This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.104.053769v1 88/5/3083    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lopez, C. F. Articles by Klein, M. L. Search for Related Content PubMed PubMed Citation Articles by Lopez, C. F. Articles by Klein, M. L.

Structure and Dynamics of Model Pore Insertion into a Membrane

Carlos F. Lopez ^*, Steve O. Nielsen ^*, Bernd Ensing ^*, Preston B. Moore  and Michael L. Klein ^*

^* Center for Molecular Modeling and Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania; and Department of Chemistry and Biochemistry, University of the Sciences in Philadelphia, Philadelphia, Pennsylvania

Correspondence: Address reprint requests to Michael L. Klein, Tel.: 215-898-8571; Email: klein{at}lrsm.upenn.edu; web: www.cmm.upenn.edu.

A cylindrical transmembrane molecule is constructed by linking hydrophobic sites selected from a coarse grain model. The resulting hollow tube assembly serves as a representation of a transmembrane channel, pore, or a carbon nanotube. The interactions of a coarse grain di-myristoyl-phosphatidyl-choline hydrated bilayer with both a purely hydrophobic tube and a tube with hydrophilic caps are studied. The hydrophobic tube rotates in the membrane and becomes blocked by lipid tails after a few tens of nanoseconds. The hydrophilic sites of the capped tube stabilize it by anchoring the tube in the lipid headgroup/water interfacial region of each membrane leaflet. The capped tube remains free of lipid tails. The capped tube spontaneously conducts coarse grain water sites; the free-energy profile of this process is calculated using three different methods and is compared to the barrier for water permeation through the lipid bilayer. Spontaneous tube insertion into an undisturbed lipid bilayer is also studied, which we reported briefly in a previous publication. The hydrophobic tube submerges into the membrane core in a carpetlike manner. The capped tube laterally fuses with the closest leaflet, and then, after plunging into the membrane interior, rotates to assume a transbilayer orientation. Two lipids become trapped at the end of the tube as it penetrates the membrane. The hydrophilic headgroups of these lipids associate with the lower tube cap and assist the tube in crossing the interior of the membrane. When the rotation is complete these lipids detach from the tube caps and fuse with the lower leaflet lipids.

This article has been cited by other articles:

				U. Zimmerli and P. Koumoutsakos Simulations of Electrophoretic RNA Transport Through Transmembrane Carbon Nanotubes Biophys. J., April 1, 2008; 94(7): 2546 - 2557. [Abstract] [Full Text] [PDF]