Cy5.5 Alkyne (also sold as sulfo-Cyanine5.5 Alkyne) is a bright and photostable near-IR dye that is spectrally similar to Alexa Fluor® 680, DyLight® 680, and IRDye® 680 dye. The Cy5.5 Alkyne is water-soluble, hydrophilic dye often a reagent of choice for assay where minimal non-specific binding and exceptional brightness is required. Cy5.5 Alkyne is pH insensitive from pH 4 to pH 10 and produces minimal autofluorescence of biological specimens in this region of the spectrum. Fluorescence of this long-wavelength Cyanine dye is not visible to the human eye but is readily detected by most imaging systems.
The NIR-fluorescent Cy5.5 Alkyne reacts with azide via a copper-catalyzed click reaction (CuAAC) to form a stable triazole linker. After the click reaction with the conjugate is still remains very bright, water-soluble, and pH-insensitive. A probe for copper-less detection (Cy5.5 DBCO) is also available for application where the presence of copper is not acceptable.