Figure 4.
(A–D) Screen snapshots of intact protein mass spectra of V21H4 samples from BiopharmaLynx. (A) Deconvoluted spectrum of V21H4 showing the attachment of a half cystamine to the C-terminal cysteine by forming a disulfide bond during refolding. (B) The deconvoluted spectrum of V21H4 after reduction with 2 mM TCEP showing the detachment of the C-terminal half cystamine. (C) The deconvoluted spectrum of the reduced V21H4 after alkylation with iodoacteamide showing the C-terminal cysteine is accessible to a sulfhydryl activation cross-linker. (D) Deconvoluted mass spectrum of V21H4 after activation by cross-linker and linkage to cysteine. V21H4 antibody activated by BM(PEG)2 generates a single activated species.