Regensburg 2025 – scientific programme

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BP: Fachverband Biologische Physik

BP 17: Poster Session II

BP 17.12: Poster

Tuesday, March 18, 2025, 18:00–20:30, P4

Supramolecular ordering in lipopolymer monolayers at the air/water interface — •Issam Assi, Heiko Ahrens, and Christiane A. Helm — Institute of Physics, University of Greifswald

Lipopolymers with covalently bound poly(ethylene oxide) (EON) bound to the head groups have been introduced to stabilize bilayer membranes. Langmuir monolayers of the lipopolymer DSPE-EON at the air/water interface show in the isotherm a transition from the liquid expanded to the liquid condensed phase, which is confirmed by in-situ Grazing Incidence X-ray Diffraction (GID at DESY, Hamburg). A laterally inhomogeneous film of condensed ordered alkyl chains embedded in a matrix of solvated polymers is formed. Small Angle GID shows these lipid domains are ordered in a hexagonal lattice (repeat distance about 12 nm). The films stay homogeneous on the micrometer scale as observed with Brewster Angle Microscopy. On transferred monolayers, these supramolecular phases were observed with AFM. Fast compression of DSPE-EO44 monolayers is necessary to maintain the hexagonal superstructure at relatively high lateral pressures, whereas slow compression induces a lamellar structure. Also, the superstructure of lipopolymers with shorter polymers (DSPE-EO11 and DSPE-EO22) was explored.

Keywords: lipopolymer; Langmuir monolayer; AFM; cell membrane; Grazing Incidence X-ray Diffraction