Tue, 08/09/2015 - 14:15
,
Campus Saarbrücken, Geb. E2 6, Raum E.04

Prof. Jens-Uwe Sommer
(
Host: Prof. Dr. Ralf Seemann and Dr. Jean-Baptiste Fleury
)
Leibniz Institute of Polymer Research Dresden

Crossing barriers: Passive transport of polymers and nano-particles through lipid bilayer membranes

Lipid bilayer membranes can be considered as a barrier or as a trap with respect to nanosized
objects depending on the hydrophobic/hydrophilic properties of the latter.
Homopolymers with a balanced hydrophobicity display a critical adsorption behavior and
are able to translocate through the membrane. This has been first shown using a coarsegrained
simulation method and can be rationalized by a potential model for the membrane
[1]. For this potential model the state of ideal homopolymer chains at various degrees of
hydrophobicity can be calculated and the translocation rates can be estimated from the
mean first passage time. The membrane potential has two basic components: A potential
barrier/trap arising from the interaction with the hydrophobic core, and a surface
component. Copolymers display a similar behavior with a major difference being the
stronger adsorption by polarization effects of the membrane surfaces. Polymers with
balanced hydrophobicity cause a strong perturbation of the lipid bilayer membrane which
results in an enhanced permeability of solvent in the immediate environment of the
adsorbed chains. This can be considered as a transient pore formation. Depending on the
sequence copolymers can be either “pore formers” or “translocaters” depending on their
contact time with the membrane in the adsorbed state [2]. Simulations of nano-particles
display similar properties. In particular patchy nano-particles which display hydrophilic and
hydrophobic components on their surface can translocate the membranes without
condensing as droplets in the bulk [3].

[1] J.-U. Sommer, M. Werner and V. Baulin, Europhys. Lett. 98, 18003 (2012)
[2] M. Werner and J.-U. Sommer, Biomacromolecules 16, 125 (2015)
[3] S. Pogodin, M. Werner, J.-U. Sommer and V. Baulin, ACS Nano 6, 10555 (2012)

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