Modeling Polymer-Biomembrane Interaction

 
A temperature responsive polymer is forced to shrink and the ends pull nanotubes from the outer vesicle membrane towards the interior (thin red lines). The polymer chains are not visible (they are too thin). A possible mechanism of the pulling process is shown in the inset.
 
Major subjects:
*statistical physics (equilibrium)
* polymer dynamics
* the Smoluchowskii formalism
 
The project will interact with a closely related project on the experimental side (KB: Aldo Jesorka)
 
Recommended literature:
1. Ilona Węgrzyn, G. D. M. J., Birgit Nagel, Martin Katterle, Simon R. Gerrard, Tom Brown, Owe Orwar, and Aldo Jesorka Membrane Protrusion Coarsening and Nanotubulation within Giant Unilamellar Vesicles. Journal of the American Chemical Society ASAP, doi:10.1021/ja207536a (2011).
2. Ambjornsson, T., Apell, S. P., Konkoli, Z., Di Marzio, E. A. & Kasianowicz, J. J. Charged polymer membrane translocation. J. Chem. Phys. 117, 4063-4073 (2002).
3. Park, P. J. & Sung, W. Polymer release out of a spherical vesicle through a pore. Phys. Rev. E 57, 730-734, doi:10.1103/PhysRevE.57.730 (1998).
4. Sung, W. in Statistical Physics Vol. 519 Aip Conference Proceedings (eds M. Tokuyama & H. E. Stanley) 458-469 (Amer Inst Physics, 2000).
 
Perequisites:
It is advantageous, but not necessary, to have a background in physics (Teknisk fysik och Teknisk matematik), or the equivalent from GU. You should be curious and you should be able to interact with people as this is truly interdisciplinary project to be carried out in a close collaboration with the experimental group. The supervision will be in Swedish or English. All writing is to be done in English as it is expected that the work to be done should result in a publication (or something close to it).
 
Background
An experimental system which demonstrates the pulling of lipid nanotubes from a model membrane by action of a smart polymer has been recently built. It is conceivable that such tubes are pulled by polymers in the living cell, since the polymer content in biological cells is very high.
 
Problem description
The goal is to determine possible mechanisms by which lipid nanotubes are pulled from the vesicle surface by the action of polymer chains. The objectives are as follows: (1) To describe how the polymer translocates out of the vesicle and to find the most likely transition states for the process. (2) To identify the main mechanism behind the tube pulling process. (3) Identify the key parameters that need to be optimized to make the process efficient.
 
Approach
Dynamics of the polymer will be modeled by using the Langevin equation formalism. Forces on the polymer will be computed by using the standard machinery of equilibrium statistical physics for computing the protein free energy. The model building will be done in a strong collaboration with the experimental group (Orwar Laboratory of Biophysical chemistry).
 
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Published: Tue 03 Sep 2013. Modified: Thu 04 May 2017