SOD1 and amyotrophic lateral sclerosis: Also importantly, those smears in G1H mice at 60 and 100 days of age disappeared when the soluble fractions were treated with β-mercaptoethanol (β-ME) prior to their loading on an SDS-PAGE gel (Fig. 6c, right panel), supporting the formation of disulfide-crosslinked SOD1 oligomers in the ALS-model mice even before the disease onset.