Proteomic identification of monoclonal antibodies from rabbit serum and analysis of FDR using differential cysteine labeling

Proteomic analysis of serum antibodies is challenging due to the non-germline origin of immunoglobulin (Ig) sequences and the complexity of Ig primary structure, with regions of hypervariable sequence interspersed within highly conserved framework sections resulting in an unusually high frequency of peptide-spectrum mis-identification using standard reference database search methods. Using a strategy of differential cysteine labeling with two alkylating reagents, we examined peptide-spectrum matches and decoy-based error modeling for the interpretation of antibody-derived mass spectral data.