FIG. 2.
Cellular uptake of PNA. (A to C) Chronically HIV-1-infected H9LAI cells were incubated with fluorescein-tagged PNA at various concentrations overnight, fixed with 3.7% formaldehyde for 20 min, washed and resuspended in PBS, and examined by fluorescence microscopy. Shown are the cells incubated with 0 (A), 30 (B), and 60 (C) μM fluorescein-tagged PNAPR2. Note that the cells treated with fluorescein-tagged PNAPR2 were resuspended in a slightly larger volume of PBS than was the untreated control so that each cell could be clearly visualized. The panel on the right-hand side is the fluorescence image, and that on the left is the phase-contrast image of the same field. The discernible fluorescent signal was seen in the majority of cells at 30 μM PNA or greater. (D) Shown at a higher magnification are the cells incubated with 30 μM PNAPR2. Note that the fluorescent signal is virtually confined to the cytoplasm. (E) H9LAI cells incubated with fluorescein-tagged PNA were also evaluated by fluorescence-activated cell sorter analysis. Curves a, b, and c represent H9LAI cells incubated with 0, 30, and 60 μM fluorescein-tagged PNAPR2, respectively. Similar results were obtained with fluorescein-tagged PNAPR4 and PNART2.