Conformational Properties of Arenicins: From the Bulk to the Air–Water Interface

Abstract

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.

Interplay of mycolic acids, antimycobacterial compounds and pulmonary surfactant membrane: A biophysical approach to disease

“…Accordingly, besides analyzing the lipidic portion of the PS monolayer, we have also used PM-IRRAS to study the secondary structure of the SP-B and SP-C at the dynamic inspiratory tension. In this regard we have focused on the analysis of the amide I band (1650 cm −1 ), which is described as more sensitive to estimate the conformation and orientation of the protein compared to the amide II band (1550 cm −1 ) [56,63]. The amide I band can therefore give information regarding the secondary structure of the proteins and according to the band position allows the identification of β-turns (1662-1682 cm −1 ), α-helices (1645-1662 cm −1 ), and β-sheets (1613-1637 cm −1 ).…”

Physical–chemical characterization of novel cationic transfection lipids and the binding of model DNA at the air–water interface

“…This peak is typical for hydrogen bonds between N-H/O]C groups of b-sheets of proteins and peptides. [53][54][55][56][57][58] To the best of our knowledge such a Bragg peak has never been observed for lipids at the air-water interface. The structure of lipid 7 provides many possibilities to build a hydrogen bond network.…”

Interactions of Two Fragments of the Human Antimicrobial Peptide LL-37 with Zwitterionic and Anionic Lipid Monolayers

“…A red-shift in the amide I band position can be attributed to the formation of hydrogen bonds [44,52,53] or a change in the helix flexibility [54]. Also, a change in the backbone hydration influences slightly the band position.…”

“…The amide bands are connected with the secondary structure of the peptide. The OH-band intensity is related to the film thickness [52] and is therefore influenced by the lipid tilt angle in condensed phases and the formation of adsorption layers.…”