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Cyanines have been used for many years as dyes, for example in photographic emulsions. Cyanine dyes began to be used widely as labels for nucleic acids in the early 1990s, when Cyanine-3, Cyanine-5 and Cyanine-7 (Figure 1) were made commercially available as succinimidyl esters. These Cyanine dyes were different from previous cyanine dyes in that they contain sulfonate groups, which makes the Cyanine dyes soluble in water (and also reduce fluorescence-quenching which can arise from dye–dye interactions). Since their introduction the Cyanine dyes have found widespread use in DNA and RNA labelling.
The Quasar® dyes, manufactured and sold by Biosearch Technologues, are replacements for the Cyanine dyes. The Quasar dyes are chemically very similar to the Cyanine dyes (Figure 2). As such, the properties of the Quasar dyes are practically identical to those of the Cyanine dyes.
Some physical properties of the Quasar dyes are compared with those of the Cyanine dyes in Table 1.
|Name||λmax / nm (absorption)||λmax / nm (emission)||Colour||E at λmax||Φ||τ / ns|
|Cyanine-3||550||570||Dark pink||136 000||0.15||-|
|Cyanine-3.5||591||604||-||116 000||0.15||< 0.3|
|Quasar 570||548||566||Dark pink||115 000||-||-|
|Quasar 670||647||670||Blue||187 000||-||-|
|Quasar 705||690||705||Blue||206 000||-||-|
Our free online Nucleic Acids Book contains information on all aspects of nucleic acids chemistry and biology.