- COMT-dependent protection of dopaminergic neurons by methionine, dimethionine and S-adenosylmethionine (SAM) against L-dopa toxicity in vitro. Werner, P., Di Rocco, A., Prikhojan, A., Rempel, N., Bottiglieri, T., Bressman, S., Yahr, M.D. Brain Res. (2001)