Cy5.5 Azide (also sold under sulfo-Cyanine5.5 Azide name) is a bright and photostable near-IR dye that is spectrally similar to Alexa Fluor® 680, DyLight 680™, and IRDye® 680 dye. Cy5.5 Azide is water-soluble, hydrophilic dye often a reagent of choice for assay where minimal non-specific binding is required. Cy5.5 Azide 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.
Cy5.5 Azide can be reacted with terminal alkynes via a copper-catalyzed click reaction (CuAAC). It also reacts with strained cyclooctyne via a copper-free “click chemistry” reaction to form a stable triazole and does not require Cu-catalyst or elevated temperatures.
For the detection of low abundance targets or where significant increase in signal intensity is desired please consider using next generation azide probes containing an internal copper-chelating motif.