Delivery of AMPAR to synapses is likely to occurs by extra-synaptic insertion of AMPARs, followed by synaptic recruitment of AMPAR through lateral diffusion on the neuronal surface. By labeling surface AMPARs with QDot conjugated antibodies, we can examine surface diffusion dynamics of AMPARs in and out of synapses. The movie below shows surface diffusion of AMPAR subunit GluR1 (captured through a Hamamatsu EMCCD camera at 10 Hz).

By fitting the QDot image with a 2D Gaussian function, one can pin-point the center of the dot with nanometer precision, and calculate the mean square displacement (MSD) and diffusion co-efficient of the receptors.