of Ca 2+ -H2O -chitosan systems show greater water structuring around sulfate groups compared to uncharged substituents, independent of sulfate location. Ca 2+ -SO3 -interactions are solvent-separated by distances that are inversely correlated with DS(SO3 -) of the polysaccharide. The simulations also predict SO 3 -and NH3 + groups affect the solvation waters and HCO3 -ions associated with Ca 2+ . Integrating the experimental and computational evidence suggests sulfate groups influence nucleation by increasing the difficulty of displacing near-surface water, thereby increasing γ net . By correlating γ net and net charge per monosaccharide for diverse polysaccharides, we suggest the solvent-separated interactions of functional groups with Ca 2+ influence thermodynamic and kinetic components to crystallization by similar solvent-dominated processes. The findings reiterate the importance of establishing water structure and properties at macromolecule -solution interfaces.

Publications:

• Brenna M. Knight; Ronnie Mondal; Nizhou Han; Nicholas F. Pietra; Brady A. Hall; Kevin J. Edgar; Valerie Vaissier Welborn; Louis A. Madsen; James J. De Yoreo; Patricia M. Dove; Kinetics of Calcite Nucleation onto Sulfated Chitosan Derivatives and Implications for Water–Polysaccharide Interactions during Crystallization of Sparingly Soluble Salts; Crystal Growth & Design, 2024

Tags:

Carbohydrates Mineralization Modeling and Simulation Nucleation

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