Fig. 4.

Confocal images from control transport experiments in vitro showing 66- to 69-kDa FITC-avidin (green; A), 60-kDa FITC-NeutrAvidin (green; B), or 310-kDa R-phycoerythrin-NeutrAvidin (purple; C) together with DRAQ5-stained nuclei (red) and a grayscale phase-contrast image. Overlaying the images in A−C demonstrated the lack of tracer visible when the gelatin substrate was not biotinylated. Bar = 50 µm. D: confocal images showing Qdot 800-streptavidin (yellow, ~20-nm radius) and anti-vascular-endothelial cadherin (blue). The row at the top demonstrates the lack of tracer visible when the gelatin substrate was not biotinylated. The row in the middle shows 3-min uptake with biotinylated gelatin, as in Fig. 3, and the row at the bottom shows that extending the uptake time from 3 to 15 min still did not result in the lines and spots seen for the smaller tracers. Bar = 20 μm. n = 3 isolations.