Fig. 1. Binding and internalization of EGF and Tf in COS-7 cells. COS-7 cells grown on coverslips were placed in KRH buffer at 35°C, and exposed to 50 ng/ml Alexa-Fluor-568-EGF and 20 µg/ml Alexa-Fluor-488-Tf. Image capture was started immediately after ligand addition. Background is pseudo colored in yellow to enhance low level signal. Colocalized signal (arrows) is pseudo colored in white. The complete time series can be seen in Movie 1 in supplementary material.