Sulfo-Cy3-PEG3-biotin potassium is a biotin-modified derivative of Cy3 (Cyanine3) dye containing a TCO group. The TCO group of Sulfo-Cy3-PEG3-biotin potassium reacts with the tetrazine functional group in highly specific click chemistry to form a covalent bond. Thus, Sulfo-Cy3-PEG3-biotin potassium can be covalently bound to some biomolecules (especially antibodies , proteins, etc.) to track their location and dynamic changes in biological samples. And because it is labeled with biotin, it is often used in affinity chromatography experiments, such as immunoprecipitation.