Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 18: Metal substrates: Adsorption of organic / bio molecules III
O 18.1: Vortrag
Dienstag, 24. März 2009, 10:30–10:45, SCH A118
Probing Orientation and Conformation of α-Helix and β-Sheet Model Peptides on Self-Assembled Monolayers with SFG and NEXAFS Spectroscopy — •Tobias Weidner, Julia Apte, Lara J. Gamble, and David G. Castner — National ESCA and Surface Analysis Center for Biomedical Problems, University of Washington, Seattle, USA
Understanding the interaction of proteins and peptides with engineered surfaces from first principles is essential for the design of biomaterials applications. In this study we characterized amphiphilic α-helix and β-strand model peptides on self-assembled monolayers (SAMs) on Au in situ using sum frequency generation (SFG) spectroscopy and ex situ using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The α-helix peptide is a 14-mer and the β-strand is a 15-mer composed of hydrophilic lysine (K) and hydrophobic leucine (L) residues. SAMs having either carboxylic acid or methyl terminal groups were used as charged and hydrophobic model surfaces, respectively. SFG peptide spectra on methyl SAMs exhibited peaks near 2965 cm−1 and 2875 cm−1 related to ordered leucine side chains. A relative phase of 0 rad for both peptides showed, that the leucines were oriented towards the interface. Features near 3200 cm−1 and 3400 cm−1 related to bound water were also observed. The spectra on carboxylic acid SAMs were dominated by a peak near 3300 cm−1, indicating substantial lysine-surface interactions. The linear dichroism of the amide π* orbital near 400.1 eV observed in the NEXAFS spectra proves the peptides are oriented parallel to the interface on both SAMs.