Preservation of fluorescence and ultrastructure. Preservation of fluorescent protein signals tagged to endocytic proteins in S. cerevisiae. (A and B) Sla1-EGFP/Abp1-mCherry, (C and D) Sla1-mCherry/Abp1-EGFP. Left panels (A and C) are live-cell fluorescence microscopy images, right panels (B and D) are fluorescent microscopy images of 300-nm resin sections on EM grids. (E and F) Slices through electron tomograms show preservation of fine structure in S. cerevisiae (E) and MDCK cells (F). Both were subjected to cryo-immobilization by HPF, FS with 0.1% uranyl acetate in acetone, and low-temperature embedding in Lowicryl resin. Example features are marked: the plasma membrane (white arrows), nuclear envelope (black arrows), cytoskeletal elements such as spindle pole body and nuclear microtubuli (black open arrow), and filopodia (white open arrow). Bars: (A–D) 2 µm; (E and F) 100 nm.