FIGURE 2.

Fluorescence intensity fluctuations recorded at the apical plasma membrane of N2a cells expressing GPR37^tGFP are generated by molecular movement. A, autocorrelation curves recorded at varying observation volume sizes show that the amplitudes of the GPR37^tGFP autocorrelation curves decrease as the pinhole size in front of the detector is increased, reflecting an increase in the number of molecules in the observation volume element. B, for varying sizes of the observation volume element, a linear relationship was observed between the number of observed molecules (N) and the (pinhole size). C, autocorrelation curves at two different pinhole sizes show that characteristic times increase with increasing the observation volume size. D, linear relationship was observed between the first characteristic time (τ_D1) and the (pinhole size). The positive intercept suggests that partitioning between domains may occur. E, linear relationship was observed between the second characteristic time (τ_D2) and the (pinhole size). The negative intercept suggests that some confinement by the cytoskeletal protein meshwork may also occur. F, linear relationship between the number of molecules characterized by slow (N₂) and fast (N₁) diffusion was observed for different surface densities of GPR37^tGFP.