Qdot® 655 Probe

Qdot® 655 probe is an excellent far red–fluorescent label with outstanding brightness and photostability for imaging and flow cytometry applications. With an emission maximum of ~655 nm, Qdot® 655 probe can be excited using a 350, 488, 595, or 615 nm laser line or standard Cy®5 filter. Optimum imaging results with brighter signals are achieved with a Qdot® 655 filter or light cube.

Made from nanocrystals of semiconductor material, Qdot® probes are broadly compatible with standard fluorescence techniques, but there are some novel aspects to their use that can be optimized to obtain the best possible results. In general they have an extremely broad excitation range and narrow emission with a large Stokes shift. Optimal brightness is generally achieved using a specific Qdot® filter.

Organic fluorophores and Qdot® probes can be readily combined in multiplexed flow cytometry or imaging studies. Longer-wavelength Qdot® probes are also ideal for multiplexed western blots.

Qdot® 655 probe dashboard

Initial brightness



For best results use a Qdot®-optimized filter and PBS or a mounting medium without antifade.



Photostability in buffer


Qdot® 655 products

The exceptional brightness and photostability of Qdot® probes make it easier to detect low-abundance targets. With narrow and symmetric emission spectra, Qdot® probes are also ideal for multiplexed fluorescence detection using a combination of Qdot® probes and organic dyes.

BPAE cells were fixed and permeabilized using the Image-iT® Fixation/Permeabilization Kit and incubated with Anti- ATP Synthase Subunit IF1 followed by GAM-QD655. Cells were labeled with ReadyProbes reagents NucBlue® Live and ActinGreen™ 488, then mounted using ProLong® Gold Antifade Reagent. Images were taken using the EVOS® FL Auto Imaging System and a 40X CoverSlip corrected Objective.

Qdot® 655 conjugation kits

We’ve developed functionalized versions of the Qdot® 655 label for the preparation of custom conjugates of proteins and other biomolecules. The first—a carboxyl-derivatized form—can be coupled to amine groups of proteins and modified oligonucleotides. The second—an amine-derivatized PEG form—can be coupled to isothiocyanates and succinimidyl esters (or with native carboxylic acids using water-soluble carbodiimides).

Amine Aldehyde-, ketone, carboxylate or phosphate

Qdot® probes and accessories

Qdot® Probes are made from nanocrystals of semiconductor material and are broadly compatible with standard fluorescence techniques, but there are some novel aspects to their use that can be optimized to obtain the best possible results. Learn more about Qdot® Probes:


Molecular Probes® Handbook

Molecular Probes HandbookThe 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.


Antifades and mounting media

Antifade reagentsHigh-performance antifade reagents like ProLong® Gold and SlowFade® Gold will inhibit the photobleaching of organic dyes but suppress the fluorescence of Qdot® probes. A better solution for imaging Qdot® probes is simply PBS or a clear, colorless toluene-based mounting medium formulated from acrylic resins without the addition of antifade components.


Cell stain tool

Cell stain toolStain 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.


Fluorescence SpectraViewer

Fluorescence SpectraviewerPlot and compare spectra and check the spectral compatibility for common fluorophores including all the Molecular Probes® fluorescent probes. The Fluorescence SpectraViewer tool is formatted for both microscope imaging and flow cytometry applications.