Mass Spectrometry

SILu™MAb and SigmaMAb Antibody Standards for Mass Spectrometry

How sharp are your peaks? Our Stable Isotope-Labeled Universal Monoclonal Antibody (SILuMAb) is a critical tool for the assessment of pharmacokinetic properties of biotherapeutics. SILuMAb is a highly purified, stable isotope-labeled IgG monoclonal antibody (expressed in a proprietary Sigma-Aldrich® CHO cell line) that utilizes universal heavy-labeled tryptic peptides as internal standards for the quantitation of monoclonal antibodies and Fc-fusion therapeutics. As a full-length protein standard with universal utility, it eliminates the need for the production of candidate-specific internal standards and reduces errors associated with fractionation, enrichment, and proteolysis. SILuMAb also offers a variety of advantages over traditional ELISA-based methods, such as superior specificity, sensitivity, and reduced matrix effects.


SILuMAb Adalimumab*
• Internal standard for analysis of
  Adalimumab in human serum
• Recombinant, stable isotope labeled,
  monoclonal antibody expressed in
  CHO cells
ADC Mimic
• SigmaMAb Antibody Drug Conjugate
  (ADC) Mimic recombinant, expressed
  in CHO cells
• IgG1 monoclonal antibody,
  non-toxic drug mimic
SILuMAb Infliximab
• SILu™MAb Infliximab recombinant,
  expressed in CHO cells
• Stable isotope-labeled, monoclonal
SILuMAb Mouse
• SILu™MAb Mouse recombinant,
  expressed in CHO cells
• Stable isotope-labeled, monoclonal
  mouse antibody
• SILuMAb K1 recombinant, expressed in
  CHO cells
• Heavy-labeled human IgG1 κ antibody
• SILu™Lite SigmaMAb Standard human
• Light IgG1 λ antibody

• SILuMAb Standard human recombinant,
  expressed in CHO cells
• Heavy-labeled IgG1 λ antibody
• SILuMAb K4 recombinant, expressed in
  CHO cells
• Heavy-labeled human IgG4 κ antibody
SILuMAb Glycan
• SILuMAb Glycan Standard mouse
• Heavy-labeled IgG2b antibody

SILuMAb is grown in serum-free 13C6 15N4 Arg / 13C6 15N2 Lys-enriched media and overlaps with the common sequences in the Fc and light chain regions with candidate antibodies. SILuMAb yields the universal stable isotope-labeled tryptic peptides via vertical integration into the LC/MS analytical workflow. By reducing errors related to fractionation, enrichment, and proteolysis, SILuMAb is superior to horizontally-integrated labeled peptide standards.

SILuMAb has been validated as an internal standard for quantitation of relevant biotherapeutics in a complex biological matrix by MRM-based LC-MS/MS:

  • SILuMAb yielded reproducible, linear curves from 6.4 μg/mL to 250 μg/mL without enrichment or depletion.
  • Good agreement was observed between multiple peptides derived from the same target.

SILuMAb has also been highly characterized:

  • Label incorporation was determined to be >98% by mass spectrometry.
  • Sequence was confirmed by peptide mapping and intact mass analysis.
  • Purity has been determined to be ≥ 90% by SDS-PAGE

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