Conformational properties of arenicins: from the bulk to the air-water interface.
The structures of two antimicrobial peptides (arenicin Ar-1 and its linear derivative C/S-Ar-1) are studied in different solutions and at the air-water interface using spectroscopic methods such as circular dichroism (CD) and infrared reflection absorption spectroscopy (IRRAS) as well as grazing incidence X-ray diffraction (GIXD) and specular X-ray reflectivity (XR). Both peptides exhibit similar structures in solution. In the buffer used for most of the experiments the main secondary structure elements are 22 % β-turn, 38 % β-sheet and 38 % random coil. The amphiphilic peptides are surface-active and form a Gibbs monolayer at the air-buffer interface. The surface activity is drastically increased by increasing the ionic strength of the subphase. The β-sheet layer is quite stable and can be compressed to higher surface pressures. This adsorption layer is very crystalline. Bragg peaks corresponding to an interstrand distance of 4.78 Å and to an end-to-end distance have been observed. This end-to-end distance can be connected with the observed differences in the layer thickness leading to the assumption that the peptides form a hairpin which is bended depending on the interactions with the counterions.
Travkova
Oksana G
OG
Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14476 Potsdam, Germany.
Andrä
Jörg
J
Möhwald
Helmuth
H
Brezesinski
Gerald
G
D000327:Adsorption; D000388:Air; D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides; D002942:Circular Dichroism; D015801:Helminth Proteins; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
D023181:Antimicrobial Cationic Peptides; D015801:Helminth Proteins; D010455:Peptides; C496888:arenicin-1, Arenicola marina; D014867:Water