EM localization of gold-conjugated 24FM in COSdel.2-155 cells. Cells were preincubated with gold-complexed 24FM as in Fig 5 and exposed to 37°C for 0, 10, 30, and 45 minutes (A, B, C, and D, respectively). In contrast to that seen in Fig 5, gold particles remained on the cell surface (arrowheads), although clusters formed within 10 minutes of exposure to 37°C. Rare intracellular particles are seen (arrow).