Thyroglobulin (Tg-FSP) Heavy
Serum thyroglobulin (Tg) fragment FSP is a clinical biomarker for the efficacy of the treatment of patients following thyroid cancer; it contains an arginine residue labelled with stable 13C and 15N isotopes.
Catalogue number crb1301686 Molecular Weight 1415.7 Sequence (one letter code)
Sequence (three letter code)
Purity >95% Storage -20°C References
Kushnir et al., (2013). Measurement of thyroglobulin by liquid chromatography-tandem mass spectrometry in serum and plasma in the presence of antithyroglobulin autoantibodies. Clin Chem., 59(6): 982. doi: 10.1373/clinchem.2012.195594.
Nishihara et al., (2022). Serum thyroglobulin evaluation on LC-MS/MS and immunoassay in TgAb-positive patients with papillary thyroid carcinoma. Eur. Thyroid J., 11: 1. Doi: 10.1530/ETJ-21-0041.
Serum levels of thyroglobulin (Tg) is considered a valuable measurement for quantitively evaluating thyroid cancer treatment efficacy. Immunoassays are commonly used for Tg level evaluation but return many false negatives. This is due to a large proportion of patients expressing anti-Tg antibodies (TgAb), which outcompete the reagent antibodies for Tg.
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is potentially better at quantification of Tg as TgAb should less influence it. Tg digestion with trypsin yields the specific peptide Tg-FSP peptide (FSPDDSAGASALL) that is a reliable target for LC-MS/MS and unique to Tg.
The Tg-FSP heavy arginine residue at position 14 is isotopically labelled with carbon-13 (9) and nitrogen-15 (1), giving this peptide a mass increase of 10 compared to the unlabelled peptide. This will allow absolute quantification applications such as quantitative proteomics, the quantification of complex protein mixtures at very low concentrations, or NMR studies.