| AVS 58th Annual International Symposium and Exhibition | |
| Biomaterial Interfaces Division | Monday Sessions |
| Session BI-MoM |
| Session: | Biomolecules at Interfaces |
| Presenter: | Tobias Weidner, University of Washington |
| Authors: | T. Weidner, University of Washington M. Dubey, University of Washington K. Li, University of Washington J. Ash, University of Washington J.E. Baio, University of Washington C. Jaye, National Institute of Standards and Technology D.A. Fischer, National Institute of Standards and Technology G.P. Drobny, University of Washington D.G. Castner, University of Washington |
| Correspondent: | Click to Email |
Biomineralization proteins act as nature's crystal engineers and adsorb onto crystal surfaces with high binding affinity and precision using specific substrate-surface binding motifs. Owing to the importance of the underlying physiological processes and a general interest in biomineralization mechanisms, the binding of regulatory proteins has attracted significant interest. We have studied statherin, which regulates the growth of hydroxyapatite (HAP) in bone and tooth enamel and prevents the buildup of excess HAP by inhibiting spontaneous calcium phosphate growth. A detailed understanding of the underlying molecular recognition mechanisms would help bioengineers and scientists to devise new biomimetic approaches for clinical applications and biomineral nanofabrication. Sum frequency generation (SFG) spectroscopy can probe protein orientation and secondary structure at the solid-liquid interface and we have recently shown it can address specific protein regions with atomic resolution when combined with isotopic labeling and solid state NMR (ssNMR) data.(1) We have combined both techniques with near edge X-ray absorption fine structure (NEXAFS) spectroscopy to characterize the structure of the binding domain of statherin, SN-15, on HAP. Protein adsorption was verified using XPS and ToF-SIMS. NEXAFS N K-edge spectra clearly show that hydrogen bonding is important for the binding of both peptides. SFG confirmed an α-helical secondary structure of SN-15 on HAP with the helix axis parallel to the surface. Deuteration was used to specifically probe the orientations of all hydrophobic side chains (leucine, isoleucine, phenylalanine) with SFG in situ. The leucine chain was tilted 120° from the surface normal (pointing towards the surface) and isoleucine was tilted 5° from the surface normal. We also employed fluorine labels to probe individual phenylalanine rings with NEXAFS spectroscopy. Measurements of ring orientations in combination with ssNMR surface distance and rotamer dynamics data allowed us to develop a clear picture of the side chain structure.
1. Weidner T, Breen NF, Li K, Drobny GP, & Castner DG (2010) A Sum Frequency Generation and Solid-State NMR Study of the Structure, Orientation and Dynamics of Polystyrene-Adsorbed Peptides. Proc. Natl. Acad. Sci. U. S. A. 107:13288–13293.