Influence of Selected Artificial Peptides on Calcium Carbonate Precipitation - A Quantitative Study

Calcium carbonate is an abundant biomineral with fascinating shapes and properties. Much effort is spent to study how creatures can control mineral formation. We present a quantitative study of the early stage of calcium carbonate precipitation in the presence of artificial peptide additives, the sequences of which were derived in phage assays to have aragonite binding affinity. A novel crystallization assay shows that the peptide additives inhibit nucleation of calcite. Analysis of the precipitated particles and comparison with nucleation inhibition confirm our recent findings, which suggest that calcitic and vateritic short-range order is already preformed in stable prenucleation clusters, which form amorphous intermediates after nucleation reflecting similar structures and finally become crystalline. In the long run, this process facilitates the control of polymorph formation by the design of the binding affinity of additives to different polymorphs (i.e., the polymorph bound weakest by the additive is to be formed as its formation is least inhibited). These findings facilitate a novel understanding of mineralization control and provide a basis for the analysis of biological peptide sequences and for the analysis of their role in biomineralization processes.