Alexa® dyes



The Alexa®, or Alexa Fluor®, dyes were introduced by Molecular Probes, Inc. (now part of Life Technologies, Inc.).

Properties and structures

A range of Alexa dyes is available, with emission wavelengths spanning the visible spectrum and extending into the infrared region of the spectrum. Some can be used in single molecule studies (Table 1).

Table 1Alexa Fluor dyes

Nameλmax / nm (absorption)λmax / nm (emission)ColourE at λmaxΦτ / ns
Alexa Fluor 350346442Blue19 000--
Alexa Fluor 405402421Blue35 000--
Alexa Fluor 430434539Green/Yellow15 000--
Alexa Fluor 488495519Green73 0000.924.1
Alexa Fluor 514518540Green80 000--
Alexa Fluor 532531554Yellow81 0000.612.5
Alexa Fluor 546556573Orange112 0000.794.1
Alexa Fluor 555555565Orange155 0000.100.3
Alexa Fluor 568578603Orange/Red88 0000.693.6
Alexa Fluor 594590617Red92 0000.663.6
Alexa Fluor 610612628Red144 000--
Alexa Fluor 633632647Far-red159 000--
Alexa Fluor 635633647Far-red140 000--
Alexa Fluor 647650668Far-red270 0000.331.0
Alexa Fluor 660663690Near-IR132 0000.371.2
Alexa Fluor 680679702Near-IR183 0000.361.2
Alexa Fluor 700702723Near-IR205 0000.251.0
Alexa Fluor 750749775Near-IR290 0000.120.7
Alexa Fluor 790782805Near-IR260 000--

Not all of the structures of the Alexa dyes are available, but some of the structures are listed in Figure 1.

Structures of selected Alexa Fluor® dyes (structures of other Alexa Fluor dyes are not published)

Figure 1 | Structures of selected Alexa Fluor® dyes (structures of other Alexa Fluor dyes are not published)


The Alexa Fluor dyes, and other dyes that emit at longer wavelengths, towards the red end of the spectrum (> 600 nm) have advantages over dyes that emit at shorter wavelengths in that there is typically less background fluorescence at longer these wavelengths. In experiments that involve cells/cell debris, other chemicals (e.g. buffers) and plastics (e.g. microplates) this can lead to increased sensitivity.

See also

Our free online Nucleic Acids Book contains information on all aspects of nucleic acids chemistry and biology.