FIG 4.

Transmission electron microscopy of EdU-labeled cells. (A) A549 cells were infected with VACV and at 3.5 h were incubated with EdU for 30 min. The cells were fixed and permeabilized with 0.1% Triton X-100 and reacted with biotin-azide, followed by streptavidin–6-nm gold. (B) Same as panel A, except that biotin-azide was omitted as a control. (C) A549 cells were infected and labeled with EdU as for panel A. The cells were then permeabilized with 0.05% saponin and reacted with biotin-azide. The cells were cryosectioned and incubated with streptavidin–10-nm gold. (D) Same as panel C, except that biotin-azide was omitted as a control. Nu, nucleus; Go, Golgi apparatus; Mi, mitochondria.