Effect of PPAA polymer on nuclear import of TAT-SA in HeLa cells at 4 h post transduction. (A) TAT-SA-A488 was first pretreated with biotinylated, endosomal-releasing peptide PPAA and then transduced into cells. Cells were fixed with PFA, permeabilized with Triton-X and immunolabeled with rabbit anti-SA Ab followed by Alexa-488-conjugated goat anti-rabbit IgG (green) and embedded with DAPI-containing Mowiol-Dabco (nucleus, blue). Scale bar, 10 μm. (B) Quantitative analysis of the relative nuclear fluorescence intensity of TAT-SA-488 in living cells in presence or absence of PPAA. Multiple series of optical sections of the nuclear area were collected by confocal microscopy prior to processing the data with the 3D LSM program.