Figure 4

Fluorescence microscopy of nuclear import assay of IBB peptide-fluorescent plasmid in the digitonin-permeabilized HeLa cells system. Digitonin treated HeLa cells were incubated with 5 μg fluorescent plasmid alone (A) or covalently coupled to IBB peptide at the ratio of 25 IBB peptide / plasmid (mol / mol) (B), or with 1 μg fluorescent BSA-NLS (C) as a positive nuclear import control. The assay was performed for 30 min at 30°C in the presence of an energy regenerating system and 50 % (vol / vol) HeLa cytoplasmic extracts. Cells were observed with a 100 × objective lens.