Exercise 6.6 - Formation of Lipid Bilayer

LEVEL II

Materials

• Lipids extracted per Exercise 6.5
• -Tocopherol
• Cholesterol
• 10 ml Teflon cup and larger polystyrene beaker
• Sable paintbrush
• 0.1 M NaCl
• Interference scale

Procedure

1. Form a working lipid bilayer solution just before use, by adding 400 mg alpha-tocopherol and 30 mg cholesterol to 1.0 ml of the extracted lipids from Exercise 6.6. 5

2. Make a chamber from a teflon cup by piercing the cup with a 1-1.5 mm hole, and placing the cup into a slightly larger polystyrene beaker.

3. Fill both the teflon cup and the outer chamber with 0.1 M NaCl.

4. Use a fine sable brush (3-5 hairs) to apply a small amount of the working solution to the hole in the teflon cup. Be careful to spread the lipid solution evenly but do not puncture the membrane which will form.

5. Observe the characteristics of the membrane formation visually.

   The solution will spread over the hole, then begin to recede and form a gradually thinning membrane. As it does so, the optical properties will change, especially if viewed with reflected light with a simple hand held magnifier (10-20X). The membrane will demonstrate interference colors as it begins to thin and will ultimately become thin enough to become completely transparent. As it becomes transparent, it becomes known as a black membrane.

6. Using an interference scale, plot the thickness of the membrane over time during its formation.

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