3T3-L1 Plasma Membrane Isolation

1. Wash cells 3x in cold HES (20 mM Hepes, pH 7.4; 1 mM EDTA, 255 mM Sucrose)
2. Dry cells well and add 0.6 mL HES (w/Protease Inhibitor) per 150 mm dish
3. Scrape cells and homogenize with dounce homogenizer for 20 strokes
4. Centrifuge @ 3,000 rpm (800g) at 4 degrees for 10 minutes
5. (Optional) Collect supernatant and spin @ 3,000 rpm at 4 degrees for 5 minutes
6. Collect supernatant and spin in TLA 100.3 rotor at 19,000 rpm for 20 minutes at 4 degress (Tube = Beckman #349622)
7. (Optional) Wash pellet in 1.0 mL HES and spin in TLA 100.3 rotor at 19,000 rpm for 20 minutes at 4 degress (Tube = Beckman #349622)
8. (Optional) To further purify PM, resuspend in 0.6 mL HES and repeat steps #4 and #6
9. Resuspend pellet in 1.0 mL HES and homogenize with dounce for 10 strokes
10. Layer the resuspended pellet on top of 10 mL 40% sucrose/HES in a 13.5 mL ultracentrifuge tube (tube = Beckman #331372)
11. Top off centrifuge tube with HES until nearly full
12. Spin in ultracentrifuge with rotor SW41 (saltiel login = 5238) at 39,000 rpm at 4 degrees for 1 hour
13. PM should appear as band at the interface of the HES and Sucrose fractions
14. Remove HES buffer above PM fraction until close to PM fraction
15. Collect ~ 0.8 mL PM containing fraction
16. Add 2.6 mL of HES to dilute sucrose
17. Spin in ultracentrifuge with TLA 100.3 rotor at 35,000 rpm for 20 minutes at 4 degress (Tube = Beckman #349622)
18. Discard supernatent
19. Pellet = purified plasma membrane