Figure 4.
(A,B) Representative frames taken from a live cell imaging experiment to monitor Aβ40 diffusion in the cell membrane; the Aβ40 molecules were labeled with HiLyte488 and HiLyte647 fluorophores. (A) Monomers and oligomers (488 channel); (B) species undergoing FRET (633 nm channel, Aβ oligomers). The trajectories obtained by linking the images of the Aβ species in (A) and (B) are shown in (C). From the ensemble plots, it is already apparent that, in contrast to the small species present in (A), the motion of the large oligomers (defined as species that undergo FRET) is highly restricted. (D) A representative plot of the MSDs as a function of time for a mobile Aβ40 species (yellow arrows and trajectories in (C); the diffusion coefficient obtained from the fit is D = 0.063 ± 0.020 μm2/s. (E) The diffusion coefficient as estimated by the MSD analysis as a function of species intensity (which correlates with size) for both Aβ42 and Aβ40. Each point represents an Aβ monomer or oligomer. (F) The estimated diffusion coefficient as a function of species intensity for only the oligomers of Aβ42 and Aβ40. Concentrations used are 1 μM Aβ42 and 2 μM Aβ40.