Mutant SOD1 and chaperones co-fractionate in the detergent insoluble fractions. Spinal cord extracts were subjected to differential detergent extraction and A) the soluble fraction was electrophoresed under reducing and denaturing conditions and stained with Coomassie (S1) and P1-P3 fractions were immunoblotted for SOD1 under non-reducing or reducing conditions (P1-P3). Asterisks indicate the position of the monomeric SOD1. High molecular weight reactivity to the SOD1 antibody was detected in the H46R/H48Q extracts but not WT TG (indicated by vertical bar). High molecular weight reactivity to SOD1 diminished with addition of a reducing agent, however a band corresponding to dimeric SOD1 persisted and is indicated by an arrow. B) Inducible heat shock protein 70 and αB-crystallin co-fractionated with mutant SOD1 in the detergent insoluble fractions of spinal cord. *p = 0.05, **p = 0.01, Bars represent the mean of 6 mice +/- SD.