Water Solutions: Solubilizing some lipids is difficult using organic solvents. Typically, lipids are suspended in methanol to aliquot, the methanol is then dried and the residue dispersed using fatty acid-free BSA solution. A general procedure for the preparation of a lipid stock solution is as follows:
Stock Solution: 125 µM of lipid in essentially fatty acid-free bovine serum albumin (BSA, 4 mg/mL)
Preparation of Stock Solution: Methanol Solution:
- Add lipid to methanol:water 95:5 (0.5 mg/mL)
- Heat mixture and sonicate until lipid is suspended. (Some lipid solutions, such as sphingosine-1-phosphate, are not clear and form a slightly hazy suspension.)
- Transfer the desired amounts of methanol:water stock solution to a glass vessel.
- Remove the methanol:water solution using a stream of dry nitrogen or a speed vacuum concentrator.
- Rotate the glass vessel during evaporation to make a thin lipid film on the tube wall.
- Store lipid film at -20 °C in a closed container.
- Add enough BSA (4 mg/mL) in water at 37 °C to the glass vessel containing the lipid film to make a 125 µM lipid solution.
- Incubate for 30 minutes at 37 °C and vortex/heat/sonicate occasionally to facilitate complete dissolution.