Alexa Fluor

General Information (more on wikipedia)

The Alexa Fluor family of fluorescent dyes is produced by Molecular Probes, a subsidiary of Invitrogen. Alexa Fluor dyes are typically used as cell and tissue labels in fluorescence microscopy and cell biology.

The excitation and emission spectra of the Alexa Fluor series cover the visible spectrum and extend into the infrared. The individual members of the family are numbered according roughly to their excitation maxima (in nm).

Alexa Fluor dyes are synthesized through sulfonation of coumarin, rhodamine, xanthene (such as fluorescein), and cyanine dyes. Sulfonation makes Alexa Fluor dyes negatively charged and hydrophilic. Alexa Fluor dyes are generally more stable, brighter, and less pH-sensitive than common dyes (e.g. fluorescein, rhodamine) of comparable excitation and emission, and to some extent the newer cyanine series. However, they also tend to be more expensive.

Similar alternatives include the Hilyte Fluor series from AnaSpec and DyLight Fluors from Pierce (Thermo Fisher Scientific).

Diffusion coefficients of Alexa 350:

  • In water:
    • Alone: $D = 570 \mu m^{2}/s$ [1]
    • Alone: $D = 300 \mu m^{2}/s$ [2]
  • In cytoplasm:
    • Alone: $D = 185 \mu m^{2}/s$ [1]

Diffusion coefficients of Alexa 488:

  • In water:
    • Alone: $D = 430 \mu m^{2}/s$ [1]
  • In cytoplasm:
    • Alone: $D = 380 \mu m^{2}/s$ [1]

Diffusion coefficients of Alexa 594:

  • In water:
    • Alone: $D = 370 \mu m^{2}/s$ [1]
  • In cytoplasm:
    • Alone: $D = 240 \mu m^{2}/s$ [1]
1. Biophysical Journal 86:2058-2077 (2004))
2. Incorporation and dynamics of membrane proteins in GUVs: website
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