Influence of active sites distribution on CaCO3 formation under model biofilms at the air/water interface

In an approach to understand the influence of structural parameters of interfaces on calcification in biomineralisation, the distribution of COOH groups as active sites in an inert matrix was varied using two-component lipid model monolayers. Octadecanoic acid (ODA) and octadecyl succinic acid (OSA), respectively, were the active components, and methyl octadecanoate (MOD) the inactive matrix. Surface pressure-area isotherms provide evidence for a different distribution of the active components in the matrix. Formation of solid calcium carbonate (CaCO3) with two-component monolayers on subphases containing aqueous CaCO3 was observed in situ by Brewster angle microscopy, where CaCO3 domains appear bright. Striking differences in kinetics and extent of CaCO3 formation were observed between monolayers containing ODA and those containing OSA of the same average surface density of COOH groups.