fluorescein  

Fluorescein derivatives are the most common fluorescent reagents for biological research because of their high absorptivity, excellent fluorescence quantum yield, and good water solubility.

Fluorescein-based dyes and their conjugates have several performance characteristics that may facilitate or limit use in certain applications. Fluorescein displays:

  • A relatively high rate of photobleaching
  • Fluorescent signal that is sensitive to pH changes
  • A relatively broad fluorescence emission spectrum
  • Fluorescence quenching on conjugation to biopolymers
We offer a broad range of fluorescein conjugates and derivatives as well as a series of high-performance fluorophores with improved characteristics for labeling and detection.

Fluorescein dashboard


Initial brightness

 
 
 
 
 
Fluorescein is a bright green fluorphore that is sensitive to changes in pH and can photobleach rapidly unless an antifade agent is used. Anti-fluorescein antibodies can be useful in amplifying a weak signal.  
     

Photostability in buffer

 
 
 
 
 
   

Photostability in antifade

 
 
 
 
 
 

Fluorescein products

We offer a broad range of fluorescein products including secondary antibodies, primary antibodies, bioconjugates, and more.

Learn more here:

 

fluorescein

HeLa cells were fixed and permeabilized using several Invitrogen products Image-iT Fixation/Permeabilization Kit then incubated with Anti-ATP Synthase Subunit IF1 and GAM-FITC secondary Ab. Cells were counterstained with NucBlue Live and ActinRed 555 then mounted using ProLong Gold Antifade Mountant and imaged using the EVOS FL Auto Imaging System and a EVOS 40X Objective, coverslip-corrected

Fluorescein reactive dyes

Select dye-labeling chemistries for conjugation with the following reactive groups: 

Amine Thiol Aldehyde, ketone, carboxylate, or phosphate

Fluorescein protein/antibody labeling kits

Select an optimized labeling kit for your target antibody or protein:

Target protein Kit Cat. No.
Site-specific antibody labeling
<1–20 µg mouse IgG1 Zenon Fluorescein Mouse IgG1 Labeling Kit Z25042
Conventional antibody/protein labeling
1 mg antibody/protein Fluorescein Antibody/Protein Labeling Kit F10240

High-performance alternatives to fluorescein

Fluorescent conjugates

The Invitrogen Molecular Probes Alexa Fluor 488 dye—with spectral properties and quantum yield nearly identical to those of fluorescein isothiocyanate (FITC)—produces brighter, more photostable conjugates. These conjugates are ideal for imaging and other applications requiring increased sensitivity and environmentally insensitive fluorescence detection.

Monitoring pH

For pH monitoring the Invitrogen Molecular Probes pHrodo Green dye is almost nonfluorescent at neutral pH and fluoresces brightly in acidic environments. Unlike fluorescein, the minimal dye fluorescence at neutral pH also eliminates the need for wash steps and quencher dyes because any non-internalized dye will be essentially nonfluorescent.

  Comparison of the relative fluorescence of goat anti–mouse IgG antibody conjugates prepared from Alexa Fluor 488 dye and from fluorescein isothiocyanate (FITC). Conjugate fluorescence is determined by measuring the fluorescence quantum yield of the conjugated dye relative to that of a reference dye and multiplying by the dye:protein labeling ratio.

Resources

Molecular Probes Handbook

The significantly revised 11th Edition is the most complete fluorescence labeling and detection reference available. The Molecular Probes Handbook can help you achieve the best experimental results for your fluorescence labeling and detection experiments. View the handbook online or order your own copy.

Go to the Handbook online
Order your copy of the Handbook

Antifade reagents

Antifade reagents suppress photobleaching and preserve the signals of your fluorescently labeled target molecules. They offer excellent compatibility with a multitude of dyes across the spectrum, making them especially valuable tools for multicolor applications. For added convenience, some formulations include the nuclear counterstain DAPI, eliminating the need for a separate counterstaining step.

See the performance of this dye in SlowFade Antifade reagents
See the performance of this dye in ProLong Antifade reagents

Cell stain tool

Stain your own cell by using our simulation tool to develop reproducible results with many of our signature fluorescent dyes. Develop your multiplexing strategy for antibody probes, reactive dyes, and counterstains to create your perfectly labeled fluorescent cell.

Go to the cell stain tool

Fluorescence SpectraViewer

Plot and compare spectra and check the spectral compatibility for common fluorophores including all of the fluorescent probes from Thermo Fisher Scientific. The Fluorescence SpectraViewer tool is formatted for both microscope imaging and flow cytometry applications.

Go to the Fluorescence SpectraViewer