Kolloqiumsvortrag: Amphilic molecules confined at the air / liquid interface
Kiel, Leibnizstraße 13, Hans-Geiger-Hörsaal
Prof. Dr. GeraldBrezesinski
(Max Planck Institute of Colloids and Interfaces, Potsdam, Germany)
Amphiphilic molecules confined at the soft air/liquid interface
Monomolecular films at the air/water interface are interesting model systems to study different problems in biophysics and material science. The structures formed in two dimensions can be com-pared with 3-dimensional structures to elucidate the role of confinements. The interactions of dis-solved biomolecules (DNA, peptides, enzymes, nanoparticles) with lipid layers can be studied using surface sensitive methods such as pressure-area isotherm measurements, Brewster angle microsco-py as well as X-ray techniques in terms of structural changes, binding affinities, and reaction yield. Additionally, Infrared Reflection Absorption Spectroscopy (IRRAS) at the air/water interface pro-vides information about the secondary structure of biomolecules adsorbed at the interface.
Some examples will be presented:
1) Amphiphilic molecules confined at the air-water interface show a rich polymorphism. The chain lattice structures in Langmuir layers have been determined by GIXD. In rare cases, molecular lattic-es are observed.
2) The structures of antimicrobial peptides (AMPs) and peptidomimetics are studied in different solutions and at the air–water interface. The amphiphilic peptides are surface-active and form Gibbs monolayers at the interface. In some cases, very crystalline adsorption layers have been observed. The interacting AMPs and peptidomimetics reveal a strong influence on the phase transition and condensed structures of anionic phospholipid monolayers.
3) Helical intermediates of amyloidogenic model peptides transform into β-sheets depending on different factors - increased concentration, orientation due to compression, and metal ions. The ef-fectiveness of the different triggers will be discussed.
4) DNA and cationic lipids build lipoplexes. Efficacy and toxicity are still two major problems that have to be faced on the way to an outstanding transfection system. Therefore, new lipids are con-stantly synthesized and investigated with respect to their transfection rates. TRXF (total reflection X-ray fluorescence) has been introduced as a simple method to study interactions of ions with charged surfaces. On this way, the protonation degree of the new transfection lipids has been quan-titatively determined.