Molecular Dynamics of Cation Hydration in the Presence of Carboxylated Molecules: Implications for Calcification

Autor: Adam F. Wallace, Laura M. Hamm, Patricia M. Dove
Rok vydání: 2011
Předmět:
Zdroj: MRS Proceedings. 1301
ISSN: 1946-4274
0272-9172
DOI: 10.1557/opl.2011.197
Popis: Biomolecules rich in aspartic acid (Asp) are known to play a role in biomineral morphology and polymorph selection, and have been shown to greatly enhance the growth kinetics of calcite. The mechanism by which these compounds favor calcification may be related to their effects upon cation solvation. Using molecular dynamics, we investigated the influence of small carboxylated molecules on the hydration states and water exchange rates of divalent cations. We show that the carboxylate moieties of Asp promote dehydration of Ca2+ and Sr2+ and that contact ion pair (CIP) formation is not required to disrupt the hydration of these cations. Ca2+- Asp and Sr2+ - Asp CIP formation decreases the total inner sphere coordination from an average of 8.0 and 8.4 in bulk water to 7.5 and 8.0, respectively. Water residence times estimated for Mg2+, Ca2+and Sr2+ follow the expected trend of decreasing residence time with increasing ionic radius. In the presence of Asp, both solvent-separated ion pair (SSIP) and CIP formation decrease the residence times of Ca2+and Sr2+ inner sphere water molecules. Comparable impacts on Mg2+ hydration are not observed. Mg2+ - Asp CIP formation is energetically unfavorable and Asp does not affect Mg2+ inner sphere water residence times.
Databáze: OpenAIRE
Externí odkaz: