The formation of silica-based cell walls in marine, single celled organisms, is regulated by protein-mineral interactions. The diatom species Cylindrotheca fusiformis assembles supermolecular silica structures via proteins called sillafins. In a silicic acid solution, specific repeat units within this protein, SSKKSGSYSGSKGSKRRIL (R5), induce the formation of silica-protein composite nanoparticles. The protein-surface interaction that drives self-assembly is likely controlled by specific contacts between the surface atoms and key protein side chains. In this study, we characterized this R5-SiO2 interaction by both near edge x-ray absorption fine structure (NEXAFS) spectroscopy and in situ sum frequency generation (SFG) spectroscopy. Two peaks within the amide I vibrational band of the SFG spectra, 1640 and 1670 cm-1, indicate that the R5 peptide retains a beta sheet conformation when interacting with SiO2. While details of the binding geometry of the single tyrosine within R5 is provided by the observed polarization dependence of the NEXAFS C1s to p* transition related to the tyrosine's phenyl ring.

Characterizing the protein-surface interactions that control diatom biomineralization<i> </i>

245th National Meeting (2013)

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