The Alexa Fluor Dye Series—Note 1.1

The Alexa Fluor dyes—a series of superior fluorescent dyes that span the visible spectrum—represent a major breakthrough in the development of fluorescent labeling reagents. Benefits of the Alexa Fluor dyes and their conjugates include:

• Brightness—Alexa Fluor conjugates exhibit more intense fluorescence than other spectrally similar conjugates.
• Photostability—Alexa Fluor conjugates are more photostable than most other fluorescent conjugates, allowing more time for image capture.
• Instrument compatibility—Absorption spectra of the Alexa Fluor conjugates are matched to the principal output wavelengths of common excitation sources.
• Color selection—Alexa Fluor conjugates are available in several distinct fluorescent colors, ranging from blue to red to near-infrared (Figure 1, Table 1).
• pH insensitivity—Alexa Fluor dyes remain highly fluorescent over a broad pH range.
• Water solubility—Alexa Fluor reactive dyes have good water solubility, so protein conjugations can be performed without organic solvents, and the conjugates are relatively resistant to precipitation during storage.

Conventional fluorophores and their conjugates can often be replaced with spectrally similar Alexa Fluor dyes and conjugates without affecting optical filter choices or other instrumentation considerations (Table 2). Each of the Alexa Fluor dyes are listed in Table 1 and described in detail in Alexa Fluor Dyes Spanning the Visible and Infrared Spectrum—Section 1.3 and in the accompanying Section 1.3 data table.

Figure 1. Emission spectra for the Alexa Fluor dye series.

Table 1. Spectral properties of Molecular Probes Alexa Fluor dyes

Table 2. Alexa Fluor dye alternatives to several common fluorophores