Test for lipid solubility of membranes

 

Materials:

Fresh beets

Solutions of the following alcohols:

22 M Methanol

8.5 M Ethanol

3.0 M n-Propanol

1.1 M n-Butanol

Razor blades

Depression slides

Stopwatch

Procedure:

1. Beet cells contain a high concentration of the red pigment anthocyanin. When exposed to a solvent, the anthocyanin will leak out of the cells and cause a red color to occur in the surrounding media. Cut thin slices of a beet so that they can be placed on a microscope slide and viewed with low resolution.(about 5X).

2. While watching the edge of the sliced beet, add the first alcohol (22 M methanol) to the slide until the beet section is submerged. Be careful not to allow the alcohol to flow off the slide. Repeat this procedure for each alcohol while using a fresh beet slice each time.

3. Immediately begin to time the dissolution of the beet cell membranes. Mark the time when a red color is first observed in the surrounding alcohol solution.

4. Repeat the entire series for 1/2 (0.5) dilutions of each of the alcohols.

5. For each dilution of each alcohol, calculate a penetration coefficient by dividing the time of pigment appearance by the molar concentration of the alcohol. Plot this penetration coefficient against the relative miscibility of the. The partition coefficient is a measure of the relative miscibility of the alcohol with lipids. In other words, the lower the partition coefficient the less soluble in lipid is the alcohol.

Alcohol, Formula, Molecular Mass, Partition Coefficient

Methanol CH3OH 32.04 0.01

Ethanol C2H5OH 46.07 0.03

n-Propanol C3H7OH 60.09 0.13

n-Butanol C4H9OH 74.12 0.58