Alexa Fluor 680 C2-Maleimide is a maleimide-functionalized derivative of Alexa Fluor 680, emitting near-infrared fluorescence with excitation/emission maxima around 680/705 nm. The maleimide group efficiently forms covalent bonds with thiol (-SH) groups in proteins or peptides, enabling specific labeling and tracking of cysteine residues. It is commonly used as a functional near-infrared fluorescent probe in life science research.