Interactions of Amphiphilic Triblock Copolymers with Lipid Membranes: Modes of Interaction and Effect on Permeability Examined by Generic Monte Carlo Simulations

Soft Matter, DOI: 10.1021/acs.macromol.5b00720 (2015)

Hauke Rabbel, Marco Werner, and Jens-Uwe Sommer

We investigate interactions of linear amphiphilic ABA triblock copolymers with lipid bilayer membranes by means of Monte Carlo simulations in a generic coarse-grained model. The polymers have hydrophilic A-blocks and B-blocks of varying hydrophobicity. The effect of different conformational states of the polymer on the induced permeability for solvent molecules is examined. We demonstrate that the local permeability of the membrane can be strongly increased in the transmembrane state, in particular for a mismatch in the hydrophobicity between the middle block and the membrane core, while the hairpin state has almost no effect on this property, especially for growing hydrophobic mismatch. We have investigated the relative stability of the two states using thermodynamic integration and have shown that only in a range of intermediate hydrophobic block lengths NB and hydrophobicities HB the transmembrane state is stable. Increasing mismatch of the B-block in terms of relative hydrophobicity and block length not only causes stronger perturbations in the membrane if the polymer is in the transmembane state but also renders this state metastable. Our studies support in particular previous experimental studies suggesting a two-state model of PEO–PPO–PEO copolymers.

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DOI: 10.1021/acs.macromol.5b00720