Silica Polycondensation by Polycationic Peptides

Biomineralisation

Diatoms are unicellular photoautotrophic organisms that protect themselves by a silica-based cell wall. Besides amorphous SiO2 polymers, the cell wall contains long-chain polyamines and silaffins. The latter are short cationic peptides with characteris­tic post-translational modifications. Both polyamines and silaf­fins appear to be involved in the polymerization of monosilicic acid [Si(OH)4] to silica (Kröger et al., Proc. Natl. Acad. Sci. USA 97, 14133-14138, 2000; Kröger et al., J. Biol. Chem. 276, 26066-26070, 2001).

Starting out from recombinant silaffin, we construct peptides for initiating silica polymeriza­tion. Both the length of these peptides and their amino acid sequences are varied and assessed with regard to silica precipitation (Ref.: Roeder et al., 2014; Zerfaß et al; 2015). In collaboration with Prof. W. Tremel (Inorganic chemistry, Mainz JGU) we have constructed by „phage display“ a peptide which binds specifically to the polymorph of calcium carbonate, vaterite (Ref.: Schüler et al., 2014).