Bioinspired Silicificationof Silica-Binding Peptide-SilkProtein Chimeras: Comparison of Chemically and Genetically ProducedProteins.

Novel protein chimeras constituted of “silk”anda silica-binding peptide (KSLSRHDHIHHH) were synthesized by geneticor chemical approaches and their influence on silica-silk based chimeracomposite formation evaluated. Genetic chimeras were constructed from6 or 15 repeats of the 32 amino acid consensus sequence of Nephila clavipesspider silk ([SGRGGLGGQG AGAAAAAGGA GQGGYGGLGSQG]n) to which one silica binding peptide wasfused at the N terminus. For the chemical chimera, 28 equiv of thesilica binding peptide were chemically coupled to natural Bombyx morisilk after modification of tyrosine groups bydiazonium coupling and EDC/NHS activation of all acid groups. Aftersilica formation under mild, biomaterial-compatible conditions, theeffect of peptide addition on the properties of the silk and chimericsilk-silica composite materials was explored. The composite biomaterialproperties could be related to the extent of silica condensation andto the higher number of silica binding sites in the chemical chimeraas compared with the genetically derived variants. In all cases, thestructure of the protein/chimera in solution dictated the type ofcomposite structure that formed with the silica deposition processhaving little effect on the secondary structural composition of thesilk-based materials. Similarly to our study of genetic silk basedchimeras containing the R5 peptide (SSKKSGSYSGSKGSKRRIL), the roleof the chimeras (genetic and chemical) used in the present study residedmore in aggregation and scaffolding than in the catalysis of condensation.The variables of peptide identity, silk construct (number of consensusrepeats or silk source), and approach to synthesis (genetic or chemical)can be used to “tune” the properties of the compositematerials formed and is a general approach that can be used to preparea range of materials for biomedical and sensor-based applications. [ABSTRACT FROM AUTHOR]