FIGURE 1.

Diffusion modes of quantum dot-labeled A_2A receptors on hippocampal neurons. A–C, representative trajectories of the FLAG-tagged wild-type A_2A receptor were recorded as outlined under “Experimental Procedures” and projected onto the bright field image of the corresponding neuron. The scale bars adjacent to the trajectories define a square of 0.8 × 0.8 μm². D–F, representative MSD plots highlighting three different diffusion modes: directed (D, green circles), Brownian/random walk (E, cyan circles), and confined (F, red circles). The lines were generated by fitting the data points to a second order polynomial (D), a straight line (E), and Equation 5 (E). G and H, the relative contribution of each diffusion mode (green, directed; cyan, Brownian; red, confined) was quantified by recording 614 and 890 trajectories for the wild-type A_2A receptor (WT, G) and 105 and 211 trajectories for the truncated A_2A receptor(1–311) (311, H), in the absence and presence of the agonist CGS21680 (+CGS, 10 μm), respectively.