Figure 4. Aβ40 and Aβ42 dimers and trimers adopt a globular shape devoid of defined secondary structure.

(a) Ω values obtained from the mobility peaks associated with the most abundant charge states for the most abundant Aβ oligomers detected (Te = tetramers, Tr = trimers, and D = dimers) Te +7 (blue), Tr +6 (green), and D +5 (orange) for LMW Aβ40 (empty bars), LMW Aβ42 (filled bars), LMW_CL Aβ40 (empty brick-pattern bars) and LMW_CL Aβ42 (filled brick-pattern bars). Data are the mean ± s.d. of three independent experiments. p-values are calculated using unpaired two-tailed Student’s t-test (**p < 0.01 and ***p < 0.001). (b) Theoretical Aβ40 dimer models constructed using reported structural restraints for Aβ aggregates (nuclear³⁶, fibrillar³⁷, and compact⁹,³⁸), as well as those obtained from REMD simulations (globular). (c) Comparison of Ω values obtained from theoretical models of the dimer structures described in (b) with the experimental measures for the non-covalent and CL Aβ40 dimers reported in (a). CD analysis of CL dimers (orange) and CL trimers (green) for (d) Aβ40 and (e) Aβ42 obtained after GdnHSCN-SEC fractionation.