Pellet was spun at 200 ×g at 4 °C for 5 min
and then an equal volume of 1.08 M sucrose solution was added and
spun at 2000 g for 5 min to remove large debris. Supernatant was
transferred to a 13.2 mL thinwall ultraclear centrifuge tube (BeckmanCoulter
344059) and layered with a gradient of 0.27 M sucrose,
0.135 M sucrose and Top solution buffer (25 mM Tris–HCl; 1 mM
EDTA; 1 mM EGTA; protease inhibitor cocktail). Spun in SW41 rotor
using a Beckman L8-70M ultracentrifuge at 35,000 rpm for 30 min at
4 °C. The top layer (white, cloudy) was transferred via a glass pipet to
a siliconized microcentrifuge tube and spun at 18,000 ×g for 10 min
and the bottom, aqueous layer was removed.