Biotin-ligand complexes with streptavidin quantum dots for in vivo cell labeling of membrane receptors.

The unique fluorescence properties of quantum dots (QDs), particularly their large extinction coefficients and photostability, make them ideal probes for tracking proteins in live cells using real-time visualization. We have shown that QDs conjugated to epidermal growth factor act as functional ligands for their receptor, erbB1. Here, we describe protocols for (1) conjugation of streptavidin-QDs to biotinylated ligand, (2) formation of ligand-QD-receptor complexes, and (3) quantification of binding and internalization of receptor complex using both high-resolution fluorescence microscopy and flow cytometry.