Figure 4. EM images of α-Syn oligomers that appear to contain circular or spherical oligomers with a diameter of ~4 nm. Portions of published images were enlarged and adjusted to have the same scale. We added yellow circles of 4.0 nm diameter around some beads. (a) An assembly in which oligomers were stabilized using formaldehyde cross-linking [51]. (b) Adapted with permission from Paslawski W, Andreasen M, Nielsen SB, et al. High stability and cooperative unfolding of alpha-synuclein oligomers. Biochemistry. 2014 Oct 7;53(39):6252-63 [52] Copyright 2014, American Chemical Society. (d-e) small and large oligomers reported by Lorenzen et al. [53] Adapted with permission from Lorenzen N, Nielsen SB, Buell AK, et al. The role of stable alpha-synuclein oligomers in the molecular events underlying amyloid formation. J Am Chem Soc. 2014 Mar 12;136(10):3859-68. Copyright 2014, American Chemical Society.