NEXAFS STUDIES OF ORIENTATION IN ADSORBED PEPTIDE & PROTEIN FILMS

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Engineering the next generation of biomaterials with the specific surface biorecognition sites needed to improve healing requires developing surface analysis methods to characterize these materials. Recent studies have shown near edge X-ray absorption fine structure (NEXAFS) is an excellent technique for characterizing the structure and orientation of self-assembled monolayers (SAMs), adsorbed peptides, and adsorbed protein films. Studies in the coming year will focus on improving our ability to quantify the orientation of adsorbed peptides and proteins and understanding how substrate properties (roughness, composition, etc.) effect peptide and protein orientation. Alpha-helix and beta-sheet peptides were found to adsorb onto highly-ordered, rubbed poly(tetrafluoroethylene) (PTFE) substrates with their helical axis (alpha-helix) and backbone (beta-sheet) parallel to the substrate. In contrast, neither peptide exhibited significant ordering when adsorbed onto diso rdered, RF GD-deposited fluoropolymer surfaces. NEXAFS results from adsorbed protein films show that orientation of their peptide backbone is only observed for non-gobular proteins (fibrinogen, fibronectin, etc.). The relationship between PTFE structural parameters (FCF bond angle, helix unwinding, helix stretching, etc.) and NEXAFS spectra have been determined with theoretical calculations.