Oligomeric αS induces cytotoxicity in SH-SY5Y cells. Conformation and cytotoxicity of αS with and without curcumin addition observed by AFM imaging, PAGE and LDH assay. (A) AFM images of αS alone: (i) monomeric αS, (ii) pre-formed oligomeric αS and (iii) fibrillar αS; and αS co-incubated with curcumin for 2-h: (iv) monomeric αS, (v) pre-formed oligomeric αS and (vi) and fibrillar αS. Scale bar = 1 μm. (B) Pre-formed oligomeric αS samples, with and without curcumin were separated on a 10% Tris/Tricine native PAGE gel and analyzed using silver staining. (C) Height distribution of oligomeric αS samples. Particle heights of pre-formed oligomeric αS samples, with (--) and without curcumin (-) were analyzed using AFM and SPIP software. (D) LDH activity of SH-SY5Y cells incubated with different morphologies of αS with or without co-incubation with curcumin. LDH release was expressed as a percentage of the Tris control samples. Data was reported as mean ± SE, n = 4. **p < 0.01 compared with the untreated control samples.