Immunofluorescent detection, co-localization, and FRET intensity in representative transfected A549 cells. Cells were stained with anti-TACE (Cy3) and anti-TNF-α (FITC) as FRET acceptor and donor, respectively (panels a-t). The staining pattern is suggestive of both cell membrane and membrane vesicle localization. In photo-bleached samples (Panels c, h, m, r) there was less than 2% initial anti-TACE (Cy3) intensity post-photobleaching. Panels u-x: FRET intensity, calculated from the difference between donor pre- and post-photobleaching intensities shown in pseudocolor.