What is C-terminal lysine variant?
Biopharmaceuticals, especially monoclonal antibody therapeutics, usually exhibit heterogeneity due to post-translational modifications or manufacture and storage related conditions. C-terminal lysine variants are one of the sources for monoclonal antibody heterogeneity, often occurring at the heavy chain. Although these variants do not show any substantial influence on the structure, stability and functions of biopharmaceutical, the determination of C-terminal lysine variants is still necessary, enabling the quality control of production.
How to determine the C-terminal lysine variants?
The C-terminal lysine variants can be determined by isoelectric focusing (IEF), ion-exchange chromatography (IEC) and LC-MS. Lysine is basic amino acid, and its lack at C-terminal alters the pI of protein, changing the position in IEF and affinity and retention time in IEC. Although IEF and IEC can be separated different variants, both methods are short of direct identification and quantification. In this case, LC-MS is a powerful tool to overcome the disadvantage in IEF and IEC.
Creative Proteomics offers the analytical services of C-terminal lysine variants based on LC-MS. Technically in brief, antibody is firstly digested with trypsin. The peptides in digestion mixture are seperated by RP-HPLC system using a C18 column, then detected in mass spectrometry. Specific and single charged ions corresponding to the C-terminal peptides will be extracted in tandem mass. The MS and MS/MS spectra acquired provide identity and quantity of lysine variants.
Automatic Determination of Disulfide Bridges in Proteins, Izabela Sokolowska, J Lab Autom. 2012, 17(6).Creative Proteomics provides the nanoLC-ESI-MS/MS with high mass accuracy and sensitivity to proper disulfide bridge and sulfhydryl groups analysis. Scientists from Creative Proteomics are professional and they can help you determine the number and position of disulfide bonds as well as low levels of potential mismatched forms.
