PHYS 549 |
| The interactions of between transmembrane peptides and lipid bilayers are important in characterizing the behavior of biological membranes. The hydrophobic matching hypothesis plays a prominent role in describing these interactions, and predicts that peptide-bilayer association is most stable when the thickness of the hydrophobic region of the lipids tends to match the length of the hydrophobic region of the peptide. We have simulated an alpha-helical transmembrane peptide (erbB-2 transmembrane domain) embedded in a mixed DMPC-DDPC bilayer, containing two types of lipids that differ only in their hydrophobic tail lengths, with an atomistic model. A hybrid MC-MD method was used to increase the equilibration speed in the DMPC-DDPC mixture. In the MC-MD method the type of lipid can be mutated by removing or adding CH2 groups to the tail of the lipid, and the ratio of two lipid types is controlled by their activity ratio. Simulation results show that the longer tail lipid DMPC is more likely to appear near the peptide. As a result, the bilayer thickness is greatest near the peptide and decreases farther away, consistent with the hydrophobic matching hypothesis. The comparison of the lipid order parameter between the target system and control system without peptide shows that DMPC is more ordered without peptide at both 100% and 50% DMPC, while DDPC is more ordered at 50% DDPC but less ordered at 100% DDPC. |
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PHYS Poster Session - General Theory
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Sci-Mix
Division of Physical Chemistry |