Figure 2. Characterization of SS-mPEG-GPx1M. (A) SS-mPEG-GPx1M form at mass ratio 1:50 stained with Coomassie Blue R-250. M, molecular weight standards. Lane 1, GPx1M. Lane 2, the reaction mixture with a molar ratio of 1:50 between GPx1M and SS-mPEG, including unmodified GPx1M and SS-mPEG-GPx1M. SDS-PAGE analysis of purified SS-mPEG-GPx1M with Coomassie Blue R-250 (B) and Iodine stain (C). Abbreviation: M: molecular weight standards. Lane 1, GPx1M. Lane 2, purified SS-mPEG-GPx1M. Lane 3, SS-mPEG. (D) MALDI-TOF-MS of reaction mixture and purified SS-mPEG-GPx1M. (a) The MS image of reaction mixture. The reaction mixture mainly included unmodified GPx1M (23805.3488 m/z) and PEGylated product (SS-mPEG-GPx1M, 28870.8557 m/z). (b) The MS image of purified SS-mPEG-GPx1M.