Abstract
Diatoms are unicellular, eukaryotic algae arisen from secondary endosymbiotic event and widespread in aquatic environment. Diatoms possess diverse array of nanopatterned solid silica structures in their outer shell. The gene silaffin-1 obtained from a diatom Cylindrotheca fuciformis encodes heptad repeat structure of relatively short strength polypeptide and this repeat unit is known to exist in silica shell of diatom and to form rapidly solidified spherical silica (biosilica) in vitro. Relationship between repeat structure of Silaffin and activity to form biosilica is so far not known. In this study, we constructed single repeat type and 7-repeat type of the silaffin genes and expressed these genes in E. coli. Obtained recombinant peptide formed biosilica in the presence of O-tetramethyl silicate (TMOS). Biosilica forming activities were further related to physicochemical conditions such as pH and temperature during reaction and to repeat unit numbers of silaffin. We further attempted to immobilize enzymes within biosilica.
