Major cause of antibody artifact bands on non-reducing SDS-PAGE and methods for minimizing artifacts

When monoclonal antibodies (mAbs) are analysed by non-reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), method-induced artifacts are a frequent phenomenon. Previous studies suggested that incomplete denaturation and disulfide-bond scrambling are two main causes of artifact bands. Thus, in practice samples are normally heated and treated with alkylating agent iodoacetamide (IAM) before loading to promote denaturation and block free sulfhydryl groups, respectively. In this work, we further studied the major cause of artifact bands on non-reducing SDS-PAGE and ways of eliminating artifacts with two purified mAbs. In both cases, it was found that artifact bands on non-gradient Tris-glycine gels are mainly caused by incomplete denaturation under typical gel conditions. In general, heating minimizes artifact bands due to incomplete denaturation but it also generates some extra bands. Combining heating with IAM treatment achieved slightly better results than heating alone. As an alternative to heating, treating the samples with 8 M urea also allows close to complete denaturation of samples and thus minimizes artifact bands. In addition, we learned that untreated samples (samples that are not heated or treated with urea) may look different on Bis-Tris gel depending on gel composition (non-gradient vs. gradient) and the buffer used (MES vs. MOPS). In certain case, the apparent lack of artifact bands on gradient Bis-Tris gel may be in fact due to insufficient resolution. In conclusion, this study further confirmed that full-denaturation of sample is critical for minimizing/avoiding artifact bands on non-reducing SDS-PAGE.