AVS 50th International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuP

Paper BI-TuP11
Multi-Technique Characterization of Self-Assembled Peptide Monolayers

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: N.T. Samuel, University of Washington
Authors: N.T. Samuel, University of Washington
K. McCrea, Polymer Technology Group
L.J. Gamble, University of Washington
D.A. Fischer, National Institute of Standards and Technology
P.S. Stayton, University of Washington
G.A. Somorjai, University of California, Berkeley
D.G. Castner, University of Washington
Correspondent: Click to Email
There is considerable interest in the immobilization of bioactive peptides for applications such as affinity separations, diagnostics, cell culture and biomedical implants. We have synthesized a series of lysine and leucine containing peptides, which are designed to attach to surfaces with different secondary structures (alpha helix, beta sheet, etc.). These peptides were attached to carboxy-terminated self-assembled monolayers and characterized with ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry), SFG (Sum Frequency Generation) and NEXAFS (Near Edge X-ray Absorption Fine Structure Spectroscopy). The ToF-SIMS spectra from these peptides were analyzed by principal component analysis. Principal component 1 (PC 1), which captures 89% of the variance in the spectrum, represents the variation in the bulk amino acid composition of the different monolayers. PC 2, which captures 10% of the variance, separates the peptides with different secondary structures, suggesting ToF-SIMS is sensitive to different secondary structures of the peptides. SFG spectra were acquired for the alpha helical peptide adsorbed onto both hydrophobic and negatively charged substrates. The hydrophobic surface spectrum showed strong peaks in the CH stretch regions while the negatively charged surface spectrum showed strong peaks in the NH stretch region. The SFG results indicate the alpha helical peptide binds differently to these two surfaces. These observations were also confirmed by ToF-SIMS experiments, which reveal a strong dependence of the amount of peptide adsorbed onto negatively charged substrates when the solution pH is varied. We have recently developed a simple protocol to attach a short thiol linker onto these peptides at their amine terminus. This provides an additional handle to immobilize these peptides onto surfaces and control their orientation. Polarization-dependent NEXAFS experiments on these monolayers are in progress.