AVS 51st International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI-MoM

Paper BI-MoM6
In situ Sum Frequency Generation Characterization of Peptide Monolayers on Hydrophobic and Charged Surfaces

Monday, November 15, 2004, 10:00 am, Room 210D

Session: In-Situ Spectroscopy of Biomolecules at Interface
Presenter: N.T. Samuel, University of Washington
Authors: N.T. Samuel, University of Washington
K. McCrea, The Polymer Technology Group
L.J. Gamble, University of Washington
R.S. Ward, The Polymer Technology Group
P.S. Stayton, University of Washington
G.A. Somorjai, University of California at Berkeley
D.G. Castner, University of Washington
Correspondent: Click to Email
Immobilization of bioactive peptides is an active research area for diagnostics, cell culture and biomedical implants. Previous studies have shown well-defined sequences of lysine (K) and leucine (L) containing peptides spontaneously adsorb onto hydrophobic substrates with either @alpha@-helix or @beta@-sheet secondary structures. In this study the adsorption of these peptides onto hydrophobic and charged surfaces has been characterized in situ with IR-Visible Sum Frequency Generation (SFG) spectroscopy. The SFG spectra in the CH, NH and OH stretch regions show the adsorption of the LK peptides onto these substrates is mediated by interactions through their leucine (hydrophobic surfaces) and lysine (charged surfaces) residues. These hydrophobic and electrostatic interactions are accompanied by ordering of the functional groups involved in the interaction. Ordering of water molecules at these interfaces is also observed. SFG spectra in the amide I region were used to examine the secondary structure of the LK peptides. For the @alpha@-helix LK peptide the @alpha@-helix secondary structure is maintained upon dehydration of the sample, even though significant changes in the side chain ordering was observed. Polarization-dependent Near-edge X-ray Absorption Fine Structure (NEXAFS) experiments were also done on the adsorbed peptides. The results demonstrate that the N1s->@pi@*@sub CONH@ feature in the Nitrogen K-edge is sensitive to the secondary structure of the adsorbed peptide. NEXAFS experiments also confirm the highly ordered nature of the adsorbed peptides.