Cyanine is the non-systematic name of a synthetic dye family belonging to the polymethine group. The word cyanin stems from the English word “cyan”, which conventionally means a shade of blue-green. Cyanine dyes exhibit large molar absorptivities (?150,000 to 300,000 M-1cm-1) and moderate quantum yields resulting in extremely bright fluorescence signals. Cyanines have proven useful in several fields including photography, biology, laser technology and analytical chemistry. AAT Bioquest offers the largest collection of cyanine dyes that maybe useful as molecular probes for a variety of biological applications. For certain biological applications, cyanines can advantageously replace other conventional dyes such as the fluoresceins and rhodamines.

Cyanine Dyes: Cy3 and Cy5

Among cyanine dyes, Cy3® which fluoresces greenish yellow (?550 nm excitation, ?570 nm emission) and Cy5® which is fluorescent in the red region (?650 nm excitation, ?670 nm emission) are the most popular. Because of their minimal spectral overlap, Cy3® and Cy5® are typically combined for 2 color detection. Cy3® can be detected by various fluorometers, imagers, and microscopes with standard filters for TRITC. Due to its high molar extinction coefficient, Cy3® dye is also easily detected by naked eye on electrophoresis gels, and in solution. Cy5® became a popular replacement for far red fluorescent dyes because of its high extinction coefficient (as small as 1 nmol can be detected in gel electrophoresis by naked eye) and its fluorophore emission maximum in the red region, where many CCD detectors have maximum sensitivity and biological objects give low background interference.

Figure 2. Absorbance (dotted line) and emission (shaded region) maxima Cy3®(left), Cy5®(middle) and Cy7®(right) dyes.

Spectral Properties

Table 1. Spectral Properties For Cyanine Dyes: Cy3 and Cy5

Cy Dye Laser Ex/Em (nm) Filter Set Extinction Coefficient (ε)1 Quantum Yield (Φ)2
Cy3 532 nm 554/568 nm Cy3/TRITC 150,000 0.15
Cy5 633-647 nm 650/669 nm Cy5 250,000 0.27
Cy7 730 nm 754/778 nm Cy7 250,000 0.3
  1. ?: is the extinction coefficient (cm-1M-1).
  2. ?: is the fluorescence quantum yield.


Sulfonated vs Non-Sulfonated Cyanines

Sulfonated and non-sulfonated cyanine dyes exhibit very similar fluorescent characteristics and for many applications they can be used interchangeably. The difference between the dyes is mainly in their solubility. Non-sulfonated cyanines must be dissolved in an organic co-solvent, such as DMF or DMSO, prior to labeling of a biomolecule. While sulfonated cyanines can be used in aqueous conditions (the charged sulfonate groups decrease dye and conjugate aggregation). For purification by dialysis against water or an aqueous buffer, sulfonated cyanines must be used for efficient removal of any unreacted dye. Purification by gel filtration, chromatography, or electrophoresis is adequate for both sulfonated and non-sulfonated cyanines.

Table 2. Spectral comparison of sulfonated and non-sulfonated Cy3, Cy5 and Cy7 dyes.
Cy3® Cy5® Cy7®
Form Sulfo Non-Sulfo Sulfo Non-Sulfo Sulfo Non-sulfo
Ex/Em (nm) 554/568 650/669 754/778
Filter Set Cy/TRITC Cy5 Cy7
? 150,000 140,000 250,000 230,000 250,000 250,000
? 0.10 0.07 0.27 0.16 0.12 0.2
Cat No. 263 191 268 195 161 198
  1. ?: is the extinction coefficient (cm-1M-1).
  2. ?: is the fluorescence quantum yield.

Cyanine Products

We offer a broad selection of cyanine products including reactive dyes and conjugation kits for labeling biomolecules, conjugates, indicators and more.

Cyanine Reactive Dyes

Select a dye-labeling chemistry for modifying the following reactive groups:

Table 2. Cyanine Reactive Dyes

Cyanine-Labeled Secondary Conjugates

Select from a variety of cyanine labeled secondary antibody and streptavidin conjugates for signal amplification detection of primary antibodies.

Table 3. Cyanine-Labeled Secondary Conjugates

Goat Anti-Mouse IgG Goat Anti-Rabbit IgG Streptavidin













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