Labeling Neuronal Membrane Receptors with Quantum Dots

This protocol describes a highly sensitive approach for tracking the motion of membrane molecules over extended time periods with single-molecule resolution. This technique uses nanometer-sized quantum dots (QDs) linked to the extracellular part of the proteins to be followed. Single-fluorophore epifluorescence imaging then reveals the membrane diffusion of the particle of interest. Two methods are presented for labeling neurons with the primary antibody of choice along with a secondary anti-Fab antibody that is either biotinylated or directly coupled to the desired QD. The behavior of QD-labeled molecules can then be followed within the cell using epifluorescence imaging.