A Piece of Membrane for Modern/Cell Biology

 

A portion of a phospholipid bilayer membrane is shown using the Spacefill display. (This large structure, 350K, takes several seconds to load; please be patient.)
The yellow box enclosing this piece is about 80Å on each side. Each phospholipid has a polar phosphatidyl choline headgroup and hydrophobic tails of oleic and palmitic fatty acids. H2O molecules cover the bottom surface and about half of the top surface.

"Dissect" the structure as follows to see specific portions of the bilayer:
Color the carbon atoms in the lower layer a darker gray.

Remove all of the H2O molecules.
  Add the H2O molecules back to both sides of the bilayer.

Show a chunk of the upper layer as Wireframe.
  Remove a chunk of the upper layer completely.
  Restore the chunk of the upper layer to its original Spacefill display.

Viewing Tip: Rotate the model after each of the above operations to get a 3-D perspective on the way the various portions of the bilayer are related to one another.

Back to Molecules for Modern/Cell Biology at CMU.

The image displayed on this page requires the Chemscape Chime plug-in.
A Chime Viewer's Guide and the download site for this plug-in are linked under Viewing Tips on the Molecules for Modern/Cell Biology at CMU page.

Credits: The coordinates are from the work of H. Heller, M. Schaefer, and K. Schulten (1993) "Molecular dynamics simulation of a bilayer of 200 lipids in the gel and in the liquid-crystal phases", J. Phys. Chem. 97, 8343-60.
Those coordinates were modified slightly by Dr. Eric Martz for his RasMol "animation" of the Lipid Bilayer; this page uses his file, "cutc2.pdb".

The structure shown here corresponds to the most ordered arrangement of the phospholipids, the so-called "crystal" phase. Similar displays of the gel and fluid phases show more disorder in the fatty acid tails of the phospholipid.
See also Dr. Eric Martz' treatment of Lipid Bilayer Membranes to view GIFs of the crystal, gel and fluid models and for downloading the coordinates of each.