title: Structure of a fusion peptide analogue at the air-water interface, determined from surface activity, infrared spectroscopy and scanning force microscopy.
abstract: We have investigated a point mutant of the HIV-1 fusion peptide in a compressed monolayer at the air-water interface. A variety of surface sensitive techniques were applied to study structural features under conditions mimicking the hydrophobic/hydrophilic environment of a biomembrane. Possible partitioning into the aqueous bulk phase and molecular areas were examined by surface activity based mass conservation plots. This shows that the peptide is practically fully accumulated in the interface. Secondary structure and orientation was analyzed by means of polarized infrared reflectivity. Brewster angle microscopy and scanning force microscopy contributed nanostructural images. At low surface pressures the molecules form anti-parallel beta-sheets lying flat on the interface. Upon a moderate increase of the lateral pressure a flat beta-turn structure appears with inter- and intramolecular H-bonds. We also observed aggregates forming fingerprint-like structures with a diameter of approximately double the hydrophobic length of a beta-turn conformation. Beyond approximately 18 mN m(-1) the beta-turns straighten up. The lowest measured tilt angle was 45 degrees at 36 mN m(-1).
authors.affiliation: Department of Biophysical Chemistry, Biocenter of the University, Basel, Switzerland.
authors.forename: S E
authors.initials: SE
authors.lastname: Taylor
authors.forename: B
authors.initials: B
authors.lastname: Desbat
authors.forename: D
authors.initials: D
authors.lastname: Blaudez
authors.forename: S
authors.initials: S
authors.lastname: Jacobi
authors.forename: L F
authors.initials: LF
authors.lastname: Chi
authors.forename: H
authors.initials: H
authors.lastname: Fuchs
authors.forename: G
authors.initials: G
authors.lastname: Schwarz
mesh_terms: D000388:Air; D000595:Amino Acid Sequence; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D015497:HIV-1 / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D006860:Hydrogen Bonding; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D017354:Point Mutation; D011312:Pressure; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D015700:HIV Envelope Protein gp41; D010446:Peptide Fragments; D014867:Water