FIGURE 1.
LC-ESI-MS of soluble hWT and ALS variant SOD1 from ALS-mouse spinal cord. A, total ion current LC chromatogram from LC-ESI-MS analysis of supernatant solution (referred to as “S1”). ALS variant and hWT SOD1 elute at ∼39–41 min (peak corresponding to hSOD1 marked with red arrow). B, raw mass spectra of SOD1 species eluting between 38 and 41 min from hWT, G37R, H46R/H48Q, and G93A mice. C, reconstructed mass spectra that were deconvoluted from the corresponding raw spectra in B (see Table 1 for mass values). D–F, oxidative modifications to SOD1 do not significantly alter retention time on HPLC column. D, LC-ESI-MS total ion current chromatogram of recombinantly purified H48Q SOD1 that has been partially oxidized in vitro with H2O2. Peak at 39–41 min corresponds to H48Q SOD1 (peak at ∼9 min is eluted salt from sample injection). E and F, raw mass spectrum (E) and deconvoluted mass spectrum (F) of H48Q SOD1 species eluting in selected region of chromatogram in D. Two SOD1 species are present and have co-eluted, demonstrating that oxidatively modified SOD1 in mouse spinal cord would have eluted with unmodified SOD1 at ∼39–41 min. Species with mass of 15839.47 Da corresponds to unmodified H48Q SOD1; species with 15869.36 Da corresponds to oxidatively modified H48Q SOD1.