Assembly and Structure of alpha-helical Peptide Films on Hydrophobic Fluorocarbon Surfaces

Journal Article · Fri Jan 01 04:00:00 EST 2010 · Biointerphases

OSTI ID:1020118

Weidner, T; Samual, N; McCrea, K; Gamble, L; Ward, R; Castner, D

The structure, orientation, and formation of amphiphilic {alpha}-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 {alpha}-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 {pi}* is likely due to the broad distribution of amide bond orientations inherent to the {alpha}-helical secondary structure. SFG spectra exhibit strong peaks near 2865 and 2935 cm{sup -1} related to aligned leucine side chains interacting with the hydrophobic surface. Water modes near 3200 and 3400 cm{sup -1} indicate ordering of water molecules in the adsorbed-peptide fluorocarbon surface interfacial region. Amide I peaks observed near 1655 cm{sup -1} 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.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: DOE - OFFICE OF SCIENCE
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1020118
• Report Number(s): BNL--95967-2011-JA
• Journal Information: Biointerphases, Journal Name: Biointerphases Journal Issue: 1 Vol. 5
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ADSORPTION
AMIDES
BUFFERS
CHAINS
DICHROISM
DISTRIBUTION
FINE STRUCTURE
KINETICS
LEUCINE
LYSINE
ORIENTATION
PEPTIDES
PERIODICITY
RESIDUES
SPECTRA
SPECTROSCOPY
SUBSTRATES
WATER
X-RAY PHOTOELECTRON SPECTROSCOPY
national synchrotron light source