Do the different single-tagged complexes penetrate equally the synaptic cleft?
To answer this question, surface tag complexes were counted for each image series and were affected as extrasynaptic, synaptic, or juxtasynaptic (300–500 nm around the labeled synapses). In total, 150,584 molecules/particles were analyzed. The percentage of tag complexes localized within synapses (synaptic over total molecule number) averaged 20% (range 0–26%). Interestingly, the synaptic content of Cy5-Ab and Cy5-BTx molecules was higher than that of QDot-Ab (Fig. 2F). However, in the juxtasynaptic membrane, this difference vanished, indicating that the size of single complexes is likely to affect the accessibility of the complexes to the highly confined synaptic cleft. Are surface diffusions of endogenous and transfected receptor similar? Recombinant receptor subunits are, and will be, widely used to study receptor trafficking during various paradigms of neuronal function. The simple but important question of whether endogenous and transfected receptors behave similarly at the neuron