Assembly and structure of α-helical peptide films on hydrophobic fluorocarbon surfaces

Tobias Weidner, Newton T. Samuel, Keith McCrea, Lara J. Gamble, Robert S. Ward, David G. Castner

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38 Citations (Scopus)

Abstract

The structure, orientation, and formation of amphiphilic α-helix model peptide films on fluorocarbon surfaces has been monitored with sum frequency generation SFG vibrational spectroscopy, near-edge x-ray absorption fine structure NEXAFS spectroscopy, and x-ray photoelectron spectroscopy XPS. The -helix peptide is a 14-mer of hydrophilic lysine and hydrophobic leucine residues with a hydrophobic periodicity of 3.5. This periodicity yields a rigid amphiphilic peptide with leucine and lysine side chains located on opposite sides. XPS composition analysis confirms the formation of a peptide film that covers about 75% of the surface. NEXAFS data are consistent with chemically intact adsorption of the peptides. A weak linear dichroism of the amide φ is likely due to the broad distribution of amide bond orientations inherent to the -helical secondary structure. SFG spectra exhibit strong peaks near 2865 and 2935 cm- related to aligned leucine side chains interacting with the hydrophobic surface. Water modes near 3200 and 3400 cm- indicate ordering of water molecules in the adsorbed-peptide fluorocarbon surface interfacial region. Amide I peaks observed near 1655 cm- confirm that the secondary structure is preserved in the adsorbed peptide. A kinetic study of the film formation process using XPS and SFG showed rapid adsorption of the peptides followed by a longer assembly process. Peptide SFG spectra taken at the air-buffer interface showed features related to well-ordered peptide films. Moving samples through the buffer surface led to the transfer of ordered peptide films onto the substrates.

Original languageEnglish
JournalBiointerphases
Volume5
Issue1
Pages (from-to)9-16
Number of pages8
ISSN1559-4106
DOIs
Publication statusPublished - 2010
Externally publishedYes

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