Sulfo-Cy3-PEG3-biotin potassium is a biotin-modified derivative of the Cy3 (Cyanine3) dye, featuring a TCO group. This TCO group can undergo a highly specific click chemistry reaction with tetrazine functional groups to form covalent bonds. Consequently, Sulfo-Cy3-PEG3-biotin potassium can be covalently linked to various biomolecules (particularly antibodies and proteins), facilitating their location and dynamic monitoring in biological samples. Additionally, due to its biotin labeling, it is commonly employed in affinity chromatography experiments, such as immunoprecipitation.