Formation of C-terminal-truncated α-synuclein oligomer can be reduced by PQQ. The dot blot analysis of truncated α-Syn119 sample with or without PQQ using anti-oligomer antibody, A11. 0 ~ 12 h incubated α-Syn119 was stained in membrane. Same samples were used to cell viability assay. 21 μM of incubated α-Syn119 in several time added to U2-OS cells. The results are expressed as a percentage of the value of "control" (PBS) (white bar), which is set as 100%. Values are expressed as mean ± SD, n = 3. Truncated α-Syn119 alone (white bar), and α-Syn119 + PQQ (black bar).