Silaffins, Cylindrotheca fusiformis

Some non-silica sol-gel materials have also been developed to immobilize bioactive molecules for the construction of biosensors and to synthesize new catalysts for the functional devices. Liu et al. [33] proved that alumina sol-gel was a suitable matrix to improve the immobilization of tyrosinase for detection of trace phenols. Titania is another kind of non-silica material easily obtained from the sol-gel process [34, 35], Luckarift et al. [36] introduced a new method for enzyme immobilization in a bio-mimetic silica support. In this biosilicification process precipitation was catalyzed by the R5 peptide, the repeat unit of the silaffin, which was identified from the diatom Cylindrotheca fusiformis. During the enzyme immobilization in biosilicification the reaction mixture consisted of silicic acid (hydrolyzed tetramethyl orthosilicate) and R5 peptide and enzyme. In the process of precipitation the reaction enzyme was entrapped and nm-sized biosilica-immobilized spheres were formed. Carturan et al. [11] developed a biosil method for the encapsulation of plant and animal cells. 

It is well known that a variety of organisms are able to produce intricately patterned species-specific siliceous materials and that they are able to do so with great fidelity. In order to understand the role(s) that biomolecules play in the formation of nano- and micro-structured biosilica, organic material associated with biosilica has been isolated, identified and studied. To date, the main focus has been a variety of investigations of R5 (in both its modified and unmodified forms) and its ability to form silica in vitro. The R5 peptide is a nineteen amino acid sequence which corresponds with silaffin-lAi of the diatom Cylindrotheca fusiformis. In order to study the role of biomolecules in (bio)silicification, we have chosen to systematically study the silica forming ability of three peptides derived fi om the diatom C. fusiformis - namely, Rl, R2, and R5. The R1 peptide is a thirty three amino acid... 

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