Fig. 4:

Freeze-fracture overview of lipid droplets (LD) in a lipid laden macrophage and their associations with endoplasmic reticulum (ER) membranes after labeling for adipophilin using the FRIL technique. In freeze-fracture, lipid droplets have a unique smooth appearance enabling their unambiguous discrimination from other organelles. Where the fracture follows the outermost layer of the droplet to give a concave fracture, the enveloping outer phospholipid monolayer is seen en face; convex fractures give mirror image (complementary) views. Some fractures skip along successive layers of the lipid, revealing a multilayered appearance, other cross-fracture the droplet to give what is essentially a cross-section of the interior. The gold label, seen as sharply defined black particles, can be seen in abundance on the outer phospholipid monolayer of the droplet, and some label is also present deeper in the interior. Adipophilin label is also apparent on areas of the ER membrane P face (PF) but not on the E face (EF).